New Findings on Stroke and Pregnancy: Implications and Interventions

Although men are generally more likely to experience stroke than women are, women in their childbearing years are at greater risk for stroke than are men of the same age. Pregnancy, childbirth, and the puerperium are the times when women are at particular risk, but there is more to the story. Recent studies found that not only is the incidence of stroke during pregnancy and the puerperium higher than was previously thought,¹ but women who have had complications during pregnancy are at higher risk for stroke later in life.²

The first study looked at data on stroke and pregnancy discharges within the Agency for Healthcare Research and Quality's Nationwide Inpatient Sample from the Healthcare Cost & Utilization Project for 2000 to 2001.¹ A total of 2850 discharges for pregnancy complicated by stroke were identified. This translated into a rate of 34.2 strokes for every 100,000 deliveries—a rate higher than was previously determined in an earlier Canadian study. That study used similar data and methodology and reported an incidence of 26 strokes for every 100,000 pregnancies.³

African Americans were at highest risk. Risk also increased with age: women aged 35 years or older were most vulnerable. Other risk factors are listed in the Table. The mortality rate was about 4%.

Study coauthor Cheryl D. Bushnell, MD, MHS, assistant professor of neurology at Duke University School of Medicine, noted that new preventive care strategies are needed to protect mothers—and their newborns—from stroke and its complications. Prevention and management of hypertension, heart disease, and diabetes are the obvious places to start.

COMPLICATED PREGNANCY AND LOOMING STROKE THREAT

Preventive strategies will not only decrease the incidence of stroke in young women during and immediately after pregnancy, they also stand to reduce the incidence of stroke in older women. A second study by Bushnell and colleagues² found that women who have had complications during pregnancy, specifically preeclampsia and gestational diabetes, are at greater risk for stroke down the line—an average of 13.5 years later.

The researchers combed through the Duke University Medical Center Perinatal Health Services Outcomes Database and identified 42,263 women who had given birth between 1979 and 2005. They then identified 164 women who had had a stroke after the puerperium and compared them with 311 controls matched by age and by month and year of delivery. What they found was striking: the women who had experienced stroke were 70% more likely to have had a complication of pregnancy than were controls. Average age at the time of stroke was 40 years.

Although a wide range of complications of pregnancy was reviewed, only preeclampsia and gestational diabetes were associated with stroke. When asked what preventive strategies could be put in place to prevent stroke down the road in women at risk, Bushnell said that prevention of preeclampsia might be the key. This is a challenge, however, because the causes of preeclampsia are unknown.

Bushnell is developing a set of tests that would assist in predicting preeclampsia. She foresees a long road through NIH approval and development. She is also undertaking proof-of-principle studies to confirm that preeclampsia is associated with heart disease and stroke risk.

"We can do that by measuring the thickness of the carotid artery," said Bushnell. "Endothelial dysfunction post-pregnancy is associated with preeclampsia, but it's never been shown as proof of principle that [affected women are] going to be at risk for stroke. That's where I'd like to take this. Once we understand what happens early after pregnancy, we can look at prepregnancy and try to prevent preeclampsia altogether."

Although protocols regarding preeclampsia and stroke prevention are relegated to the future, practical steps to prevent stroke in women whose pregnancy complications augur risk are relatively simple however, they require planning and diligence. These steps include regular monitoring of blood pressure and blood glucose levels and encouraging weight control.

Bushnell noted that these measures generally are not undertaken, but if they became a routine part of postnatal and ongoing care for women who have had complications of pregnancy, the overall incidence of stroke might decrease. Indeed, her institution offers a weight management program for women who have recently given birth. "They teach new moms how to incorporate an exercise routine into their lives," explained Bushnell. She added that a woman's knowledge about her stroke risk, based on whether she had preeclampsia or another complication of pregnancy, may act as an incentive to avail herself of post- natal health maintenance programs.

RACIAL AND SOCIOECONOMIC COMPONENTS OF RISK

Of particular concern was that an overwhelming majority—73%—of the women affected by stroke were African American. The incidence of hypertension is higher in African Americans than in white persons. This might account for the higher rate of stroke among African American women in the study, according to Bushnell.

When asked whether socioeconomic issues play a role, Bushnell conceded that prenatal care might be suboptimal in low-income minority populations—a circumstance that a colleague of hers, Monique V. Chireau, MD, assistant professor of obstetrics and gynecology at Duke, is about to investigate.

The study will look at outcomes of complications of pregnancy and patient satisfaction among Medicaid recipients. Among the goals of the study are insight into and amelioration of factors that contribute to infant mortality and health care disparities associated with socioeconomic and racial phenomena.

In addition to shedding light on infant mortality rates and health care quality and access among Medicaid recipients who experience complications of pregnancy, Bushnell said the information gleaned might fortify her own research. "It will be interesting to see, from an observational point, what happens there. That's another cohort where we might be able to do some of these other tests" on preeclampsia and stroke risk, she said.