Gestational Diabetes and Hypertension = Huge Risk for Later Disease

Pam Harrison

November 21, 2017

Having both gestational diabetes and high blood pressure together during the same pregnancy substantially increases the risk of developing type 2 diabetes, hypertension, and cardiovascular disease afterward, new research indicates.

Although the link between gestational diabetes and subsequent type 2 diabetes is well-known, as is the association between high blood pressure in pregnancy and future risk of hypertension, little is known about the combined associations of both conditions in pregnancy with future risks, including those for cardiovascular disease (CVD), say the authors of the study, led by Romina Pace, MD, of McGill University, Montreal, Quebec, published in the American Journal of Epidemiology.

"The problem with looking at gestational diabetes and gestational hypertension separately is that if they are considered independently in a mathematical model, their individual effects could be underestimated because they're interrelated — that is, having one also increases the chances of having the other," senior author Kaberi Dasgupta, MD, associate professor of medicine, McGill University Health Centre, told Medscape Medical News in an email.

The researchers discovered that either diabetes or high blood pressure during a pregnancy increases a woman's future risk of diabetes by 15-fold. But the risk was 37 times higher among women who had both conditions during the same pregnancy.

Having either condition also doubled a woman's future risk of hypertension. But this risk was six times higher among women who had both gestational diabetes and hypertension.

"We found quite a dramatic combined effect," said Dasgupta.

Results

The investigators identified women who were diagnosed with gestational diabetes between 1990 and 2007 and compared them with a group of women who never developed gestational diabetes.

Hypertension in pregnancy was then identified in matched pairs of mothers with gestational diabetes or without it, all of whom had singleton live births in Quebec.

Out of a total of 63,438 couples analyzed, 44.4% of mothers had been diagnosed with gestational diabetes during pregnancy; 3.5% developed hypertension only and 5.6% had both gestational diabetes and hypertension. The women were then classified by gestational diabetes and gestational hypertension status as having neither, either, or both.

About half of the mothers were under the age of 30 while the remaining half were between 30 and 39 years of age.

They followed the women after the pregnancy and birth.

"Over a mean of 13.0 years…mothers with gestational diabetes, gestational hypertension, or both conditions had higher incidences of diabetes, hypertension, and [a composite of] CVD/mortality compared with those with neither," the researchers report.

Adjusted Hazard Ratios (HRs) for Type 2 Diabetes, Hypertension, and a Composite of CVD and Mortality by Gestational Diabetes and Gestational Hypertension Status

Outcome Mothers
Future diabetes HR
Either 14.7
Both 36.9
Future hypertension HR
Either 1.9
Both 5.7
CVD/mortality HR
Either 1.4
Both 2.4

Median Time to Diagnosis Was Shorter if Both Conditions Present

The median time to the diagnosis of type 2 diabetes among women who developed it following both pregnancy-related complications was 4.6 years; this was a little longer, at 5.3 years, among women who had had either gestational diabetes or hypertension and then developed type 2 diabetes.

In women who had neither condition during pregnancy, but subsequently developed type 2 diabetes, this occurred at a median of 11.2 years after pregnancy.

For incident hypertension, the medium time to diagnosis was 6 years for mothers who developed it following both conditions during pregnancy, compared with a median of 9.3 years for mothers who subsequently developed it after only one of the complications during pregnancy (and 10.8 years in women with neither condition in pregnancy).

And among mothers with a history of both gestational diabetes and hypertension, the medium time to the outcome of CVD (defined as one hospitalization or procedure code for coronary artery disease, coronary artery bypass graft, angioplasty, stroke, carotid endarterectomy, or all-cause mortality) was 10.8 years compared with 11.4 years for women with a history of either condition and 11.5 years for those with neither.

A Major Public Health Concern: Don't Forget Healthy Behaviors After Childbirth

Dr Dasgupta observed, "All too often, once the baby is born and the gestational diabetes and gestational hypertension go away, health behaviors are put on the back burner — understandably, given the demands of parenthood.

"However, it is important, at least once things settle down, to try to build a home environment that helps moms and dads make healthy choices in the longer term," developing and maintaining good eating and physical-activity habits, he added.

In an editorial accompanying the study, Lewis Kuller, MD, DrPH, and Janet Catov, PhD, both from the University of Pittsburgh, Pennsylvania say this "large database provided a unique opportunity to evaluate the subsequent risks over time of diabetes, hypertension, and a composite of CVD and death.

"One of the most important messages from the current study is how pressing the need is to control the high rates of diabetes and hypertension seen in women with a history of gestational diabetes or gestational hypertension and especially of both," they say.

"Body weight and obesity are the likely common drivers of postpregnancy diabetes and hypertension, [and] various strategies for both prevention and treatment to reduce diabetes and hypertension are available," they note.

"These include nonpharmacological approaches such as those used in the Diabetes Prevention Program (DPP) — exercise and diet — new drug therapies that lead to both decreased complications of diabetes and weight reduction, and bariatric surgery, especially for women with grade 2 and 3 obesity who have prediabetes or are unable to lose weight," they suggest.

Drs Kuller and Catov also emphasize that other nonpharmacological approaches including breast feeding can help delay or even prevent progression to type 2 diabetes in women with a history of gestational diabetes.

"Obesity, diabetes, and hypertension have been increasing over time," the editorialists warn, "This is a major public-health concern [and] an epidemic in great need of control."

Neither the study authors nor the editorialists had any relevant financial relationships.  

Am J Epidemiol. 2017;186:1115-1124. Article, Editorial

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