Why do I need progesterone after embryo transfer, and is it normal to feel this bloated and tired?

Progesterone is the hormone that prepares and maintains the uterine lining so an embryo can implant and an early pregnancy can be supported. In many IVF and frozen transfer cycles, the body doesn't make enough on its own, either because of how the ovaries were stimulated or because a medicated cycle without ovulation was used. That is why extra progesterone, called luteal phase support, is prescribed. It can be given as vaginal gels or pessaries, oral or under-the-tongue tablets, or injections, sometimes in combination. Side effects are very common and include bloating, breast tenderness, tiredness, sleepiness, mood changes, constipation and mild cramping. Vaginal forms can cause discharge or irritation; injections can cause soreness or lumps at the injection site. These symptoms are similar to early pregnancy symptoms, so they don't tell you whether treatment has worked. Do not stop or reduce progesterone without your doctor's advice, even if you have spotting or a negative home test, as stopping early can affect a pregnancy that is developing. Contact your doctor if you have heavy bleeding, severe pain, a hot, red or very painful injection site, signs of allergy, calf pain or swelling, chest pain or breathlessness. Ask your centre how long you'll need to continue if the test is positive.