Management of pregnancy - VA/DoD Clinical Practice Guidelines ...

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VA/DoD Clinical Practice Guideline For Pregnancy Management where the cutoff value depends on the specific test selected. Diagnostic testing provides yes or no (i.e., affected or not affected) results. Screening modalities include measurement of maternal serum analytes, ultrasound evaluation, or a combination of maternal serum analyte and ultrasound evaluation. These modalities can variably be applied in each of the three trimesters of pregnancy but are typically performed in the first and second trimesters. The information obtained from these modalities can be combined to yield a complex array of screening strategies, each with its own inherent strengths and weaknesses including varied accuracy rates. Multiple screening and testing modalities are now defined and offered but the individual tests/strategies are not uniformly available. Due to the complex nature of the testing strategies, the potential harm of both screening and diagnostic testing, their varied local availability, and their inherent elective nature, it is imperative that detailed counseling be provided to the prospective mother prior to electing or declining a specific testing strategy. Ultrasound can be diagnostic of certain fetal anomalies but a fetal tissue sample is necessary to diagnose or exclude fetal karyotype abnormalities. Fetal tissue samples are usually obtained by chorionic villus sampling (CVS), amniocentesis, or fetal cord blood sampling (cordocentesis). Each of these methods has limitations and inherent risks of provoking a pregnancy loss. Some large studies have shown amniocentesis to be significantly less likely to cause pregnancy loss than cordocentesis or CVS but the risk of CVS in experienced hands has been reported to be very low in other studies. Amniocentesis is also the most widely available of the diagnostic methods. Chorionic villus sampling provides an earlier result than either amniocentesis or cordocentesis. RECOMMENDATIONS 1. All pregnant women, regardless of age, should be offered a prenatal screening test for the most common clinically significant fetal anomalies as a routine part of prenatal care. [B] 2. Women presenting for care at appropriate gestational ages should have aneuploidy screening and diagnostic options available to them that provide first-trimester results as well as strategies that provide second-trimester results. The specific first-trimester screening strategy made available by or in the institution must be decided prior to embarking upon that strategy. [B] 3. Initial limited and comprehensive prescreen/pretest counseling methods may include written or multimedia communication, one-on-one, or group counseling formats. Posttest and late entry counseling should be provided in an individualized one-on-one format. [B] 4. Screening programs should show respect for the needs and quality of life of the woman and her family. Counseling should be nondirective and should respect a woman’s choice to accept or to refuse any or all of the testing or options offered at any point in the process. [I] 5. The following modes of prenatal screening/diagnostic testing should be available for women receiving prenatal care in the DoD/VA: [B] (see Appendix E) a. No test at all b. Screening with results in first trimester c. Screening with results in second trimester d. Diagnostic/invasive test in first and second trimester. 6. In order to make these screening and diagnostic options available, each institution providing prenatal care should provide locally or arrange for access to: genetic counseling, first- and second-trimester serum marker assessment, first-trimester nuchal translucency (NT) measurement, basic and comprehensive second-trimester ultrasound assessment, first-trimester chorionic villus sampling and second-trimester amniocentesis. [I] 7. All women considered high-risk, due to maternal age, personal or family history, or the result of a previous test, should be offered the choice of a first- or second-trimester screening strategy and the choice of first- or secondtrimester diagnostic testing including appropriate comprehensive pre- and post-test genetic counseling. [I] 8. A comprehensive ultrasound may be offered as a primary or follow-on screening test. [B] Interventions Page - 69
VA/DoD Clinical Practice Guideline For Pregnancy Management 9. First-trimester NT should be interpreted for risk assessment only when performed by a trained sonographer who is accredited to provide this service [B] and when offered together with biochemical markers. [A] 10. For women who undertake first-trimester screening (FTS), second-trimester serum alpha fetoprotein (AFP) screening and/or ultrasound examination should be offered to screen for open neural tube defects (ONTD). [B] 11. 12. Pregnant women with persistent unexplained elevations of maternal serum alphafetoprotein (MSAFP) are at increased risk for adverse perinatal outcome and should receive specialized prenatal care. [B] The Quad Marker Screen should be used rather than the Triple Marker Screen when second-trimester serum screening is undertaken. [B] DISCUSSION Common Chromosome Conditions The most common chromosome conditions associated with advanced maternal age involve the presence of an additional chromosome (21, 18, 13, or X). Of these, trisomy 21, 18, and 13 are associated with congenital anomalies and mental handicap. Most families who have a child with an open neural tube defect (ONTD), Down syndrome (DS) or trisomy 18 (T18) have no prior family history of the same. The incidence of ONTD varies with racial background and geographical location. While maternal age is the key risk factor for trisomy 21, 18 and 13, more than half of children born with DS are born to women less than 35 years old. Using a maternal age of 35 as a cutoff for offering diagnostic testing will only identify about 40 percent of affected pregnancies (Summers et al., 2003). The incidence of DS approximates one in 700 births regardless of race or geographical location. Prenatal Screening Maternal serum analyte screening with multiple serum markers (e.g., alphafetoprotein, human chorionic gonodatropin [HCG], unconjugated estriol and inhibin) has been demonstrated to be a cost-effective means of antenatal screening for several categories of serious fetal structural abnormalities, fetal aneuploidy, and placental abnormalities. Specific structural fetal abnormalities include open neural tube defects (ONTD) (e.g., anencephaly and open spinal defects), ventral wall defects (e.g., omphalocele and gastroschisis), as well as other rare conditions (e.g., skin disorders and congenital nephrosis). The specific fetal aneuploid conditions commonly detected through maternal serum analyte screening include Down syndrome (trisomy 21) and Edward’s Syndrome (trisomy 18). Sex chromosome abnormalities or other aneuploid conditions are less reliably detected. ONTDs occur in one to two/1,000 live births; 90 to 95 percent of ONTD cases occur in mothers without risk factors such as a positive family history, medical therapy for maternal seizure disorder, or pregestational diabetes mellitus. ONTDs are associated with high rates of perinatal mortality, morbidity, and long-term developmental disability. Ventral wall defects occur in 0.5 to one infant/1,000 live births and are associated with an increased incidence of associated serious fetal anomalies and aneuploidy, omphalocele, or fetal growth restriction. Both require immediate postnatal surgical treatment for optimal outcome. The practice of using solely the cut-off of maternal age of 35 or over to identify at-risk pregnancies is inferior to screening tests that consist of maternal serum markers and ultrasound assessment of nuchal translucency (Resta et al., 2005). Several large, multicenter trials have shown that in the first trimester, a combination of nuchal translucency measurement, serum markers, and maternal age is a very effective screening test for Down syndrome (Malone et al., 2003; Wald et al., 2003; Wapner et al., 2003). First-trimester screening can lead to a diagnosis of fetal aneuploidy much earlier in the pregnancy than second-trimester screening/diagnostic methods. Earlier detection allows the woman and her family to make decisions about continuing the pregnancy in a more private manner (diagnosis can be made before it is evident that the patient is pregnant) (ACOG, 2007; Malone et al., 2005). Ultrasound has become a valid method to screen for ONTD (Lennon et al., 1999). Interventions Page - 70
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