Sibling Recurrence Risk of Non-Chromosomal Birth Defects: A Population-Based Study in Florida, 2000-2019

To estimate sibling recurrence risk for non-chromosomal birth defects using statewide, population-based data.

We analyzed data from the Florida Birth Defects Registry to identify singleton siblings born 2000-2019 with any of 43 non-chromosomal birth defects. Multivariable logistic regression was used to estimate adjusted odds ratios (ORs) and 95% confidence intervals (CIs) for the association between birth defect occurrence in the older sibling (exposure) and in the younger sibling (outcome). Two analytic scenarios were considered: (1) any birth defect in the younger sibling, and (2) concordant recurrence, defined as a defect within the same body region. Models adjusted for maternal sociodemographic and perinatal characteristics from linked birth certificate and hospital discharge data.

The study population included 1,372,831 sibling pairs, of which 29,611 (2.2%) had an older sibling with a birth defect. Among sibling pairs in which the older sibling was affected, 4.8% of younger siblings also had a birth defect. Younger siblings had over twice the odds of having any birth defect if their older sibling was affected compared to those with an unaffected older sibling (adjusted ROR: 2.1, 95% CI: 2.0-2.2). Recurrence risk varied by body system, with the highest adjusted odds of concordant recurrence observed for orofacial defects (adjusted ROR: 18.7, 95% CI: 13.9-25.1).

Our findings provide contemporary, system-specific estimates of sibling recurrence that may inform family counseling, preconception care, and clinical decision-making.