Fetal Loss and Preterm Birth Caused by Intraamniotic Haemophilus influenzae Infection, New Zealand

Abstract

Invasive Haemophilus influenzae infection during pregnancy can cause preterm birth and fetal loss, but the mechanism is unclear. We investigated 54 cases of pregnancy-associated invasive H. influenzae disease in 52 unique pregnancies in the Auckland region of New Zealand during October 1, 2008‒September 30, 2018. Intraamniotic infection was identified in 36 (66.7%) of 54 cases. Outcome data were available for 48 pregnancies. Adverse pregnancy outcomes, defined as fetal loss, preterm birth, or the birth of an infant requiring intensive/special care unit admission, occurred in 45 (93.8%) of 48 (pregnancies. Fetal loss occurred in 17 (35.4%) of 48 pregnancies, before 24 weeks' gestation in 13 cases, and at >24 weeks' gestation in 4 cases. The overall incidence of pregnancy-associated invasive H. influenzae disease was 19.9 cases/100,000 births, which exceeded the reported incidence of pregnancy-associated listeriosis in New Zealand. We also observed higher rates in younger women and women of Māori ethnicity.

Keywords: Haemophilus influenzae; New Zealand; bacteremia; bacteria; fetal loss; infection; intraamniotic; maternal sepsis; neonatal sepsis; placenta; pregnancy; preterm birth; sepsis; sepsis in pregnancy.

Figure 1

Sites from which Haemophilus influenzae was isolated in maternal cases (A) and neonatal cases (B), New Zealand. Overlapping colored circles and ovals indicate multiple types of samples collected from the same cases. BC, blood culture; CSF, cerebrospinal fluid; HVS, high vaginal swab.

Figure 2

Relative risk for pregnancy-associated invasive Haemophilus influenzae infection, by ethnicity, in a multivariable regression model, New Zealand. Error bars indicate 95% CIs.