Determination of the probable date of delivery using vaginal cytology as an index.

70 normal pregnant females were used for the study, 47 of whom had vaginal cytological follow-up from week 32 till the first stage of labour. 23 additional patients had vaginal smears made in the first stage of labour. The combined intermediate cell value was used as an index of impending labour with values at week 38 being 90.35 +/- 0.0863, week 39 being 89.41 +/- 0.1934, week 40 being 81.25 +/- 0.0558 and at labour being 78.75 +/- 0.0995. The primigravidae showed a stepwise, gradual decrease in mean intermediate cell value from week 38 onwards, while the multigravidae showed a drop only at week 40. From this study, it has been shown, that it is possible to predict labour. It was also evident that there is a difference in reactivity of a primigravida versus multigravida to decreases in circulating progesterone as gauged by intermediate cell counts.