Objectives: To assess the efficacy of oral micronized progesterone SR 300 in preventing preterm labour after arresting it, with changes in dosage timing. The main purpose of this study is to find out whether there is a clinico pharmacological correlation if same drug is given at different timings Materials and Methods: Prospective randomized study was done at our institution. Total sample size of 130 women who came in preterm labour and process of preterm labour was arrested with Tocolytics were included in the study group. Sample was divided into 2 groups of 65 womens in each group in view of prevention of preterm labour. One group was given MNP SR 300 at 9am and 2nd group was given MNP SR 300 at 9pm by oral route. They were studied for the difference in maternal outcomes like prolongation of gestational age at delivery and neonatal outcome like birth weight, maturity, morbidity and mortality. Results: Both the group were comparable with respect to age and parity. Our study showed that there was no statistically significant difference with respect to maternal and fetal outcome with changes in timings to two groups who were given MNP SR 300 orally at 9am and 9pm. Conclusion: More studies on big samples are recommended to further analyse our results, since this the only study till date.