I have been trying to find information on selective reduction. How is the procedure done? What are the risks to mother and babies? What week of the pregnancy is the best time, and how long can you wait?

Lynn

Perhaps the worst complication of assisted reproduction procedures is a multifetal pregnancy -- that is, a pregnancy involving more than one or two fetuses. The desire to achieve a pregnancy creates a strong incentive for patients to produce multiple embryos with IVF. However, the financial and emotional costs of these pregnancies are unacceptable.

Fetal reduction is the termination of one or more of these fetuses, leaving the rest to continue to term. With success rates of 80 percent or more, this procedure appears both relatively safe (for the mother and the remaining fetuses) and an effective alternative to avoiding the many complications associated with pregnancies greater than twins or triplets. The procedure is usually performed between 9 and 11 weeks of pregnancy.

One study examined 127 multifetal pregnancies that were reduced to twin pregnancies and compared these with 354 fraternal twin pregnancies. Miscarriage rate was higher in the reduced twin pregnancies (12.6 percent compared with 2.5 percent). The reduced twins delivered about a week earlier on average, and as such these babies' weight was slightly lower at birth.