Temporal trends in age at menarche and age at menopause: a population study of 312 656 women in Norway.

STUDY QUESTION: Have mean age at menarche or mean age at natural menopause changed from the 1939 birth cohort to the 1964 birth cohort? SUMMARY ANSWER: We estimated a minor decrease in mean age at menarche and an increase by nearly 3 years in mean age at natural menopause. WHAT IS KNOWN ALREADY: In the Western world, age at menarche decreased across birth cohorts from the early 1800s until the 1950s. Whether mean age at menarche has continued to decrease in birth cohorts after the 1950s remains uncertain. It is also uncertain whether mean age at natural menopause has changed across birth cohorts. STUDY DESIGN, SIZE, DURATION: We performed a retrospective population study of 312 656 women who were born in Norway during the years 1936-1964. PARTICIPANTS/MATERIALS, SETTING, METHODS: The data were obtained by two self-administered questionnaires from women who participated in the Norwegian breast cancer screening program (BreastScreen Norway) during the years 2006-2014. We used flexible parametric survival models with restricted cubic splines to estimate mean age at menarche, mean age at menopause and mean number of years between menarche and menopause according to the women's year of birth. The women who were still having menstrual periods contributed with follow-up time until the time of data collection, and the women who had reported surgical removal of the uterus and/or both ovaries prior to natural menopause contributed with follow-up time until the time of surgery. MAIN RESULTS AND THE ROLE OF CHANCE: The mean age at menarche was 13.42 years (95% CI: 13.40-13.44 years) among women born during 1936-1939, and it was 13.24 years (95% CI: 13.22-13.25 years) among women born during 1960-1964. The mean age at natural menopause increased from 50.31 years (95% CI: 50.25-50.37 years) among women born during 1936-1939 to 52.73 years (95% CI: 52.64-52.82 years) among women born during 1960-1964. The mean number of years between menarche and menopause increased from 36.83 years (95% CI: 36.77-36.89 years) to 40.22 years (95% CI: 40.11-40.34 years). LIMITATIONS, REASONS FOR CAUTION: Information about age at menarche and age at menopause was based on self-reports. WIDER IMPLICATIONS OF THE FINDINGS: Late menopause is associated with increased risk of breast cancer but also with increased life expectancy. Thus, higher mean age at menopause may partly explain the increase in breast cancer incidence after menopause and the increase in life expectancy in recent time. Also, a longer interval between menarche and menopause could suggest that the number of years of female fecundity has increased. STUDY FUNDING/COMPETING INTEREST(S): This work was funded by the South-Eastern Norway Regional Health Authority [grant number 2016112 to M.S.G.] and by the Norwegian Cancer Society [grant number 6863294-2015 to E.K.B.]. The authors declare no conflicts of interest.

The relation of age at menarche with age at natural menopause: a population study of 336 788 women in Norway.

STUDY QUESTION: Is age at menarche associated with age at menopause or with duration of the reproductive period (interval between menarche and menopause)? SUMMARY ANSWER: The association of age at menarche with age at menopause was weak and non-linear, and the duration of the reproductive period decreased by increasing age at menarche. WHAT IS KNOWN ALREADY: It remains uncertain whether age at menarche is associated with age at menopause. Some studies report that women with early menarche also have early menopause. Other studies report that women with early menarche have late menopause, or they report no association. The duration of the reproductive period may be an indicator of the cumulative endogenous exposure to estrogens and progestogens during life course and is associated with risk of breast cancer and endometrial cancer. STUDY DESIGN, SIZE, DURATION: A retrospective cohort study of 336 788 women, aged 48-71 years, in the BreastScreen Norway during the years 2006-2014 was performed. PARTICIPANTS/MATERIALS, SETTING, METHODS: Information about age at menarche and menopausal status was obtained by self-administered questionnaires. We used time to event approaches to estimate the associations. MAIN RESULTS AND THE ROLE OF CHANCE: Median age at menopause was 51 years in most menarche groups. Women with menarche at age 16 years or age ≥ 17 years had menopause 1 year later [median: 52 years, interquartile range (IQR): 49-54 years] than women with menarche at age 13 years (median: 51 years, IQR: 49-54 years, reference) (crude hazard ratio (HR) = 0.95; 95% CI: 0.93-0.97 and 0.95; 95% CI: 0.92-0.99, Pnon-linearity < 0.001). The reproductive period decreased with increasing age at menarche (Pnon-linearity < 0.001), and women with menarche at age ≤ 9 years had 9 years longer median reproductive period than women with menarche at age ≥ 17 years (median: 43 versus 34 years). Adjustment for year of birth did not change the HR estimates notably. LARGE SCALE DATA: Not applicable. LIMITATIONS, REASONS FOR CAUTION: Information about age at menarche and age at menopause was based on self-reports. Particularly for age at menarche, the long time interval between the event and data collection may have caused imprecise reporting. WIDER IMPLICATIONS OF THE FINDINGS: Our study suggests that age at menarche is a strong indicator for the duration of women's reproductive period. Our findings should encourage studies of the independent role of duration of the reproductive period on the risk of breast cancer and endometrial cancer, since these cancers have been associated with exposure to estrogens and progestogens. STUDY FUNDING/COMPETING INTEREST(S): The present study was funded by the Norwegian Cancer Society [Grant number 6863294-2015]. The authors declare no conflicts of interest.

Association of placental weight with cerebral palsy: population-based cohort study in Norway.

OBJECTIVE: To study the risk of cerebral palsy (CP) associated with placental weight, and also with placental weight/birthweight ratio and placental weight/birth length ratio. DESIGN: Population-based cohort study. SETTING: Perinatal data in the Medical Birth Registry of Norway were linked with clinical data in the CP Register of Norway. POPULATION: A total of 533 743 singleton liveborn children in Norway during 1999-2008. Of these, 779 children were diagnosed with CP. METHODS: Placental weight, placental weight/birthweight ratio, and placental weight/birth length ratio were grouped into gestational age-specific quartiles. Odds ratios (OR) with 95% confidence intervals (95% CI) for CP were calculated for children with exposure variables in the lowest or in the highest quartile, using the second to third quartile as the reference. MAIN OUTCOME MEASURES: CP and CP subtypes. RESULTS: Overall, children with low placental weight had increased risk for CP (OR 1.5, 95% CI 1.2-1.7). Low placental weight/birthweight ratio (OR 1.2, 95% CI 1.0-1.4) and low placental weight/birth length ratio (OR 1.5, 95% CI 1.2-1.8) were also associated with increased risk for CP. In children born at term, low placental weight was associated with a twofold increase in risk for spastic bilateral CP (including both quadriplegia and diplegia) (OR 2.1, 95% CI 1.5-2.9). In children born preterm, high placental ratios were associated with increased risk for spastic quadriplegia. CONCLUSIONS: Our results suggest that placental dysfunction may be involved in causal pathways leading to the more severe subtypes of CP. TWEETABLE ABSTRACT: Low placental weight increases the risk for cerebral palsy, especially for the spastic bilateral subtype.

Maternal hCG concentrations in early IVF pregnancies: associations with number of cells in the Day 2 embryo and oocytes retrieved.

STUDY QUESTION: Do number of cells in the transferred cleavage stage embryo and number of oocytes retrieved for IVF influence maternal hCG concentrations in early pregnancies? SUMMARY ANSWER: Compared with transfer of a 2-cell embryo, transfer of a 4-cell embryo results in higher hCG concentrations on Day 12 after transfer, and more than 20 oocytes retrieved were associated with low hCG concentrations. WHAT IS KNOWN ALREADY: Maternal hCG concentration in very early pregnancy varies considerably among women, but is likely to be an indicator of time since implantation of the embryo into the endometrium, in addition to number and function of trophoblast cells. STUDY DESIGN, SIZE, DURATION: We followed 1047 pregnancies after IVF/ICSI from oocyte retrieval until Day 12 after embryo transfer. Women were recruited in Norway during the years 2005-2013. PARTICIPANTS/MATERIALS, SETTING, METHODS: Successful pregnancies after transfer of one single embryo that had been cultured for 2 days were included. Maternal hCG was quantified on Day 12 after embryo transfer by chemiluminescence immunoassay, which measures intact hCG and the free ß-hCG chain. Information on a successful pregnancy, defined as birth after >16 weeks, was obtained by linkage to the Medical Birth Registry of Norway. MAIN RESULTS AND THE ROLE OF CHANCE: Transfer of a 4-cell embryo resulted in higher maternal hCG concentrations compared with transfer of a 2-cell embryo (134.8 versus 87.8 IU/l, P < 0.05). A high number of oocytes retrieved (>20) was associated with low hCG concentrations (P < 0.05). LIMITATIONS, REASONS FOR CAUTION: The factors studied explain a limited part of the total variation of hCG concentrations in early pregnancy. Although embryo transfer was performed at the same time after fertilization, we do not know the exact time of implantation. A further limitation to our study is that the number of pregnancies after transfer of a 2-cell embryo was small (27 cases). WIDER IMPLICATIONS OF THE FINDINGS: Number of cells in the transferred embryo and number of oocytes retrieved may influence the conditions and timing for embryo implantation in different ways and thereby influence maternal hCG concentrations. Such knowledge may be important for interpretation of hCG concentrations in early pregnancy.

The prevalence of pre-eclampsia in migrant relative to native Norwegian women: a population-based study.

OBJECTIVE: To compare the prevalence of pre-eclampsia in migrant women with Norwegian women, and to study the prevalence of pre-eclampsia by length of residence in Norway. DESIGN: Observational study. SETTING: The Medical Birth Registry of Norway. POPULATION: All Norwegian, Pakistani, Vietnamese, Somali, Sri Lankan, Filipino, Iraqi, Thai and Afghan women who gave birth after 20 weeks of gestation during the period 1986-2005 in Norway. METHODS: The prevalence of pre-eclampsia was calculated by country of birth. The association of country of birth and length of residence in Norway with pre-eclampsia was estimated as the odds ratio (OR) with 95% confidence interval (CI), using Norwegian women as a reference. We made adjustments for maternal age, parity, multifetal pregnancy, year of delivery and maternal diabetes in multivariable analysis. MAIN OUTCOME MEASURE: Pre-eclampsia. RESULTS: Migrant women had a lower prevalence of pre-eclampsia than Norwegian women (2.7% versus 3.7%, P < 0.001). Vietnamese (OR, 0.36; CI, 0.29-0.45), Afghan (OR, 0.52; CI, 0.30-0.90) and Thai (OR, 0.57; CI, 0.45-0.73) women had the lowest risk of pre-eclampsia relative to Norwegian women. Adjustment for the variables above or separate analyses for nulliparous women did not change the estimates notably. Using Norwegian women as the reference, the risk of pre-eclampsia increased by length of residence for migrant women: adjusted OR of 0.64 (0.59-0.70) at <5 years and 0.91 (0.84-0.99) at ≥5 years of residence. CONCLUSIONS: The risk of pre-eclampsia was lower in migrants relative to Norwegian women, but increased by length of residence in Norway.

Is unilateral oophorectomy associated with age at menopause? A population study (the HUNT2 Survey).

STUDY QUESTION: Is unilateral oophorectomy associated with age at menopause? SUMMARY ANSWER: Women who had undergone unilateral oophorectomy entered menopause 1 year earlier than women with two ovaries intact. WHAT IS ALREADY KNOWN: There is substantial variation in age at natural menopause. Unilateral oophorectomy implies a significant reduction of the ovarian follicular reserve. Thus, one might expect that the time to menopause is shortened by several years in women who have undergone unilateral oophorectomy. STUDY DESIGN, SIZE AND DURATION: A retrospective cohort study of 23 580 Norwegian women who were included in the population-based HUNT2 Survey during the years 1995-1997. PARTICIPANTS/MATERIALS, SETTING, METHODS: Data were obtained by two self-administered questionnaires at study inclusion. Cox proportional hazard models were used to estimate relative risks of menopause according to unilateral oophorectomy status with and without adjustment for birth cohort, parity, smoking, body mass index (BMI) and age at menarche. MAIN RESULTS AND THE ROLE OF CHANCE: Women who had undergone unilateral oophorectomy were younger at menopause [mean 49.6 years; 95% confidence interval (CI): 49.2-50.0] than women without unilateral oophorectomy (mean 50.7 years; 95% CI: 50.6-50.8) (P < 0.001). The crude relative risk of menopause was 1.28 (95% CI: 1.15-1.42) and remained similar after adjustment for the study factors above (adjusted relative risk 1.27; 95% CI: 1.14-1.41). In addition, recent birth cohort and high BMI were associated with higher age at menopause. LIMITATIONS, REASONS FOR CAUTION: Information on unilateral oophorectomy was based on self-reports. Some women may therefore have been misclassified. WIDER IMPLICATIONS OF THE FINDINGS: Although the effect of unilateral oophorectomy on the age at menopause is similar to that of smoking, it is weaker than anticipated from the loss of ovarian follicular reserve. Thus, compensatory mechanisms may occur in the remaining ovary.

Concentrations of human chorionic gonadotrophin in very early pregnancy and subsequent pre-eclampsia: a cohort study.

STUDY QUESTION: Are low serum concentrations of human chorionic gonadotrophin (hCG) in very early pregnancy associated with pre-eclampsia risk? SUMMARY ANSWER: Low hCG concentrations in very early pregnancy are associated with increased risk of severe pre-eclampsia. WHAT IS KNOWN ALREADY: Low maternal serum concentrations of hCG early in pregnancy may indicate impaired proliferation or invasion of trophoblast cells, and thus low hCG concentrations may serve as a marker for impaired placental development. Impaired placental development is assumed to be a cause of pre-eclampsia, but there is little prospective evidence to support this hypothesis. STUDY DESIGN, SIZE, DURATION: We performed a prospective cohort study of pregnancies after IVF at Oslo University Hospital 1996-2010 with linkage to the Medical Birth Registry of Norway to obtain information on pre-eclampsia development. PARTICIPANTS/MATERIALS, SETTING, METHODS: We included 2405 consecutive singleton pregnancies and examined the association of maternal serum hCG concentrations (measured using Elecsys, Roche) on Day 12 after embryo transfer with the risk of any pre-eclampsia and of mild and severe pre-eclampsia. MAIN RESULTS AND THE ROLE OF CHANCE: HCG concentrations were inversely associated with pre-eclampsia risk in a dose-dependent manner (Ptrend 0.02). Compared with women with hCG ≥150 IU/l, women with hCG <50 IU/l were at 2-fold higher overall risk of pre-eclampsia [absolute risk 6.4 versus 2.8%; odds ratio (OR) 2.3, 95% confidence interval (CI) 1.2-4.7]. The inverse association was restricted to severe pre-eclampsia (Ptrend 0.01), thus, women with hCG <50 IU/l were at 4-fold higher risk of severe pre-eclampsia than women with hCG ≥150 IU/l (absolute risk 3.6 versus 0.9%; OR 4.2, 95% CI 1.4-12.2). For mild pre-eclampsia, there was no corresponding association (Ptrend 0.36). LIMITATIONS, REASONS FOR CAUTION: Results for IVF pregnancies may not be generalizable to spontaneously conceived pregnancies. WIDER IMPLICATIONS OF THE FINDINGS: Plausible causes of low maternal hCG concentrations very early in pregnancy include impaired placental development and delayed implantation. Thus, these results provide prospective evidence to support the hypothesis that impaired placental development may be associated with subsequent development of severe pre-eclampsia. STUDY FUNDING/COMPETING INTEREST: The study was financially supported by the Research Council of Norway. None of the authors has any conflict of interest to declare.

Pregnancy week at delivery and the risk of shoulder dystocia: a population study of 2,014,956 deliveries.

OBJECTIVE: To study whether pregnancy week at delivery is an independent risk factor for shoulder dystocia. DESIGN: Population study. SETTING: Medical Birth Registry of Norway. POPULATION: All vaginal deliveries of singleton offspring in cephalic presentation in Norway during 1967 through 2009 (n = 2,014,956). METHODS: The incidence of shoulder dystocia was calculated according to pregnancy week at delivery. The associations of pregnancy week at delivery with shoulder dystocia were estimated as crude and adjusted odds ratios using logistic regression analyses. We repeated the analyses in pregnancies with and without maternal diabetes. MAIN OUTCOME MEASURES: Shoulder dystocia at delivery. RESULTS: The overall incidence of shoulder dystocia was 0.73% (n = 14,820), and the incidence increased by increasing pregnancy week at delivery. Birthweight was strongly associated with shoulder dystocia. After adjustment for birthweight, induction of labour, use of epidural analgesia at delivery, prolonged labour, forceps-assisted and vacuum-assisted delivery, parity, period of delivery and maternal age in multivariable analyses, the adjusted odds ratios for shoulder dystocia were 1.77 (1.42-2.20) for deliveries at 32-35 weeks of gestation, and 0.84 (0.79-0.88) at 42-43 weeks of gestation, using weeks 40-41 as the reference. In pregnancies affected by diabetes (n = 11,188), the incidence of shoulder dystocia was 3.95%, and after adjustment for birthweight the adjusted odds ratio for shoulder dystocia was 2.92 (95% CI 1.54-5.52) for deliveries at weeks 32-35 of gestation, and 0.91 (95% CI 0.50-1.66) at 42-43 weeks of gestation. CONCLUSION: The risk of shoulder dystocia was associated with increased birthweight, diabetes, induction of labour, use of epidural analgesia at delivery, prolonged labour, forceps-assisted and vacuum-assisted delivery, parity and period of delivery but not with post-term delivery.

Paternal age, placental weight and placental to birthweight ratio: a population-based study of 590,835 pregnancies.

STUDY QUESTION: Is the age of the father associated with placental weight or the ratio of placental weight to birthweight? SUMMARY ANSWER: Placental weight and placental to birthweight ratio increased according to increasing paternal age, also after adjustment for maternal age. WHAT IS KNOWN ALREADY: High paternal age and also high placental to birthweight ratio have been associated with adverse pregnancy outcome. STUDY DESIGN, SIZE AND DURATION: We performed a population-based study and included all singleton births after 22 weeks of gestation in the Medical Birth Registry of Norway (n = 590,835) during the years 1999-2009. PARTICIPANTS/MATERIALS, SETTING, METHODS: We compared mean placental weight and placental to birthweight ratio between paternal age groups. The association of paternal age with placental weight was estimated by linear regression analyses, and adjustments were made for maternal age, birthweight, parity, offspring sex, gestational age at birth, maternal smoking, pre-eclampsia, maternal diabetes mellitus and pregnancy after assisted reproductive technology (ART). MAIN RESULTS AND THE ROLE OF CHANCE: In pregnancies with fathers aged 20-24 years old, the mean placental weight was 656.2 g [standard deviation (SD) 142.8], whereas it was 677.8 g (SD 160.0) in pregnancies with fathers aged 50 years or older (P < 0.001). The mean offspring birthweight in pregnancies with fathers aged 20-24 year old was 3465.0 g (SD 583.8), and it was 3498.9 g (SD 621.8) when the father was 50 years or older (P < 0.001). The placental to birthweight ratio in the corresponding paternal age groups were 0.191 (SD 0.039) and 0.196 (SD 0.044) (P < 0.001). In multivariable linear regression analysis the placentas in pregnancies fathered by a man of 50 years or older were estimated to weigh 13.99 g [95% confidence interval (CI) 10.88-17.10] more than in pregnancies with a 20-24-year-old father (P < 0.001) after adjustment for maternal age, birthweight, parity, offspring sex, gestational age at birth, maternal smoking, pre-eclampsia, maternal diabetes mellitus and pregnancy after ART. LIMITATIONS, REASONS FOR CAUTION: Paternal age explains only a small proportion of the total variation in placental weight. WIDER IMPLICATIONS OF THE FINDINGS: Our findings may increase the understanding of the father's role in human pregnancy. STUDY FUNDING/ COMPETING INTEREST(S): Norwegian Resource Centre for Women's Health, Norway. No conflict of interest. TRIAL REGISTRATION NUMBER: N/A.

Placental weight in singleton pregnancies with and without assisted reproductive technology: a population study of 536,567 pregnancies.

BACKGROUND: Pregnancies conceived by assisted reproductive technology (ART) are at increased risk of adverse outcomes. Previous studies have suggested increased placental weight and increased placental weight/birthweight ratio in pregnancies associated with adverse outcomes. We therefore studied the association of ART with placental weight and placental weight/birthweight ratio. METHODS: We included all singleton births in the Medical Birth Registry of Norway during the period 1999-2008 (n = 536 567, including 8259 after ART). We divided placental weight and placental weight/birthweight ratio into quartiles, and calculated the proportions of ART and spontaneous pregnancies in the lowest and the highest quartile by length of gestation. Thereafter, we estimated crude and adjusted odds ratios (ORs) for being in each quartile of placental weight for ART pregnancies with spontaneous pregnancies as the reference. The analyses were repeated with ART pregnancies subgrouped into IVF or ICSI. RESULTS: Mean placental weight was 678.9 g in pregnancies conceived by ART, and 673.0 g in pregnancies after spontaneous conception. ART pregnancies were overrepresented in the highest quartile of placental weight and underrepresented in the highest quartile of birthweight, independent of length of gestation at delivery. Thus, placental weight/birthweight ratio was higher in ART pregnancies. For ART pregnancies, the OR for being in the highest quartile of placental weight was 1.37 (95% confidence interval 1.30-1.45) after adjustment for length of gestation, offspring birthweight, parity, fetal sex, maternal age, pre-eclampsia and diabetes. There was no difference in placental weight/birthweight ratio between IVF and ICSI pregnancies. CONCLUSIONS: We found larger placentas and a higher placental weight/birthweight ratio among pregnancies conceived by ART compared with spontaneous pregnancies, and the difference was independent of length of gestation at delivery and ART method.

Serum long chain n-3 fatty acids (EPA and DHA) in the pregnant mother are independent of risk of type 1 diabetes in the offspring.

BACKGROUND: This article aims to study whether higher proportions of the long chain n-3 fatty acids eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA) in the phospholipid fraction of serum samples in pregnancy were associated with a lower risk of childhood onset type 1 diabetes in the offspring. METHODS: In a prospective cohort of nearly 30 000 pregnant women who gave birth in Norway during 1992-1994, we analysed serum samples from 89 women whose child developed type 1 diabetes and was included in the nationwide Norwegian Childhood Diabetes Registry and 125 randomly selected women whose child did not develop type 1 diabetes before 15 years of age. Specific fatty acids were expressed as the proportion of total fatty acids (g/100 g) in the phospholipid fraction in serum analysed using solid phase extraction and gas chromatography with flame ionization detection. RESULTS: There was no significant association between EPA or DHA in maternal serum and risk of type 1 diabetes in the offspring. Odds ratio (OR) for upper versus lower quartile of EPA was 0.75 [95% confidence interval (CI) 0.34-1.65], test for trend p = 0.4, and for DHA OR = 0.71 (95% CI 0.33-1.53), test for trend p = 0.6. No significant association was found for the sum of n-3 fatty acids, or for n-6/n-3 ratio in the mother with risk of type 1 diabetes in the offspring. CONCLUSIONS: Our data did not support the hypothesis that higher proportions of maternal EPA or DHA during pregnancy are associated with a lower risk of type 1 diabetes in the offspring.

Fear of childbirth and duration of labour: a study of 2206 women with intended vaginal delivery.

OBJECTIVE: To assess the association between fear of childbirth and duration of labour. DESIGN: A prospective study of women from 32 weeks of gestation through to delivery. SETTING: Akershus University Hospital, Norway. POPULATION: A total of 2206 pregnant women with a singleton pregnancy and intended vaginal delivery during the period 2008-10. METHODS: Fear of childbirth was assessed by the Wijma Delivery Expectancy Questionnaire (W-DEQ) version A at 32 weeks of gestation, and defined as a W-DEQ sum score ≥ 85. Information on labour duration, use of epidural analgesia and mode of delivery was obtained from the maternal ward electronic birth records. MAIN OUTCOME MEASURES: Labour duration in hours: from 3-4 cm cervical dilatation and three uterine contractions per 10 minutes lasting ≥ 1 minute, until delivery of the child. RESULTS: Fear of childbirth (W-DEQ sum score ≥ 85) was present in 7.5% (165) of women. Labour duration was significantly longer in women with fear of childbirth compared with women with no such fear using a linear regression model (crude unstandardized coefficient 1.54; 95% confidence interval 0.87-2.22, corresponding to a difference of 1 hour and 32 minutes). After adjustment for parity, counselling for pregnancy concern, epidural analgesia, labour induction, labour augmentation, emergency caesarean delivery, instrumental vaginal delivery, offspring birthweight and maternal age, the difference attenuated, but remained statistically significant (adjusted unstandardized coefficient 0.78; 95% confidence interval 0.20-1.35, corresponding to a 47-minute difference). CONCLUSION: Duration of labour was longer in women with fear of childbirth than in women without fear of childbirth.

Mode of delivery and postpartum emotional distress: a cohort study of 55,814 women.

OBJECTIVE: To assess the association between mode of delivery and maternal postpartum emotional distress. DESIGN: A prospective study of women from 30 weeks of gestation to 6 months postpartum. SETTING: Pregnant women in Norway during the period 1998-2008. POPULATION: A total of 55,814 women from the Norwegian Mother and Child Cohort Study. METHODS: Emotional distress was reported in a short form of the Hopkins Symptom Checklist-25 (SCL-8) at 30 weeks of gestation and at 6 months postpartum. Information on mode of delivery was obtained from the Medical Birth Registry of Norway. MAIN OUTCOME MEASURES: Changes in SCL-8 score from 30 weeks of gestation to 6 months postpartum and presence of emotional distress at 6 months postpartum. RESULTS: Women with instrumental vaginal, emergency caesarean or elective caesarean deliveries had similar changes in SCL-8 score between 30 weeks of gestation and 6 months postpartum, as compared with women with unassisted vaginal delivery (adjusted regression coefficient, 0.00, 95% CI -0.01 to 0.01; 0.01, 95% CI 0.00-0.02; and -0.01, 95% CI -0.02 to 0.00, respectively). The corresponding odds ratios (ORs) associated with the presence of emotional distress at 6 months postpartum (SCL-8 ≥ 2.0) were: OR 1.01, 95% CI 0.86-1.18; OR 1.13, 95% CI 0.97-1.32; and OR 0.96, 95% CI 0.79-1.16, respectively. These estimates were adjusted for emotional distress during pregnancy and other potential confounding factors. Emotional distress during pregnancy showed the strongest association with the presence of emotional distress at 6 months postpartum (adjusted OR 14.09, 95% CI 12.77-15.55). CONCLUSIONS: Mode of delivery was not associated with a change in SCL-8 score from 30 weeks of gestation to 6 months postpartum or with the presence of emotional distress postpartum.

Percentiles of intrauterine placental volume and placental volume relative to fetal volume: A prospective magnetic resonance imaging study.

INTRODUCTION: We aimed to provide percentiles of intrauterine placental growth and placental growth relative to fetal growth (placental to fetal ratio) by measuring placental and fetal volumes by magnetic resonance imaging (MRI). METHODS: In this prospective study, 107 unselected singleton pregnancies were examined by MRI at gestational week 27 and 37. Based on the estimated volumes of the placenta and the fetus, we calculated median and percentiles at gestational weeks 27 and 37. RESULTS: Median placental volume at gestational week 27 was 513 cm3 (Inter Quartile Range (IQR) 182 cm3), and 831 cm3 (IQR 252 cm3) at week 37. The 10th - 90th percentiles included placental volumes between 392 and 717 cm3 at gestational week 27, and 631-1087 cm3 at week 37. The placental to fetal ratio was significantly higher at gestational week 27 than at week 37, with a median ratio of 0.54 (IQR 0.18) and 0.31 (IQR 0.08), respectively (p < 0.001). The 10th-90th percentiles included placental to fetal ratios between 0.43 and 0.73 at gestational week 27 and 0.25-0.39 at week 37. DISCUSSION: At gestational week 27, the placental volume was about half the size of the fetal volume, whereas at week 37, the placental volume was about one third of the fetal volume. This finding suggests that placental growth was less prominent than fetal growth after gestational week 27. Knowledge about the distribution of intrauterine placental size in the general population of pregnancies are prerequisites for diagnosing abnormal placental size.

Placental weight and excess postpartum haemorrhage: a population study of 308,717 pregnancies.

OBJECTIVE: To investigate whether placental weight may be positively associated with the prevalence of excess postpartum haemorrhage because large placentas have large surface areas. DESIGN: Registry-based cross-sectional study. SETTING: Population study. POPULATION: All singleton deliveries after 21 weeks of gestation in Norway during 1999-2004 (n = 308,717). METHODS: Data were obtained from the Medical Birth Registry of Norway, which is based on compulsory notification of births by the midwife or doctor in charge of the delivery. MAIN OUTCOME MEASURE: Excess postpartum haemorrhage was defined as bleeding of 500 ml or more within 2 hours of delivery. RESULTS: There was a gradual increase in the prevalence of excess postpartum haemorrhage with increasing placental weight (test for trend, P < 0.05). Having a placenta of 1100 g or more was associated with 2.5 times (odds ratio 2.54, 95% CI 2.31-2.79) higher prevalence than having a placenta of 300-499 g, after adjustment for offspring birthweight, parity, caesarean section and placenta-related and delivery-related complications. A large placenta relative to birthweight was also associated with higher prevalence of excess postpartum haemorrhage. CONCLUSION: The size of the placental surface may explain the positive association of placental weight with the prevalence of postpartum haemorrhage. In pregnancies with a large placenta relative to offspring birthweight, other factors that enhance bleeding may also play a role.

The association of maternal age with placental weight: a population-based study of 536,954 pregnancies.

OBJECTIVE: To study the association of maternal age with placental weight, birthweight and placental weight/birthweight ratio. DESIGN: Population-based study. SETTING: Medical Birth Registry of Norway. POPULATION: All singleton births in Norway in the period 1999-2008 (n = 536,954). METHODS: Z-scores of placental weight and birthweight were calculated and divided into deciles. The proportions with a small or a large placenta were calculated within each maternal age group. Also, the odds ratios of having a small (lowest decile) and a large (highest decile) placenta, according to maternal age, were estimated, with and without adjustment for birthweight in grams, parity, smoking, pre-eclampsia and diabetes. MAIN OUTCOME MEASURES: Placental weight, birthweight and placental weight/birthweight ratio. RESULTS: The mean placental weight increased with maternal age: 647.1 g in women below the age of 20 years and 691.3 g in women aged 45 years or older. Among the oldest group of women (≥45 years) 15.8% of placentas were in the highest decile of placental weight z-score, whereas this was true for just 7.0% of women below the age of 20 years (Wald test, P < 0.001). Using women younger than 20 years of age as a reference, the odds ratio for having a placenta in the highest decile of placental weight z-score was 2.50 (95% CI 1.92-3.26) for women aged 45 years or older, after adjustment for offspring birthweight, parity, maternal smoking, pre-eclampsia and diabetes. CONCLUSION: We found an association between increased placental weight and maternal age, and this finding may be important in understanding the causes of adverse events associated with high maternal age.