Подпись:Another reproductive technology is in vitro fertilization (IVF), or the creation of a test-tube baby. In 1978, Louise Brown, the first test-tube baby, was born in England. Since that time, thousands of babies have been conceived in this fashion. The name is a bit deceiving, however, because these babies are not born in a test tube; rather, they are conceived in a petri dish, which is a shallow circular dish with a loose-fitting cover.

Many of the women who use this method have Fallopian tube blockage, which prevents fertilization in their tubes. Fertility drugs are usually used before the proce­dure to help the ovaries release multiple ova, and between four and six ova are re­trieved (with the use of microscopic needles inserted into the abdominal cavity). Natural-cycle IVF, in which no fertility drugs are used and immature ova are collected from the ovaries, has also been used (Marcus, 2003). In fact, natural-cycle IVF has been used since the early beginnings of the procedure and was used when Louise Brown was conceived.

After collection, the ova are put into a petri dish and mixed with washed sperm. Once fertilization has occurred, the zygotes are transferred to the woman’s uterus, where they should develop normally. Implantation problems with IVF are the biggest hurdle to overcome; it is estimated that only 5% to 30% implant (D. Wells et al., 2002). To in­crease the chances of implantation, typically several embryos are introduced at one time, which increases the possibility of multiple births. A pregnancy with multiple fetuses may lead to several negative health consequences for both the mother and child, including hypertension, miscarriage, cesarean delivery, low birthweight, and prematurity (Davies,

2005) . We will discuss some of these complications later in this chapter.

Preimplantation genetic diagnosis (PGD) can identify embryos that contain gene defects or missing chromosomes (Johannes, 2004; Sher et al., 2005). It is estimated that by 2004, approximately PGD-screened 1,500 babies were born worldwide. A PGD screening costs between $4,000 and $5,000.