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2mo ago

Harvard Study Links Maternal Age and Genes to Same-Sex Birth Patterns

Drawing on data from 58,000 U.S. mothers the study suggests biological changes in older women may skew birth sex ratios pending broader validation

Une étude menée par des chercheurs de l’université d’Harvard a révélé que, en fonction de certains facteurs, les femmes avaient plus de chances de n’avoir que des enfants du même sexe.
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Overview

  • Harvard team led by Siwen Wang analyzed data from the Nurses' Health Study covering over 58,000 U.S. mothers who gave birth between 1956 and 2015.
  • They found that families with three sons have a 61% chance of a fourth son and those with three daughters a 58% chance of a fourth daughter.
  • Women aged 29 or older at first birth showed a roughly 13% higher likelihood of having children all of one sex compared with those younger than 23.
  • Potential biological mechanisms include age-related changes in menstrual cycle length and vaginal pH that may favor X- or Y-bearing sperm.
  • Genome analysis linked NSUN6 variants to all-girl families and TSHZ1 variants to all-boy families, though the findings require replication in more diverse cohorts.