Pregnancy Linked to Increased Stroke in Younger, Not Older, Women

Fran Lowry

November 04, 2016

The risk for pregnancy-associated stroke appears to be heightened in younger, but not older, women, new research suggests.

In a population-based study that looked at all strokes in New York State over a 10-year period, stroke risk was more than doubled in pregnant or postpartum females aged 12 to 24 years and increased significantly by 60% in women 25 to 34 years, compared with stroke risk in similarly aged nonpregnant females.

The study was published online October 24 in JAMA Neurology.

"All the literature says that you have a higher risk of pregnancy-associated stroke the older you are and that the risk of pregnancy-associated stroke is greater in women who are older when they have their babies, but I was seeing quite young women with pregnancy-associated strokes," lead author Eliza C. Miller, MD, from New York Presbyterian Hospital/Columbia University Medical Center, New York City, told Medscape Medical News.

Dr Eliza C. Miller

"However, there was limited information on age-specific risk of pregnancy-associated stroke compared with stroke risk in nonpregnant women," Dr Miller said.

She and her colleagues analyzed the New York State Department of Health database from 2003 to 2012 to identify all stroke admissions for women aged 12 to 55 years and determine age-specific incidence risk ratios for pregnancy-associated stroke compared with non–pregnancy-associated stroke.

The women were divided into the following age cohorts: 12 to 24, 25 to 34, 35 to 44, and 45 to 55 years.

There were 19,146 women hospitalized with stroke during the study period. Of these, 797 (4.2%) were pregnant or postpartum.

In a surprise finding, the youngest group of pregnant and postpartum women aged 12 to 24, had more than double the risk for stroke compared with nonpregnant women in that age group, with an incidence rate ratio (IRR) of 2.2 (95% confidence interval [CI], 1.9 - 2.6).

However, in older women (those 35 years and older) the risk for pregnancy-associated stroke was no greater than it was for women in the same age group who were not pregnant.

Table. Cumulative Incidence and IRRs in Pregnant vs Nonpregnant Women

Age (y) PAS per 100,000 Deliveries NPAS per 100,000 Nonpregnant Women IRR (95% CI)
<24 14 6.4 2.2 (1.9 - 2.6)
25 - 34 21.2 13.5 1.6 (1.4 - 1.7)
35 - 44 33 30.9 1.1 (0.9 - 1.2)
45 - 55 46.9 73.6 0.6 (0.3 - 1.4)

NPAS = non–pregnancy-associated stroke; PAS = pregnancy-associated stroke.

 

"Despite stroke being a rare event in young women, 18% of all strokes in women younger than 35 years were associated with pregnancy, and in contrast, among the older women, 1.4% of strokes were associated with pregnancy," Dr Miller said.

The analysis also revealed that black and Hispanic race/ethnicity increased the risk for pregnancy-associated stroke but only in the younger (<35 years) cohort, but not in older women.

"Hispanic ethnicity had an even higher association than black race, and this new finding is important, given the rapidly growing young Hispanic population throughout the US," she said.

"This study nicely shows that pregnancy- and postpartum-associated strokes occurred in women less than 35 years of age but not in older women," commented Teshamae Monteith, MD, from University of Miami Health Systems, Florida.

"Further studies are needed to understand why the stroke risk was greater mostly in young Hispanic and African American pregnant women, in addition to gaining a better understanding of the factors that contribute to this increased risk," Dr Monteith told Medscape Medical News.

"There are several reasons why stroke may be more common in the young pregnant woman. The traditional vascular risk factors are the most common cause of stroke in older women and are more likely more important than pregnancy-related factors," she said.

"There appears to be race and ethnic disparities in pregnancy-related stroke risks for young women. Factors underlying these disparities require further exploration. In addition, it would be interesting to see if risk factors such as active migraine, which is more common in younger women, may account for some of the age-related discrepancies in stroke risks," Dr Monteith said.

Dr Miller and Dr Monteith have disclosed no relevant financial relationships.

JAMA Neurol. Published online October 24, 2016. Abstract

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