Women in their early 30s have lower risk of giving birth prematurely

  • Forum
  • 04/11/2018

  • Mathieu-Robert Sauvé
Credit: Thinkstock

In 5 seconds

A multidisciplinary team finds that women aged 30 to 34 years have more healthy, full-term pregnancies than expectant mothers 10 years younger.

Mothers aged 30 to 34 years have more full-term pregnancies and healthier babies than those in the 20-to-24 age group. These are the findings of a new  epidemiological study led by an Université de Montréal researcher which looked at over 165,000 births in 32 Quebec hospitals from 2008 to 2011.

“We’ve always assumed that the risk of complications for the mother increases with age; we didn’t know there was a U-shaped curve in the age group of 30 to 34,” explained François Audibert, a professor of obstetrics and gynecology.

 Dr. Audibert coordinated the study, which was co-authored with four other researchers from UdeM, Université de Sherbrooke and the Institut national de la santé et de la recherche médicale de France: respectively, Florent Fuchs, Barbara Monet, Thierry Ducruet and Nils Chaillet.

While reluctant to venture an explanation of the sociological factors influencing the study’s findings, Dr. Audibert pointed out that the differences observed between later pregnancies and those occurring in a woman’s early 20s are significant.

Pregnancy complications rise with age

“Women who have their babies between the ages of 20 and 25 give birth prematurely more often than women who are 10 years older,” he said. On the other hand, pregnancy complications linked to health problems such as diabetes and hypertension rise proportionally with age.

Published in the January 2018 edition of PLOS One, the study has some surprising findings, especially concerning the rates of preterm birth (less than 37 weeks of pregnancy) and very preterm birth (less than 32 weeks). A graph clearly shows a U-shaped distribution of preterm birth risk among age groups. From 20 to 24 years, the risk of preterm birth is 6.8 per cent, whereas it drops to 5.7 per cent in the 30-to-34 age group, before rising again to 7.8 per cent in women over 40.

“While our intention is certainly not to recommend that women avoid bearing children earlier or later in life, we thought it was important to shine a light on this statistical anomaly, which reflects a little-known reality,” Dr. Audibert explained.

Delaying motherhood an increasing trend

The researchers based their epidemiological study on an analysis of data collected on 185,000 births in Quebec as part of QUARISMA, a research project conducted jointly by the Society of Obstetricians and Gynaecologists of Canada and Ste-Justine University Hospital Centre to assess the impact of professional training on the reduction of C-section rates.

“This study yielded a lot of data that were unrelated to the primary objective of our investigation but that were nonetheless relevant,” said Dr. Audibert, who mentioned that he was very pleased with the interdisciplinary nature of the project team, whose work was enriched by the presence of an anthropologist.

Factors such as multiple pregnancy, fetal malformation and intra-uterine fetal death were excluded from the sample to avoid skewing the data. A total of 165,195 births were included in the final study.

“Women are having their first child later in life, not only in Quebec, but in all developed countries,” said Dr. Audibert, who emigrated from France in 2003 to join UdeM's Faculty of Medicine. “Even though, biologically, they enter their peak reproductive years starting at the age of 20, there are many variables affecting women’s choice to delay motherhood.”

It is now up to sociologists to find an explanation for why women who give birth in their early 20s have more health problems that represent risk factors for their pregnancy – and in some cases, their baby – than expectant women in their mid-30s.

About the CHU Sainte-Justine Research Centre

CHU Sainte-Justine Research Centre is a leading mother-child research institution affiliated with Université de Montréal. It brings together more than 200 research investigators, including over 90 clinicians, as well as 350 graduate and post-graduate students focused on finding innovative means of prevention, faster and less invasive treatments, and personalized approaches to medicine. The Centre is part of CHU Sainte-Justine, which is the largest mother-child hospital in Canada and second most important pediatric hospital in North America.