Salivary estriol
Studies on the physiology of parturition in sheep have
demonstrated the role of fetal hypothalamo-pituitary-adrenal
(HPA) axis and the resultant increase in the production of
estriol from the placenta at the onset of labor. Extrapolated to
the human pregnancy, premature activation of HPA axis in
preterm labor may increase the serum and salivary levels of
estriol in the mother and this may predict the onset of preterm
labor early. Two prospective trials showed that salivary estriol
was more effective in predicting preterm labor than traditional
risk assessment 13. However, this test has very poor sensitivity
and specificity and has a very high false positive rate, which
may increase the cost of prenatal care due to unnecessary
intervention. There is a diurnal variation of the maternal
salivary estriol level and it has been reported that administration
of betamethasone to effect surfactant production may
suppress maternal salivary estriol levels 14. Both these factors
may pose difficulties in interpretation of the results.
Screening for bacterial vaginosis (BV)
Infection is closely associated with PPROM, which accounts
for almost one third of preterm labor. Abnormal genital tract
flora at 26-32 weeks of gestation was associated with preterm
birth with an odds ratio (OR) of 1.4 to 2 15,16. Routine
screening for Group B streptococcus (GBS) in the antenatal
population for GBS carrier status prior to 32 weeks of
gestation may not identify women at high risk of preterm
rupture of membranes or of preterm labor 17. Attempts have
been made to screen for bacterial infections in the vagina so
that antibiotic treatment can be instituted to prevent PPROM
and hence, preterm labor. Such an approach would potentially
reduce the incidence of preterm births by about 25%. BV