MedicalResearch.com: What are the main findings of the study?
Dr. Ladhani: Pregnancy was associated with an increased of serious infection by a bacterium called Haemophilus influenzae which is usually associated with respiratory tract infections. Nearly all the H. influenzae were unencapsulated; that is, they did not have an outer sugar capsule which is often required to make the bacterium more virulent. The encapsulated H. influenzae type b (Hib), for example, was the most common cause of bacterial meningitis in your children prior to routine immunisation. We also found that infection with unencapsulated H. influenzae was associated with poor pregnancy outcomes, including miscarriages, stillbirth and premature birth.
MedicalResearch.com: Were any of the findings unexpected?
Dr. Ladhani: Previous studies with small number of cases had indicated a possible increase associated with pregnancy but there are few case reports of severe unencapsulated H. influenzae infection during pregnancy, but none of the studies have been large enough to accurately estimate the increased risk during pregnancy or to assess pregnancy outcomes.
MedicalResearch.com: What should clinicians and patients take away from your report?
1. Invasive unencapsulated H. influenzae infections are uncommon in healthy adults, but can cause serious illness in pregnant women.
2. We only assessed cases where unencapsulated H. influenzae was isolated from an sterile site. The true burden of infection may be higher if we also consider non-invasive infections such as pneumonia and lower genital tract infections, which were not captured in our surveillance.
3. Clinicians should consider unencapsulated H. influenzae as a serious pathogen during pregnancy and ensure that appropriate microbiological tests are done to identify this bacterium not only in pregnant women who develop a serious infection but also those with early miscarriage, stillbirth and premature birth.
4. We also have to move towards merging maternal and infant case notes in order to better understand the true burden of perinatal infection. We identified a number of newborn babies who were seriously unwell at birth but the causative pathogen was not identified, most likely because their mother had received antibiotics during labor. Integrated case notes would allow us to better assess the devastating effects of specific infections in pregnant women as well as newborn babies
MedicalResearch.com: What recommendations do you have for future research as a result of this study?
1. We need to determine the true burden of unencapsulated H. influenzae and other bacteria such as group A and group B streptococci on early pregnancy fetal losses. Such cases are often under-investigated, especially for infection. A systematic assessment of all early pregnancy losses over a period of time would provide invaluable information on the contribution of serious infections and identify strategies for prevention
2. Further studies are also needed to test whether the unencapsulated H. influenzae causing serious infections in pregnancy are genetically the same as those causing respiratory tract infections. This information would be vital for developing vaccines for preventing unencapsulated H. influenzae infections in the future.
Risk of Invasive Haemophilus influenzae Infection During Pregnancy and Association With Adverse Fetal Outcomes
Sarah Collins, MPH; Mary Ramsay, FFPHM; Mary P. E. Slack, FRCPath; Helen Campbell, MSc; Sally Flynn, FIBMS; David Litt, PhD; Shamez N. Ladhani, MRCPCH, PhD
JAMA. 2014;311(11):1125-1132. doi:10.1001/jama.2014.1878