Effect of COVID-19 lockdown on maternity care and maternal outcome in the Netherlands: a national quasi-experimental study.

OBJECTIVES: The COVID-19 pandemic and associated lockdowns disrupted health care worldwide. High-income countries observed a decrease in preterm births during lockdowns, but maternal pregnancy-related outcomes were also likely affected. This study investigates the effect of the first COVID-19 lockdown (March-June 2020) on provision of maternity care and maternal pregnancy-related outcomes in the Netherlands. STUDY DESIGN: National quasi-experimental study. METHODS: Multiple linked national registries were used, and all births from a gestational age of 24+0 weeks in 2010-2020 were included. In births starting in midwife-led primary care, we assessed the effect of lockdown on provision of care. In the general pregnant population, the impact on characteristics of labour and maternal morbidity was assessed. A difference-in-regression-discontinuity design was used to derive causal estimates for the year 2020. RESULTS: A total of 1,039,728 births were included. During the lockdown, births to women who started labour in midwife-led primary care (49%) more often ended at home (27% pre-lockdown, +10% [95% confidence interval: +7%, +13%]). A small decrease was seen in referrals towards obstetrician-led care during labour (46%, -3% [-5%,-0%]). In the overall group, no significant change was seen in induction of labour (27%, +1% [-1%, +3%]). We found no significant changes in the incidence of emergency caesarean section (9%, -1% [-2%, +0%]), obstetric anal sphincter injury (2%, +0% [-0%, +1%]), episiotomy (21%, -0% [-2%, +1%]), or post-partum haemorrhage: >1000 ml (6%, -0% [-1%, +1%]). CONCLUSIONS: During the first COVID-19 lockdown in the Netherlands, a substantial increase in homebirths was seen. There was no evidence for changed available maternal outcomes, suggesting that a maternity care system with a strong midwife-led primary care system may flexibly and safely adapt to external disruptions.

Birth-weight centile at term and school performance at 12 years of age: linked cohort study.

OBJECTIVE: Birth weight, fetal growth and placental function influence cognitive development. The gradient of these associations is understudied, especially among those with a birth weight considered appropriate-for-gestational age. The aim of this study was to evaluate the associations between birth-weight centile and intellectual development in term/near-term infants across the entire birth-weight spectrum, in order to provide a basis for better understanding of the long-term implications of fetal growth restriction and reduced placental function. METHODS: This was a population-based cohort study of 266 440 liveborn singletons from uncomplicated pregnancies, delivered between 36 and 42 weeks of gestation. Perinatal data were obtained from the Dutch Perinatal Registry over the period 2003-2008 and educational data for children aged approximately 12 years were obtained from Statistics Netherlands over the period 2016-2019. Regression analyses were conducted to assess the association of birth-weight centile with school performance. The primary outcomes were mean school performance score, on a scale of 501-550, and proportion of children who reached higher secondary school level. RESULTS: Mean school performance score increased gradually with increasing birth-weight centile, from 533.6 in the 1st -5th birth-weight-centile group to 536.8 in the 81st -85th birth-weight-centile group. Likewise, the proportion of children at higher secondary school level increased with birth-weight centile, from 43% to 57%. Compared with the 81st -85th birth-weight-centile group, mean school performance score and proportion of children at higher secondary school level were significantly lower in all birth-weight-centile groups below the 80th centile, after adjusting for confounding factors. CONCLUSIONS: Birth-weight centile is associated positively with school performance at 12 years of age across the entire birth-weight spectrum, well beyond the conventional and arbitrary cut-offs for suspected fetal growth restriction. This underlines the importance of developing better tools to diagnose fetal growth restriction and reduced placental function, and to identify those at risk for associated short- and long-term consequences. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Effect of parental and ART treatment characteristics on perinatal outcomes.

STUDY QUESTION: Do parental characteristics and treatment with ART affect perinatal outcomes in singleton pregnancies? SUMMARY ANSWER: Both parental and ART treatment characteristics affect perinatal outcomes in singleton pregnancies. WHAT IS KNOWN ALREADY: Previous studies have shown that singleton pregnancies resulting from ART are at risk of preterm birth. ART children are lighter at birth after correction for duration of gestation and at increased risk of congenital abnormalities compared to naturally conceived children. This association is confounded by parental characteristics that are also known to affect perinatal outcomes. It is unclear to which extent parental and ART treatment characteristics independently affect perinatal outcomes. STUDY DESIGN, SIZE, DURATION: All IVF clinics in the Netherlands (n = 13) were requested to provide data on all ART treatment cycles (IVF, ICSI and frozen-thawed embryo transfers (FET)), performed between 1 January 2000, and 1 January 2011, which resulted in a pregnancy. Using probabilistic data-linkage, these data (n = 36 683) were linked to the Dutch Perinatal Registry (Perined), which includes all children born in the Netherlands in the same time period (n = 2 548 977). PARTICIPANTS/MATERIALS, SETTING, METHODS: Analyses were limited to singleton pregnancies that resulted from IVF, ICSI or FET cycles. Multivariable models for linear and logistic regression were fitted including parental characteristics as well as ART treatment characteristics. Analyses were performed separately for fresh cycles and for fresh and FET cycles combined. We assessed the impact on the following perinatal outcomes: birth weight, preterm birth below 37 or 32 weeks of gestation, congenital malformations and perinatal mortality. MAIN RESULTS AND THE ROLE OF CHANCE: The perinatal outcomes of 31 184 out of the 36 683 ART treatment cycles leading to a pregnancy were retrieved through linkage with the Perined (85% linkage). Of those, 23 671 concerned singleton pregnancies resulting from IVF, ICSI or FET. Birth weight was independently associated with both parental and ART treatment characteristics. Characteristics associated with lower birth weight included maternal hypertensive disease, non-Dutch maternal ethnicity, nulliparity, increasing duration of subfertility, hCG for luteal phase support (compared to progesterone), shorter embryo culture duration, increasing number of oocytes retrieved and fresh embryo transfer. The parental characteristic with the greatest effect size on birth weight was maternal diabetes (adjusted difference 283 g, 95% CI 228-338). FET was the ART treatment characteristic with the greatest effect size on birth weight (adjusted difference 100 g, 95% CI 84-117) compared to fresh embryo transfer. Preterm birth was more common among mothers of South-Asian ethnicity. Preterm birth was less common among multiparous women and women with 'male factor' as treatment indication (compared to 'tubal factor'). LIMITATIONS, REASONS FOR CAUTION: Due to the retrospective nature of our study, we cannot prove causality. Further limitations of our study were the inability to adjust for mothers giving birth more than once in our dataset, missing values for several variables and limited information on parental lifestyle and general health. WIDER IMPLICATIONS OF THE FINDINGS: Multiple parental and ART treatment characteristics affect perinatal outcomes, with birth weight being influenced by the widest range of factors. This highlights the importance of assessing both parental and ART treatment characteristics in studies that focus on the health of ART-offspring, with the purpose of modifying these factors where possible. Our results further support the hypothesis that the embryo is sensitive to its early environment. STUDY FUNDING/COMPETING INTEREST(S): This study was funded by Foreest Medical School, Alkmaar, the Netherlands (grants: FIO 1307 and FIO 1505). B.W.M. reports grants from NHMRC and consultancy for ObsEva, Merck KGaA, iGenomics and Guerbet. F.B. reports research support grants from Merck Serono and personal fees from Merck Serono. A.C. reports travel support from Ferring BV. and Theramex BV. and personal fees from UpToDate (Hyperthecosis), all outside the remit of the current work. The remaining authors report no conflict of interests. TRIAL REGISTRATION NUMBER: N/A.

Optimal timing of delivery in small for gestational age fetuses near term: a national cohort study.

OBJECTIVE: Our aim was to study the competing risks of antepartum versus intrapartum/neonatal death in small for gestational age (SGA) and non-SGA fetuses. STUDY DESIGN: We performed a national cohort study using all singletons delivered between 36 and 42(6/7) weeks without hypertension, preeclampsia, diabetes, congenital anomalies, or noncephalic presentation from the Netherlands Perinatal Registry (1999-2007). The resultant cohort was divided in three groups based on birth weight by gestational age (SGA < P5 group, 61,021 deliveries; SGA P5-10 group, 58,902 deliveries; non-SGA group 1,168,523 deliveries). We compared the mortality risk of delivery with expectant management. RESULTS: Delivery was associated with more mortality than expectant management for 1 week from 39 weeks onward in the non-SGA group (relative risk [RR], 1.26; 95% confidence interval [CI], 1.05-1.50). For the SGA < P5, expectant management for 1 more week was associated with more mortality from 38 weeks onward although this only reached statistical significance from 40 weeks onward (RR, 2.46; 95% CI, 1.80-3.36). CONCLUSION: At 36 and 37 weeks, delivery is associated with a higher risk of mortality in SGA < P5 fetuses than expectant management. Delivery of SGA < P5 fetuses at 38 and 39 weeks is associated with the best perinatal outcome whereas for non-SGA fetuses this is at 39 to 40 weeks.

Optimal timing of near-term delivery in different ethnicities: a national cohort study.

OBJECTIVE: To study possible ethnic disparities in perinatal mortality and morbidity independent of the occurrence of pregnancy complications. In addition, to study the probabilities of adverse neonatal outcome for delivery, compared with 1 week of expectant management for each week of gestational age in the range of 36-42 weeks of gestation. DESIGN: National cohort study. SETTING: The Netherlands. POPULATION: All women who were recorded as being of white European (982,318), Mediterranean (94,130), or African-Caribbean (25,253) descent with singleton cephalic births delivered between 36(+0) and 42(+6) weeks of gestation. Women with hypertension, pre-eclampsia, or diabetes, or with fetuses that were small for gestational age (below the tenth percentile) or with congenital abnormalities, were excluded. Data were obtained from the Netherlands Perinatal Registry (1999-2007). METHODS: Numbers of antepartum and intrapartum/neonatal death, and neonatal morbidity, were expressed using the fetus/neonate-at-risk approach. For each week of gestation, we compared the probability of adverse neonatal outcome (intrapartum/neonatal death in that week) for delivery with the probability of adverse neonatal outcome for expectant management (antepartum death in that week plus intrapartum/neonatal death and morbidity in the subsequent week). RESULTS: Women of Mediterranean and African-Caribbean descent who were near term were at increased risk of antepartum and intrapartum/neonatal death, and neonatal morbidity, compared with white European women. Expectant management from 40 weeks of gestation onwards was associated with an increased probability of adverse neonatal outcome in white European women and in women of Mediterranean descent, compared with delivery (risk ratio, RR 1.45, 95% confidence interval, 95% CI 1.25-1.68, versus RR 1.69, 95% CI 1.11-2.60, and with number needed to deliver to prevent one adverse neonatal outcome being 563 and 364, respectively). This was not observed for women of African-Caribbean descent. CONCLUSIONS: Ethnic disparities in perinatal outcomes were observed, with higher risks for women of Mediterranean descent. Expectant management in white European and Mediterranean women after 39 weeks of gestation is associated with an increased risk of adverse neonatal outcome.

Increasing trends in a low 5-min Apgar score among (near) term singletons: a Dutch nationwide cohort study.

OBJECTIVE: To investigate trends in low Apgar scores in (near) term singletons using the Dutch Perinatal Registry. METHODS: In a cohort of 1,583,188 singletons liveborn ≥35 weeks of gestation in the period 2010-2019, we studied trends in low 5-min Apgar scores (<7 and <4) using Cochrane Armitage trend tests. RESULTS: The proportion of infants with low Apgar scores <7 and <4 increased significantly between 2010-2019 (1.04-1.42% (p < 0.001), 0.17-0.19% (p = 0.009), respectively). Neonatal mortality remained unchanged. Induction of labour, epidural analgesia and planned caesarean section showed an increasing trend. Instrumental vaginal delivery and emergency caesarean section were performed less frequently over time, but these intervention subgroups showed the highest relative increase in infants with low Apgar scores. CONCLUSIONS: In the Netherlands, the risk of a low 5-min Apgar score increased over the last decade. The highest relative increase was observed in subgroups of instrumental vaginal delivery and emergency caesarean section.

The association of obstetric anal sphincter injury and mediolateral episiotomy with increasing birth weight and duration of second stage of labour in spontaneous vaginal delivery.

OBJECTIVES: Analysis of the association of mediolateral episiotomy (MLE) with obstetric anal sphincter injury (OASI) in women with spontaneous vaginal delivery. DESIGN: Population-based cohort study with data from the Netherlands Perinatal Registry, describing 541 055 women who delivered a singleton live born infant in cephalic presentation spontaneously at term. Risk indicators for OASI were tested using univariate and multivariate analysis. Additional analysis for the interaction of MLE with other risk indicators was performed. RESULTS: The rate of OASI was 4.2 % in 215 241 nulliparous and 1.4 % in 325 814 multiparous women. In nulliparous and multiparous women MLE was associated with a reduction of OASI (adjusted OR (aOR) 0.3, 95 % CI 0.30-0.34 and aOR 0.32, 95 % CI 0.30-0.34). The association of MLE with a reduced rate of OASI was stronger in high birthweight and in prolonged 2nd stage groups. In nulliparous women, the number needed to treat (NNT) for the use of MLE to prevent one OASI is 31 in general. With MLE, the OASI rate reduced from 11.5 % to 2.9 with a NNT of 12 in the group with a birth weight ≥ 4000 g and a duration of the second stage of labour of 60-120 min. The NNT is 9 In the group with a birth weight ≥ 4000 g and a duration of the second stage of labour ≥ 120 min (reduction rate of OASI from 14.2 % to 3.5 %). CONCLUSIONS: Use of MLE is associated with a reduction of OASI in spontaneous vaginal delivery. In nulliparous women, an episiotomy with an anticipated birth weight > 4000 g and a duration of the 2nd stage of more than 60 min should be considered.

Effects of nationwide adjustment of tocolysis protocol in the Netherlands on neonatal outcomes in women with threatened preterm birth and delivery at 30-32 weeks of gestation: A cohort study.

Objective: In 2019 the Dutch national prevention of preterm birth (PTB) protocol was adjusted to withhold tocolysis for threatened PTB above 30 weeks of gestation due to insufficient evidence regarding its effectiveness on improving perinatal outcomes. The aim of this study is to evaluate neonatal outcomes of children born in the Netherlands between 30 and 32 weeks of gestation before and after the national protocol change. Study design: We performed a nationwide retrospective cohort study comparing outcomes of births in the years 2018 (tocolysis) and 2020 (no tocolysis). Tocolytic therapy consisted of either nifedipine or atosiban. Data were extracted from the national Perinatal Registry (PERINED). Women with a spontaneous PTB from 30 + 0 to 31 + 6 weeks of gestation were included. The primary outcome was a composite of mortality, severe intraventricular hemorrhage, severe necrotizing enterocolitis, cystic periventricular leukomalacia, and retinopathy of prematurity needing therapy. Secondary outcomes included additional neonatal outcomes. The odds ratio (OR) with corresponding 95 % confidence interval (CI) was calculated by logistic regression analysis for the year 2020 compared with 2018. Results: Composite neonatal outcome did not differ between 2018 compared to 2020 (8.4 % (18/215) vs 8.2 % (25/306), OR 0.95; 95 % CI 0.51-1.77). No difference in composite neonatal outcome was found when analyzing groups as singletons (7.1 % vs 9.3 %, OR 1.35; 95 % CI 0.64-2.87), and multiples (13.3 % vs 5.9 %, OR 0.41; 95 % CI 0.13-1.26). Conclusion: There was no significant difference in composite neonatal outcome in pregnancies resulting in spontaneous PTB between 30 and 32 weeks of gestation in 2018 (with tocolysis) compared to 2020 (no tocolysis). These results support the protocol adjustment to withhold tocolytic treatment in women with threatened PTB above 30 weeks of gestation.

Risk indicators for obstetrical anal sphincter injury in vaginal birth after caesarean section compared to first vaginal delivery.

OBJECTIVES: Comparison of the rate of obstetric anal sphincter injury (OASI) between women having their first vaginal birth after caesarean section (CS) and true nulliparous women with a vaginal delivery. Assessment of risk indicators for OASI in women with vaginal birth after one CS (VBAC). STUDY DESIGN: 28 535 women with their first VBAC and a cohort of 275 439 nulliparous women with a vaginal delivery of a liveborn infant in a cephalic position from the Dutch perinatal registry were analyzed. We compared the OASI rate with univariate and multivariate analysis. In women with VBAC possible risk indicators for OASI were assessed using univariate and multivariate logistic regression analysis. RESULTS: The rate of OASI was 5.2% in women with vaginal birth after CS and 4.0% in women with a first vaginal delivery. The adjusted OR (aOR) for vaginal birth after an elective CS was higher (aOR 1.34, 95% CI 1.23-1.47) compared to vaginal birth after an emergency CS (aOR 1.16, 95% CI 1.08-1.25). In women with vaginal birth after emergency CS, the aOR for the indication non-progressive labor was 1.18 (95% CI 1.08-1.29), whereas CS for suspected fetal distress was not significantly associated with obstetric anal sphincter injury in VBAC. In the 28 535 women with a VBAC, mediolateral episiotomy (MLE), birth weight < 3000 g and maternal age < 25 years were associated with a significantly lower rate of OASI. A gestational age of 42 weeks, birth weight ≥ 3500 g, operative vaginal delivery and duration of the 2nd stage of labour of ≥ 60 min were associated with a significantly higher rate of OASI. CONCLUSIONS: Women with a VBAC have a higher rate of OASI in comparison with women with a first vaginal delivery, with the exception of women with a vaginal birth after an emergency CS for suspected fetal distress. Factors associated with a significantly lower rate for OASI were MLE, maternal age < 25 and birth weight < 3000 g. A gestational age of 42 weeks, birth weight between 3500 and 4000 g and ≥ 4000 g, operative vaginal delivery and duration of the 2nd stage of delivery longer dan 60 min were associated with a significantly higher rate of OASI.

Recurrence risk of preterm birth in subsequent twin pregnancy after preterm singleton delivery.

OBJECTIVE: To determine the risk of preterm birth in a subsequent twin pregnancy after previous singleton preterm birth. DESIGN: Cohort study. SETTING: Nationwide study in the Netherlands. POPULATION: In all, 4071 nulliparous women who had a singleton delivery followed by a subsequent twin delivery between the years 1999 and 2007 were studied. METHODS: Outcome of subsequent twin pregnancy of women with a history of preterm singleton delivery was compared with pregnancy outcome of women with a history of term singleton delivery. First deliveries were subdivided into iatrogenic and spontaneous preterm deliveries. Furthermore analyses were performed by subgroups for gestational age at the time of singleton delivery. MAIN OUTCOME MEASURE: Spontaneous preterm birth (<37 weeks of gestation) in subsequent twin pregnancy. RESULTS: In the index singleton pregnancy, preterm birth occurred in 232 (5.7%) of 4071 women. The risk of subsequent twin preterm birth was significantly higher after previous singleton preterm delivery (56.9 versus 20.9%; odds ratio 5.0; 95% CI 3.8-6.6). Risk of subsequent twin preterm birth was dependent on the severity of previous singleton preterm birth and was highest after preceding spontaneous instead of iatrogenic singleton preterm delivery. CONCLUSION: Preterm birth of a singleton gestation is associated with an increased risk of spontaneous preterm birth in a subsequent twin pregnancy.

Trends in preterm birth: singleton and multiple pregnancies in the Netherlands, 2000-2007.

OBJECTIVE: Several studies have reported increasing trends in preterm birth in developed countries, mainly attributable to an increase in medically indicated preterm births. Our aim was to describe trends in preterm birth among singleton and multiple pregnancies in the Netherlands. DESIGN: Prospective cohort study. SETTING: Nationwide study. POPULATION: We studied 1,451,246 pregnant women from 2000 to 2007. METHODS: We assessed trends in preterm birth. We subdivided preterm birth into spontaneous preterm birth after premature prelabour rupture of membranes (pPROM), medically indicated preterm birth and spontaneous preterm birth without pPROM. We performed analyses separately for singletons and multiples. MAIN OUTCOME MEASURES: The primary outcome was preterm birth, defined as birth before 37 weeks of gestation, with very preterm birth (<32 weeks of gestation) being a secondary outcome. RESULTS: The risk of preterm birth was 7.7% and the risk of very preterm birth was 1.3%. In singleton pregnancies, the preterm birth risk decreased significantly from 6.4% to 6.0% (P < 0.0001), mainly as a result of the decrease in spontaneous preterm birth without pPROM (3.6-3.1%, P < 0.0001). In multiple pregnancies, the preterm birth risk increased significantly (47.3-47.7%, P = 0.047), mainly as a result of medically indicated preterm birth, which increased from 15.0% to 17.9% (P < 0.0001). CONCLUSION: In the Netherlands, the preterm birth risk in singleton pregnancies decreased significantly over the years. The trend of increasing preterm birth risk reported in other countries was only observed in (medically indicated) preterm birth in multiple pregnancies.

Travel time from home to hospital and adverse perinatal outcomes in women at term in the Netherlands.

OBJECTIVE: To study the effect of travel time, at the start or during labour, from home to hospital on mortality and adverse outcomes in pregnant women at term in primary and secondary care. DESIGN: Population-based cohort study from 2000 up to and including 2006. SETTING: The Netherlands Perinatal Registry. POPULATION: A total of 751,926 singleton term hospital births. METHODS: We assessed the impact of travel time by car, calculated from the postal code of the woman's residence to the 99 maternity units, on neonatal outcome. Logistic regression modelling with adjustments for gestational age, maternal age, parity, ethnicity, socio-economic status, urbanisation, tertiary care centres and volume of the hospital was used. MAIN OUTCOME MEASURES: Mortality (intrapartum, and early and late neonatal mortality) and adverse neonatal outcomes (mortality, Apgar <4 and/or admission to a neonatal intensive care unit). RESULTS: The mortality was 1.5 per 1000 births, and adverse outcomes occurred in 6.0 per 1000 births. There was a positive relationship between longer travel time (≥20 minutes) and total mortality (OR 1.17, 95% CI 1.002-1.36), neonatal mortality within 24 hours (OR 1.51, 95% CI 1.13-2.02) and with adverse outcomes (OR 1.27, 95% CI 1.17-1.38). In addition to travel time, both delivery at 37 weeks of gestation (OR 2.23, 95% CI 1.81-2.73) or 41 weeks of gestation (OR 1.52, 95% CI 1.29-1.80) increased the risk of mortality. CONCLUSIONS: A travel time from home to hospital of 20 minutes or more by car is associated with an increased risk of mortality and adverse outcomes in women at term in the Netherlands. These findings should be considered in plans for the centralisation of obstetric care.

Increased adverse perinatal outcome of hospital delivery at night.

OBJECTIVE: To determine whether delivery in the evening or at night and some organisational features of maternity units are related to perinatal adverse outcome. DESIGN: A 7-year national registry-based cohort study. SETTING: All 99 Dutch hospitals. POPULATION: From nontertiary hospitals (n = 88), 655 961 singleton deliveries from 32 gestational weeks onwards, and, from tertiary centres (n = 10), 108 445 singleton deliveries from 22 gestational weeks onwards. METHODS: Multiple logistic regression analysis of national perinatal registration data over the period 2000-2006. In addition, multilevel analysis was applied to investigate whether the effects of time of delivery and other variables systematically vary across different hospitals. MAIN OUTCOME MEASURES: Delivery-related perinatal mortality (intrapartum or early neonatal mortality) and combined delivery-related perinatal adverse outcome (any of the following: intrapartum or early neonatal mortality, 5-minute Apgar score below 7, or admission to neonatal intensive care). RESULTS: After case mix adjustment, relative to daytime, increased perinatal mortality was found in nontertiary hospitals during the evening (OR, 1.32; 95% CI, 1.15-1.52) and at night (OR, 1.47; 95% CI, 1.28-1.69) and, in tertiary centres, at night only (OR, 1.20; 95% CI, 1.06-1.37). Similar significant effects were observed using the combined perinatal adverse outcome measure. Multilevel analysis was unsuccessful; extending the initial analysis with nominal hospital effects and hospital-delivery time interaction effects confirmed the significant effect of night in nontertiary hospitals, whereas other organisational effects (nontertiary, tertiary) were taken up by the hospital terms. CONCLUSION: Hospital deliveries at night are associated with increased perinatal mortality and adverse perinatal outcome. The time of delivery and other organisational features representing experience (seniority of staff, volume) explain hospital-to-hospital variation.

Anonymous non-response analysis in the ABCD cohort study enabled by probabilistic record linkage.

Selective non-response is an important threat to study validity as it can lead to selection bias. The Amsterdam Born Children and their Development study (ABCD-study) is a large cohort study addressing the relationship between life style, psychological conditions, nutrition and sociodemographic background of pregnant women and their children's health. Possible selective non-response and selection bias in the ABCD-study were analysed using national perinatal registry data. ABCD-study data were linked with national perinatal registry data by probabilistic medical record linkage techniques. Differences in the prevalence of relevant risk factors (sociodemographic and care-related factors) and birth outcomes between respondents and non-respondents were tested using Pearson chi-squared tests. Selection bias (i.e. bias in the association between risk factors and specific outcomes) was analysed by regression analysis with and without adjustment for participation status. The ABCD non-respondents were significantly younger, more often non-western, and more often multiparae. Non-respondents entered antenatal care later, were more often under supervision of an obstetrician and had a spontaneous delivery more often. Non-response however, was not significantly associated with preterm birth (odds ratio 1.10; 95% CI 0.93, 1.29) or low birthweight (odds ratio 1.16; 95% CI 0.98, 1.37) after adjustment for sociodemographic risk factors. The associations found between risk factors and adverse pregnancy outcomes were similar for respondents and non-respondents. Anonymised record linkage of cohort study data with national registry data indicated that selective non-response was present in the ABCD-study, but selection bias was acceptably low and did not influence the main study questions.

Indicators for intervention during the expulsive second-stage arrest of labour.

OBJECTIVE: To identify antepartum and intrapartum indicators of obstetric interventions during the expulsive second-stage arrest of labour. DESIGN: Retrospective cohort study. SETTING: The Netherlands. POPULATION: A cohort of 389,086 women with singleton, cephalic, term, live-birth deliveries from 2002 to 2004 who had entered the expulsive second stage of labour. Of all these deliveries, 37,899 (9.7%) were complicated by expulsive second-stage arrest of labour. Women with a prior Caesarean section or women undergoing an elective Caesarean section were excluded. METHODS: All deliveries in the Netherlands from 2002 to 2004 were registered in the Netherlands Perinatal Registry, which contains the linked and validated data of three databases. Uni- and multivariable logistic regression analyses were performed. MAIN OUTCOME MEASURES: Ante- and intrapartum indicators for interventions during expulsive second-stage arrest of labour. RESULTS: Primiparous delivery was the most important antepartum indicator for intervention during expulsive second-stage arrest. Using multivariable analysis the following antepartum indicators were associated with intervention for expulsive second-stage arrest of primiparous labour: maternal age, gestational age, diabetes, hypertension and labour induction. Prominent intrapartum indicators for primiparous deliveries were fetal head position and oxytocin augmentation. CONCLUSION: Multiple significant antepartum and intrapartum indicators associated with intervention for expulsive second-stage arrest of labour were identified in this large retrospective study. Prominent were the associations of parity, maternal age and fetal head position with expulsive second-stage arrest. The identified factors should be further evaluated in prospective studies that aim to develop prediction models.

Perinatal mortality and morbidity in a nationwide cohort of 529,688 low-risk planned home and hospital births.

OBJECTIVE: To compare perinatal mortality and severe perinatal morbidity between planned home and planned hospital births, among low-risk women who started their labour in primary care. DESIGN: A nationwide cohort study. SETTING: The entire Netherlands. POPULATION: A total of 529,688 low-risk women who were in primary midwife-led care at the onset of labour. Of these, 321,307 (60.7%) intended to give birth at home, 163,261 (30.8%) planned to give birth in hospital and for 45,120 (8.5%), the intended place of birth was unknown. METHODS: Analysis of national perinatal and neonatal registration data, over a period of 7 years. Logistic regression analysis was used to control for differences in baseline characteristics. MAIN OUTCOME MEASURES: Intrapartum death, intrapartum and neonatal death within 24 hours after birth, intrapartum and neonatal death within 7 days and neonatal admission to an intensive care unit. RESULTS: No significant differences were found between planned home and planned hospital birth (adjusted relative risks and 95% confidence intervals: intrapartum death 0.97 (0.69 to 1.37), intrapartum death and neonatal death during the first 24 hours 1.02 (0.77 to 1.36), intrapartum death and neonatal death up to 7 days 1.00 (0.78 to 1.27), admission to neonatal intensive care unit 1.00 (0.86 to 1.16). CONCLUSIONS: This study shows that planning a home birth does not increase the risks of perinatal mortality and severe perinatal morbidity among low-risk women, provided the maternity care system facilitates this choice through the availability of well-trained midwives and through a good transportation and referral system.

An efficient validation method of probabilistic record linkage including readmissions and twins.

OBJECTIVE: To describe an efficient, generalizable approach to validate probabilistic record linkage results, in particular by a model-guided detection of linking errors, and to apply this approach to validate linkage of admissions of newborns. METHODS: Our double-blind validation procedure consisted of three steps: sample selection, data collection and data analysis. The linked Dutch national newborn admission registry contained 30,082 records for 2001 including readmissions (7.4%) and twins (9.7%). A highly informative sample was selected from the linked file by oversampling uncertain links based on model-derived linking weight. Four hundred and eight fax forms with minimal registry information (admissions of 191 children) were sent out to different pediatric units. The pediatricians were asked to create a short detailed patient history from independent sources. The linkage status and additional record data was validated against this external information. RESULTS: Response rate was 97% (395/408 faxes). Accuracy of the linkage of singleton admissions was high: except for some expected errors in the uncertain area (0.02% of record pairs), linkage was error-free. Validation of multiple birth readmissions showed 37% linkage errors due to low data quality of the multiple birth variables. The quality of the linked registry file was still high; only 1.7% of the children were from a multiple birth with multiple admissions, resulting in less than 1% linking error. CONCLUSIONS: Our external validation procedure of record linkage was feasible, efficient, and informative about identifying the source of the errors.

[Higher perinatal mortality in The Netherlands than in other European countries: the Peristat-II study]. / Hoge perinatale sterfte in Nederland vergeleken met andere Europese landen: de Peristat-II-studie.

OBJECTIVE: Comparison of perinatal mortality in The Netherlands with that in other European countries (Peristat-II), and with data collected 5 years previously (Peristat-I). DESIGN: Descriptive study. METHOD: Indicators ofperinatal mortality which were developed for Peristat-I were used again in Peristat-II. Data on perinatal mortality in 2004 were delivered by 26 European countries. The Dutch data originated from national registers of midwives and gynaecologists and the National Neonatology Register. RESULTS: In Peristat-I, from 22 weeks gestation, The Netherlands had the highest fetal mortality rate (7.4 per 1,000 total number of births). Furthermore, after Greece, The Netherlands had the highest early neonatal mortality rate (3.5 per 1,000 live births). In Peristat-II from 22 weeks gestation, after France, The Netherlands had the highest fetal mortality rate (7.0 per 1,000 total number of births). Of all western European countries, The Netherlands had the highest early neonatal mortality rate (3.0 per 1,000 live births). Over the past 5 years the perinatal mortality rate in The Netherlands has dropped from 10.9 to 10.0 per 1,000 total births but this drop has been faster in other countries. CONCLUSION: The Netherlands has a relatively high number of older mothers and multiple pregnancies, but this only partly explains the high Dutch perinatal mortality rate which still ranks unfavourably in the European tables. More research is necessary to gain insight into the prevalence of risk factors for perinatal mortality compared with other European countries. In addition, perinatal health and the quality ofperinatal healthcare deserve a more prominent position in Dutch research programmes.

[Perinatal mortality in The Netherlands 2000-2006; risk factors and risk selection]. / Perinatale sterfte in Nederland gedurende 2000-2006; risicofactoren en risicoselectie.

OBJECTIVE: To gain insight in recent perinatal mortality figures in The Netherlands and their relation with important risk factors, risk groups and risk selection among pregnant women. DESIGN: Retrospective cohort study. METHOD: The National Obstetrical Registrations and the National Neonatal Registration were linked into The Netherlands Perinatal Registry to prevent double counting. From this database, data on 1.3 million births in the years 2000-2006 were analysed with perinatal mortality as outcome measure. RESULTS: In 2006, perinatal mortality was 9.8 per 1000 total births (foetal mortality 6.8 per 1000 births and early neonatal mortality 3.1 per 1000 live births). Maternal age (< 20 and > or = 40 years) and high multiparity (> or = 4) were risk factors for perinatal mortality but showed low prevalence (< 3%). Non-Western ethnicity and nulliparity were important risk factors (relative risk of both 1.4) with a prevalence of 16% and 46%, respectively. The very preterm births (22.0-25.6 weeks of gestation) provided 29% ofall perinatal mortality with a mortality risk of 935 per 1000 births. Full-term births (> or = 37.0 weeks) accounted for 26% of all perinatal mortality with a mortality risk of 2.8 per 1000 births. In the full-term born group, perinatal mortality was 0.4 per 1000 births in home births, 2.7 per 1000 births in outpatient clinics and 4.5 per 1000 births when the women were referred to the gynaecologist before start of labour. CONCLUSION: At a population level, low or high maternal age and high parity are less important risk factors than expected. More detailed research is indicated into the mortality ofvery preterm births but also offull-term born children.

[Perinatal outcomes in the four largest cities and in deprived neighbourhoods in The Netherlands]. / Perinatale uitkomsten in de vier grote steden en de prachtwijken in Nederland.

OBJECTIVE: To analyse the association between neighbourhood, ethnicity and adverse perinatal outcome in pregnant women from the 4 largest cities (Amsterdam, Rotterdam, The Hague and Utrecht; G4) and elsewhere in The Netherlands. DESIGN: Descriptive, retrospective. METHOD: The perinatal outcome of 877,816 single pregnancies during the years 2002-2006, derived from The Netherlands Perinatal Registry, was analysed for the ethnicity (Western or non-Western) and the neighbourhood (deprived or not) of the pregnant women in the G4 and elsewhere in The Netherlands. Adverse perinatal outcome was defined as perinatal mortality, congenital abnormalities, intra-uterine growth restriction, preterm birth, Apgar score after 5 minutes < 7 and/or admission to a neonatal intensive-care unit. RESULTS: The overall perinatal mortality rate was higher in the G4 than elsewhere in The Netherlands (11.1 per thousand versus 9.3 per thousand; p < 0.001; 95% confidence interval of the difference: 1.2-2.4 per thousand). The same was true for the sum of adverse perinatal outcomes (154.9 per thousand versus 138.9 per thousand). In the G4 the perinatal mortality among non-Western women was higher than among Western women (13.2 per thousand versus 9.5 per thousand). Residing in Dutch deprived neighbourhoods was associated with a higher perinatal mortality than outside deprived neighbourhoods (13.5 per thousand versus 9.3 per thousand). The relative risks of living in deprived neighbourhoods for adverse pregnancy outcomes are higher among Western than among non-Western women. CONCLUSION: Pregnant women in the G4 have an increased risk ofadverse perinatal outcomes. The risks of residing in a deprived neighbourhood are even higher, especially among Western women. The findings are important for new strategies to improve perinatal outcomes.