A New York State study found that younger, not older women suffered an increase risk of stroke, both during pregnancy and in postpartum.
Younger women — not older women — had an increased risk of stroke during pregnancy and the postpartum period compared to non-pregnant women of the same age, according to the results of a new study published online October 24, 2016 in JAMA Neurology.
Overall, pregnancy-associated stroke (PAS) accounted for 15 percent of strokes in women aged 12 to 24 years; 20 percent of strokes in women aged 25 to 34 years; 5 percent of strokes in women aged 35 to 44 years; and 0.05 percent of strokes in women aged 45 to 50 years.
Previous studies have suggested that the risk of PAS increases with older maternal age, probably due to increased prevalence of vascular risk factors like hypertension and diabetes, the study authors noted. But those studies rarely used age-matched non-pregnant control groups to determine age-related risks of PAS. The findings suggest that although there is a higher incidence of PAS among older women, pregnancy imparts an increased risk of stroke only for younger women compared to their non-pregnant, age-matched counterparts.
“Although older women have an increased risk of many pregnancy complications, a higher risk of stroke may not be one of them,” the study authors, led by Eliza C. Miller, MD, a neurology resident at the Columbia University College of Physicians and Surgeons, wrote. “These results have potential implications for research aimed at better characterizing and preventing PAS and clinically in term of counselling patients.”
For their study, the researchers used billing codes from the New York State Department of Health inpatient database to identify all women between the ages of 12 and 55 who were admitted to a hospital with a stroke between 2003 and 2012. The stroke types in the analysis included transient ischemic attack or ischemic stroke, intracerebral hemorrhage, subarachnoid hemorrhage, cerebral venous thrombosis, and nonspecified PAS, including postpartum stroke. The researchers used delivery codes to identify women who were pregnant or postpartum.
They found that 19,146 women were hospitalized with stroke during the study period; of these, 797 were pregnant or postpartum at the time of stroke. The incidence of PAS increased with age; for every 100,000 pregnant or postpartum women, PAS occurred in 14 women aged 12 to 24 years compared to 46.9 women aged 45 to 55 years.
However, the increase in PAS risk — as determined by the incidence risk ratio (IRR) generated using comparisons to age-matched non-pregnant control groups — decreased with increasing age. Among women in the 12-to-24 age group, non-pregnancy-associated strokes occurred in 6.4 of every 100,000 non-pregnant women, corresponding to an IRR of 2.2; by contrast, non-pregnancy-associated strokes occurred in 73.7 of every 100,000 non-pregnant women, corresponding to an IRR of 0.6.
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