fertility news

The task of preventing multiple pregnancies in patients undergoing ovulation induction with or without intrauterine insemination (IUI) is more difficult than it is for patients undergoing in vitro fertilization (IVF) because there are no simple strategies to reduce the risk. The best approach is to monitor patients at high risk for multiples and either cancel the insemination cycle or convert them to an IVF cycle in which the number of embryos to be returned to the uterus can be controlled.

The best approach to preventing multiple pregnancy in ART is to limit the number of embryos transferred. The American Society for Reproductive Medicine (ASRM) has published guidelines however in the US patients and physicians jointly decide on the number of embryos to be transferred. The decision is based on the patient’s age, embryo quality and other criteria such as the patient’s success in prior cycles. For patients who have been unsuccessful in multiple cycles there may be a greater sense of urgency and a strong desire to transfer more embryos than would normally be prudent.

In other countries the maximum number of embryos a physician can transfer is legislated. In England, no more than two embryos can be transferred while in Canada, the maximum number is three. The ultimate goal of all physicians in the field is to achieve high pregnancy rates while transferring just one embryo however, that goal may be difficult to attain.

In recent years the ability of embryologists to culture embryos out to the blastocyst stage has enabled physicians to make better decisions regarding which embryos to select for transfer. There is data to suggest the transfer of two blastocysts results in the same pregnancy rate as the transfer of three. The obvious goal therefore should be to transfer one embryo without sacrificing pregnancy rates. There has been a consistent drop in the percentage of high order multiple pregnancies from ART because the number of embryos transferred has been reduced. In data published by the CDC high order multiples dropped from 7% in 1996 to 3.9% in 2002.

References:
American Society for Reproductive Medicine (ASRM) Guide for Patients: Multiple pregnancy and birth: twins, triplets and higher order multiples 2001.

Centers for Disease Control and Prevention, American Society for Reproductive Medicine, Society for Assisted Reproductive Technology. 2002 assisted reproductive technology success rates. Atlanta: Department of Health and Human Services, Centers for Disease Control and Prevention, 2004.

Multiple pregnancy associated with infertility therapy. The Practice Committee of the American Society for Reproductive Medicine. 2004; 82: Supplement 1 (S153-157).