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Syncope in Pregnancy May Signal Worse Birth Outcomes

Pregnant women who experienced episodes of syncope — or fainting — had higher rates of adverse pregnancy outcomes, as well as postpartum cardiovascular events, researchers found.

Women who experienced syncope had a higher rate of preterm birth and a higher incidence of congenital anomalies, with the highest rates of these adverse events among women who had an episode of syncope in the first trimester, reported Padma Kaul, PhD, of the University of Alberta in Canada, and colleagues.

Moreover, women with an episode of syncope also had higher rates of cardiac arrhythmias and syncope episodes within a year after pregnancy versus women with no syncope, the authors wrote in the Journal of the American Heart Association.

“There are very limited data on the frequency of fainting during pregnancy [and] fainting during pregnancy has previously been thought to follow a relatively benign course,” Kaul said in a statement. “The findings of our study suggest that timing of fainting during pregnancy may be important.”

Researchers examined data from 2005 to 2014 in the Alberta Pregnancy-Birth Cohort, a cohort of pregnant women and offspring in Alberta, Canada. Syncope during pregnancy was defined via ICD-9 or ICD-10 codes.

Of the approximately 481,000 pregnancies, 4,667 had an episode of syncope (9.7 per 1,000 pregnancies). From 2005 to 2014, the incidence of syncope rose from 7.6 per 1,000 pregnancies to 11 per 1,000 pregnancies, respectively, for an age-adjusted 5% increase per year, the authors said (rate ratio 1.05, 95% CI 1.04-1.06, P<0.01).

Women with episodes of syncope during pregnancy tended to be younger, primiparous, were less likely to be married and had higher rates of preexisting medical conditions. Not surprisingly, they were also more likely to have a history of syncope before pregnancy compared with women without syncope during pregnancy.

Examining timing of syncope, about a third of women had their first episode during the first trimester, 44% in the second trimester, and a little under a quarter in the third trimester.

There was a higher rate of preterm birth among women experiencing syncope during pregnancy compared with those without syncope (16.3% vs 15.0%, P=0.02). The authors also found higher rates of preterm birth among women with syncope in their first trimester (18.3%) versus the second and third trimesters (15.8% and 14.2%, respectively, P<0.01 for all).

They also found that over a median follow-up period of about 5 years for pregnancies with and without syncope, there were higher rates of presentation of congenital anomalies in the syncope group (3.1% vs 2.3% in non-syncope group, P=0.023). Once again, the highest prevalence of congenital anomalies was among offspring of women with episodes of syncope in the first trimester (3.4%).

Among the approximately 130,000 women with at least one pregnancy or birth during the study time period, adjusted analyses found higher odds of preterm birth (adjusted OR 1.3, 95% CI 1.1-1.4), small-for-gestational age infants (adjusted OR 1.2, 95% CI 1.0-1.4), and congenital anomalies (adjusted OR 1.4, 95% CI 1.0-1.8) for women with their first episode of syncope during the first trimester versus women with no syncope in pregnancy.

A higher portion of women with syncope during pregnancy had cardiac arrhythmias (0.8% vs 0.2% for no syncope) and syncope episodes within a year of delivery (1.4% vs 0.2% for no syncope, P<0.01 for both), the authors said.

Study limitations included the fact that it did not include women with symptoms of syncope who had not sought medical attention, and that it used ICD codes, both of which may underestimate the true incidence of syncope.

The study was supported by the Cardiac Arrhythmia Network of Canada.

Kaul and co-authors disclosed no relevant relationships with industry.