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Down Syndrome screening

The question below was submitted to www.yoatzot.org, Nishmat's Women's Health and Halacha (Jewish Law) website for the lay public.

"Is there a halacha regarding the AFP test? If there is none, I am wondering what your recommendation is in my situation.

"I am 15 weeks pregnant with my fourth child. I never took the test before because I told the doctor that I would not abort the baby. My doctor was always supportive of this decision. This time I will be turning 35 during the pregnancy and the doctor feels that since the odds of various problems occurring are now higher I should take the test. He is of the opinion that even if I would not end the pregnancy it is better to be prepared. I am hesitant because of the high rate of false positives and the likelihood of the doctor then recommending an amnio. I know that there is some risk involved in that procedure. Thank you for your time."

The woman was answered as follows from the site:

The first decision is purely personal - would you (and your husband) rather be prepared for the birth of a child with a disability, or would rather not know in advance and deal with it if and when it happens? No one else can answer this for you. Based on this decision, you can decide which test you want to do.

There are several screening tests for Down Syndrome. The AFP test was originally designed to check for neural tube defects (e.g., spina bifida) [1]. In a fetus with such a defect, alpha fetoprotein [AFP] is high. Later, it was discovered that low AFP correlates with a statistically greater chance of Down Syndrome [2-3]. When additional serum markers are included, Down Syndrome can be statistically predicted with even greater accuracy [4].

This test is useful for younger women to determine whether it is worth doing an invasive test [5]. It is only a statistical correlation and not a definite indicator of a defect [6-7]. In other words, this test does not diagnose the condition, it simply raises the need for further testing. It is probably worth having the test done to look for neural tube defects [8].

Another test often used in standard screening for Down Syndrome is nuchal fold thickness [8]. This is an ultrasound that is done at about 12-13 weeks [5]. It has been shown that the skin of the neck on fetuses with Down Syndrome is thicker than for a normal fetus; this difference is the basis for the test [8]. In laboratory conditions it has been shown to pick up about 85% of Down fetuses [9]. The combination of tests help determine whether or not to do an invasive test [10].

The false positive rate when a combination of tests is used is between 2-3% [11].

Halachically there is a debate as to whether one should do the invasive tests such as amniocentesis. One attitude is that, since one would not abort a fetus with Down Syndrome, one should not risk causing a miscarriage with an invasive test. The other attitude is that it is worth doing the test, as the fetus usually is not affected and the mother can then be relaxed about this issue. If your rabbi feels the latter, and you feel this way as well, at the age of 35, it might make more sense to do the amniocentesis directly if you feel that the knowledge even in the absence of abortion would help you be better prepared.

 

[1] Brock DJ, Scrimgeour JB, Steven J, Barron L, Watt M. Maternal plasma alpha-fetoprotein screening for fetal neural tube defects. Br J Obstet Gynaecol 1978;85:575-81.

[2] Merkatz IR, Nitowsky HM, Macri JN, Johnson WE. An association between low maternal serum alpha-fetoprotein and fetal chromosomal abnormalities. Am J Obstet Gynecol 1984;148:886.

[3] Cuckle HS, Wald NJ, Lindenbaum RH. Maternal serum alpha-fetoprotein measurement: a screening test for Down syndrome. Lancet 1984;1:926.

[4] Alldred SK, Deeks JJ, Guo B, Neilson JP, Alfirevic Z. Second trimester serum tests for Down's Syndrome screening. Cochrane Database of Systematic Reviews 2012, Issue 6. Art. No.: CD009925.

[5] ACOG Committee on Practice Bulletins. ACOG Practice Bulletin No. 77: Screening for fetal chromosomal abnormalities. Obstet Gynecol 2007;109:217-27.

[6] Malone FD, Canick JA, Ball RH, et al. First-trimester or second-trimester screening, or both, for Down's syndrome. N Engl J Med 2005;353:2001.

[7] ACOG practice bulletin. Clinical management guidelines for obstetrician-gynecologists. Number 44, July 2003. (Replaces Committee Opinion Number 252, March 2001). Obstet Gynecol 2003;102:203.

[8] Benacerraf BR, Frigoletto FD, Laboda LA. Sonographic diagnosis of Down syndrome in the second trimester. Am J Obstet  Gynecol 1985;153:49-52.

[9] Benn P, Wright D, Cuckle H. Practical strategies in contingent sequential screening for Down syndrome.
Prenat Diagn. 2005 Aug;25(8):645-52.

[10] ACOG Practice Bulletin No. 88, December 2007. Invasive prenatal testing for aneuploidy. Obstet Gynecol. 2007 Dec;110(6):1459-67.

[11] Wald NJ, Rodeck C, Hackshaw AK, Rudnicka A. SURUSS in perspective. BJOG 2004;111:521.


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