Improved criteria to identify risk for spontaneous preterm birth due to
a short cervix
Objective Does the combined analysis of compounds in vaginal secretions
plus vaginal microbiota composition improve the ability to predict risk
for spontaneous preterm birth (SPTB) in women with a short cervix.
Design Prospective observational study Setting Three hospitals in Brazil
Samples Vaginal secretions from 568 women at 21-24 weeks gestation with
cervical length measurement. Method Vaginal microbiome composition was
determined by analysis of the V1-V3 region of the bacterial 16S
ribosomal RNA gene. D- lactic acid and tissue inhibitor of matrix
metalloproteinase (TIMP)-1 in vaginal secretions were measured by ELISA.
Main outcome measures SPTB in relation to cervical length and dominant
vaginal bacteria. Results When Lactobacillus crispatus was the dominant
bacterium the concentration of TIMP-1 was lower, and D-lactic acid was
higher, than when either L. iners or Gardnerella vaginalis predominated
(p < 0.001). By ROC analysis, a D-lactic acid level
< 0.7 mM, and a TIMP-1 level > 1.5 ng/ml best
predicted the absence of L. crispatus dominance. Vaginal levels of
TIMP-1 were highest (p = 0.024) and D-lactic acid levels were lowest
(p=0.032) in women with the shortest cervical length. The absence of L.
crispatus dominance increased the sensitivity for predicting a SPTB from
22.4% to 81.8% or 78.3% in women with a cervical length
<25mm or <30mm, respectively. Conclusions Low
vaginal D-lactic acid and high TIMP-1 indicates the loss of L. crispatus
dominance and increased risk for SPTB in women with a short cervix.