The prevention of preterm birth (PTB) poses a global challenge, as 14.9 million infants (11%) are estimated to be born before 37 completed weeks of gestation each year. In Europe, PTB rates range between 5.2% in Iceland and 10.4% in Cyprus.
Up to 40% of PTBs are associated with genital tract infections. The vaginal pH can reflect changes in the vaginal milieu and may therefore serve as an indicator of a local infection at an early stage. Furthermore, an increased vaginal pH ≥ 5.0 in pregnancy is associated with more caesarean sections, poorer neonatal outcome and increased admission rates to a neonatal intensive care unit. In numerous studies, bacterial vaginosis (BV) has been discussed as a cause for PTB. However, a Cochrane review showed that an effective eradication of BV during pregnancy did not decrease PTB rates. It was suggested, that a routine measurement of the antenatal vaginal pH could reduce the overall PTB rate through a more rapid identification, and subsequent treatment, of abnormal vaginal flora. In 2000, promising results prompted an implementation of a self-assessment programme in five German federal states, which meanwhile became established nationwide albeit a lack of rigorous evidence for its benefits. Observational study findings remain heterogeneous. It is therefore questionable, whether a routine assessment of the vaginal pH can contribute to reduce PTB. Therefore, it was decided to conduct a systematic review and meta-analysis investigating, whether an increased antenatal vaginal pH >4.5 is associated with an increased preterm birth rate.