Effect of Parity and Advanced Maternal Age on Obstetric Outcome

Abstract

Increasing numbers of women are becoming pregnant later in life, and there is concern over the potential risk of such pregnancies to the health of both the mother and the fetus. Whether or not advanced maternal age is associated with various obstetric complications is controversial, and the effect of parity on risk is unclear. This retrospective cohort study examined the role of parity on obstetric outcomes in pregnant women aged 40 years or older. The authors obtained data from the databases of two university hospitals and evaluated various known obstetric risk factors in a cohort of 16,427 singleton pregnancies delivered between January 1998 and December 2001. Of the 15,727 pregnancies (95.7%) that satisfied the inclusion criteria, 606 (3.9%) were in women aged 40 years or older. Nulliparous women age 40 or more were more likely than younger nuliparas to have a body mass index (BMI) >25 (28.5% versus 21.3%; P < .014), pregestational diabetes mellitus (1.0% versus 0.1%; P < .003), and chronic hypertension (2.0% versus 0.3%; P < .001), as well as gestational diabetes, preeclampsia, antepartum and postpartum hemorrhage, cesarean birth, delivery before 37 weeks, and spontaneous preterm delivery before 37 weeks. However, nulliparous women in both age groups had the same incidence of preterm birth, labor before 32 weeks of pregnancy, perinatal mortality rate, incidence of small for gestational age neonates, and low Apgar scores. Older multiparas were more likely than younger multiparas to have antepartum and postpartum hemorrhage and delivery before 37 weeks. Birth weights were similar between the two groups but older multiparas were more likely to have an infant with an Apgar score less that 7 at 1 minute. Multiple logistic regression analysis for variables such as smoking status, high BMI, antepartum hemorrhage, hypertension, and preexisting and gestational diabetes, showed that, in nulliparous women advanced age was associated only with cesarean delivery (49.0% versus 20.8%, P < .001), preterm birth before 37 weeks (16.0% versus 7.0%, P < .001), spontaneous preterm labor before 37 weeks (5.5% versus 1.0%, P < .001), and low birth weight (15.5% versus 7.1%, P < .001). In multiparous women, advanced age was associated with cesarean delivery (27.3% versus 15.7%, P < .001) and preterm birth before 37 weeks (9.6% versus 6.7%, P < .024). These findings indicate that several important obstetric outcome parameters are influenced by parity in women aged 40 years or older. Advanced age is associated with adverse obstetric outcomes primarily in nulliparas, although both nulliparous and multiparous older women are at increased risk of preterm birth.