The Committee in succession Geneti...

The Committee in succession Genetics of the American corporation of Obstetricians and Gynecologists (ACOG) has issued a recently made known report entitled, "ACOG Committee Opinion No. 296: First-Trimester Screening for Fetal Aneuploidy." The report appears in the July 2004 issue of Obstetrics and Gynecology

According to the report, first-trimester screening for genetic foibles is now an option for pregnant women still only if certain criteria are met recent technologies, such as measuring nuchal translucency (NT) have allowed for earlier, noninvasive screening for chromosomal abnormalities and, when combined with serum screening in the first trimester, have detection rates comparable with standard second-trimester screening.

First-trimester screening proposes several potential advantages over second-trimester screening. When exhibition results are negative, it may help resolve into maternal anxiety earlier. If flows are positive, it allows women to take advantage of first-trimester prenatal diagnosis by dint of chorionic villus sampling (CVS) at 10 to 12 weeks of gestation or second-trimester amniocentesis (15 weeks). Detecting puzzles earlier in the pregnancy may allow women to prepare for a child with health question s It also provides women the option to terminate the pregnancy earlier, which is associated with reduc maternal morbidity.

During the past decade, research has shown an association between fetuses with certain chromosomal abnormalities and ultrasonographic findings of an abnormally increased NT (an area at the back of the fetal neck) between 10 and 14 weeks of gestation. The newer first-trimester screening [i]modus operandi[/i] includes measurement of NT, independent beta subunit of human chorionic gonadotropin ([beta]-hCG), and pregnancy-associated plasma protein-A (PAPP-A). It has a detection rate for Down syndrome comparable with the more commonly used second-trimester screening using four serum markers (alphafetoprotein, [beta]-hCG, unconjugated estriol, inhibin-A).

Women who veil positive are at an increased risk for having a child with Down syndrome These women may then decide to have a diagnostic criterion such as amniocentesis or CV to determine if the fetus is affected because screening experiments can give false-positive results.

First-trimester screening also can help descry other chromosomal abnormalities such as trisomy 18 In addition, measurement of NT may help discover pregnancies at risk for major heart wants in the fetus. However, first-trimester screening cannot be used as a screening exhibition for spina bifida.

Sonographer training and ongoing quality assurance are essential if NT is used as a screening order Because small differences in NT measurements can have a large impact upon the risk prediction of Down syndrome sonographers ne to be monitored closely ACOG does not approve using the NT measurement from itself to screen for Down syndrome because it has a high positive veil rate when used without serum markers. Although first-trimester screening is an option for a certain number of women, it should only be proffered if the following criteria are met:

* Appropriate ultrasound training and ongoing quality-monitoring programs are in place.

* There are sufficient information and resources to provide comprehensive counseling to women regarding the different screening options and limitations of these tests

* Access to an appropriate diagnostic criterion is available when screening proofs are positive.

COPYRIGHT 2004 American Academy of Family Physicians

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