Abstract: Prenatal testing that will benefit the health of the mother or fetus is permitted (and even encouraged) in Jewish law. Testing to determine fetal problems for which the solution is termination of pregnancy is controversial, as abortion to prevent the birth of an ill fetus is generally not permitted. The couple should be counseled as to the availability of prenatal tests in keeping with their halachic framework. They should be given the chance to think through the risk/benefit ratio of even non invasive procedures, prior to their being performed.
Prenatal Maternal Testing
All routine tests whose purpose is to assure the health of the mother pose no halachic problems and should be performed. This includes blood pressure monitoring and screening for diabetes and preeclampsia. Occasionally, women who have had many children will not see the need for of such testing and allow other family obligations to lead to poor compliance with testing. The importance of such testing should be stressed .
Genetic Testing for Genetic Diseases
Testing for genetic diseases can be done at different life stages. Each raises its own halachic concerns. When testing is done prior to marriage, there is a concern that it could lead to the dissolution of an otherwise appropriate union. Furthermore, misconceptions about the significance of carrier status might lead to difficulty in finding a mate even if there is no medical reason to fear the birth of an affected child. When the testing is done after marriage, there is concern that it might inhibit the couple from having children. If the testing is done after conception there is the concern that it might lead to an abortion. As the halachic concerns regarding premarital testing are the weakest, premarital testing should be encouraged in this patient population. However, if testing was not done at that point, it can be offered at later stages as well.
Testing for genetic diseases comprises two forms of testing: testing for hereditary disease and testing for aneuploidy. The former can be done at any of the stages above. The later requires the presence of a fetus and thus can only be done during the pregnancy itself. Each form has related halachic issues.
Testing for Hereditary Diseases
Anonymous carrier testing done prior to engagement alleviates the above concerns. Within the Jewish community, a system of premarital genetic testing for a number of conditions has been established. This project is called Dor Yeshorim [http://doryeshorim.org worldwide or http://www.doryes.com/ in Israel]. Individuals are tested before beginning the search for a marriage partner, but are not told the results of the test. A couple considering marriage notifies Dor Yeshorim and is informed whether or not there is a problem. The couple is not told what disease they carry, just that the match is likely to lead to a child affected by one of these conditions. Dor Yeshorim currently offers several different panels of tests from which one can choose.
As this system takes the halachic concerns into consideration, it has the approval of many leading halachic authorities. It is also subsidized. However, Dor Yeshorim will only test people prior to an official engagement, and does not give specific test results. Therefore, some couples will choose to have the testing done openly through their health care provider.
If a couple has not been tested prior to marriage, they can be tested pre-conception. If both members of the couple are found to be carriers for a significant genetic disease, in-vitro fertilization with pre-implantation genetic diagnosis may be permitted. Each couple considering this procedure must ask an individual halachic question. Where there is a known family history of a genetic defect, it is likely that IVF will be permitted to allow pre-implantation genetic diagnosis. It is halachically much easier to allow implantation of unaffected fetuses than to allow abortion. Once conception has taken place, the only remaining intervention is abortion.
Prenatal Testing for Aneuploidy
The most common aneuploidy currently tested for in clinical practice is Trisomy 21. Currently, screening includes first-trimester risk assessment at 11 to 14 weeks (this may include ultrasound nuchal cord thickness assessment) and maternal serum analysis (quad) screening at 15 to 20 weeks. These are designed to give a woman a more accurate estimate of the likelihood of an aneuploid fetus than age-related risk alone. Ultrasound and maternal serum analysis are considered screening procedures and thus, if positive, both require follow up by an invasive procedure (amniocentesis or chorionic villi sampling). . Currently, it is clinically possible to isolate fetal DNA from maternal blood during pregnancy. While this is could be considered a diagnostic procedure, at present it is not considered reliable enough to be the sole form of diagnosis and thus it too needs follow up by an invasive procedure 
Halachic authorities differ regarding the permissibility of invasive prenatal tests. Much of the debate focuses on how the test results could be used productively, and especially on whether abortion would be permitted if a genetic defect were found.
Many authorities would allow abortion in cases where the fetus is clearly not viable, such as Trisomy 18. If there is reason to suspect such a condition, invasive tests would be permitted. Even though some studies indicate that this condition may be detected on ultrasound alone , a rabbi may request an invasive test for confirmation prior to deciding to permit an abortion.
When invasive tests are used to screen for conditions like Down syndrome, where abortion is generally not permitted, rabbinic authorities differ. Some maintain that, since abortion is not an option, one should not increase the risk of miscarriage with an invasive test. Others consider the test worthwhile because in most cases the fetus is not affected  and the parents can be reassured about this issue . Even if the fetus is affected, the family may be better able to cope if they are prepared in advance. A couple considering these tests should discuss them with their rabbi before they are performed.
Chorionic villi sampling (CVS) used to be done as early as six weeks of gestation. This was helpful for religious couples, as it was just possible to get results within 40 days after mikveh immersion, when it is easier to permit abortion. However, due to the risk of limb defects, the test is no longer performed quite so early in pregnancy  and this advantage is lost. CVS continues to have the advantage that it can be performed early enough that a woman can still hide her pregnancy. This needs to be balanced against the slightly higher risk of miscarriage than that for amniocentesis . The couple should ask for the statistics for the center where the procedure is done prior to consulting with the rabbi.
Amniocentesis is performed via the abdomen and is unlikely to cause vaginal bleeding; therefore, it does not render a woman niddah. There is debate as to whether CVS makes a woman niddah. This question should be asked prior to its performance.
A second trimester ultrasound is often done to look for structural abnormalities in the fetus . The ultrasound itself presents no halachic issues. Knowing in advance about abnormalities can, at times, allow for delivery in the appropriate care setting and increase the infant's chance of survival. That goal is halachically encouraged. Finding abnormalities to allow for abortion is more difficult although in certain extreme cases (e.g. anencephaly) it might be permitted. Case specific questions need to be asked.
Implications for Care: Prenatal diagnosis is not in itself prohibited by Jewish law. However, a full discussion of the implications of each test should be performed prior to embarking on testing so the couple can think through the risks and benefits of such testing in the context of their halachic beliefs. Such careful counseling would be of benefit to all patients.
Preconception testing presents fewer halachic problems than testing while the woman is already pregnant, as PGD is easier to permit than is abortion.
Abortion is not easily permitted for a malformed but viable fetus. However, as halacha is case law, an individual question should always be asked.
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