Canadian research finds older mothers at higher risk for childbirth complications

Choosing to have kids at an older age is an increasing trend in high-income countries. In parallel, severe maternal morbidity – childbirth complications resulting in short or long-term health consequences to the mother and possibly the baby – are increasing as well.

A group of scientists from The Hospital for Sick Children (SickKids), Sunnybrook Health Sciences Centre and the Institute of Health Policy, Management and Evaluation at the University of Toronto (IHPME) wanted to investigate whether there’s an association between increased maternal age and a higher risk for severe maternal morbidity.

They analyzed data from 3.1 million pregnancies across Canada and revealed mothers under the age of 19 or over 30 were at an increased risk for severe maternal morbidity and mortality, with women over the age of 44 being at the greatest risk compared to mothers aged 20 to 24 who are at the lowest risk. The findings were published in JAMA Network Open on August 23, 2019.

Severe maternal morbidity is a broad term encompassing many different childbirth-related complications such as eclampsia, blood loss requiring transfusion and sepsis. While maternal mortality has decreased in developed countries over the past 25 years, evidence suggests severe maternal morbidity is rising across Canada.

“Over the past two decades, there has been a trend towards increasing maternal age in many high-income countries. In parallel, we’re also seeing a rise in severe maternal morbidity. We wanted to investigate whether there was an association between these two factors,” says the study’s lead author, Dr. Kazuyoshi Aoyama, Anaesthesiologist in the Department of Anaesthesia and Pain Medicine and Associate Scientist in the Child Health Evaluative Sciences program at SickKids.

Using data from the Canadian Institute for Health Information (CIHI), the researchers confirmed severe maternal morbidity is on the rise in Canada. There was a 9.8 per cent increase over the study period from 17.2 incidents per 1,000 deliveries in 2004-05 to 18.9 incidents per 1,000 deliveries in 2014-15. This trend coincided with an increase over time in maternal age and in the proportion of pregnancies to older mothers.

Extremes of maternal age were associated with an increased risk for severe maternal morbidity and mortality, with women over the age of 44 being at the greatest risk, in comparison to those aged 20 to 24. The researchers say the typical physiological changes from aging may make older mothers more vulnerable to the significant physiological impacts of pregnancy. For example, increased blood pressure and lower cardiac output can occur as natural effects of aging and, in pregnant women, they may also contribute to placental insufficiency, a pregnancy complication where the placenta is unable to deliver an adequate supply of nutrients to the fetus, which can impact fetal growth.

“The increased risk of severe maternal morbidity with increasing maternal age in Canada should be an important consideration for prospective parents,” says Aoyama, who is also an Assistant Professor in the Department of Anaesthesia at the University of Toronto. “But this finding is also a clear sign to public health professionals and clinicians that early interventions are needed to detect acute complications and prevent their progression in high-risk mothers.”

Other risk factors for severe maternal morbidity included pre-existing health conditions, income level and the province of residence. The researchers hope to build on this work by investigating the health of infants born to mothers who experienced severe maternal morbidity.

This work was supported by the Canadian Institutes of Health Research. It is an example of how SickKids, Sunnybrook and IHPME are making Ontario healthier, wealthier and smarter.