Haemophilus Influenzae Bacterial Infection Linked to Poor Pregnancy Outcomes

Pregnancy and Haemophilus InfluenzaePrevious research published earlier in the year suggested a link between bacteria and premature preterm rupture of membranes (PPROM) in pregnant women, often resulting in preterm birth. Now a new study published in the journal JAMA suggests that pregnancy puts women at an increased risk for infection with the bacterium Haemophilus influenzae, subsequently increasing the risk of fetal loss, preterm birth, and stillbirth.

Haemophilus influenzae, or H. influenzae, is a bacterium that can cause a severe infection, usually in infants and children younger than five years of age. The most severe types of H. influenzae diseases include pneumonia (lung infection), bacteremia (bloodstream infection), and meningitis (infection of the covering of the brain and spinal cord). There are six identifiable types of Haemophilus influenzae bacteria (a through f) and other non-identifiable types (called nontypeable).

Past studies have also suggested that pregnancy increases the risk of invasive H. influenzae disease. However, the association was based on a small number of cases.

For the present study, researchers led by Sarah Collins of Public Health England in the United Kingdom sought to investigate the link between pregnancy and H. influenzae infection further. The researchers analyzed the outcomes of invasive H. influenzae disease over a four-year period in women from England and Wales between the ages of 15 and 44 years old using data gathered from doctors between 2009 and 2012.

According to the data, confirmed infections of invasive H. influenzae disease was low at 0.50 per 100,000 (171 women). However, 42 percent (71 of 171) of the women were pregnant at the time of infection.

The researchers discovered that pregnant women have an increased risk of infection from an unencapsulated (nontypeable) strain of H. influenzae bacterium.

Additionally, 93.6 percent of the women infected with the unencapsulated strain during the first 24 weeks of pregnancy experienced fetal loss and 6.4 percent experienced extremely premature birth. When infection occurred after the first 24 weeks of pregnancy, 28.6 percent of the infected women experienced premature birth and 7.1 percent experienced stillbirth.

Compared with the national average rate of pregnancy loss in the UK, the risk of loss was 2.9 times higher following invasive H. influenzae disease.

In other words, pregnancy appears to increase the risk of infection with H. influenzae bacterium, and H. influenzae infection appears to increase the risk of negative pregnancy outcomes including fetal loss, stillbirth, and premature birth.

Comment the researchers on the findings, “Even though none of the pregnant women died in this study, the high rate of pregnancy loss makes H. influenzae an important pathogen to identify early and treat rapidly.”

The researchers also warn that the study involved only follow-up of laboratory-confirmed invasive cases, so estimates should be considered minimums. The actual rates of infection and negative pregnancy outcomes are likely higher.


Risk of Invasive Haemophilus influenzae Infection During Pregnancy and Association With Adverse Fetal Outcomes:
Specific Bacterial Infection Linked to Poor Pregnancy Outcomes:

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