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    ACOG on Prenatal diagnostic testing for genetic disorders

     

    Testing in fetal death or stillbirth

    Chromosomal microarrays have also replaced karyotypes as the recommended diagnostic test in evaluating tissue from a fetal demise. In addition to greater sensitivity, chromosomal microarrays do not require cultured cells. This has long been a major problem in studying miscarriages, as witnessed by a disproportionate number of 46, XX results, a reflection of unwitting laboratory analysis of maternal cells. It is difficult to avoid maternal admixture (decidua) in cultures of products of conception. With chromosomal microarrays, however, DNA alone from identifiable fetal tissue (villi) will suffice to generate results, without need for cell culture; thus, the percentage of informative cases has greatly increased (90%).

    Next: Pearls and pitfalls of genetic screening

    ACOG recommends that if only a karyotype were possible, cell culture should be initiated from amniotic fluid obtained by amniocentesis. This should maximize the rate of successful cell culture required for a karyotype.

    Prenatal diagnosis procedures in maternal infection

    Practice Bulletin 162 appropriately counsels that transmission of chronic maternal infection to the fetus is increased if an invasive procedure is performed in a mother who has hepatitis B, hepatitis C, or human immunodeficiency virus (HIV). However, risks can be mitigated. The once prohibitively high rate of maternal to fetal transmission in HIV is now greatly decreased when affected women receive combination antiretroviral therapy. In the study on which Practice Bulletin 162 recommendation was based, 30 of 2528 fetuses (~1% of ART-treated HIV) women were infected.8 Notwithstanding this 1%, Practice Bulletin 162 states that the risk of “newborn infection is not increased after amniocenteses, maternal viral load is low or undetectable.” A recommendation is made, however, to perform the necessary invasive procedure once viral loads are undetectable.

    Conclusion

    Practice Bulletin 162 states that loss rates following an invasive prenatal diagnostic procedure should now be communicated to be 1 in 769 for amniocentesis and 1 in 455 for CVS. For most practitioners, these new numbers will be more in sync with their clinical impressions. Also transformative in Practice Bulletin 162 is that chromosomal microarrays and not a karyotype should be ordered whenever an invasive prenatal procedure (CVS, amniocenteses) is performed. This holds whether evaluation is for a miscarriage or stillbirth.

    REFERENCES

    1. Akolekar R, Beta J, Picciarelli G, Ogilvie C, D’Antonio F. Procedure-related risk of miscarriage following amniocentesis and chorionic villus sampling: a systematic review and meta-analysis. Ultrasound Obstet Gynecol 2015;45:16–26.

    2. Kuliev A, Jackson L, Froster U, Brambati B, Simpson JL, Verlinsky Y, et al. Chorionic villus sampling safety. Report of World Health Organization/EURO meeting in association with the Seventh International Conference on Early Prenatal Diagnosis of Genetic Diseases, Tel Aviv, Israel, May 21, 1994. Am J Obstet Gynecol 1996;174:807–11.

    3. Botto LD, Olney RS , Mastroiacovo P, Khoury MJ, Moore CA, Alo CJ, et al. Chorionic villus sampling and transverse digital deficiencies: evidence for anatomic and gestational-age specificity of the digital deficiencies in two studies. Am J Med Genet 1996;62:173–8.

    4. Odibo AO, Gray DL, Dicke JM, Stamilio DM, Macones GA, Crane JP. Revisiting the fetal loss rate after second-trimester genetic amniocentesis: a single center’s 16-year experience. Obstet Gynecol 2008;111:589–9

    5. Borgida AF, Mills AA, Feldman DM, Rodis JF, Egan JF. Outcome of pregnancies complicated by ruptured membranes after genetic amniocentesis. Am J Obstet Gynecol 2000;183:937–9.

    6. Wapner RJ, Martin CL, Levy B, Ballif BC, Eng CM, Zachary JM, et al. Chromosomal microarray versus karyotyping for prenatal diagnosis. N Engl J Med 2012;367:2175–84.

    7. de Wit MC, Srebniak MI, Govaerts LC, Van Opstal D, Galjaard RJ, Go AT. Additional value of prenatal genomic array testing in fetuses with isolated structural ultrasound abnormalities and a normal karyotype: a systematic review of the literature. Ultrasound Obstet Gynecol 2014; 43:139–46.

    8. Mandelbrot L, Jasseron C, Ekoukou D, Batallan A, Bongain A, Pannier E, et al. Amniocentesis and mother-to-child human immunodeficiency virus transmission in the Agence Nationale de Recherches sur le SIDA et les Hepatites Virales French Perinatal Cohort. ANRS French Perinatal Cohort (EP F). Am J Obstet Gynecol 2009;200:160.e1–9.

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