Pregnancy outcome in partners of male professional divers in Norway.

BACKGROUND: Diving is associated with both acute and long-term effects in several organ systems. Reduced semen quality after extreme diving and a reduced proportion of males in the offspring of divers have previously been reported. AIMS: To study pregnancy outcomes in partners of professional male divers. METHODS: The cohort of divers registered with the Norwegian Inshore Diving Registry was linked to the Medical Birth Registry of Norway (MBRN). RESULTS: In total, 6186 male divers had 10395 children registered in the MBRN during the study period. Of these, 52% were boys, compared to 51% in the general population. The partners of a subgroup of divers who were most likely to be occupationally exposed at the time of conception reported that early miscarriage was more frequent (27%) than in the general population (21%; relative risk 1.21, 95% confidence interval 1.05-1.39). Otherwise, there was a lower risk of adverse pregnancy outcomes such as preterm birth, stillbirth, low birthweight, small for gestational age and low Apgar score compared to the general population. Birthweight above 4000g was more frequent. CONCLUSIONS: We observed no reduced sex ratio in the offspring of occupational divers. Except for an increase in self-reported early miscarriage in the partners of exposed divers, we observed no excess risk of any of the adverse perinatal pregnancy outcomes studied.

Maternal obesity and excess of fetal growth in pre-eclampsia.

OBJECTIVE: To assess whether the reported excess of large for gestational age (LGA) neonates in pre-eclamptic women delivering at term is attributable to maternal obesity. DESIGN, SETTING AND POPULATION: Population-based observational study including 77,294 singleton pregnancies registered in the Medical Birth Registry of Norway between 2007 and 2010. METHODS: Comparison of birthweight percentiles and z-scores between women with and without pre-eclampsia. MAIN OUTCOME MEASURES: Odds ratio (OR) of LGA and z-scores of birthweight in relation to pre-eclampsia. RESULTS: Pre-eclamptic women delivering at term had increased risk of having LGA neonates. Unadjusted ORs with 95% confidence interval (95% CI) of LGA above the 90th and 95th birthweight centiles were 1.4, 95% CI 1.2-1.6 and 1.6, 95% CI 1.3-1.9, respectively. The excess of LGA persisted after including gestational diabetes and diabetes types 1 and 2 in a multivariate analysis (corresponding ORs 1.3, 95% CI 1.1-1.5 and 1.4, 95% CI 1.2-1.7), but disappeared after adjusting for maternal prepregnant body mass index (ORs 1.1, 95% CI 0.9-1.2 and 1.1, 95% CI 0.9-1.3). CONCLUSIONS: This study suggests accelerated fetal growth in a subset of pre-eclamptic women delivering at term. The excess of LGA neonates is attributable to maternal obesity among pre-eclamptic women delivering at term. The maternal obesity epidemic may lead to an increased prevalence of both pre-eclampsia and LGA neonates among women delivering at term.

Degree of fetal growth restriction associated with schizophrenia risk in a national cohort.

BACKGROUND: Accumulating evidence suggests that fetal growth restriction may increase risk of later schizophrenia but this issue has not been addressed directly in previous studies. We examined whether the degree of fetal growth restriction was linearly related to risk of schizophrenia, and also whether maternal pre-eclampsia, associated with both placental dysfunction and poor fetal growth, was related to risk of schizophrenia. METHOD: A population-based cohort of single live births in the Medical Birth Registry of Norway (MBRN) between 1967 and 1982 was followed to adulthood (n=873 612). The outcome was schizophrenia (n=2207) registered in the National Insurance Scheme (NIS). The degree of growth restriction was assessed by computing sex-specific z scores (standard deviation units) of ' birth weight for gestational age' and ' birth length for gestational age'. Analyses were adjusted for potential confounders. Maternal pre-eclampsia was recorded in the Medical Birth Registry by midwives or obstetricians using strictly defined criteria. RESULTS: The odds ratio (OR) for schizophrenia increased linearly with decreasing birth weight for gestational age z scores (p value for trend=0.005). Compared with the reference group (z scores 0.01­1.00), the adjusted OR [95% confidence interval (CI)] for the lowest z-score category (

Familial risk of obstetric anal sphincter injuries: registry-based cohort study.

OBJECTIVE: To investigate the aggregation of obstetric anal sphincter injuries (OASIS) in relatives. DESIGN: Population-based cohort study. SETTING: The Medical Birth Registry of Norway from 1967 to 2008. POPULATION: All singleton, vertex-presenting infants weighing 500 g or more. Through linkage by national identification numbers, 393 856 mother-daughter pairs, 264 675 mother-son pairs, 134 889 mothers whose sisters later became mothers, 132 742 fathers whose brothers later became fathers, 131 702 mothers whose brothers later became fathers and 88 557 fathers whose sisters later became mothers were provided. METHODS: Comparison of women with and without a history of OASIS in their relatives. MAIN OUTCOME MEASURE: Relative risk of OASIS after a previous OASIS in the family. RESULTS: The risk of OASIS was increased if the woman's mother or sister had OASIS in a delivery (aRR 1.9, 95% CI 1.6-2.3; aRR 1.7, 95% CI 1.6-1.7, respectively). If OASIS occurred in one brother's partner at delivery, the risk of OASIS in the next brother's partner was modestly increased (aRR 1.2, 95% CI 1.1-1.4). If OASIS occurred in one sister at delivery, the risk of OASIS in the brother's partner was also increased a little (aRR 1.2, 95% CI 1.1-1.4). However, there was no excess occurrence in sisters whose brothers' partners had previously had OASIS (aRR 1.1, 95% CI 0.9-1.3). CONCLUSIONS: There appears to be increased familial aggregation of OASIS. These risks are stronger through the maternal rather than the paternal line of transmission, suggesting a strong genetic role that shapes aggregation of OASIS within families. These observations must be cautiously interpreted because of bias from unmeasured confounding factors may have impacted the findings.

Parity in patients with chronic inflammatory arthritides childless at time of diagnosis.

OBJECTIVE: To assess parity in women with chronic inflammatory arthritides (CIA) childless at time of diagnosis. METHODS: Patients were selected from the Norwegian Disease-Modifying Anti-Rheumatic Drug (NOR-DMARD) registry. Each patient was matched by year of birth with 100 reference women from the Norwegian Population Registry. Data linkage for patients and references with the Medical Birth Registry of Norway (MBRN) identified all offspring until time of linkage (October 2007). Patients and corresponding references childless at the time of diagnosis were included in the analyses. Kaplan-Meier curves visualized the proportion of childless women and were compared by a log rank test. RESULTS: In all, 156 rheumatoid arthritis (RA), 107 other chronic arthritides (OCA), and 75 juvenile idiopathic arthritis (JIA) patients were childless at time of diagnosis. At the time of data linkage, the proportions (%) of childless RA/OCA/JIA patients versus references were 61.5/62.6/57.3 versus 46.9/42.9/41.0, respectively, all differences statistically significant. The log rank test showed lower parity in all diagnostic groups compared with references (p < 0.001 for RA and OCA and p = 0.002 for JIA). No difference in parity was observed between RA and OCA patients, but both diagnostic groups had lower parity than JIA patients (p = 0.001). Disease characteristics were similar between childless and fertile patients. CONCLUSIONS: Reduced parity was observed in all diagnostic groups compared with references. RA and OCA patients had lower parity than JIA patients, indicating that having the disease as a young adult may influence parity more than having the disease in childhood.

Risk of recurrence and subsequent delivery after obstetric anal sphincter injuries.

OBJECTIVE: To investigate the recurrence risk, the likelihood of having further deliveries and mode of delivery after third to fourth degree obstetric anal sphincter injuries (OASIS). DESIGN: Population-based cohort study. SETTING: The Medical Birth Registry of Norway. POPULATION: A cohort of 828,864 mothers with singleton, vertex-presenting infants, weighing 500 g or more, during the period 1967-2004. METHODS: Comparison of women with and without a history of OASIS with respect to the occurrence of OASIS, subsequent delivery rate and planned caesarean rate. MAIN OUTCOME MEASURES: OASIS in second and third deliveries, subsequent delivery rate and mode of delivery. RESULTS: Adjusted odds ratios of the recurrence of OASIS in women with a history of OASIS in the first, and in both the first and second deliveries, were 4.2 (95% CI 3.9-4.5; 5.6%) and 10.6 (95% CI 6.2-18.1; 9.5%), respectively, relative to women without a history of OASIS. Instrumental deliveries, in particular forceps deliveries, birthweights of 3500 g or more and large maternity units were associated with a recurrence of OASIS. Instrumental delivery did not further increase the excess recurrence risk associated with high birthweight. A man who fathered a child whose delivery was complicated by OASIS was more likely to father another child whose delivery was complicated by OASIS in another woman who gave birth in the same maternity unit (adjusted OR 2.1; 95% CI 1.2-3.7; 5.6%). However, if the deliveries took place in different maternity units, the recurrence risk was not significantly increased (OR 1.3; 95% CI 0.8-2.1; 4.4%). The subsequent delivery rate was not different in women with and without previous OASIS, whereas women with a previous OASIS were more often scheduled to caesarean delivery. CONCLUSION: Recurrence risks in second and third deliveries were high. A history of OASIS had little or no impact on the rates of subsequent deliveries. Women with previous OASIS were delivered more frequently by planned caesarean delivery.

Mothers' negative affectivity during pregnancy and food choices for their infants.

OBJECTIVE: The objective of this study was to analyze whether maternal negative affectivity assessed in pregnancy is related with subsequent infant food choices. DESIGN: The study design was a cohort study. SUBJECTS: The subjects were mothers (N=37 919) and their infants participating in the Norwegian Mother and Child Cohort Study conducted by the Norwegian Institute of Public Health. MEASUREMENTS: Maternal negative affectivity assessed prepartum (Hopkins Symptom Checklist 5 (SCL-5) at weeks 17 and 30 of pregnancy), introduction of solid foods by month 3 and feeding of sweet drinks by month 6 (by the reports of the mothers) were analyzed. RESULTS: Mothers with higher negative affectivity were 64% more likely (95% confidence interval 1.5-1.8) to feed sweet drinks by month 6, and 79% more likely (95% confidence interval 1.6-2.0) to introduce solid foods by month 3. These odds decreased to 41 and 30%, respectively, after adjusting for mother's age, body mass index (BMI) and education. CONCLUSION: The maternal trait of negative affectivity is an independent predictor of infant feeding practices that may be related with childhood weight gain, overweight and obesity.

Postpartum onset of rheumatoid arthritis and other chronic arthritides: results from a patient register linked to a medical birth registry.

BACKGROUND: It is known that onset of rheumatoid arthritis (RA) is increased post partum. OBJECTIVE: To compare incidence rates between RA and other chronic arthritides (OCA) 0-24 months after delivery, and to compare the incidence rates within each group 0-24 versus 25-48 months post partum. METHODS: Premenopausal women from a Norwegian patient register were linked with the Medical Birth Registry of Norway to study the interval between delivery and time of diagnosis. Cox regression analysis with adjustments for age at delivery and birth order was applied to compare proportions of incident cases of RA and OCA with onset 0-24 months post partum. Poisson regression analysis with adjustment for the population at risk was applied to estimate the incidence rate ratio (IRR) 0-24 versus 25-48 months post partum. RESULTS: Of 183 RA and 110 patients with OCA diagnosed after delivery, 69 (37.7%) had RA and 31 (28.2%) OCA during the first 24 months post partum (p = 0.09). The IRR (95% CI) for diagnosis during 0-24 months versus 25-48 months was 1.73 (1.11 to 2.70) (p = 0.01) for RA, 1.05 (0.59 to 1.84) (p = 0.86) for OCA. The IRR was 2.23 (1.06 to 4.70) and 1.87 (0.67 to 5.21), respectively, when only considering diagnoses after the first pregnancy. Clinical characteristics were similar within each diagnostic group. CONCLUSION: The proportions of incident cases with onset 0-24 months after delivery were not different between RA and OCA. A peak in incidence during 0-24 months was seen in the RA group, both when considering all pregnancies and only the first pregnancy.

Pregnancy and birth after kidney donation: the Norwegian experience.

Reports on pregnancies in kidney donors are scarce. The aim was to assess pregnancy outcomes for previous donors nationwide. The Medical Birth Registry of Norway holds records of births since 1967. Linkage with the Norwegian Renal Registry provided data on pregnancies of kidney donors 1967-2002. A random sample from the Medical Birth Registry was control group, as was pregnancies in kidney donors prior to donation. Differences between groups were assessed by two-sided Fisher's exact tests and with generalized linear mixed models (GLMM). We identified 326 donors with 726 pregnancies, 106 after donation. In unadjusted analysis (Fisher) no differences were observed in the occurrence of preeclampsia (p = 0.22). In the adjusted analysis (GLMM) it was more common in pregnancies after donation, 6/106 (5.7%), than in pregnancies before donation 16/620 (2.6%) (p = 0.026). The occurrence of stillbirths after donation was 3/106 (2.8%), before donation 7/620 (1.1%), in controls (1.1%) (p = 0.17). No differences were observed in the occurrence of adverse pregnancy outcome in kidney donors and in the general population in unadjusted analysis. Our finding of more frequent preeclampsia in pregnancies after kidney donation in the secondary analysis must be interpreted with caution, as the number of events was low.

Occurrence of placental abruption in relatives.

OBJECTIVE: The aim of this study was to assess the recurrence of placental abruption by severity, comparing the risk in a woman with that of recurrence in her sister and in the partner of her brother. DESIGN: Prospective observational study. SETTING: General population. POPULATION: Population-based study based on records of pregnancies from the Medical Birth Registry of Norway; 377.902 sisters with 767 395 pregnancies, 168,142 families incorporating 2-10 sisters, and 346,385 brothers with 717,604 pregnancies in their partners were identified. METHODS: Placental abruption with preterm birth, birthweight below 2500 g or perinatal death was defined as severe, other cases as mild. Because of the nested family data structure, multilevel multivariate regression was used. MAIN OUTCOME MEASURES: Placental abruption (severe and mild). RESULTS: Adjusted odds ratios of recurrence of mild and severe abruption were 6.5 (1.7%) and 11.5 (3.8%), respectively, compared with risks of 0.2 and 0.3% in the total population. After a severe abruption, odds ratios in her sisters were 1.7-2.1, whereas mild abruption produced no increased recurrence in sisters. The estimated heritability between sisters of severe abruption was 16%. No excess rate of abruption was observed between sisters and brothers' partners, between brothers' partners, or from brothers' partners to sisters. The odds ratios for a third abruption after a second abruption and a second severe abruption were 38.7 (19%) and 50.1 (24%), respectively. CONCLUSIONS: The recurrence risk of placental abruption in the same woman was higher after severe than mild abruption. Severe abruption was associated with a two-fold risk in sisters. Pregnancies following a second abruption should be considered very high risk.

Placenta weight percentile curves for singleton deliveries.

OBJECTIVE: To produce population-based, gender- and gestational-age-specific centile curves for placental weight. DESIGN: Population study. SETTING: Medical Birth Registry of Norway. POPULATION: All singleton live births in Norway from 1 January 1999 to 31 December 2002. METHODS: In a cohort of children born in Norway, placental weights and the ratio of the birthweight to the placental weight were analysed to produce percentile curves. MAIN OUTCOME MEASURES: Placental weight, birthweight-to-placental weight ratio. RESULTS: Tables and figures are presented for placental percentiles curves according to gestational age and gender. Also, tables and figures are presented for the ratio of birthweight to placental weight. CONCLUSIONS To our knowledge, this is the first time that population percentile curves have been produced for placental weights and hence for the ratio of birthweight to placental weight. These percentile curves may act as a reference for other populations as well until population-specific curves can be produced.

Sudden unexplained infant death in 20 regions in Europe: case control study.

BACKGROUND: After striking changes in rates of sudden unexplained infant death (SIDS) around 1990, four large case-control studies were set up to re-examine the epidemiology of this syndrome. The European Concerted Action on SIDS (ECAS) investigation was planned to bring together data from these and new studies to give an overview of risk factors for the syndrome in Europe. METHODS: We undertook case-control studies in 20 regions. Data for more than 60 variables were extracted from anonymised records of 745 SIDS cases and 2411 live controls. Logistic regression was used to calculate odds ratios (ORs) for every factor in isolation, and to construct multivariate models. FINDINGS: Principal risk factors were largely independent. Multivariately significant ORs showed little evidence of intercentre heterogeneity apart from four outliers, which were eliminated. Highly significant risks were associated with prone sleeping (OR 13.1 [95% CI 8.51-20.2]) and with turning from the side to the prone position (45.4 [23.4-87.9]). About 48% of cases were attributable to sleeping in the side or prone position. If the mother smoked, significant risks were associated with bed-sharing, especially during the first weeks of life (at 2 weeks 27.0 [13.3-54.9]). This OR was partly attributable to mother's consumption of alcohol. Mother's alcohol consumption was significant only when baby bed-shared all night (OR increased by 1.66 [1.16-2.38] per drink). For mothers who did not smoke during pregnancy, OR for bed-sharing was very small (at 2 weeks 2.4 [1.2-4.6]) and only significant during the first 8 weeks of life. About 16% of cases were attributable to bed-sharing and roughly 36% to the baby sleeping in a separate room. INTERPRETATION: Avoidable risk factors such as those associated with inappropriate infants' sleeping position, type of bedding used, and sleeping arrangements strongly suggest a basis for further substantial reductions in SIDS incidence rates.

Plasma total homocysteine, pregnancy complications, and adverse pregnancy outcomes: the Hordaland Homocysteine study.

BACKGROUND: Total homocysteine (tHcy) measured in serum or plasma is a marker of folate status and a risk factor for cardiovascular disease. OBJECTIVE: Our objective was to investigate associations between tHcy and complications and adverse outcomes of pregnancy. DESIGN: Plasma tHcy values measured in 1992-1993 in 5883 women aged 40-42 y were compared with outcomes and complications of 14492 pregnancies in the same women that were reported to the Medical Birth Registry of Norway from 1967 to 1996. RESULTS: When we compared the upper with the lower quartile of plasma tHcy, the adjusted risk for preeclampsia was 32% higher [odds ratio (OR): 1. 32; 95% CI: 0.98, 1.77; P for trend = 0.02], that for prematurity was 38% higher (OR: 1.38; 95% CI: 1.09, 1.75; P for trend = 0.005), and that for very low birth weight was 101% higher (OR: 2.01; 95% CI: 1.23, 3.27; P for trend = 0.003). These associations were stronger during the years closest to the tHcy determination (1980-1996), when there was also a significant relation between tHcy concentration and stillbirth (OR: 2.03; 95% CI: 0.98, 4.21; P for trend = 0.02). Neural tube defects and clubfoot had significant associations with plasma tHcy. Placental abruption had no relation with tHcy quartile, but the adjusted OR when tHcy concentrations >15 micromol/L were compared with lower values was 3.13 (95% CI: 1.63, 6. 03; P = 0.001). CONCLUSION: Elevated tHcy concentration is associated with common pregnancy complications and adverse pregnancy outcomes.

Testicular cancer and parental use of fertilizers in agriculture.

Testicular cancer incidence is increasing rapidly in several countries. Environmental causes acting early in life are suspected but have not yet been identified. We conducted a cohort study to identify parental risk factors for testicular cancer among farmers' sons. Children born in 1952-1991 to parents who were farm holders at the time of the agricultural censuses in 1969-1989 were identified in the Central Population Register (Oslo, Norway). The resulting cohort of male offspring (n = 166,291) were followed up in the Cancer Registry of Norway (Oslo, Norway) for 1965-1991. Exposure indicators were derived from census information on activities on the farm. The cancer incidence was compared with that of the total rural population, and potential risk factors were analyzed by Poisson regression. In a follow-up of 2,924,663 person-years, 158 incident cases of testicular cancer were identified. The study population had a higher incidence of testicular cancer than did the total rural population, particularly at ages 15-19 years and in western Norway. Specific fertilizer regimens on the farm were associated with testicular cancer (rate ratio = 2.44; 95% confidence interval = 1.66-3.56), in particular nonseminoma (rate ratio = 4.21; 95% confidence interval = 2.13-8.32). The rate ratio estimates were highest for boys ages 15-19 years and for a subset of study subjects who were considered more likely to have grown up on a farm. Nondifferential misclassification and bias toward unity are likely because exposure information was available only at the farm level and only for census years. The fertilizer indicators were not available early in life for most subjects, and precise interpretations are difficult. A hypothesis worth considering is that excess nutrient run-off from agriculture constitutes a risk. However, inferences concerning the biological basis of our observations can scarcely be made.

The spectrum of congenital anomalies of the VATER association: an international study.

The spectrum of the VATER association has been debated ever since its description more than two decades ago. To assess the spectrum of congenital anomalies associated with VATER while minimizing the distortions due to small samples and referral patterns typical of clinical series, we studied infants with VATER association reported to the combined registry of infants with multiple congenital anomalies from 17 birth defects registries worldwide that are part of the International Clearinghouse for Birth Defects Monitoring Systems (ICB-DMS). Among approximately 10 million infants born from 1983 through 1991, the ICB-DMS registered 2,295 infants with 3 or more of 25 unrelated major congenital anomalies of unknown cause. Of these infants, 286 had the VATER association, defined as at least three of the five VATER anomalies (vertebral defects, anal atresia, esophageal atresia, renal defects, and radial-ray limb deficiency), when we expected 219 (P<0.001). Of these 286 infants, 51 had at least four VATER anomalies, and 8 had all five anomalies. We found that preaxial but not other limb anomalies were significantly associated with any combination of the four nonlimb VATER anomalies (P<0.001). Of the 286 infants with VATER association, 214 (74.8%) had additional defects. Genital defects, cardiovascular anomalies, and small intestinal atresias were positively associated with VATER association (P<0.001). Infants with VATER association that included both renal anomalies and anorectal atresia were significantly more likely to have genital defects. Finally, a subset of infants with VATER association also had defects described in other associations, including diaphragmatic defects, oral clefts, bladder exstrophy, omphalocele, and neural tube defects. These results offer evidence for the specificity of the VATER association, suggest the existence of distinct subsets within the association, and raise the question of a common pathway for patterns of VATER and other types of defects in at least a subset of infants with multiple congenital anomalies.

Post-term birth: risk factors and outcomes in a 10-year cohort of Norwegian births.

OBJECTIVE: To identify factors associated with post-term birth and factors associated with adverse outcomes in post-term births. METHODS: The sample was a 10-year cohort (1978-1987) of term (n = 379,445) and post-term (n = 65,796) births from the Medical Birth Registry of Norway. Gestational age was based on mothers' recall of the last menstrual period. Multivariate analyses included proportional hazards regression and binomial logistic regression. RESULTS: After controlling for covariates, there was only a slightly increased risk of perinatal mortality in post-term as compared with term births (adjusted relative risk [RR] 1.11; 95% confidence interval [CI] 0.97, 1.27). For post-term births, risk factors for perinatal mortality were small size for gestational age (SGA) (adjusted RR 5.68; 95% CI 4.37, 7.38) and maternal age 35 years or older (adjusted RR 1.88; 95% CI 1.22, 2.89), whereas large size for gestational age (LGA) was a protective factor (adjusted RR 0.51; 95% CI 0.26, 1.00). Similar risk factor RRs were found for perinatal mortality in term births. Fetal distress was associated with both SGA and post-term birth; labor dysfunction and obstetric trauma were associated with both LGA and post-term birth; shoulder dystocia and maternal hemorrhage were associated with LGA only. CONCLUSIONS: Among post-term births, maternal complications were generally associated with larger fetal size, and fetal complications were associated with smaller fetal size. The evidence for an adverse impact on perinatal mortality of post-term birth is weak once other factors are taken into account.

Predicting preeclampsia in the second pregnancy from low birth weight in the first pregnancy.

OBJECTIVE: To evaluate the effect of low birth weight adjusted for gestational age in first pregnancies on preeclampsia in second pregnancies and to estimate the proportion of preeclampsia in second pregnancies attributable to histories of LBW for gestational age. METHODS: We conducted a cohort study based on linked data from the Medical Birth Registry of Norway, which covered all births in 1967-1992. RESULTS: Women who delivered infants under the third percentile birth weight were three times more likely to have initial or recurrent preeclampsia in second pregnancies than those who delivered infants at or above the tenth percentile. After adjusting for maternal age, year of birth, interpregnancy interval, education, chronic hypertension, diabetes mellitus, and change of partner, the increased risk persisted. Birth weight below the tenth percentile in the first delivery accounted for 10% of the total cases of preeclampsia in the second pregnancy and 30% of recurrent cases. CONCLUSION: A history of low birth weight adjusted for gestational age is associated significantly with subsequent occurrence as well as recurrence of preeclampsia. These findings are consistent with the hypothesis of a shared etiologic factor or recurrent pathophysiologic mechanism for preeclampsia and fetal growth restriction. A history of fetal smallness for gestational age is found in a substantial proportion of all cases of preeclampsia and thus seems to be important in the etiology of preeclampsia.

Perinatal mortality in breech presentation sibships.

OBJECTIVE: To compare perinatal mortality in breech presentation delivered vaginally and by cesarean in individual births and in sibships. METHODS: A national, population registry-based study, 1967-1994, was conducted, with maternal record linkage of sibships, comprising the first to the third birth of a mother. The main outcome was perinatal mortality. Odds ratios of perinatal mortality were calculated and adjusted by logistic regression analysis. RESULTS: The overall relative perinatal mortality was 4.3 (95% confidence interval [CI] 4.1, 4.5) in breech compared with nonbreech presentation and 5.4 (95% CI 4.7, 6.2) in vaginal compared with cesarean delivery. The relative perinatal mortality in breech compared with nonbreech presentation was lowest in birth order one compared with birth orders two and three. In breech vaginal delivery compared with cesarean delivery, the opposite effect of birth order was found. The highest perinatal mortality was found in a current breech presentation of a sibship with no previous breech births. In birth subsequent to breech births, perinatal mortality was more or less independent of current presentation, without respect to delivery method. The increased perinatal mortality in breech presentation is explained partly by its association with other risk factors for perinatal death. CONCLUSION: Women with recurring breech presentation represent a lower risk of adverse perinatal outcome. This might be explained by a biologic mechanism or by increased quality of antenatal care. An increased mortality in subsequent nonbreech siblings after a breech presentation was surprising.

Reproductive career after breech presentation: subsequent pregnancy rates, interpregnancy interval, and recurrence.

OBJECTIVE: To assess subsequent pregnancy rates and recurrence of breech, as well as interpregnancy interval after a breech presentation. METHODS: We conducted a national population registry-based study using data from 1967 to 1994, with maternal record linkage of sibships, comprising the first to the fourth birth of a mother. RESULTS: The subsequent pregnancy rate after a surviving breech birth was lower than after a surviving nonbreech birth. Women with two births, of which one was a perinatal loss, had a higher subsequent pregnancy rate, compared with those who had surviving infants. The subsequent pregnancy rate was lower after a cesarean delivery irrespective of presentation. The interpregnancy interval was shorter if the previous infant died, whereas presentation did not influence the interval. The adjusted odds ratio of recurrence of breech increased from 4.32 (95% confidence interval [CI] 4.08, 4.59) after one previous breech delivery to 28.1 (95% CI 12.2, 64.8) after three. CONCLUSION: Breech and cesarean delivery lowered the subsequent pregnancy rate, probably because of the women's decision not to reproduce. Thus, preconceptional counseling with information, support, and reassurance regarding future pregnancies and deliveries might reduce the discouraging effect. A high odds ratio of recurrence of breech suggests effects of recurring specific causal factors of either genetic or more permanent environmental origin.