# Social disadvantage is associated with impaired increase in salivary diurnal melatonin amplitude throughout pregnancy

## TL;DR

Pregnant women facing social disadvantage show reduced increases in melatonin levels, which could affect pregnancy health.

## Contribution

This study is the first to show that social disadvantage blunts the natural increase in melatonin during pregnancy.

## Key findings

- Salivary diurnal melatonin concentration increases during pregnancy but less so in those with high social disadvantage.
- High social disadvantage scores correlate with significantly lower melatonin amplitude and peak values.
- The increase in melatonin amplitude over pregnancy is reversed in socially disadvantaged participants.

## Abstract

Melatonin regulates daily rhythms and is important for maintaining a healthy pregnancy. Certain socioeconomic factors may affect melatonin release. This study evaluates whether the increase in melatonin with advancing gestation is associated with social disadvantage.

Data were prospectively collected from a socioeconomically diverse cohort of participants with singleton pregnancies (n = 921) at a Midwest academic center. Participants self-collected saliva every four hours over a 24-hour period once per trimester. Diurnal melatonin concentration was measured, and for each trimester, the maximum and mean diurnal melatonin concentration values were obtained. Cosinor-fitting was performed to obtain peak, mesor, and amplitude values, and melatonin profiles were also analyzed by calculating area under the curve. Participants were dichotomized by high and low social disadvantage score (SDS), and diurnal melatonin parameters were compared between participants with high and low SDS.

Mean diurnal melatonin concentration increased at an average rate of 0.19 pg/mL/week, and amplitude increased by 0.04 pg/mL/week. Participants with high SDS had significantly lower diurnal melatonin concentration amplitudes, means, mesors, and peaks than those with low SDS. Participants with high SDS had a 2.19 [95%CI = 1.94, 2.47] adjusted relative risk for low diurnal amplitude melatonin and had a smaller increase in diurnal melatonin amplitude over weeks of pregnancy than those with low SDS (−0.04 vs. 0.11 pg/mL/week, p<.001).

Average salivary diurnal melatonin concentration increases across pregnancy, but the degree of increase varies among pregnant participants and is associated with social disadvantage.

Statement of SignificanceDuring pregnancy, melatonin increases with gestational age and may promote placental homeostasis, fetal maturation, and uterine contractions. In this study, we evaluated whether the increase in melatonin with advancing gestation is modified by social disadvantage. We found that salivary diurnal melatonin concentration mean and amplitude increased as pregnancy progressed, but this increase was blunted or even reversed in participants with high social disadvantage scores. Future research should evaluate strategies to intervene, either via behavioral changes or pharmacologic therapy, to mitigate the negative impacts of social disadvantage on maternal melatonin rhythms.

During pregnancy, melatonin increases with gestational age and may promote placental homeostasis, fetal maturation, and uterine contractions. In this study, we evaluated whether the increase in melatonin with advancing gestation is modified by social disadvantage. We found that salivary diurnal melatonin concentration mean and amplitude increased as pregnancy progressed, but this increase was blunted or even reversed in participants with high social disadvantage scores. Future research should evaluate strategies to intervene, either via behavioral changes or pharmacologic therapy, to mitigate the negative impacts of social disadvantage on maternal melatonin rhythms.