Association between COVID-19 lockdown measures and the incidence of iatrogenic versus spontaneous very preterm births in the Netherlands: a retrospective study.

BACKGROUND: The COVID-19 pandemic led to regional or nationwide lockdowns as part of risk mitigation measurements in many countries worldwide. Recent studies suggest an unexpected and unprecedented decrease in preterm births during the initial COVID-19 lockdowns in the first half of 2020. The objective of the current study was to assess the effects of the two months of the initial national COVID-19 lockdown period on the incidence of very and extremely preterm birth in the Netherlands, stratified by either spontaneous or iatrogenic onset of delivery, in both singleton and multiple pregnancies. METHODS: Retrospective cohort study using data from all 10 perinatal centers in the Netherlands on very and extremely preterm births during the initial COVID-19 lockdown from March 15 to May 15, 2020. Incidences of very and extremely preterm birth were calculated using an estimate of the total number of births in the Netherlands in this period. As reference, we used data from the corresponding calendar period in 2015-2018 from the national perinatal registry (Perined). We differentiated between spontaneous versus iatrogenic onset of delivery and between singleton versus multiple pregnancies. RESULTS: The incidence of total preterm birth < 32 weeks in singleton pregnancies was 6.1‰ in the study period in 2020 versus 6.5‰ in the corresponding period in 2015-2018. The decrease in preterm births in singletons was solely due to a significant decrease in iatrogenic preterm births, both < 32 weeks (OR 0.71; 95%CI 0.53 to 0.95) and < 28 weeks (OR 0.53; 95%CI 0.29 to 0.97). For multiple pregnancies, an increase in preterm births < 28 weeks was observed (OR 2.43; 95%CI 1.35 to 4.39). CONCLUSION: This study shows a decrease in iatrogenic preterm births during the initial COVID-19-related lockdown in the Netherlands in singletons. Future studies should focus on the mechanism of action of lockdown measures and reduction of preterm birth and the effects of perinatal outcome.

Risk of preterm birth after prior term cesarean.

OBJECTIVE: To determine the risk of overall preterm birth (PTB) and spontaneous PTB in a pregnancy after a caesarean section (CS) at term. DESIGN: Longitudinal linked national cohort study. SETTING: The Dutch Perinatal Registry (1999-2009). POPULATION: 268 495 women with two subsequent singleton pregnancies were identified. METHODS: A cohort study based on linked registered data from two subsequent pregnancies in the Netherlands. MAIN OUTCOME MEASURES: The incidence of overall PTB and spontaneous PTB with subgroup analysis on gestational age at first delivery and type of CS (planned or unplanned). RESULTS: Of 268 495 women with a singleton first pregnancy who delivered at term, 15.76% (n = 42 328) had a CS. The incidence of PTB in the second pregnancy was 2.79% (n = 1182) in women with a previous CS versus 2.46% (n = 5570) in women with a previous vaginal delivery (adjusted odds ratio [aOR] 1.14, 95% confidence interval [CI] 1.07-1.21). This increased risk is mainly driven by an increased risk of spontaneous PTB after previous CS at term (aOR 1.50, 95% CI 1.38-1.70). Analysis for type of CS compared with vaginal delivery showed an aOR on spontaneous PTB of 1.86 (95% CI 1.58-2.18) for planned CS and an aOR of 1.40 (95% CI 1.24-1.58) for unplanned CS. CONCLUSIONS: CS at term is associated with a marginally increased risk of spontaneous PTB in a subsequent pregnancy. TWEETABLE ABSTRACT: Caesarean section at term is associated with a marginally increased risk of spontaneous PTB in a subsequent pregnancy.

Midpregnancy Cervical Length in Nulliparous Women and its Association with Postterm Delivery and Intrapartum Cesarean Delivery.

OBJECTIVE: To evaluate the association between midpregnancy cervical length and postterm delivery and cesarean delivery during labor. STUDY DESIGN: In a multicenter cohort study, cervical length was measured in low-risk singleton pregnancies between 16 and 22 weeks of gestation. From this cohort, we identified nulliparous women who delivered beyond 34 weeks and calculated cervical length quartiles. We performed logistic regression to compare the risk of postterm delivery and intrapartum cesarean delivery to cervical length quartiles, using the lowest quartile as a reference. We adjusted for induction of labor, maternal age, ethnicity, cephalic position, preexisting hypertension, and gestational age at delivery. RESULTS: We studied 5,321 nulliparous women. Women with cervical length in the 3rd and 4th quartile were more likely to deliver at 42(+0) to 42(+6) weeks (adjusted odds ratio [aOR] 2.02, 95% confidence interval [CI] 1.07-3.79 and aOR 1.97, 95% CI 1.06-3.67, respectively). The frequency of intrapartum cesarean delivery increased with cervical length quartile from 9.4% in the 1st to 14.9% in the 4th quartile (p = 0.01). This increase was only present in intrapartum cesarean delivery because of failure to progress and not because of fetal distress. CONCLUSION: The longer the cervix at midtrimester the higher the risk of both postterm delivery and intrapartum cesarean delivery.

Should the individual preterm birth risk be incorporated into the embryo transfer policy in in vitro fertilisation? A decision analysis.

OBJECTIVE: To assess by proof of principle whether the individual risk for preterm birth (PTB) should be incorporated into the embryo transfer policy in in vitro fertilisation (IVF). DESIGN AND SETTING: A theoretical decision analysis. METHODS AND MAIN OUTCOME MEASURES: A decision tree was built to compare the consequences of different chances of PTB on the outcome of single embryo transfer (SET) or double embryo transfer (DET) in patients with different prognosis of conception. Based on patient characteristics, three scenarios of prognosis of conception were considered and the consequences of SET and DET were calculated for different chances of PTB in these groups. The primary outcome was the health of the children born. Sensitivity analyses were performed for both prognosis for conception and chances of PTB. RESULTS: In women with good fertility prospects, one IVF cycle with DET increases the ongoing pregnancy rate (OPR) from 29 to 39% compared with SET, whereas the chances of poor neonatal outcome in these extra pregnancies range from 1.4 to 11% per pregnancy depending on the individual PTB risk. However, for women with poor fertility prospects, DET increases the OPR from 8 to 11% with minimal additional poor neonatal outcome, ranging from 0.3 to 4.0% per pregnancy for women with a low or high PTB risk, respectively. Our findings were robust in multiple sensitivity analyses. CONCLUSION: In an IVF programme, the optimal embryo transfer strategy is dependent on the singleton and multiple pregnancy chances of a woman, but also on her PTB risk. In women with low PTB risk, DET increases the OPR for a small additional risk of neonatal complications. Our analysis pleads for a tailored management strategy, taking into account the personalised prognosis for (multiple) pregnancy and PTB.

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.

Impact of obstetric history on the risk of spontaneous preterm birth in singleton and multiple pregnancies: a systematic review.

BACKGROUND: Information about the recurrence of spontaneous preterm birth in subsequent twin/singleton pregnancies is scattered. OBJECTIVES: To quantify the risk of recurrence of spontaneous preterm birth in different subtypes of subsequent pregnancies. SEARCH STRATEGY: An electronic literature search in OVID MEDLINE and EMBASE, complemented by PubMed, to find recent studies. SELECTION CRITERIA: Studies comparing the risk of spontaneous preterm birth after a previous preterm and previous term pregnancy. DATA COLLECTION AND ANALYSIS: The absolute risk of recurrence with a 95% confidence interval and the absolute risk of preterm birth after a term delivery were calculated. Data from studies were pooled using the Mantel-Haenszel method. MAIN RESULTS: We detected 13 relevant studies. The risk of recurrence of preterm birth was significantly increased in all preterm pregnancy subtypes, compared with their term counterparts. Women pregnant with twins after a previous preterm singleton had the highest absolute risk of recurrence (57.0%, 95% CI 51.9-61.9%), and after a previous term singleton their absolute risk was 25% (95% CI 24.3-26.5%). Women pregnant with a singleton after a previous preterm twin pregnancy have an absolute recurrence risk of 10% (95% CI 8.2-12.3%), whereas a singleton pregnancy after delivering a previous twin up to term yields a low absolute risk of only 1.3% (95% CI 0.8-2.2). Women pregnant with a singleton after a previous preterm singleton have an absolute recurrence risk of 20% (95% CI 19.9-20.6). AUTHOR'S CONCLUSIONS: The risk of recurrence of preterm birth is influenced by the singleton/twin order in both pregnancies, and varies between 10% for a singleton after previous preterm twins to 57% for twins after a previous preterm singleton.

Is short first-trimester crown-rump length associated with spontaneous preterm birth?

OBJECTIVE: To assess the association between first-trimester crown-rump length (CRL) and the risk of spontaneous preterm birth before 32 weeks' gestation. METHODS: We performed a matched case-control study of 129 women with spontaneous preterm birth at < 32 weeks' gestation (cases) and 129 women with term deliveries (controls) using data stored in the ultrasound and obstetric databases of our tertiary referral center. Cases and controls were individually matched based on maternal age, parity, history of preterm birth and medical indication for antenatal care. Fetal CRL measured between 8 + 0 and 13 + 6 weeks was expressed as multiples of the median (MoM) expected CRL, based on last menstrual period. We investigated the association between CRL-MoM and spontaneous preterm birth using logistic regression analysis. RESULTS: CRL-MoM was not associated with spontaneous preterm birth: odds ratio (OR) 1.10 (95% CI, 0.89-1.36) per 0.10 MoM increase in CRL. Timing of measurement did not influence the model (P = 0.59). This was confirmed when restricting the analysis to the 93 pairs with CRL measurements made between 10 + 0 and 13 + 6 weeks: OR for preterm birth 1.07 (95% CI, 0.83-1.37) per 0.10 MoM increase in CRL. CONCLUSION: A short CRL in the first trimester is not associated with spontaneous preterm birth before 32 weeks' gestation, thus short CRL cannot be used to identify women at increased risk of preterm birth.

Effect of interpregnancy interval on the success rate of trial of labor after cesarean.

OBJECTIVE: The objective of this study is to investigate the association between interpregnancy interval and success of vaginal birth after cesarean. STUDY DESIGN: Retrospective 10-year cohort study of pregnant women with one prior cesarean, who opted for trial of labor (n=36 653). Interpregnancy interval is the time between cesarean and next conception. Vaginal birth success rates were compared between six interval groups. Analysis was performed pooled as well as stratified for induction of labor. Adjusted odds ratios were calculated. RESULTS: Success rate in the reference group (12 to 24 months) was 72%. Success rates were similar among those with an interval of less than 24 months. Intervals of 24 months or more showed a decrease in success rate; 70% in 24- to 35-month intervals (adjusted odds ratio 0.92 (0.87 to 0.98)), 67% in 36- to 59-month intervals (adjusted odds ratio 0.87 (0.81 to 0.94)) and 62% in intervals of more than 60 months (adjusted odds ratio 0.77 (0.67 to 0.88)). CONCLUSION: An interpregnancy interval of <24 months is not associated with a decreased success of vaginal birth after cesarean. Success rates decrease when interval increases.

Variation in preterm birth rate and the role of short cervical length across two populations: a comparative cohort study.

OBJECTIVE: To examine variation in preterm birth (PTB) rates between nulliparous women from two different populations and to investigate the contribution of short cervical length to any observed variation. STUDY DESIGN: A comparative study between two cohorts of singleton nulliparous women from the Netherlands and Chicago, USA was performed. Women with a non-anomalous singleton pregnancy who underwent routine transvaginal cervical length measurement between 16+0 and 21+6 weeks of gestation with a known pregnancy outcome were selected. Fetuses with congenital anomalies, intrauterine fetal deaths and deliveries before 24+0 weeks were excluded. Total, spontaneous and iatrogenic PTB rates were calculated for both populations and compared with univariable and multivariable logistic regression. RESULTS: We included 3409 women from the Netherlands and 3334 women from Chicago. The median cervical length was slightly lower in the Netherlands compared with Chicago (42 vs 44 mm, P<0.0001), but the rate of cervical length of ⩽25 mm was comparable (0.9% vs 0.8%, P=0.69). The total rate of PTB prior to 37 weeks was comparable between locations (8.0% in the Netherlands vs 7.3% in Chicago, P=0.27) but PTB prior to 32 weeks was higher in the Netherlands (1.3% vs 0.5%, P=0.002). Multivariable regression revealed that women from the Netherlands, compared with women from Chicago, are at increased risk for spontaneous PTB between 24 and 27 weeks and between 28 and 31 weeks (adjusted odds ratio (aOR) 5.3, 95% confidence interval (CI) 1.5 to 19 and 3.1, 95% CI 1.2 to 8.3, respectively). In contrast, the number of late spontaneous PTB between 34 and 36 weeks did not differ between both populations (4.1% vs 4.3% aOR 1.1, 95% CI 0.87 to 1.5). CONCLUSIONS: Despite similar percentages of short cervix, there are marked differences in early PTB rates between the Netherlands and Chicago, possibly indicating different phenotypes of PTB. A high frequency of spontaneous early preterm birth is not always accompanied by an increase in the frequency of a short cervix.

Trial of labor after cesarean: attempted operative vaginal delivery versus emergency repeat cesarean, a prospective national cohort study.

OBJECTIVE: To compare neonatal and maternal outcomes of attempted operative vaginal delivery with emergency repeat cesarean in trial of labor after cesarean. STUDY DESIGN: Prospective 8-year cohort analysis using the Netherlands Perinatal Registry, including women with one prior cesarean giving birth through operative vaginal delivery or emergency repeat cesarean (n=12860). A multivariate analysis was performed. Odds ratios (OR) and adjusted odds ratios (aOR) were calculated. RESULTS: Attempted operative vaginal delivery increases the risk on neonatal birth trauma (aOR 15.0 (5.94 to 38.0)) and postpartum hemorrhage (aOR 2.59 (2.17 to 3.09)), and lowers the risk of wet lung syndrome (aOR 0.53 (0.35 to 0.80)) and neonatal convulsions (aOR 0.47 (0.24 to 0.91)). CONCLUSION: We found a highly increased risk of neonatal birth trauma and a moderately increased risk of postpartum hemorrhage but slightly lower risks of wet lung syndrome and neonatal convulsions after attempted operative vaginal delivery compared with emergency repeat cesarean.

Elective repeat cesarean delivery compared with trial of labor after a prior cesarean delivery: a propensity score analysis.

OBJECTIVE: To determine neonatal and short term maternal outcomes according to intentional mode of delivery following a cesarean delivery (CD). STUDY DESIGN: Women pregnant after CD between January 2000 and December 2007 were categorized according to whether they had an elective repeat CD (ERCD) or a Trial of Labor (TOL). Prognostically equal ERCD and TOL groups were created using the propensity score matching technique. Conditional logistic regression was performed to assess differences in neonatal and maternal outcomes. POPULATION: Women in their second ongoing pregnancy with a history of CD. RESULTS: After ERCD the rates of low 5min Apgar score (OR 0.3, 95%CI 0.2-0.5, p<0.001), meconium aspiration (OR 0.0, 95%CI 0-0.7, p=0.02) and birth trauma (OR 0.08, 95%CI 0.002-0.5, p<0.001) were lower compared to TOL. The rate of transient tachypnoea of the newborn (TTN) appears higher in the ERCD group (OR 1.7, 95%CI 1.0-2.8, p=0.04). Uterine rupture (OR 0.1, 95%CI 0.003-0.8, p=0.02) and hemorrhage (OR 0.6, 95%CI 0.5-0.8, p<0.001) occurred less in the ERCD group. CONCLUSION: Neonatal and short term maternal morbidity appears to be lower after ERCD than after TOL. Only TTN was seen more often after ERCD.

Is cervical length associated with maternal characteristics?

OBJECTIVE: Women with a mid-trimester short cervical length (CL) are at increased risk for preterm delivery. Consequently, CL measurement is a potential screening tool to identify women at risk for preterm birth. Our objective was to assess possible associations between CL and maternal characteristics. STUDY DESIGN: A nationwide screening study was performed in which CL was measured during the standard anomaly scan among low risk women with a singleton pregnancy. Data on maternal height, pre-pregnancy weight, ethnicity, parity and gestational age at the time of the CL measurement were collected from January 2010 to December 2012. Univariable and multivariable linear regression analyses were performed to assess the relationship between CL and maternal characteristics. RESULTS: We included 5092 women. The mean CL was 44.3mm. No association was found between CL and maternal height or gestational age of the measurement. Maternal weight was associated with CL (p=0.007, adjusted R(2) 0.03). Separate analysis for BMI did not change these results. Ethnicity, known in 2702 out of 5092 women, was associated with CL (mean CL in Caucasian women 45.0mm, Asian 43.9mm, Mediterranean 43.1mm, and African 41.8mm, p=0.003), as well as parity (mean CL multiparous 45.3mm, nulliparous 43.5mm, p<0.0001). CONCLUSION: Shorter mid-trimester cervical length is associated with higher maternal weight, younger maternal age, nulliparity and non-Caucasian ethnicity, but not with maternal height.