Pregnancy symptoms and depo injections

Patient: My girlfriend and i had unprotected sex about 3 weeks ago. She is on the depo shot and was supposed to get in renewed in the next 5 days after the night we had sex. There was a little blood that came out of her during sex that i found on me. Its been three weeks and she claims that she is having pregnancy symptoms but im not for sure she got the depo shot around January 4th and it is now january 25th. What can you tell me about the depo shot and is there a good chance that she really could be pregnant??

Doctor: Depo injections for pregnancy are given every three months to prevent pregnancy. It contains synthetic progesterone and no estrogen, stops the ovaries from releasing eggs and causes the cervical mucus to thicken and changes the uterine lining, making it harder for sperm to enter or survive in the uterus. Usually, this type of contraceptive method protects for 13 weeks. Since you had unprotected sex within a week before the next injection, the chances of pregnancy is unlikely, however your girlfriend may want to do a pregnancy test just to be sure. Pregnancy has to be ruled out completely in order to start the next dose. The medication could change the way menses used to be and sometimes causes irregular periods. I hope this answers your question, take care.