Dallas, Texas - Pregnant women who faint (syncope) during pregnancy, especially in their first trimester, may have a higher risk of health problems for themselves and their babies according to new research published in Journal of the American Heart Association, the Open Access Journal of the American Heart Association/American Stroke Association.

This is the first study to analyze the incidence and impact of fainting during pregnancy in a large population. Researchers examined 481,930 pregnancies in Alberta, Canada between 2005 and 2014 for trends in timing, frequency and health complications for infants and women occurring in the first year after pregnancy among women who fainted during their pregnancies.

They found 4,667 women had a fainting episode and nearly a third (32.3%) of them occurred in the first trimester. About 44% occurred in the second trimester and 23.6% in the third trimester, while 8% had more than one fainting episode.

Researchers also found:

  • The incidence of congenital anomalies among children born of pregnancies with multiple fainting episodes was 4.9%, significantly higher than the 2.9% among children of pregnancies with only one fainting spell.  
  • The rate of premature birth, at 18.3%, was higher in pregnancies with fainting during the first trimester, compared to 15.8% during the second trimester, 14.2% in the third trimester and 15% for pregnancies without fainting.
  • Within one year after delivery, women who fainted during pregnancy had higher rates of abnormal heart rhythms and fainting episodes, compared to women who didn’t faint during pregnancy.
  • After an average follow-up of 4.5 to 5 years, the rates of congenital anomalies were 3.1% for children of pregnancies with syncope compared 2.6% for those without syncope.

“There are very limited data on the frequency of fainting during pregnancy,” said Padma Kaul, Ph.D., senior study author and professor of medicine at the University of Alberta in Canada. In our study, fainting during pregnancy occurred in about 1%, or 10 per 1,000 pregnancies, but appears to be increasing by 5% each year."

“Fainting during pregnancy has previously been thought to follow a relatively benign course,” Kaul said. “The findings of our study suggest that timing of fainting during pregnancy may be important. When the faint happens early during pregnancy or multiple times during pregnancy, it may be associated with both short and long term health issues for the baby and the mother.”

The data suggest that women who faint during pregnancy should have closer monitoring and potential follow-up with a cardiologist after the birth, she said.

Although the research provides real-world data on fainting during pregnancy in a large population base with universal health care, it has a few limitations. Because the study is retrospective and observational it may underestimate the true incidence of syncope during pregnancy. Researchers said their findings should be confirmed in other large population-based studies.

Co-authors are Safia Chatur, M.D.; Sunjidatul Islam, MBBS, MSc; Linn Moore, Ph.D.; Roopinder Sandhu, M.D.; and Robert Sheldon, M.D. Author disclosures are on the manuscript.

The Cardiac Arrhythmia Network of Canada funded the study.