Contemporary risks of maternal morbidity and adverse outcomes with increasing maternal age and plurality.

OBJECTIVE: To evaluate the risks of pregnancy complications and adverse outcomes associated with increasing maternal age and higher plurality.
DESIGN: Population-based, historic cohort study.
SETTING: US birth certificates and infant death certificates. PATIENT(S): Live births of > or =20 weeks gestation between 1995-2000: 22,991,306 singleton, 316,696 twin, and 12,193 triplet pregnancies. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Pregnancy-associated hypertension, incompetent cervix, tocolysis, premature rupture of membranes, excessive bleeding at delivery, delivery <29 weeks, and infant death. RESULT(S): Compared to singletons, the risks for all adverse outcomes among multiple pregnancies were significantly elevated, and were highest for tocolysis, delivery <29 weeks, and infant mortality. Within pluralities, increasing maternal age was associated with significantly higher risks of pregnancy-associated hypertension, excessive bleeding, and incompetent cervix, but for twin and triplet pregnancies, significantly lower risks for tocolysis (ages > or =40, singleton adjusted odds ratio [AOR] 0.97, twin AOR 0.67, triplet AOR 0.72), delivery <29 weeks (ages > or =40, singleton AOR 1.55, twin AOR 0.72, triplet AOR 0.52), and infant mortality (ages > or =40, singleton AOR 1.34, twin AOR 0.71, triplet AOR 0.42). CONCLUSION(S): Older maternal age and higher plurality are each associated with increasing risks for many pregnancy complications, but with significantly lower risks of tocolysis, early preterm birth, and infant mortality.