Pregnancy and Genetics

Genetics has changed dramatically in the last few years as the impact of understanding human DNA has advanced. A few years ago, the ability to screen for genetic risk was very limited. Today, it is possible to screen for hundreds of genetic diseases with a simple blood test. However, genetic testing is a very sensitive topic for many families and before any genetic testing can be recommended, it is extremely important to discuss the meaning of these tests, particular with respect to their belief and values around the abortion issues.

There are two times in the reproductive lifetime of a family when genetic issues need to be explored:

Prior to conception or even, prior to marriage The optimal time to determine genetic risk is before pregnancy. Testing can be done to determine whether or not a family is at genetic risk and, if so, try to figure out how to proceed. Examples could be:

  1. A family history: hemophilia, Huntington’s disease
  2. Sickle Cell or Thalessemia Screening
  3. The 21 gene Ashkenazi Jewish Panel
  4. Cystic Fibrosis or Spinal Muscle Atrophy screening
  5. Multi gene recessive disease screening—this tests 400+ recessive genes simultaneously. (Counsyl test)

The question is when you find a couple at risk, what do you do about it? One option is in-vitro fertilization (IVF). Prior to putting the embryos back in a woman’s uterus, they are screened so only an unaffected embryo is used. This is called Pre-Implantation Genetics. This is costly, and for families with strong Pro-Life sentiments unacceptable. Another option is sperm donation from an unaffected male.

The second time is during the pregnancy. Natural conception occurs, and then the embryo is tested to see if it is affected. Specimens can be obtained either 1) by chorionic villus biopsy (CVS), amniocentesis or isolation of free fetal DNA from the mother’s blood.

The free fetal DNA (Harmony test or Verifi test) is particularly exciting since it virtually 100% accurate for Down Syndrome screening and highly accurate for Trisomy 18 and 13. It is also non-invasive and causes no risk to the baby. This technology can also be used for paternity testing and antenatal sex determination.

Chorionic Villus Biopsy (CVS) involves taking a small portion of the placenta with a needle at 11-14 weeks, growing fetal cells on tissues culture and then studying these cells for various genetic diseases. The risk of harming the pregnancy is less than 1%.

Amniocentesis involves passing a needle into the sac of \fluid around the baby at 15-20 weeks. Cells isolated from the fluid are grown on tissues culture and then studied these cells for various genetic diseases. The risk of harming the pregnancy is less than 0.5%.

If the tests are positive, then a decision needs to be made whether to abort the fetus. Tough choices.