Why did the multiple pregnancy rate increase?
About one-third of the increase in multiple pregnancies is due to the fact that more women over age 30 are having babies (2). Women in this age group are more likely than younger women to conceive multiples.
The remainder of the increase is due to the use of fertility treatments, including fertility-stimulating drugs and assisted reproductive technologies (ART), such as in vitro fertilization (IVF). In IVF, eggs are removed from the mother, fertilized in a laboratory dish and then transferred to the uterus. About 44 percent of ART pregnancies result in twins, and about 5 percent in triplets or more (3).
Doctors now monitor fertility treatments carefully so that women have fewer, but healthier, babies. This involves limiting the number of embryos transferred during IVF. In 2006, the American Society for Reproductive Medicine and the Society for Assisted Reproductive Technology issued updated guidelines on the best number of embryos to transfer, depending on a woman’s age and other factors (4). For example, the guidelines recommend that doctors transfer no more than two embryos for women under age 35, and consider transferring only one embryo for women in this age group who are considered most likely to become pregnant.
Doctors monitor women taking certain fertility drugs with ultrasound. If ultrasound shows that a large number of eggs could be released during a treatment cycle, the doctor can stop the treatment and counsel the woman accordingly.
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