Pregnancy and birth after assisted reproduction.

Pregnancy and birth after IVF has attracted much critical attention. Overall, pregnancy rates are about 30-40% with three transferred embryos. Abortion rates are high before 19 weeks of gestation, at 8% of established pregnancies, and ectopic pregnancies are regular occurrences. Pregnancy rates are highest (35%) in women aged 20-24 years, declining to 10% at and above age 40. The use of intracytoplasmic sperm injection (ICSI) and blastocyst transfer has transformed the establishment of pregnancies for couples with differing indications. High rates of implantation are achieved with blastocyst transfers, although many embryos die in vitro before this stage. Twins and triplets can result in up to 50% of pregnancies. Heterotopic pregnancies are rare. Abortion afflicts fetuses before 12 weeks (vanishing fetuses). Rates of spontaneous abortion can be as high as 50% with quadruplets and quintuplets, and may be even higher in cases of fetal aneuploidy. At birth, prematurity is high, especially with twins or higher multiple pregnancies. Fetal reduction is used to reduce multiple pregnancies for singletons. Ovarian hyperstimulation is a risk associated with multiple pregnancy.