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

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.

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.

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).

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.

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.