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Pregnant Women May Be More Vulnerable to Potentially Dangerous Infection: Study

Screening for H. influenzae not recommended for now, expert says

TUESDAY, March 18, 2014 (HealthDay News) -- Mothers-to-be may be more susceptible to an infection associated with poor pregnancy outcomes, a new study suggests.

Haemophilus influenzae -- not the same bug as "the flu" -- is a bacterium that commonly causes respiratory illness in young children and the elderly. Also called H. influenzae, it can be dangerous to the fetus of a pregnant woman who develops an invasive infection, say the authors of a new study in the March 19 Journal of the American Medical Association.

"Although invasive H. influenzae disease is uncommon in healthy adults, pregnant women are at significantly higher risk compared to non-pregnant women," said study author Dr. Shamez Ladhani, a pediatric infectious disease consultant at the immunization, hepatitis and blood safety department of Public Health England, in London.

Ladhani said the microbe is potentially very dangerous to an unborn or newborn baby of an infected mother-to-be, and can lead to miscarriage, stillbirth and premature birth.

He said it's known that pregnant women are generally at an increased risk for serious bacterial infections compared to non-pregnant women, and that those infections are responsible for about 10 percent of pregnancy-related deaths. With that in mind, he and his colleagues wanted to investigate more closely H. influenzae's impact on fetal health.

Their study included 171 English and Welsh women of reproductive age (15 to 44 years old) who were part of a national surveillance of invasive H. influenzae disease. About half were pregnant. The researchers analyzed data collected between 2009 and 2012. The data came from health care providers who had completed clinical questionnaires about the women who'd tested positive for the infection on lab tests.

Ladhani said the health of a woman's baby appeared to be influenced by when during pregnancy the mother developed the serious infection, which can cause blood poisoning.

The invasive form of H. influenzae infection during the first 24 weeks of pregnancy was associated with fetal loss in nearly 94 percent of cases, and extremely premature birth in about 6 percent, the study found.

During the second half of pregnancy, infection was linked with premature birth in nearly 29 percent and stillbirth in about 7 percent of 28 cases, according to the study.

"If it happens in the first half of pregnancy, then this invariably results in miscarriage. If it happens early in the second half of pregnancy, then the baby is born prematurely and often has prolonged and complicated stays in the neonatal intensive care unit along with being at risk of all the long-term complications of prematurity," Ladhani explained.

Pregnancy loss following invasive H. influenzae disease was 2.9 times higher than the U.K. national average, the authors noted.

Ladhani said if the infection occurred near the time of birth, the baby did not suffer from the risk of prematurity complications, but blood poisoning often occurred and the baby required neonatal intensive care treatment.

In an accompanying journal editorial, Dr. Morven Edwards wrote, "As an immediate goal, laboratories should be aware that H. influenzae . . . are potential pathogens in pregnant women and neonates."

Edwards, a professor in infectious diseases with the pediatrics department at Baylor College of Medicine in Houston, added: "Moving forward, it will be important to determine the scope of infection caused by this pathogen in other geographic regions."

Dr. Catherine Herway, assistant director of maternal-fetal medicine at Staten Island University Hospital, in New York City, said it's too early to culture (test) all pregnant women for H. influenzae. She echoed Edwards' editorial comment that more research is needed to better understand its prevalence in other areas.

"This study was done on a population in England and Wales. We'd need to reproduce these results in our own patient populations, even in different geographical areas of the U.S.," said Herway, who noted that insurance is not likely to pay for such tests.

Herway also pointed out that in the study "a large portion of women had coexisting illness going on" and she said doctors who have pregnant patients whose immune systems are suppressed or who have other health conditions should be on the alert for H. influenzae infection.

"In the low-risk general population, it really shouldn't be much of an issue," Herway said.

More information

Visit the U.S. Centers for Disease Control and Prevention for more on H. influenzae infection.

SOURCES: Shamez Ladhani, M.D., Ph.D., pediatric infectious disease consultant, health protection services, immunization, hepatitis and blood safety department, Public Health England; Catherine Herway, M.D., assistant director, maternal-fetal medicine, Staten Island University Hospital, New York City; March 19, 2014, Journal of the American Medical Association
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