The Maternal Age Cut-Off for an Increase in Composite Adverse Outcomes.

Objective: To investigate whether there is a specific maternal age cut-off at which there is an increase in maternal and neonatal adverse outcomes.

Methods: A retrospective study comparing maternal and neonatal outcomes between nulliparous women of different ages. The receiver operating characteristic model with the Youden index was used to find the best age cut-off using cesarean delivery (CD) and composite adverse outcomes. A multivariable logistic regression analysis was calculated after adjusting for smoking, induction of labour, epidural use, hypertensive disorders, gestational diabetes, and birth weight.

Results: The study included 11 343 nulliparous women. Age 28 years was found to be the cut-off age at which we found a significant increase in adverse outcomes. Women older than age 28 years had a higher risk of CD than women younger than 28 years (35.7% vs. 21.3%, P < 0.0001). They were also more likely to deliver prematurely (11.9% vs. 7.9%; P < 0.0001) and had higher rates hypertensive disorders (2.3% vs. 1.1%; P < 0.0001) and gestational diabetes mellitus (0.4% vs. 0.1%; P = 0.001). Furthermore, their babies were more likely to be growth restricted (1.1% vs. 0.3%; P < 0.0001). There were no differences in the rates of induction of labour or macrosomia. After adjusting for confounders, we found that women older than 28 years had higher risks of CD and adverse outcomes than younger women (aOR 1.9 [95% CI 1.744-2.1] and aOR 1.6 [95% CI 1.6-1.77], respectively).

Conclusion: Increasing maternal age is independently associated with adverse maternal and neonatal outcomes with an age cut-off of 28 years. Women older than age 28 years are at higher risk for composite adverse outcomes than younger women.