Synthetic preparations of the hormone progesterone, injectibles prevent conception by disrupting the natural hormone balance. Surplus progesterone, scientists believe, inhibits ovulation; makes the cervical mucus thick and scant, creating a barrier for the sperm; and makes the uterus lining less suitable for embryo implanting. And unlike the pill, supposed to be taken everyday, one dose of Net-En can keep pregnancy at bay for three months. Besides, explains N.C. Saxena, chief of reproductive health unit at the Indian Council of Medical Research (ICMR), progestin injectibles are suitable for breast-feeding women for whom oral pills are contraindicated. At any rate, argues H.S. Juneja, director of the Mumbai-based Institute for Research in Reproduction (IRR), no contraceptive is free from side-effects, which are rarely fatal. In comparison, risk from unwanted pregnancies is much higher.