Hi, Thanks for consulting us. I would like to revise some facts about Depo provera birth control with you. Birth control with Depo-Provera begins immediately after the first shot if given within the first five days of a woman s menstrual period. It may take about one week to effect if given after the first five days of the cycle. So,to ensure that our patient is not pregnant at the time of the first injection, the first injection should be given ONLY during the first 5 days of cycle, ONLY within the first 5-days postpartum if not breast-feeding and if exclusively breast-feeding, ONLY at the end of sixth postpartum week. A deviation from these precautions usually result in failures. We all know that LMP is no longer considered the most reliable marker to date a pregnancy, rather we rely more on dating ultrasound because LMP can be wrong in 40% of pregnant ladies. In other words we seek for lab evidence now. It is considered a good practice to do a pregnancy test ( preferably serum beta hCG) before initiating a new contraception to minimize the chances of undiagnosed/ unsuspected pregnancies. This can save us from situations like yours. As patients are lay persons & they cannot be blamed for any mishap. Doctors usually have to take the responsibility, if anything goes wrong. Last but not the least, no ill effects on the developing baby have been shown to occur if Depo Provera is given accidentally to a pregnant lady or in the very rare case where a woman becomes pregnant despite the injection. Hope this is somehow helpful for you. Best regards.