Depo-Provera begins working 24 hours after the first injection and continues to work as long as injections are given every 10-13 weeks. It is a very effective method of birth control. According to Contraceptive Technology, only three out of 1000 women who receive their shots on time become pregnant during the first year of use. As long as the first sexual intercourse occurred more than 24 hours after her first injection and as long as your girlfriend is getting her shots on time, there is very little risk of pregnancy.
2. January 2012
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