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Hypertension before pregnancy increases chance of miscarriage

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*Heart defects in infant predict cardiac problems in mother later in life, researchers find
Elevated blood pressure before conception may increase the chances for pregnancy loss, according to an analysis by researchers at the National Institutes of Health. The authors conclude that lifestyle changes to keep blood pressure under control could potentially reduce the risk of loss.

The study appears in journal Hypertension.

The analysis found that for every 10 mmHg increase in diastolic blood pressure (pressure when the heart is resting between beats), there was an 18-percent-higher risk for pregnancy loss among the study population. Millimeter of mercury, or mmHg, is the unit of measure used for blood pressure. The researchers also found a 17 percent increase in pregnancy loss for every 10 mmHg increase in mean arterial pressure, a measure of the average pressure in the arteries during full heart beat cycles. The study was conducted by researchers at the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD).

“Elevated blood pressure is linked to heart disease, stroke, and kidney disease” said the study’s senior author, Enrique Schisterman, Ph.D., chief of the Epidemiology Branch at NICHD. “Our findings suggest that attaining a healthy blood pressure before pregnancy could not only have benefits later in life, but also reduce the chances for pregnancy loss.”

Also, according to new research in the American Heart Association’s journal Circulation, women who give birth to infants with congenital heart defects may have an increased risk of cardiovascular hospitalizations later in life.

The study of more than one million women is the first to show congenital heart defects in newborns may be a marker for an increased risk of their mothers developing heart problems, including heart attack and heart failure, years after pregnancy.

Researchers analyzed data on women who delivered infants between 1989 and 2013 in Quebec, Canada, who had critical, noncritical or no heart defects. They tracked the women up to 25 years after pregnancy for hospitalizations related to cardiovascular disease including heart attack, heart failure, atherosclerotic disorders and heart transplants.

Compared to mothers of infants without congenital heart defects, researchers found: 43 percent higher risk of any cardiovascular hospitalization in women whose offspring had critical heart defects; and 24 percent higher risk of any cardiovascular hospitalization in women whose infants had noncritical defects.

How heart defects in infants relate to post-pregnancy cardiovascular disease in their mothers is unclear, the study notes, and a genetic component cannot be excluded. In addition, because 85 percent of infants with heart defects now survive past adolescence, the psychosocial impact of congenital heart disease on caregivers may have a cumulative effect over the long term.

“Caring for infants with critical heart defects is associated with psychosocial and financial stress, which may increase the mothers’ long-term risk for cardiovascular disease,” said Nathalie Auger, M.D., the study’s lead author and an epidemiologist at the University of Montreal Hospital Research Centre in Montreal, Quebec, Canada.

Researchers believe the study provides an opportunity for these mothers to benefit from early prevention strategies and counseling to reduce their risk of cardiovascular disease — the leading cause of death in women.

Healthcare providers, like obstetricians, who treat and follow mothers in the early stages of dealing with children who have heart defects can help women understand and minimize their risk, Auger said.

“Those physicians are very well-positioned to inform women about this possibility, the greater risk of heart disease, and to provide recommendations for targeting other risk factors like smoking, obesity and physical activity,” she said.

Some limitations of the research include the fact that women were young at the start of study, so for many, the 25-year follow-up did not extend past menopause, which excluded the highest risk period for cardiovascular disease. And, because researchers used existing medical data, they didn’t have detailed risk factor information on the women, such as body weight and smoking status. These are important points that should be considered in future studies, researchers noted.

Meanwhile, NICHD researchers analyzed data collected as part of the Effects of Aspirin in Gestation and Reproduction (EAGeR) trial, which sought to determine if daily low-dose aspirin (81 milligrams) could prevent miscarriage in women who had a history of pregnancy loss.

The EAGeR trial enrolled more than 1,200 women ages 18 to 40 years and took blood pressure readings before the women were pregnant and again in the fourth week of pregnancy. Average diastolic blood pressure for the women in the study was 72.5 mmHg; normal blood pressure in adults is a diastolic reading of below 80 mmHg. The authors began to see an increase in pregnancy loss among women who had a diastolic reading above 80 mmHg (approximately 25 percent of the participants). None of the women in the study had stage II high blood pressure (above 90 mmHg in systolic high blood pressure or above 140 mmHg in systolic blood pressure).

The researchers note that the study does not prove that elevated blood pressure causes pregnancy loss. It is possible that another, yet-to-be identified factor could account for the findings. They added, however, that the relationship between preconception blood pressure and pregnancy loss remained the same when they statistically accounted for other factors that could increase pregnancy loss, such as increasing maternal age, higher body mass index or smoking.

“Our results suggest that further research could help determine if treating elevated blood pressure and other health risks before conception improves pregnancy outcomes,” said the study’s first author, Carrie Nobles, Ph.D., a postdoctoral fellow in the NICHD Epidemiology Branch.


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