To find out the safety, effectiveness and tolerability of using desogestrel (75 microg/day), a progesterone only pill on lactating mother, a prospective clinical study was undertaken among 200 lactating women during the period from 1st January 2010 to 13th June 2011 at Gice Clinic, Kalyani, Nadia, West Bengal. The same number of cases were taken as placebo for comparison. Desogestrel was started after six weeks of delivery for six months. Patients were reviewed at 8th, 12th, 16th, 24th weeks and one year. The very interesting results were found from the follow-up study that desogestrel (75 microg/day) did not alter the amount and composition of breast milk, pregnancy was not reported as compared to placebo. The drug had good tolerability, less side-effects and did not affect the growth and development of breastfed babies. Due to the safety, good efficacy, tolerability and less side-effects it is concluded that desogestrel (75 microg/day) was well accepted in majority of women (97.5%) and provided good contraceptive efficacy during the lactating period. This treatment does not have any effect on the growth and development of breastfed baby.