Other options for infertility involve the freezing of embryos and sperm for later fertilization. This can be beneficial for men and women who are diagnosed with illnesses (such as cancer) whose treatment might interfere with their ability to manufacture healthy sperm or ova (recall Lance Armstrong’s story in Chapter 5, Sex in Real Life, “Testicular Cancer,” on page 151). Sperm can be frozen and stored in liquid nitrogen for many years through a process called sperm cryopreservation.
The sperm can be collected from the testis, epididymis, or from an ejaculate. The effectiveness of the sperm, once thawed, is variable, and sometimes the sperm do not survive the thawing process. Embryo cryopreservation is also possible; but, like sperm, not all embryos can survive the freezing and thawing process.
Recently, researchers in several countries have been experimenting with ova cryopreservation. Originally the intention was to thaw and fertilize frozen ova for IVF or ICSI. Large numbers of immature ova can be retrieved from unstimulated ovaries, whereas mature ova can be retrieved only after the use of fertility drugs (Hardy et al.,
2002) . The practice of ova freezing has been difficult because the ova seem to be vulnerable to chromosomal damage by freezing (Gosden, 2005; Wininger & Kort, 2002). If this procedure is successful, women who choose to delay childbearing until later in life could store ova while they are young. It could also give women who must undergo radiation and/or chemotherapy for cancer an option to save ova for a later pregnancy (Roberts & Oktay, 2005). At this time, only sperm and embryos are routinely frozen for use later on.
The fetus in place in the uterus.
Question: Do physicians ever mix up ova or embryos during embryo transplants? How do they know whose is whose?
Embryos are rarely mixed up because collection requirements are strictly followed. However, even using these methods, accidents can happen. In late 1998, there was a case of African-American and white twin boys born to a white couple who had undergone an embryo transplant in New York. In 2002, African-American twins were born to a white couple. Both of these were the result of embryo mix-ups during implantation. In many such cases, the offspring are returned to the biological parents if possible, and the birthing parents are given visitation rights. What is really interesting about these cases is that the main reason physicians knew there was a mix-up was because of skin color. How many cases go undetected when skin color isn’t a giveaway?
C’K A HEALTHY PREGNANCY
Pregnancy is divided into three periods called trimesters. Throughout these trimesters important fetal development occurs as a pregnant woman’s body changes and adjusts to these developments. We will now explore these changes.