Prenatal Genetic Testing - Nishmat Yoatzot Halacha

Introduction

Prenatal genetic testing provides information about genetic conditions that could affect a fetus. Some tests can be performed before conception. (Learn more here). This page discusses tests performed at various stages of pregnancy, including initial screens that can lead to further testing.

Tests offered during pregnancy fall into two broad categories: screening tests and diagnostic tests:

Screening tests are typically offered to all pregnant women. If positive, they suggest an increased probability of a medical concern with the fetus or pregnancy. With any screening test, there is a risk of false positive or false negative results. This should be discussed with one’s healthcare provider.

Diagnostic tests are generally indicated when there is already a medical concern, such as when a screening test is positive or when there are particular risk factors. Diagnostic prenatal tests give more precise results, but can be more invasive.

While information about the fetus can often help the parents and medical team prepare in advance for the health needs of the baby, potential benefits of the tests should be weighed against the potential risks.

Parents need to make a shared decision with their healthcare team about which tests should be performed. Often, prenatal genetic testing simply alleviates concerns. However, unexpected results can create complex and sensitive situations. Prior to testing, it is important to think through a test’s potential personal, medical, and halachic implications.

Deciding About Prenatal Testing

On a personal level, parents should consider how they might use the test results—to provide care during pregnancy, birth, and postpartum; to educate themselves and prepare for a baby with special medical needs; to identify a medical intervention that can be completed in utero; or even to contemplate termination of a pregnancy. Would having additional information cause excessive stress and anxiety or enable them to prepare?

From a Jewish medical ethics perspective, we have both permission and an obligation to heal when we can. At the same time, there are limitations to our human pursuit of healing, as God is the ultimate healer.

Some religious authorities apply these limitations to prenatal testing, maintaining that it goes beyond the scope of what we are permitted to know, as conception and childbirth are ultimately in God’s hands. Others maintain that prenatal testing is within the scope of the halachic permissibility and obligation to heal (“v’rapo yerapeh”), since information about the parent or the fetus can potentially prevent illness, disability, or, in some cases, loss of life.

Halachically, specific questions arise about the permissibility of each test: What does the test entail, and how might it potentially risk the well-being of the mother or fetus? Are some tests considered halachically obligatory because of their life-saving potential? Are actions that might follow the tests—such as undertaking Preimplantation Genetic Diagnosis in a future pregnancy, or termination of pregnancy—prohibited, permitted, or obligatory?

Each situation is best discussed with medical experts and a halachic authority on a case-by-case basis. Expectant parents grappling with difficult decisions often benefit from counseling and spiritual support as well.

Screening Tests

A pregnant woman can undergo blood tests and an ultrasound to identify the likelihood that the fetus has a genetic anomaly. While there are various halachic approaches to the permissibility of doing these screening tests, we follow the view that it is halachically permissible to do these tests without asking a personal halachic question.

Blood tests

Abnormal levels of certain substances released from the placenta into the mother’s blood can suggest a chromosomal anomaly or an anatomic defect, such as a neural tube defect. Tests for these substances can include:
- A first trimester test to measure PAPP-A and hCG.
- The Quad screen, performed during weeks 15-22 of pregnancy, to measure hCG, AFP, unconjugated estradiol, and inhibin A.
Cell-free DNA, or NIPT (noninvasive pregnancy test) tests for the baby’s DNA in the mother’s blood, and is another test used to detect a chromosomal anomaly. This test is performed at 10 weeks or later.

Ultrasound

The Nuchal Translucency test is a first-trimester ultrasound that measures the thickness of an area of fluid collection found behind the fetus’s neck. If the Nuchal Translucency test and the blood tests are normal, the parents can be reassured that their baby is unlikely to have a chromosomal anomaly.

A thicker Nuchal Translucency measurement indicates an increased chance that the fetus has a genetic anomaly. However, even when used in conjunction with the blood tests described above, this test is not a diagnosis, and many women with positive screens will go on to have babies without a genetic or anatomic anomaly. If the test results raise concerns, the couple may consider speaking with a genetic counselor or pursuing further ultrasounds or diagnostic testing.

Diagnostic Tests

Diagnostic tests may be performed where there is reason to suspect that the fetus may have a genetic anomaly, such as in the case of advanced maternal age, family medical history, or abnormal screening tests.

Prior to proceeding with these tests, it is important to ask the medical team why the test is recommended, what information may be learned, what may be gained from having this information, and what risks the test entails. These considerations should be discussed with one’s health care provider in order to make a shared decision about the procedure.

We follow the view that this information, and the relative necessity of performing an invasive procedure, should be discussed with an experienced halachic authority prior to undergoing these tests.

Chorionic Villus Sampling (CVS)

Chorionic Villus Sampling (CVS) typically offered during weeks 10-13 of pregnancy, is a test in which a small sample of placental tissue is obtained and analyzed. Since the placenta and the fetus almost always share the same genetic material, this testing can confirm or diagnose a genetic anomaly. However, it will not test for neural tube defects.

CVS holds some advantage over amniocentesis, since it is performed earlier in pregnancy, which may open up more options for follow-up. However, not all women are candidates for CVS, and the results are not always 100% conclusive.

There are various methods of performing CVS. In the transabdominal method, the provider inserts a needle through the abdomen and into the uterus to withdraw the sample. A transabdominal procedure does not make a woman niddah.

The transvaginal method involves directing an ultrasound-guided catheter (small tube) through the vagina and into the cervix, and then using a small syringe at the far end of the catheter to remove some placental tissue.

With transvaginal CVS, a woman should ask her doctor about the diameter of any instruments inserted into the cervix. The catheter size is commonly 17mm (5.3Fr) or 20mm (5.7Fr). We follow the halachic position that instruments narrower than 19mm in diameter do not render a woman niddah (learn more here). Therefore, insertion of a 17mm catheter would not make a woman niddah, whereas a 20mm catheter would.

A woman may have staining after CVS. This is generally due to trauma to the placenta, cervix or the uterus during the procedure. We follow the position that this bleeding is dam makkah and does not make a woman niddah. Nevertheless, it is recommended to take precautions, such as wearing colored underwear or disposable pantyliners, to avoid any questions.

Depending on the route and timing of the CVS procedure, it may be associated with slightly increased risks to the pregnancy, such as pregnancy loss or limb-deformity.

Amniocentesis

Amniocentesis is a diagnostic test in which a small sample of amniotic fluid is obtained in order to test for chromosomal defects, neural tube defects, or other potential genetic anomalies. This test is typically offered during weeks 15-20 of pregnancy. A long, thin needle, guided by an ultrasound, is inserted through the abdomen and into the amniotic sac to withdraw a sample of the amniotic fluid. The fluid contains cells from the fetus that can be tested for genetic information.

Because the test is performed through the abdomen, it is unlikely to cause vaginal bleeding, and does not make a woman niddah.

There is a slight increase in the risk of miscarriage following an amniocentesis, although the exact percentage of risk is dependent on various factors including week of pregnancy, practitioner experience, positioning of the fetus, and more. These risks should also be discussed with one’s medical practitioner in advance.

Future Implications

As the sophistication of testing has evolved over time, halachic perspectives on prenatal testing have shifted. Previously, a primary halachic concern was the risk entailed by various tests, whereas now a foremost halachic consideration is the implications of test results.

We anticipate that, as medicine continues to advance, the halachic landscape will continue to be enriched.

For further personalized discussion and guidance, please reach out via this website, the Yoatzot hotline, or a Yoetzet Halacha Fertility Counselor.

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