Multiple pregnancy as a potential risk factor for postpartum depression: The Japan Environment and Children's Study

BACKGROUND

Postpartum depression (PPD) results in adverse consequences for both mother and infant. However, the association between multiple pregnancy and PPD is unknown because of the difference in the estimated prevalence rate of PPD based on country, ethnicity, and study type. Thus, this study aimed to determine whether Japanese women with multiple pregnancy were at a high risk of developing PPD at 1 and 6 months postpartum.

METHODS

In this nationwide prospective cohort study (the Japan Environment and Children's Study), conducted between January 2011 and March 2014, 77,419 pregnant women were enrolled. PPD was assessed using the Edinburgh Postnatal Depression Scale (EPDS) 1 and 6 months postpartum. A score of ≥13 points implied "positive" for PPD. Multiple logistic regression analyses estimated the association between multiple pregnancy and PPD risk.

RESULTS

Overall, 77,419 pregnancies (singleton, n = 76,738; twins, n = 676; triplets, n = 5) were included; 3.6 % and 2.9 % of pregnant women had PPD at 1 and 6 months postpartum, respectively. Compared with singleton pregnancy, multiple pregnancy was not associated with PPD at 1 month, but at 6 months postpartum (adjusted odd ratios: 0.968 [95 % confidence interval {CI}, 0.633-1.481] and 1.554 [95 % CI, 1.046-2.308], respectively).

LIMITATIONS

1) Some potential PPD risk factors could not be evaluated, 2) PPD was not diagnosed by psychiatrists, and 3) depressive symptoms at 6 months postpartum were considered PPD; however, definitions may vary.

CONCLUSIONS

Japanese women with multiple pregnancy may be regarded as a target group for follow-up and postpartum depression screening for at least 6 months during the initial postpartum period.

Sexual difference in 2nd-to-4th digit ratio among 1.5-year-old Japanese children: A cross-sectional study of Aichi regional adjunct cohort of the Japan Environment and Children's Study (JECS-A)

BACKGROUND

A sex difference in the second-to-fourth digit ratio (2D:4D, males < females) has been described in Japanese fetuses and children, and its possible links to autism spectrum disorders (ASDs) have been discussed. Accordingly, this sexual difference in representative neonates merits examination.

AIMS

This study aimed to examine 2D:4D measurements and sexual differences in Japanese toddlers aged 1.5 years.

STUDY DESIGN AND SUBJECTS

The digit lengths used to calculate 2D:4D were measured using an easy-to-use photography method. A total of 1045 JECS-A (the Aichi regional sub-cohort of the Japan Environment and Children's Study) children (males, 523; females, 522) aged 1.5 years were analyzed.

RESULTS

The mean ages for the males and females were 575.3 ± 13.1 and 575.9 ± 17.1 days, respectively. Histograms of left and right 2D:4D were normally distributed regardless of sex (left male, 0.909 ± 0.048; left female, 0.913 ± 0.049, d = 0.08; right male, 0.938 ± 0.055; right female, 0.937 ± 0.049, d = 0.02). Because of high dispersion in the data, t-tests did not support a significant sex difference in 2D:4D. Post-hoc statistical power was calculated as 0.124 and the effect size for the sex difference in 2D:4D was 0.036.

CONCLUSIONS

This study failed to confirm sexual differences in 2D:4D in 1.5-year-old Japanese children. This may be because digit measurement is difficult in this group, resulting in reduced effect sizes, or because rapid growth attenuates the in utero sexual dimorphism. This evidence is useful for the light it casts on the extreme male brain theory of ASDs.

Association of blood mercury levels during pregnancy with infant birth size by blood selenium levels in the Japan Environment and Children's Study: A prospective birth cohort

BACKGROUND

It is necessary to determine whether there are adverse health effects of prenatal exposure to long-term, low levels of mercury and selenium. However, there are limited that reports on the association between mercury levels by selenium levels and birth size. Therefore, we examined whether maternal mercury levels during pregnancy had any effect on infant birth size, and size, and whether selenium levels influenced this relationship.

OBJECTIVES

To examine the association between mercury and selenium levels during pregnancy with infant birth size.

METHODS

The Japan Environment and Children's Study is a prospective birth cohort conducted between 2011 and 2014. Total mercury levels and total selenium levels in maternal blood during the second and third trimesters were measured using Inductively Coupled Plasma-Mass Spectrometry. Birth weight and small-for-gestational-age were confirmed by medical records. Small-for-gestational-age was defined as birth weight below the 10th percentile according to standard percentile for gender, parity, and gestational age. Multiple linear and logistic regression analyses were used to examine the association between maternal mercury exposure and birth weight or small-for-gestational-age adjusted for confounders (including maternal age and body mass index pregnancy).

RESULTS

Overall, 15,444 pregnant women were included in this study. Median (inter-quartile range) of blood mercury and selenium levels were 3.66 (2.59-5.18) ng/g and 170.0 (158.0-183.0) ng/g, respectively. Compared to infants of mothers with the highest blood selenium level, those of mothers with the lowest blood selenium level had neither a significant birth weight increase (9 g, 95% confidence interval: -6, 25) nor a significant odds ratio for small-for-gestational-age (0.903, 95% confidence interval: 0.748, 1.089). Compared to infants of mothers with the lowest blood mercury level, those of mothers with the highest blood mercury level had neither a significant birth weight reduction (-12 g, 95% confidence interval: -27, 4) nor a significant odds ratio for small-for-gestational-age (0.951, 95% confidence interval: 0.786, 1.150). Compared to infants of mothers with the lowest quartile of maternal blood mercury level, all infants of mothers with the highest quartile of maternal blood mercury level had a reduced birth head circumference of 0.073 cm (95% confidence interval: -0.134, -0.011).

CONCLUSIONS

There was no association between maternal blood mercury levels and small-for-gestational-age and birth weight among 15,444 pregnant women. In a Japanese population, which has a relatively higher blood mercury level than reported in Western population, reduced birth size was not found to be associated with blood mercury levels, with the exception of birth head circumference.