In the present study, we observed an association between antenatal depression symptoms and low birth weight. Women with significantly higher EPDS score were more likely to have low birth weight infants. This association persisted after adjusting for confounders, including pre-pregnancy BMI, neonate gender, maternal age, degree of education, high-risk women and parity. Findings in previous studies regarding the association between antenatal depression and low birth weight remain inconsistent and inconclusive. This inconsistent may result in different sample size, confounders adjusted, depression symptoms measurements.
In order to facilitate large-scale epidemiological investigation, EPDS was used as the depression symptom measurement. Although clinician administered diagnostic instruments are the gold standard, they are time-consuming and staff intensive to administer . Conversely, patient-rated screening instruments are easier to use. Because adverse obstetrical outcomes can have significant, long-term, negative health impacts, it would be useful to screen depression at the initial obstetric visit predicts the risk of adverse pregnancy outcomes. EPDS is the only instrument designed to exclude somatic depressive symptoms that are also common symptoms of pregnancy. The effectiveness in antenatal women has been verified by previous studies with excellent reliability[11, 13]. Additionally, a Chinese translation of the EPDS has been demonstrated to have good reliability and validity. We focused on depression symptoms rather than clinically diagnosed depression. The results showed that depression symptoms during pregnancy still had a positive effect on LBW after adjusting several confounders.
Our findings are in keeping with those studies in America black women with large sample size. Some studies[18-20]agreed that depression symptoms are one of the causes of LBW, especially in Neggers’s study, depression symptoms rather than depression was concerned. In consistent with our results, Negger et al found that women who are depressed during pregnancy are at increased risk of giving birth to low birth weight(AOR =1.4, 95% CI : 1.1-1.7), in which the measure of depression was conducted by the Center for Epidemiologic Studies Depression Scale (CES-D). Although the depression measure was not the same, we both concerned about the depression symptoms rather than the diagnosis of depressive disorder. However, our attention is paid on the second trimester, suggesting that the depressive stage should be concerned and controlled in earlier pregnancy. Additionally, EPDS is more convenient to use in crowd. Evans's study used EPDS to screen depression symptoms at 18 and 32 weeks respectively in 13,194 British women, showed that depression symptoms at 18 weeks increased the risk of LBW, but the risk was disappeared after adjusting smocking . This study mainly focused on white women. We have noticed that the results in white women or in multiple races are more inconsistent, and the correlation in many studies’ tend to insignificant. Whether the association between depression and LBW are affected by race, socioeconomic level remains to be further explored.
Relevant studies from China and with large sample size are limited. Yang's case-control study in Wuhan found that antenatal depression or anxiety is not significantly associated with LBW, but individuals with antenatal depression combined with anxiety are at a higher risk of LBW . However, the self-designed questionnaires, rather than a typical screening scale were used in the study for measuring depressive states. Existing reviews tend to suggest that depression, especially in early pregnancy, may be a risk factor for LBW[23, 24].Our study added a support to this view, but more evidence is needed.
And we found young mothers (<25 years of age) seem to be more susceptible to antenatal depression. This may be related to the anxiety or depression of younger pregnant women who are lack of acknowledgement about pregnancy. There are also studies showing that depression has the tendency to occur in younger pregnancy women . We also found that antenatal depression symptoms were more common among temporary residents than permanent residents. This may be related to immigration factors, such as dialect, social isolation, life adaption, unfair opportunities, economic problems or the realization of health care .
There are several mechanisms that have been proposed to underlie the association between antenatal depression and neonatal outcomes. The hypothesis which proposed that the association is mediated by the hypothalamic-pituitary- adrenocortical axis, which stimulates the release of stress hormones such as cortisol and catecholamines, has been most extensively investigated . Emerging research suggests that antenatal maternal cortisol mediates the association between self-reported depression and gestational age at birth and fetal growth rate .Other possible mechanisms include adverse health behaviors associated with depression. Depressed women are more likely to smoke and drink during pregnancy than non-depressed women.
There are limitations in this study. Firstly, in the present study, we just made the depression symptoms measure at the second-trimester, which might fail to detect the trend of changes throughout the entire duration of pregnancy. Depression is often a lifelong relapsing and remitting condition. Therefore, some depression cases occurred at the third-trimester might be misclassified into the non-exposed group, in which case the effect size of antenatal depression on LBW might be diluted. Therefore, in this study, the adverse effects of depression on low birth weight may be more severe. Secondly, potential confounding bias cannot be eliminated completely. Due to lacking the history of low birth weight delivering, this study can’t adjust them. In addition, various complications during pregnancy may not be adjusted, but this study adjusted the corresponding surrogate indicators, namely whether pregnant women with high risk. This limitation may mask the association between depression and preterm birth, thereby underestimating the degree of association.