Prenatal testing of an embryo or fetus is available in most jurisdictions in Canada but is not mandatory. Some parents would like to obtain information about the characteristics of an embryo or fetus before birth, whereas others would prefer to wait until after the birth to consider possible abnormalities. Will it have a deformed foot? Will it carry or have a genetic abnormality? Prenatal testing is often done if there are reasons to suspect the fetus might harbor some kind of defect. In other instances, the parents may simply want to know: Will it be a boy or a girl? Several technologies are available to answer these questions prenatally. What use is made of the information obtained this way is a controversial issue, especially if it results in a decision to abort the fetus. It would have eugenic implications only if a decision to terminate the pregnancy were made because of some kind of genetically transmissible defect carried by the fetus, and only if a child born with such a defect would nevertheless be viable and capable of reproducing as an adult. The rarity of such cases implies that eugenic consequences of prenatal testing are likely to be trivially small (Wahlsten, 2015).
Ultrasound can be applied to the mother’s abdomen directly over the fetus in order to visualize its larger anatomical features on a video monitor. The ultrasound cannot be heard and has such a low intensity that it does not harm the mother or the fetus. There is virtually no risk of infection from this method. The sound is sent by a transmitter and the sound waves reflected back from the body of the fetus are detected by a receiver. The technician doing the test passes the device over different places on the abdomen and watches the image on the screen in order to find the best position for seeing different body parts. In some hospitals the mother can also watch the action on the screen. Sex can be known by observing the genital region. Boys have a distinct bulge where the penis is located. Large deformities of the feet or hands can also be detected, as can large defects of the face such as cleft lip. Hydrocephalus would be evident too. The best ultrasound machines can even see the internal organs of the child. Ultrasound is useful mainly in a relatively mature fetus where all the organs have formed and are fairly large. Best results are obtained in the third trimester of pregnancy, a time when abortion of the fetus is relatively difficult and can pose a danger to the mother’s health.
Amniocentesis can be used to sample the amniotic fluid in which the fetus is floating in the womb. Under guidance from ultrasound, the technician inserts a large needle through the wall of the mother’s abdomen into the uterus and then through the chorion and amnion. A small sample of aminiotic fluid is withdrawn and the small wound is closed. When done properly, risk of damage to the fetus or infection is low, but there is some risk. The cells floating in the amniotic fluid come from the fetus and have the same genetic makeup as the fetus. The DNA of the fetus can then be assessed for a wide range of possible defects to determine if the child would likely have a genetic disease or carry a genetic mutation. This is sometimes done because of a family history of a particular kind of disease such as Huntington disease or because of advanced parental age that is associated with an increased risk for abnormal chromosomes. The DNA test will reveal whether the fetus carries the defective Huntington gene or an extra chromosome. As DNA sequencing technology improves and gets cheaper, it is becoming possible to determine the entire DNA sequence of the fetus in order to check for a mutation in any one of thousands of genes. The results from whole-genome sequencing will usually be very difficult to interpret because most fetuses carry a few novel mutations not present in either parent, and the connection between many mutations and outright disease is often not known.
Non-invasive prenatal screening (Petch, Caulfield and Okun, 2014) examines a sample of the mother’s blood to find DNA from the fetus that is derived from cells that often cross the placental barrier. The DNA of the fetus differs from that of the mother, and it can be assessed for a wide range of genetic and chromosomal abnormalities, just as is done using amniocentesis. The procedure is not widely practiced in Canada and is available mainly via private clinics. Because the screening method is not perfectly predictive, it is considered good practice to confirm any suspected abnormality with amniocentesis (Perinatal Services BC, 2014). Ontario recently approved the procedure for older women who have a higher risk of conceiving a fetus with Down syndrome. The first large scale study of the procedure is now being done in Alberta (Harris, 2014). Eventually it may provide a relatively inexpensive way to avoid most instances of the more invasive amniocentesis.
Prenatal testing is controversial because of what the parents and doctor may decide when they get the results of the test. In some countries the parents may want to have a boy and will direct that a female fetus be aborted. A child with a deformed foot or face may also prompt the parents to ask that the pregnancy be terminated. Likewise, it may be terminated if the fetus has Down syndrome (extra copy of chromosome 21) or a severe genetic mutation known to cause disease. The decision to terminate a pregnancy is made by the parents and doctor, not by an edict from a government agency. It is usually not decided in order to improve the biological qualities of the future population of a country and therefore is not a eugenic measure. Instead it is done to relieve the parents of the burden of caring for a deformed or genetically defective child and save the government the costs of future medical care. In the case of fetal sex selection, it is done for purely social reasons. Having two X chromosomes and being female is not an abnormal condition.
Harris, G. (2014) New prenatal screening less-invasive. Alberta Health Services, Sept. 12, 2014. (http://www.albertahealthservices.ca/10409.asp#)
Perinatal Services BC. (2014) Non-invasive prenatal testing (NIPT) availability in BC. March. (http://www.perinatalservicesbc.ca/NR/rdonlyres/58AFCAE0-945E-4ACB-8EC6-99CE2817128A/0/NIPTlistofoptionsupdated18March2014.pdf)
Petch, J., Caulfield, T. and Okun, N. (2014) Non-invasive prenatal testing and chromosomal microarray: changing the landscape of prenatal genetic testing. Healthy Debate, May 1, 2014. (http://healthydebate.ca/2014/05/topic/non-invasive-prenatal-testing)
Wahlsten, D. (2015) The consequences of eugenic sterilization in Alberta. In F. W. Stahnisch and E. Kurbegović (Eds.), In progress. Athabasca University Press, in press.