Older maternal age and higher plurality: What are the risks?

Abstract

BARBARA LUKE, MORTON B. BROWN, University of Miami, Coral Gables, Florida, University of Michigan, Biostatistics, Ann Arbor, Michigan OBJECTIVE: Since 1980, the percent of women ages 35 and older giving birth has increased threefold for singletons, fourfold for twins, and sixfold for triplets. Our objective was to evaluate the risks of complications with increasing maternal age and increasing plurality. STUDY DESIGN: The study population included pregnancies among women ages 25 and older from the 1995-2000 Birth Cohort Linked Birth/Infant Death Data Set for singletons and from the 1995-2000 Matched Multiple Birth Data Set for twins and triplets: 14,359,932 singleton (SI), 234,996 twin (TW), and 11,240 triplet (TR) pregnancies. Maternal age groups included ages 25-29, 30-34, 35-39, and 40C. Adjusted odds ratios (AORs) and 95% confidence intervals were calculated to evaluate the risk 1) with increasing maternal age within each plurality, with ages 25-29 as the reference group; and 2) with increasing plurality within each age group, with singletons as the reference group. RESULTS: Within each plurality, increasing maternal age was associated with significantly higher risks of diabetes, chronic hypertension, pregnancyassociated hypertension, and eclampsia, but for multiples, lower risks of tocolysis (at 40C, SI-AOR 1.00 vs TW-AOR 0.67, TR-AOR 0.66), birth less than 29 weeks (at 40C, SI-AOR 1.62 vs TW-AOR 0.72, TW-AOR 0.52), and infant mortality (at 40C, SI-AOR 1.44 vs TW-AOR 0.69, TW-AOR 0.29). Within age groups, increasing plurality was associated with significantly higher risks of nearly all complications, often magnifying those associated with increasing maternal age. For example, compared to singletons, the risk of eclampsia among women ages 25-29 was TW-AOR 3.19, TR-AOR 4.21 versus TW-AOR 3.62, TR-AOR 6.78 among women ages 40C. CONCLUSION: Older maternal age and higher plurality are each associated with increasing risks for many pregnancy complications. Despite this, compared to their younger counterparts, women ages 40C pregnant with multiples had the lowest risks of tocolysis, early preterm delivery, and infant mortality.