Unexplained infertility’s determinants, correlation with bacterial vaginosis and anti-sperm antibodies among Congolese women: a case‒control study

Unexplained infertility (UI) affects 15–30% of infertile couples. This can be a very distressing experience for couples and challenging for clinicians because the diagnostic evidence is still weak. This study aimed to determine the risk factors for UI and its correlation with both bacterial vaginosis (BV) and anti-sperm antibodies (ASAs) among Congolese women. A matched case‒control study was conducted from August 2023 to July 2024. The sample included 144 individuals with UI and 144 fertile nonpregnant women attending postnatal consultations at Hôpital du Cinquantenaire de Kisangani. Logistic regression analysis was used to ascertain the determinants of UI, and the Phi (φ) coefficient was computed to evaluate correlations. Independent risk factors for UI included businesswomen (AOR = 4.21 [1.81–9.77]), resourceful women (AOR = 7.32 [1.59–33.77]), university education (AOR = 1.88 [1.02–3.46]), polygamous unions (AOR = 2.49 [1.16–5.37]), obesity (AOR = 2.21 [1.34–3.65]), sex with casual partners (AOR = 10.21 [3.45–30.17]), alcohol consumption (AOR = 1.83 [1.13–2.96]), use of indigenous products in the vagina (AOR = 2.41 [1.01–5.76]), premature menarche (AOR = 3.59 [1.136–11.37]), unsafe abortion (AOR = 5.93 [2.01–17.48]), BV (AOR = 8.91 [4.83–16.44]), and positive ASA (AOR = 14.9 [8.18–27.13]). BV (φ coefficient = 0.38) showed a moderate positive correlation with UI, and ASA (φ coefficient = 0.50) exhibited a strong positive correlation. UI among Congolese women was linked to sociodemographic, behavioural, and clinical factors. BV and ASA emerged as major correlates of UI. While these associations highlight the multifactorial nature of UI, causality cannot be inferred. Comprehensive infertility evaluations should consider screening for BV and ASA. Future research should investigate the management of ASA and BV in relation to UI to enhance fertility outcomes.