Everyone tells expectant parents it’s a “50-50 chance,” but turns out biology class might have oversimplified things. Harvard researchers found that, after analyzing over 146,000 pregnancies, some families may actually have weighted odds—meaning that if the first two children are girls, the chances are high that the next one will be as well.
Younger moms especially skew towards having all boys or all girls, thanks to factors like vaginal acidity and shorter menstrual cycles that influence sperm survival. With the U.S. fertility rate dropping to a record low (below 1.6 children per woman last year), the stats matter—so maybe hold off painting the nursery pink or blue just yet.
