Ob-Gyn questions? Ask a gynecologist online.
Hello, I am an OB/GYN and can help you with this. Do you know if you homozygous (two copies) or heterozygous (one copy) for Factor V Leiden? Have you ever had a blood clot? Either way, Plan B is progesterone only and should not increase your risk for blood clot. If you are pregnant or become pregnant, whether or not you have one copy or two copies of the gene will determine if you have to take medication during pregnancy.
That history is good news. If you are heterozygous (only one copy from your mom) and have never had a blood clot, you may not have to take medication during pregnancy depending on the recommendations of your doctor. Also with this history, your chances of having any adverse effects with Plan B is low. Plan B should be taken as soon as possible after unprotected sex (preferably within 72 hours and no more than 5 days after) if pregnancy is not desired. If you are heterozygous for Factor V Leiden, you can use progesterone only methods for birth control (Depo shot, Nexplanon implant, or IUD). You can discuss the best method for you with your doctor. Please let me know if you have any more questions.
You are very welcome!