The placental transfer of mifepristone (RU 486) during the second trimester and its influence upon maternal and fetal steroid concentrations

Article Abstract:

Mifepristone (RU 486) is a synthetic drug that stops the action of progesterone, the hormone necessary for the maintenance of a pregnancy. In some countries, mifepristone is used to achieve early therapeutic abortions. Abortions performed between the 12th and 24th week of pregnancy (second trimester) can be induced using prostaglandins, a hormone-like substance involved in the onset of labor. Second trimester abortions are more easily induced with fewer side effects when mifepristone is given before prostaglandin infusion. Similarly, mifepristone might be useful in improving the induction of labor at the end of pregnancy by softening the cervix before labor induction agents are given. However, mifepristone is transferred through the placenta to the fetus. Since mifepristone can reduce the level of progesterone and glucocorticoids (hormones involved in a variety of physiological processes), the use of this drug late in pregnancy could potentially effect the fetus. Before mifepristone can be used to enhance labor, the effects on the fetus must be known. The hormonal changes experienced by the mother and fetus during mifepristone treatments were assessed during second trimester pregnancy terminations. Six women between 16 and 19 weeks of pregnancy received 600 milligrams of mifepristone, and six women received a placebo prior to prostaglandin-induced termination of pregnancy. Mifepristone and its by-products were measured in the blood of the mother, the fetus, and in the fluid surrounding the fetus. There were no significant changes in the concentration of progesterone, cortisol (glucocorticoid), estrogen, or aldosterone (hormone that regulates fluids) in the mother's blood. However, the fetuses in the mifepristone-treated group had significantly higher aldosterone levels than the fetuses of women receiving the placebo (an average of 1,699 versus 999 pmol per liter). Concentrations of progesterone, estrogen, and cortisol were unchanged. Although, the small study population precludes any definitive statements regarding the effects of mifepristone on fetal hormones, further studies are warranted before mifepristone can be used to enhance labor induction. (Consumer Summary produced by Reliance Medical Information, Inc.)

Maternal-fetal exchange, Fetus, Physiological aspects, Steroid hormones, Labor, Induced (Obstetrics), Induced labor

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The efficacy of oral mifepristone (RU 38,486) with a prostaglandin E1 analog vaginal pessary for the termination of early pregnancy: complications and patient acceptability

Article Abstract:

Vacuum aspiration is a popular technique used in England and Wales to terminate unwanted pregnancies. Although the surgical procedure is relatively safe, some complications do arise. RU 38,486 is a drug given orally that blocks receptors on cells of the uterus which have a particular affinity for progesterone, the hormone necessary to maintain a pregnancy. When prostaglandin, a hormone-like substance that causes uterine contractions, is given in combination with RU 38,486, the expulsion of the fetus is enhanced. A pessary (a device inserted into the vagina) containing prostaglandins was inserted 48 hours after RU 38,486 had been administered to 100 pregnant women. Pregnancies were terminated in all patients, 95 complete and four incomplete (where some of the products of conception were retained). Nausea was experienced by 25 percent of the women and 15 percent vomited after RU 38,486 was administered. The prostaglandins given afterwards caused 13 percent of the women to vomit, 10 percent to have diarrhea and 23 percent to have pain requiring a pain killer. A pelvic infection was noted in one patient. Of the 40 women asked about the character of the blood loss with the termination, 16 (40 percent) reported a normal blood flow, eight (20 percent) reported a lighter than normal blood flow and 16 (40 percent) reported a heavier than normal blood flow. When asked if they would repeat the procedure a second time, 88 percent stated they would, while nine percent stated they definitely would not. Most of the women who would not repeat the procedure had incomplete terminations (three percent) or painful termination (six percent). A nonsurgical method of pregnancy termination has many advantages. The high success rate with minimal complications make RU 38,486 an attractive alternative to current surgical methods of abortion. (Consumer Summary produced by Reliance Medical Information, Inc.)

Health aspects, Product/Service Evaluation, Drug therapy, Abortion, Pregnancy, Unwanted, Unwanted pregnancy, Mifepristone (Medication)

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Transfer of prostaglandins to the fetus after prostaglandin E2 vaginal pessary administration

Article Abstract:

Labor can be induced by administering oxytocin which increases muscle contractions in the uterus. Although the use of oxytocin is widely used and considered safe, some imbalances of substances in the blood known as electrolytes can result. The induction of labor using prostaglandins has not resulted in reports of similar imbalances. Prostaglandins are substances made from fatty acids that are involved in many physiological processes during labor and delivery. An alteration in the balance of prostaglandins in the fetal blood can contribute to a poor fetal outcome. Prostaglandins for labor induction were administered by vaginal pessary, a device placed inside the vagina, to determine if they are transferred to the fetal circulation. Circulating maternal prostaglandins were found to be elevated; prostaglandin levels were also high in the blood of the fetus. Although no immediate adverse effects were evident, the long-term effects of maternal treatment with prostaglandins can potentially affect the well-being of the fetus. Further studies are warranted.

Research, Dosage and administration, Fetal blood

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