The vaginal microbiome plays an important role in pregnancy. In a healthy pregnancy with term delivery (after 37 weeks), there is typically an increase in vaginal lactobacilli. In this way, the vaginal microbiome becomes more stable and offers more resistance against infections. In contrast, vaginal dysbiosis and infections are more commonly seen in pregnancies complicated by premature rupture of membranes and spontaneous preterm birth.

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Spontaneous preterm birth can have many different causes. In about 2/3 of the cases, an ascending infection from the vagina plays a central role. Often these infections are subclinical (without typical infection symptoms such as pain, abnormal vaginal discharge, or fever). As a result, we usually only diagnose the consequences of the infection (premature contractions, shortening or opening of the cervix, premature rupture of membranes), rather than the infection itself. This explains why antibiotics usually come too late to prevent premature birth. Even the preventive administration of antibiotics does not seem to solve the underlying problem, namely the abnormal vaginal microbiome. Moreover, a possible side effect of antibiotics is that they also eliminate the "healthy" lactobacilli. For this reason, we are looking for ways to support a healthy vaginal microbiome, rather than treating infections or their consequences. In this regard, probiotics are a promising strategy.

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Probiotics are living bacteria that can contribute to health. There are countless probiotic food supplements on the market worldwide, all with different compositions and indications. However, not all probiotics are beneficial for the vaginal microbiome and not all lactobacilli are adapted to survive in the human vagina. The probiotic in this study has a unique composition and is not available on the market. We investigate the effect of probiotic intake on the vaginal microbiome and on pregnancy duration in women with an increased risk for spontaneous preterm delivery.