Interaction between maternal thyroid hormone levels and pregnancy-related anxiety on birth outcomes-A birth cohort...

Maternal thyroid hormone levels and pregnancy-related anxiety (PRA) influence pregnancy outcomes. However, their potential interactive effects on birth outcomes remain poorly understood.

This large prospective cohort study was conducted from May 2013 to September 2014 at the Ma'an Shan Maternal and Child Health Center. A total of 1798 mother-infant pairs from the Ma'an Shan Birth Cohort (MABC) participated. PRA assessments and thyroid hormone level tests were performed during the first trimester (1-13 weeks), second trimester (14-27 weeks), and third trimester (after 28 weeks) of gestation.

Second- and third-trimester free thyroxine (FT4) levels were negatively associated with birth weight and reduced large for gestational age (LGA) risk. A high - level FT4 trajectory during pregnancy was also negatively related to birth weight. PRA in the third trimester increased the risk of small for gestational age (SGA) infants, and a high - level PRA trajectory raised LGA risk. Interaction analyses showed that in non-anxious pregnant women during the second and third trimesters, higher FT4 levels significantly reduced LGA risk (OR = 0.90, 95 % CI: 0.83, 0.98; OR = 0.93, 95 % CI: 0.88, 0.99). In women with persistent high anxiety, persistent low FT4 was associated with increased LGA risk (OR = 1.48, 95 % CI: 1.04, 2.10).

Gestational thyroid hormone levels and PRA may interact to influence birth outcomes. Specifically, persistently low thyroid hormone levels combined with chronic high anxiety during pregnancy could increase the risk of LGA infants.