Women who experienced severe complications during pregnancy were more than twice as likely to die at any time after their last pregnancy, including post partum and beyond, based on data from more than 1 million women.
“Current data suggest that up to 88% of maternal deaths are preceded by severe maternal morbidity,” but the long-term risk of mortality and the effect of severe maternal morbidity has not been well studied, wrote U. Vivian Ukah, MPH, PhD, of McGill University, Montreal, and colleagues.
In a longitudinal cohort study published in Obstetrics & Gynecology, the researchers identified 1,229,306 pregnant women who delivered in Quebec between 1989 and 2016.
The primary outcome of in-hospital mortality after the last pregnancy, either post partum (within 42 days of delivery) or long term (43 days to 29 years after delivery).
Overall, 2.9% of the study population experienced severe maternal morbidity, with an associated mortality rate of 0.86 per 1,000 person-years versus 0.41 per 1,000 person-years in women without severe maternal morbidity. The median time to death for women with severe maternal mortality was 6.8 years, compared with 151 years for those without severe maternal morbidity.
The death rate at any time after delivery, post partum and beyond, was twice as high among women with severe maternal morbidity. The morbidities most often associated with long-term mortality after 42 days were severe cardiac complications (hazard ratio, 7.00), acute renal failure (HR, 4.35), and cerebrovascular accidents (HR, 4.03).
However, the mortality risk following severe maternal morbidity decreased over time, the researchers noted. Severe maternal morbidity was associated with 6.73 times the mortality risk, compared with no morbidity, during the period from 43 days to 11 months, but this difference dropped to 1.91, 1.77, and 1.18 times the risk, compared with no comorbidity, at 1-4 years, 5-9 years, and 10-29 years, respectively.
The study findings were limited by several factors, including the inability to prove causality, the use of only in-hospital mortality data, and the potential for missed cases that fell outside the Canadian Perinatal Surveillance System definition of severe maternal morbidity, the researchers noted.
However, the results suggest that identifying severe maternal morbidity may help identify women at risk for postpartum and long-term premature mortality. “Women with severe maternal morbidity may benefit from continued surveillance and preventative interventions to reduce the risk of premature mortality,” they concluded.
Increased morbidity rates drive need for research
“In this retrospective longitudinal cohort study of over 1.2 million women delivering in Quebec between 1989 and 2016, Dr. Ukah and her colleagues demonstrated the association between severe maternal morbidity [SMM] and an accelerated risk of mortality beyond the postpartum period, compared with women who do not experience SMM,” Rachel Humphrey, MD, a maternal-fetal medicine specialist at Advent Health in Orlando, said in an interview. “This study is important as there has been a steady increase in SMM in recent years. In the United States, the CDC reports that SMM affected more than 50,000 women in 2014 alone. Across multiple countries the decline in overall health of women giving birth is felt to contribute to SMM. As the rates of preexisting conditions such as maternal obesity, hypertension, diabetes, and advanced age increases, we can assume that SMM will increase as well. This study clearly depicts the association between SMM and maternal death at 43 days to years after the complicated delivery. We can assume that, as SMM increases, so will the risk of mortality beyond the postpartum period for these women who initially survive their serious pregnancy complication.”
Dr. Rachel Humphrey
Dr. Humphrey said that, in some respects, the study results are to be expected. “It is logical to assume that a patient with a life-threatening issue at delivery such as severe cardiac complications, acute renal failure and cerebrovascular accident would be at higher risk for long-term morbidity and mortality. This study also adds to the large body of evidence linking socioeconomic deprivation with SMM. But there were unexpected findings in this study. I did not expect certain types of SMM to be associated with an increased risk of death years after the event.For example, hysterectomy at delivery carried a hazard ratio of 3.54 for death at 5-9 years after the event. The association between severe hemorrhage and fully adjusted hazard ratio was similarly increased at 2.96 [2.37-3.71].”
More screening and prospective studies needed
“Recognizing the association between SMM and accelerated long-term risk of mortality is a first step in determining what interventions might improve health and longevity in women who experience SMM,” said Dr. Humphrey. “With the absence of prospective studies, it still is logical to assume that close medical follow-up and lifestyle interventions are appropriate in this population. Screening for and actively managing chronic conditions such as diabetes, dyslipidemia, and hypertension seems appropriate for these patients.”
As for further research, “I am interested to know through prospective clinical trials if specific health maintenance screens and interventions would have a positive impact on the life expectancy of survivors of SMM,” said Dr. Humphrey. “I applaud this team for providing data up to 27 years after an obstetric complication, and I am interested to see if Dr. Ukah and her team will continue their research to determine if there is a ‘second peak’ in mortality in the survivors of SMM when they are elderly. Finally, I would be interested to see more detailed data from this team on the associations between socioeconomic deprivation and short- and long-term mortality for women in their study. This information may help further fuel the movement toward social changes to maximize the health of the women and families we serve.”
The study was supported by the Heart & Stroke Foundation of Canada and awards to the lead author and others from the Fonds de recherche du Québec-Santé. The researchers and Dr. Humphrey had no financial conflicts to disclose.