Overview

• Families with three same-gender children have a 61% chance of a fourth boy and a 58% chance of a fourth girl, exceeding the expected 50:50 ratio.
• Researchers analyzed two U.S. longitudinal cohorts from 1956 to 2015, covering more than 146,000 pregnancies among 58,007 women.
• Maternal age correlates positively with same-gender clustering in offspring, with higher maternal age boosting the likelihood of consecutive same-sex births.
• Genome-wide association identified maternal gene variants such as NSUN6 on chromosome 10 and TSHZ1 on chromosome 18 as linked to predominantly female or male birth patterns.
• Study authors and independent experts emphasize the need for validation in diverse populations and mechanistic research to explain the statistical associations.