Maternal stress and sex ratio at birth in Sweden over two and a half centuries: a retest of the Trivers-Willard hypothesis.

ABSTRACT:

Study question

Is there a negative relationship, as predicted in the Trivers-Willard hypothesis (TWH), between the intensity of maternal stress and sex ratio at birth (SRB)?

Summary answer

Using a comprehensive data set with multiple indicators of maternal stress, most measures of stress show no statistically significant association with SRB over a period spanning 243 years, indicating no support for the TWH.

What is known already

Evolutionary biologists have proposed a widely discussed hypothesis that women in poor and stressful conditions during pregnancy are more likely to give birth to girls, and exposure to stressful events may therefore lead to a reduction in sex (male-to-female) ratio at birth. The empirical evidence so far is mixed.

Study design, size, dura

SUBMITTER: Wu H 

PROVIDER: S-EPMC8648295 | biostudies-literature | 2021 Sep

REPOSITORIES: biostudies-literature