Diabetes in pregnancy tied to future heart disease risk

Women with pregnancy-related diabetes are at higher risk for developing cardiovascular disease in the decade after childbirth, a research review suggests.

While so-called gestational diabetes has long been linked to an increased risk of heart disease later in life, some previous research suggests this risk may depend on whether the condition evolves into Type 2 diabetes that persists after delivery.

Researchers examined data from nine previous studies with almost 5.4 million mothers. Overall, about 8,000 women with a history of gestational diabetes experienced cardiovascular events like heart attacks and strokes, as did more than 93,000 women without this pregnancy complication.

"This study demonstrates that women with gestational diabetes have a 2-fold higher risk of major cardiovascular events than their peers," said senior study author Dr. Ravi Retnakaran of the University of Toronto and an endocrinologist at Mount Sinai Hospital in Toronto.

"This increased risk is not dependent upon [Type 2 diabetes]," Retnakaran said by email. "The risk differential between women with gestational diabetes and their peers emerges within the first decade after pregnancy."

Compared to women who didn't have gestational diabetes, those who did had a 2.3-fold greater risk of events like heart attacks and strokes within the first decade after giving birth.

Even when researchers looked only at women who didn't have Type 2 diabetes after pregnancy, they still found gestational diabetes associated with a 56 per cent higher risk of serious cardiac events.

Type 2 diabetes is associated with obesity and aging and has long been linked to an increased risk of cardiovascular problems like heart attacks and strokes.

Separately, in a study published Wednesday in The Lancet Diabetes & Endocrinology, Retnakaran's team found that the current glucose screening test, used in pregnancy to diagnose gestational diabetes, can identify future risk of heart disease in women who do not have gestational diabetes but do have mildly elevated blood glucose levels.

The second study included 12,307 women who had gestational diabetes and 246,857 women without in Ontario who had a glucose challenge test in pregnancy with a delivery between July 2007 and December 2015. The women were followed for nearly four years after delivery for the development of cardiovascular disease. There were 138 cardiovascular events over the follow-up period.

The findings showed that a screening test that is already being performed in clinical practice has the capacity to identify future risk of cardiovascular disease in women at an early point in the development of the disease, Retnakaran said in a release.

While the research wasn't designed to prove whether or how gestational diabetes might directly cause cardiovascular events, it's possible that risk factors like obesity might contribute to both diabetes in pregnancy and heart problems down the line, researchers write in Diabetologia.

"Although it is not entirely clear, most people believe that pregnancy is like a stress test for future diabetes and heart disease," said Dr. Jacinda Mawson Nicklas, a researcher at the University of Colorado School of Medicine in Aurora who wasn't involved in the study.

"So it is not that gestational diabetes causes increased risk, but that when a woman gets gestational diabetes she is revealing an increased risk that was already there," Nicklas said by email.

Gestational diabetes common

Women who do develop gestational diabetes may need regular heart health checkups even while they're still relatively young, the study authors conclude.

There's a lot women can do to lower their risk of cardiovascular disease before they conceive, Nicklas said. This includes starting pregnancy at a healthy weight and exercising and eating well during pregnancy.

"However gestational diabetes is common and can happen even in normal weight women," Nicklas said. "If a woman gets gestational diabetes it is important to work closely with her doctor to control her blood sugars"

After pregnancy, women who have had gestational diabetes should maintain a heart healthy diet and lifestyle and see their doctor for screening, said Dr. Jennifer Stuart of Brigham and Women's Hospital and Harvard Medical School in Boston.

"Adopting a healthy lifestyle after pregnancy — eating a healthy diet, being physically active, not smoking, and not being overweight or obese — may reduce the risk of heart disease and stroke in women with a history of gestational diabetes," Stuart, who wasn't involved in the study, said by email.