Certain Bacteria May Target Pregnant Women, Harm Fetus

H Influenzae seemed to target pregnant women and brings high risk of miscarriage

(RxWiki News) Pregnant women are prone to morning sickness, fluid retention and even thinning hair. But new research suggests they are also more prone to developing a certain infection that can cause problems for their unborn child.

British researchers found that pregnant women had a greater risk for an infection with bacteria known as invasive unencapsulated Haemophilus influenzae (H. influenzae) than women who were not pregnant. Many of the women who were infected miscarried.

H. influenzae is a bacterial infection that typically causes upper respiratory infections in young children and the elderly. There are different forms of the bacteria. The unencapsulated H. influenzae is more common than the other types and is the one most often associated with pregnancy.

"Ask your doctor about special precautions to avoid infections while pregnant."

The researchers, led by Sarah Collins, MPH, of Public Health England, noted that while the bacteria is more prevalent in pregnant women, it is not a common bacteria. 

Pregnant women in general were more than 17 times more likely to get the infection than non-pregnant women, Collins and team found.

Pregnancy loss following invasive H. influenzae disease was 2.9 times higher than the United Kingdom's national average for pregnancy loss in women without the infection, these researchers reported.

This prospective study involved clinical questionnaires being sent to family doctors who cared for women aged 15 to 44 in England and Wales from 2009 to 2012. The diagnosis of H. influenzae was made with positive cultures. The doctors were asked to complete questionnaires within three months of an infectious diagnosis. They identified a total of 2,568 cases of invasive H. influenzae. Cause of death was retrieved from post-mortem reports or death registration data.

A total of 75 women were pregnant at the time they were infected, and 74 of the fetuses were carried by 72 women who had the unencapsulated form of the infection. Of these 74 fetuses, 43 were miscarried, two were stillborn, and there were 29 live births. Of the live births, 11 were born before 37 weeks gestation (premature).

Premature babies face a number of risks themselves, because they often have problems associated with not being fully developed at birth.

The results were most ominous for women who became infected early in their pregnancy. The researchers found that when pregnant women became infected before 24 weeks gestation, they miscarried almost 94 percent of the time.

The researchers made it clear that although the infection can wreak havoc, it’s relatively rare. “The association between H. influenzae and pregnancy has been difficult to assess because the infection is relatively uncommon," they wrote.

They also can only speculate as to why the bacteria is more common among pregnant women, but believe it may be harbored in the genital tract.

In an accompanying editorial, Morven Edwards, MD, of the Baylor Institute of Medicine in Texas, noted that “infectious diseases are a potentially preventable cause of adverse pregnancy outcomes” and suggested a need to clarify the role of bacterial infection in fetal loss.

This study and editorial appeared March 14 in the Journal of the American Medical Association (JAMA).

Several authors of this study disclosed financial ties to the pharmaceutical industry.

Review Date: 
March 25, 2014