One technique that may improve, at least marginally, the chances of successful implantation of the embryo is called «assisted hatching.» A small opening is made in the outer layer of the embryo, by means of a tiny laser beam; this opening seems to enhance the embryo’s attachment to the wall of the uterus. The technique is similar to the gardener’s trick of pricking the hard outer shell of some seeds before planting, to encourage germination.
To help support the lining of the uterus during the time when the new embryo is implanting, progesterone is usually given for 10 to 14 days. Progesterone is the hormone produced naturally by the ovaries in the second half of a woman’s cycle, so this administration of progesterone mimics what happens in natural conception. Sometimes ultrasound exam shows that the lining of the woman’s uterus is not ready for implantation of the embryo and the embryos will be saved until the next cycle.
One side effect of ART can be the hyperstimulation of the ovaries, producing cystsЎЄcollections of fluidЎЄwhich can burst, causing pain, vomiting, and distension of the abdomen. Sometimes these symptoms are so severe that hospital admission is required. This is less of a problem than it used to be, because we now understand better how to «fine-tune» what’s happening in the ovaries, monitoring with ultrasound and adjusting the hormone doses. Twin pregnancy is still common, however. When two embryos are transferred into the uterus, usually one does not develop, and a single baby (called a «singleton») results. In about 20 percent of cases, however, both embryos develop. The rate of twins in mothers receiving ART is about twenty times that of the general population. Many couples are delighted to have twins, but, these pregnancies have more risk than singleton pregnancies and there is a greater possibility of losing both babies.
In the last step of a cycle of ART, the embryo or embryos are introduced into the uterus by means of a tiny cannula (tube) passed through the cervix. Generally this process takes only a few minutes and is no more uncomfortable than having a Pap smear taken.
In women over 35, clinical pregnancy results in about 30 percent of women after a single cycle of ART, and the baby is delivered successfully in 15 to 20 percent of these cases. Success rates decrease, however, with the age of the woman; and in women over 42, only about 2 percent produce live births if the woman’s own eggs are used. Studies of ART records show that a successful pregnancy carried to term takes an average of six cycles. Barbra and Cory are among the lucky ones. They achieved a successful pregnancy on Barbra’s second cycle of ART. Only one embryo developed, and Barbra delivered a healthy son at 38 weeks. (Statistically, ART is slightly more likely to produce boys than girls.)
There are variations on this basic ART theme. GIFT, or gamete intra-Fallopian transfer, is the transfer of the egg and the sperm separately into the Fallopian tube, with fertilization taking place in the Fallopian tube; this is feasible only if there is no Fallopian tube disease or blockage. ZIFT, zygote intra-Fallopian transfer, is the transfer of the fertilized egg into the Fallopian tube. In both instances, transfer to the Fallopian tubes is technically similar to harvesting the eggs. Again, the woman needs to have healthy, patent Fallopian tubes. GIFT and ZIFT are rarely used now; we mention them because you may have friends who have had these procedures or you may come across them in your reading. Also, as we mentioned, when a cycle of regular IVF is unsuccessful in couples where there is no apparent problem with the man’s sperm, it may be decided that in the next cycle ICSI will be used to try to achieve fertilization, because this has been shown to be useful in some cases.
Последние обсуждения