Progesterone is a hormone that is naturally present in females, but some women do not make sufficient amounts of it, resulting in a need for progesterone injections. These injections are considered helpful for infertile women and those in the first trimester of pregnancy, because low progesterone levels can make it difficult to achieve a healthy pregnancy. Increasing progesterone levels is also useful during late pregnancy to prevent preterm labor. Extra progesterone also is sometimes offered to women who have abnormal uterine bleeding, because shots of this hormone can stop the issue. Progesterone shots typically require intramuscular injection in the buttocks area, so many doctors advise patients to have help administering the shot if it is not given by a physician.
Women struggling with infertility often need progesterone injections during the luteal phase, just after they ovulate. The boost of progesterone can ensure that their uterine lining is thick enough to support implantation of an embryo. While progesterone levels are often boosted with an injection after in-vitro fertilization (IVF), they can also be increased with this method when an embryo is conceived naturally. As long as there is suspicion that a woman does not create enough progesterone to become pregnant without assistance, she may be given progesterone injections.
Sustaining the uterine lining long enough for an embryo to implant is also important during early pregnancy. Some women are unaware of their low progesterone levels until they become pregnant and start to notice signs of an impending miscarriage, such as vaginal bleeding. This may be a sign that the uterine lining is being shed, which will eventually flush out the embryo, so progesterone injections are often given in an attempt to keep the lining thick and in place. This type of shot is also often useful in late pregnancy, when it can stop preterm labor.
Additionally, progesterone injections may be offered to women who are not pregnant but are experiencing abnormal bleeding. For example, women suffering from amenorrhea, or the absence of a period, may need shots of progesterone to start menstruating again. Women with excessive vaginal bleeding may also benefit from progesterone injections, which can help straighten out a hormonal imbalance. It should be noted that even though progesterone is often prescribed to eliminate both abnormal bleeding and amenorrhea, it can also cause these issues in patients who previously did not experience them. Other side effects of progesterone shots include breast tenderness, weight changes and nausea.