Is there an interaction between cervical length and cervical microbiology in the pathogenesis of preterm labour?

Transvaginal ultrasound of the cervix is increasingly used to estimate cerv ical length during pregnancy. Initially used to determine a possible need f or cervical suture, the technique has been shown to be of value in the pred iction of preterm delivery. In addition, bacterial vaginosis has been shown to be associated with an increased risk of preterm delivery. We hypothesis ed that shortening of the cervix and potential cervical pathogens, in parti cular the presence of bacterial vaginosis, act synergistically in the patho genesis of premature labour. Three hundred and sixteen women were recruited for prospective longitudinal follow-up, with both transvaginal ultrasound and cervical bacteriology performed at approximately 18 and 28 weeks gestat ion. A strong correlation was found between a shortened cervix and preterm delivery (p < 0.02 at 18 weeks; p < 0.001 at 28 weeks). Women with both a s hort cervix and cervical pathogens had the highest risk of preterm delivery (43%), although not significantly greater than a short cervix with normal cervical flora (31% preterm delivery). In the presence of a normal cervical length, preterm delivery rates in the presence of normal nora and potentia l cervical pathogens were much lower (9% and 5% respectively).