The Effects on Fetus of Progesterone Used for Labor

Progesterone is a hormone that the body produces naturally as a way of supporting a pregnancy. If a woman has indicators that suggest she is at risk for premature labor, she may be prescribed supplementary progesterone in an effort to avoid early onset of labor. Progesterone as a treatment for preterm labor is generally believed to be quite safe for both the mother and her developing fetus, especially considering the health risks to babies associated with being born prematurely.

Function of Progesterone

• During a woman's menstrual cycle, certain cells in her body starts to manufacture progesterone after she ovulates in preparation for a possible pregnancy. If the progesterone-producing cells are not supported by pregnancy hormones, they start to degrade and progesterone levels drop. Dropping progesterone levels signal the body to begin menstruation. If a woman instead becomes pregnant, pregnancy hormones keep the progesterone-producing cells alive and functional, and the progesterone helps to support the pregnancy and facilitate various changes in the body.

Risks of Preterm Labor

• Preterm labor is defined as labor that begins before 37 completed weeks of pregnancy. According to MayoClinic.com, babies born before 37 weeks have an increased risk of "low birth weight, breathing difficulties, underdeveloped organs and potentially life-threatening infections." The risk of having a baby more than three weeks early increases with a history of preterm birth, being pregnant with two or more babies, diabetes, infections, physical abnormalities of the cervix or uterus, smoking and other health concerns. Some difficulties are not seen in the child until years after a preterm delivery.

Use of Progesterone to Prevent or Delay Preterm Labor

• Progesterone relaxes the smooth muscles of the body, which is one of the causes of heartburn during pregnancy. Weekly injections of progesterone can slow or stop contractions of the uterus and may help to facilitate the prolonging of the pregnancy with certain types of preterm labor risks. Progesterone treatment is not 100 percent effective. Studies have shown that it reduces the risk of preterm delivery by approximately one-third, and is much less effective when the mother is carrying more than one child.

Risks of Progesterone to Mother

• According to Healthline, the risks to the mother of progesterone treatment is minimal and generally limited to irritation associated with the injection itself.

Risks of Progesterone to Baby

• There are anecdotal concerns, originating in the 1970's, about risks of fetal limb deformities and stillbirths associated with progesterone treatment. Careful studies on animals and humans have determined that progesterone treatment does not cause an increased risk of fetal limb deformities or stillbirths. The risk of any drug causing limb deformities after 16 weeks gestation is mitigated as the major formation of these structures occurs before 12 weeks. In animals given dozens of times higher doses of progesterone, there were still no reports of deformations, altered sex ratios or other birth defects.

Weighing the Risks

• Although any medical intervention during pregnancy needs to proceed with caution, progesterone treatments have been shown to be safe, both in animal trials and in years of use in humans. There are alternative treatments available, but these do not work as well or have undesirable side effects. Considering the very real health concerns related with preterm delivery, a woman, in conjunction with her doctor, may decide that the benefits of progesterone treatments outweigh the risks in her situation.