Chorioamnionitis in the Second Trimester Secondary to Multidrug-Resistant Haemophilus influenzae Infection

Nontypeable Haemophilus influenzae (NTHi) is an emerging perinatal pathogen linked to chorioamnionitis, preterm birth, and early pregnancy loss. This case report describes the presentation, microbiologic findings, and management of second-trimester NTHi-associated chorioamnionitis, emphasizing diagnostic challenges and antimicrobial implications.

A 22-year-old woman at 22 weeks 3 days' gestation presented with preterm prelabor rupture of membranes (PPROM) and vaginal bleeding. Evaluation included cervical examination and bedside ultrasound. Placental tissue was collected for culture and antimicrobial susceptibility testing. The hospital course, clinical interventions, and postpartum outcomes were recorded. A literature review of reported cases was conducted to contextualize the findings and inform management strategies.

On admission, cervical dilation was 3 cm, and fetal heart tones were present. Ultrasound demonstrated anhydramnios. Maternal inflammatory markers were elevated, consistent with chorioamnionitis. Despite the use of antibiotics, spontaneous vaginal delivery occurred at 22 weeks 3 days, complicated by cord avulsion and manual placental extraction. Placental cultures grew NTHi resistant to ampicillin and amoxicillin-clavulanate but susceptible to ceftriaxone, azithromycin, and ciprofloxacin. Postpartum complications included retained products of conception requiring dilation and curettage. Reported cases similarly support ascending genital tract infection as the most likely source and demonstrate increasing antimicrobial resistance in pregnancy-associated isolates.

NTHi represents an uncommon yet clinically important cause of second-trimester chorioamnionitis and early pregnancy loss. Clinicians should consider NTHi in cases of intrauterine infection when standard pathogens are not identified or when empiric antibiotic therapy fails. Early recognition, comprehensive microbiologic evaluation, and antibiotic selection guided by susceptibility patterns are essential to optimize maternal and fetal outcomes. Rising antimicrobial resistance among NTHi strains underscores the need for continued surveillance and evidence-based management strategies in pregnancy.