Dec. 22, 1999 (Los Angeles) -- A hormone commonly produced during pregnancy can help doctors identify the best candidates for drug rather than surgical treatment of tubal ectopic pregnancy, according to a new study in TheNew England Journal of Medicine.
Ectopic pregnancy is the implantation of an embryo, or fertilized egg, in a location other than the uterus, where it should be normally, says fertility specialist Barry Ripps, MD. Ectopic pregnancies usually occur in one of the fallopian tubes and are sometimes called tubal ectopic pregnancy. The embryos are rarely normal and never viable, Ripps explains. Tubal ectopic pregnancy used to be treated with surgery, but more and more doctors are prescribing injections of a drug called methotrexate, which prevents the cells of the embryo from multiplying. However, it has been difficult to predict who would respond to this treatment. This study suggests that levels of human chorionic gonadotropin (HCG), a hormone made by placental cells that attach the fetus to the uterine wall, reflects the size of the developing embryo and can predict who will respond to treatment with methotrexate. Women whose HCG levels are 15,000 or less seem to have the best chance of success. The age of the fetus can vary among individuals with this level, but usually corresponds to an age of around eight to nine weeks.
The study also demonstrates that other factors, such as size of the embryo or the presence of fluid in the abdominal cavity, were not important predictors of treatment efficacy, says Ripps, an associate professor of medicine and board-certified reproductive endocrinologist and fertility specialist at the University of Florida in Pensacola. He was not involved in the study.
Lead author Gary Lipscomb, MD, and his colleagues at the University of Tennessee in Memphis reviewed the cases of 350 women with ectopic pregnancies who received injections of methotrexate. In some of these patients, heart activity in the fetus was detectable. If a patient's HCG level did not decline by at least 15% between four and seven days after the injection, she would receive another injection. Subsequent doses were given if HCG levels remained high or if fetal heart activity was still present. Women who did not respond after three doses underwent surgery to terminate the pregnancy, except for one woman who received four doses of HCG. In all, 320 women were treated successfully with methotrexate.
Of 287 women whose HCG levels were 10,000 or less, 268 were successfully treated with methotrexate. The treatment was successful in 282 (92%) of the 305 women whose HCG levels were 15,000 or less. Fetal heart activity was present in fewer of the successfully treated women than in those in whom treatment was a failure. The authors conclude that initial level of HCG is the best indicator of treatment success.
Methotrexate interferes with the metabolism of rapidly growing cells and often is used to treat cancer, Ripps tells WebMD. Side effects are rare in patients who undergo one-time treatment, but termination of the pregnancy may cause pain and cramps. Studies Ripps has conducted at the University of Florida suggest that, like women who undergo surgery, 80-90% of patients preserve an open fallopian tube after methotrexate treatment, making it possible for them to bear children in the future.