Association of Lower Socioeconomic Position in Pregnancy with Lower Diurnal Cortisol Production and Lower Birthweight in Male Infants

Abstract

Purpose: Low maternal socioeconomic position (SEP) has been associated with adverse neonatal outcomes, including preterm birth, low birthweight, intrauterine growth restriction, and infant mortality. A key biological mechanism that has been proposed to explain this association is hypothalamic-pituitary-adrenal (HPA) activity, yet the association between SEP and HPA activity in pregnancy has received little attention. In this study we aimed to examine the associations between SEP and 2 forms of maternal cortisol regulation-diurnal slope and wakening response-across pregnancy. Furthermore, we aimed to assess whether these associations differed by the sex of the fetus.

Methods: A total of 217 pregnant women aged 18 to 40 years with singleton pregnancies participated. Women were excluded from participating if they were aged <18 or >40 years and if they were at risk for maternal or obstetric complications. Women provided information on socioeconomic characteristics of adults contributing to the participants' household to compute a Hollingshead Four Factor Index of Social Status score of SEP. Women provided salivary cortisol samples on awakening, 30 minutes after wakeup, and at bedtime, at 3 times over pregnancy and once 30 days postpartum to calculate the diurnal slope and cortisol awakening response (CAR). Using linear regression analyses, we examined the relationships between maternal SEP and maternal diurnal slope and CAR. We explored the relationships between maternal SEP and cortisol by fetal sex using linear regression analyses. We also explored links between maternal SEP, maternal cortisol, and infant birth outcomes.

Findings: Women of lower SEP displayed smaller awakening responses and less change over the day compared with women of higher SEP. SEP was significantly associated with attenuated diurnal slope only among women carrying female fetuses, whereas for CAR, the association between SEP and attenuated CAR was significant only for women carrying male fetuses. Lower SEP was associated with decreased birthweight, and this association was partially explained by maternal HPA activity in pregnancy.

Implications: Women of low SEP displayed attenuated HPA activity across the perinatal period, and patterns varied by fetal sex and cortisol metric. Findings are in need of replication. More research is needed to understand the links between SEP, HPA activity, and neonatal health.

Keywords: cortisol; pregnancy; sex; socioeconomic position.

Figure 1

Socioeconomic position^a and maternal diurnal cortisol differs by fetal sex Note: ^aSEP = Socioeconomic Position (measured using the Hollingshead Four Factor Index of social position). PP= postpartum. Cortisol values were log transformed for analyses. Raw values are presented in the figure.