Maternal Hypertension, Diabetes, and Preterm Birth Risk among Infants with Trisomy 21 in Texas, 1999-2018.

BACKGROUND:The preterm birth rate among infants with trisomy 21 is more than twice the rate among the general population. Maternal hypertension and diabetes are established risk factors for preterm birth in the general population; however, their impact on pregnancies of infants with trisomy 21 is unknown. This study aimed to evaluate the association between maternal hypertensive disorders/diabetes and preterm birth among infants with trisomy 21. METHODS:We utilized data from the Texas Birth Defects Registry for deliveries between 1999 and 2018 (n = 9355). We conducted Poisson regression to estimate crude and adjusted risk ratios for preterm birth associated with any maternal hypertension and any diabetes, and their subtypes (pregestational, gestational). We also evaluated the risk associated with exposure to both (co-occurring) conditions compared to neither. Stratified analyses were conducted by racial/ethnic subgroups, preterm subtypes (< 32 weeks and 32-36 weeks), and presence/absence of congenital heart defects as part of secondary analyses. RESULTS:We found that maternal hypertension and diabetes were associated with 50% and 21% higher risk for preterm birth, respectively, while the presence of both conditions versus neither was associated with a 71% higher risk. The association with hypertension was much stronger for delivery at < 32 weeks aRR 2.60 (95% CI 1.83, 3.70) than for delivery at 32-36 weeks aRR 1.46 (95% CI 1.28, 1.66). CONCLUSIONS:Our findings shed light on the role of maternal hypertension and diabetes in preterm birth risk among infants with trisomy 21, particularly when both conditions co-occur and for extremely to very preterm birth.