Heart Disease & Pregnancy

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Obesity exacerbates the risk of heart complications in pregnant women with heart disease.
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Because maternal and fetal health are intertwined, health complications in fetuses and newborns are also more common in women with heart disease.

Researchers at the Toronto General Hospital Research Institute have found that women with heart disease who have obesity are more likely to experience cardiac complications during pregnancy.

During pregnancy, a mother’s heart works harder than usual to support the growing baby. This extra stress on the heart can lead to complications, especially in those women with pre-existing heart conditions.

Obesity can also put strain on the heart and blood vessels; however, no previous study has explored the impact on pregnancy for women with pre-existing heart disease who also have obesity. TGHRI Clinician Investigator Dr. Candice Silversides and postdoctoral researcher Dr. Birgit Pfaller led a decade-long prospective cohort study to examine the effect of maternal obesity on pregnancy complications in 600 women with heart disease.

Over the study period, women with heart disease had 790 pregnancies. Researchers tracked heart complications (e.g., heart failure, cardiac arrest, arrhythmias or stroke) during pregnancy and up to 6-months after giving birth.

The results showed that in women with heart disease, obesity increases the risk for heart complications almost twofold. The rate of heart complications during pregnancy among women with obesity was 23%, compared to 14% among women who were not obese.

Moreover, the researchers found that obesity was an independent predictor of cardiac complications, meaning that women with obesity are at higher risk for adverse heart events during pregnancy regardless of their heart condition.

The study also tracked other types of complications such as pre-eclampsia—high blood pressure caused by pregnancy. The study found that 70% of the women with heart disease that developed pre-eclampsia were overweight or obese.

“For young women with heart disease, understanding the risks of pregnancy and optimizing health prior to pregnancy are very important aspects of cardiac care,” says Dr. Silversides.  “The findings from this study, which identify a modifiable risk factor, are important to discuss when counselling women with heart disease about pregnancy.”


This study was supported by the Allan E. Tiffin Trust and UHN Foundation, including a donation from Mrs. Josephine Rogers. Dr. Silversides is supported by the Miles Nadal Chair in Pregnancy and Heart Disease.

Pfaller B, Siu SC, D'Souza R, Wichert-Schmitt B, Kumar Nair GK, Haberer K, Maxwell C, Silversides CK. Impact of Obesity on Outcomes of Pregnancy in Women With Heart Disease. J Am Coll Cardiol. 2021 Mar 16;77(10):1317-1326. doi: 10.1016/j.jacc.2021.01.010.


(L-R) TGHRI Clinician Investigator Dr. Candice Silversides and postdoctoral researcher and first author Dr. Birgit Pfaller.