Obesity before pregnancy predicts future heart health

Body mass index, pregnancy complications, and cardiovascular risk.


A new study from Northwestern Medicine found that being overweight or obese before or during pregnancy is the main reason some women develop heart problems later in life. While previous research connected pregnancy issues like preeclampsia and gestational diabetes to heart disease risk, this study shows that obesity before pregnancy is the real cause.

Before this study, researchers were uncertain whether obesity or pregnancy complications significantly impacted heart disease risk in the years following pregnancy. This extensive study, involving many locations and a diverse group of participants, is the first to clarify this question. 

It concluded that pre-pregnancy obesity is responsible for pregnancy complications and future heart disease risk. The study followed participants, half overweight or obese, from the start of their first pregnancy until several years after giving birth.

Corresponding author Dr. Sadiya Khan, the Magerstadt Professor of Cardiovascular Epidemiology at Northwestern University Feinberg School of Medicine and a Northwestern Medicine physician, said, “We demonstrate, for the first time, that adverse pregnancy outcomes are primary indicators and not the root cause of future heart health. This means that pregnancy reveals the risk for heart disease that is already there.”

The study’s findings will be published on October 10 in the Circulation Research journal.

For this study, data came from the nuMoM2b Heart Health Study, which tracked 4,216 first-time pregnant women from the beginning of their pregnancies to an average of 3.7 years after giving birth. When they started the study, the average age of these women was 27 years old. 

About 53% had an average body mass index (BMI), 25% were overweight, and 22% had obesity. The study found that compared to those with a normal BMI at the start of pregnancy, those who were overweight or obese had a higher risk of developing pregnancy-related high blood pressure conditions.

The researchers aimed to study the connections between being overweight before pregnancy, pregnancy-related high blood pressure issues, other pregnancy problems, and heart health years after childbirth.

They thought these pregnancy problems might reveal underlying heart risks because pregnancy is like a natural test for the heart. Dr. Khan explained that “if pre-pregnancy obesity is the main reason for these risks, we should focus on preventing it through interventions. Instead of waiting for heart problems to occur, we want to stop them from happening in the first place.”

Dr. Khan’s research focuses on a crucial time called the “Zero trimester,” which is the period before pregnancy. By improving health during this time, individuals can enhance their outcomes for pregnancy and long-term health.

However, reaching people before they become pregnant can be challenging. So, early pregnancy presents an opportunity to advise on heart-healthy habits like diet and exercise when people are already meeting with doctors during prenatal visits.

Dr. Khan emphasizes that we shouldn’t recommend weight loss during pregnancy. However, we should provide counseling and monitor appropriate weight gain during pregnancy. This is when you’re seeing the doctor often and are healthy, so it’s a good time to make healthy choices.

Research shows pregnant women can safely manage their weight gain by eating and exercising moderately or vigorously.

Pregnant individuals in the study were seen at eight medical centers in the U.S., including Northwestern University. They were 18 or older and had no history of high blood pressure or diabetes before pregnancy.

About 15% of the participants had pregnancy complications related to high blood pressure, 11% had low birthweight babies, 8% had preterm births, and 4% had gestational diabetes. After pregnancy, those with high blood pressure complications were 97% more likely to have high blood pressure, and 31% were more likely to have high cholesterol.

For some complications, body weight didn’t make a difference. For example, being overweight or obese didn’t increase the risk of preterm birth or low birth weight.

However, all participants who experienced preterm births had higher risks of developing high blood pressure, high blood sugar, or high cholesterol after pregnancy. Having a baby with low birthweight didn’t increase these risks.

The study was funded by NHLBI grant R01 HL161514, with additional support from the Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Center for Advancing Translational Sciences, Office of Research on Women’s Health, and the Office of Disease Prevention.

Journal Reference:

  1. Sadiya S. Khan, Lucia C. Petito et al., Pre-pregnancy obesity predicts future heart health. Circulation Research. DOI: 10.1161/CIRCRESAHA.123.322762.