Association between very advanced maternal age and adverse pregnancy outcomes: a cross sectional Japanese study

While several studies have demonstrated the increased risk of pregnancy complications for women of advanced age, few studies have focused on women with very advanced age (≥ 45), despite the increasing rate of pregnancy among such women. Furthermore, how such risks of increase in age differ by maternal characteristics are also poorly understood. Thus, we aimed to clarify pregnant outcomes among women with very advanced age and how the effect of age differs by method of conception and parity.

We used the national multicenter Japan Society of Obstetrics and Gynecology perinatal database, including 365,417 women aged 30 years or older who delivered a singleton between 2005 and 2011. We divided women into four groups based on age (years): 30-34, 35-39, 40-44, and ≥45, and compared risk of adverse birth outcomes between the groups using Poisson regression. Effect modification by parity and use of assisted reproductive technology (ART) was also evaluated.

Compared with women aged 30-34 years, women aged 45 or older had higher risk of emergency cesarean delivery [adjusted risk ratio (aRR): 1.77, 95% confidence interval (95% CI): 1.58-1.99], preeclampsia (aRR: 1.86, 95% CI: 1.43-2.42), severe preeclampsia (aRR: 2.03, 95% CI: 1.31-3.13), placenta previa (aRR: 2.17, 95% CI: 1.60-2.95), and preterm birth (aRR: 1.20, 95% CI: 1.04-1.39). The effect of older age on risk of emergency cesarean section, preeclampsia, and preterm birth were significantly greater among those who conceived naturally compared to those who conceived by ART. The effect on emergency cesarean section was stronger among primiparous women, whereas the risk of preeclampsia associated with older age was significantly greater among multiparous women.

Very advanced maternal age (≥ 45) was related to greater risk for adverse birth outcomes compared to younger women, especially for maternal complications including cesarean section, preeclampsia, severe preeclampsia, and placenta previa. The magnitude of the influence of age also differed by conception method and by parity.