Maternal age over 40 is associated with an increased risk of preterm birth

Pregnant mothers aged 40 and over may have an increased risk for preterm birth, regardless of confounding factors, according to a study published January 31, 2018 in the open-access journal PLOS ONE by Florent Fuchs from CHU Sainte Justine, Canada and colleagues.

Maternal age at pregnancy has been increasing worldwide and so has the risk for preterm birth. However, the association between maternal age and preterm birth remains a topic of ongoing research.

Fuchs and colleagues sought to investigate the impact of maternal age on preterm birth in a large cohort. The researchers analyzed the previously-collected data from the QUARISMA randomized controlled trial, which had taken place in 32 hospitals in Quebec, Canada, from 2008 to 2011.

The researchers identified five different age groups among the 165,282 pregnancies included in the study, and compared them based on maternal characteristics, gestational and obstetric complications, and risk factors for prematurity. Some of the known risk factors identified more commonly in older mothers (40 and over) included placental praevia, gestational diabetes, medical history, use of assisted reproduction technologies and occurrence of an invasive procedure. On the other hand, nulliparity, past drug use and smoking were more prevalent in younger mothers (30 and under).

Even after adjusting for confounding factors, the researchers found that advanced maternal age (40 or over) was associated with preterm birth. Meanwhile, a maternal age of 30-34 years was associated with the lowest risk of prematurity.