The normal concentration gradient between fetal plasma and maternal serum is on the order of 50,000:1. Conversely, AFP is found in steadily increasing quantities in maternal serum after 12 weeks. As shown in Figure 14-1, its concentration increases steadily in both fetal serum and amnionic fluid until 13 weeks’ gestation, after which, levels rapidly decline. It is the major serum protein in the embryo and fetus and is thus analogous to albumin. Maternal Serum Alpha-Fetoprotein Screening (MSAFP)Īlpha-fetoprotein (AFP) is a glycoprotein synthesized by the fetal yolk sac and later by the fetal gastrointestinal tract and liver. It is recommended that all women at low risk take 400 μg of folic acid orally every day before conception and through the first trimester, to reduce the NTD risk by as much as 80 percent ( Chap. The policy of routine fortification of cereal grains with folic acid, which has been in place in the United States since 1998, provides approximately 200 additional micrograms of folic acid daily and may reduce the first occurrence of NTDs in low-risk women by approximately 20 percent (Honein, 2001). Folic acid supplementation may not decrease the risk for NTDs in those with valproic acid exposure, pregestational diabetes, first-trimester fever or hot tub exposure, or defects associated with a genetic syndrome (American College of Obstetricians and Gynecologists, 2013b). This is particularly important if a woman has one or more prior affected children or if either the pregnant woman or her partner has such a defect. Most women at increased risk for NTDs benefit from 4 mg folic acid taken daily before conception and through the first trimester. In the United States, the risk may be twice as high among Mexican-born women (Velie, 2006). in the United States (Cragan, 2009 Dolk, 2010). births in the United Kingdom, which compares with 0. For example, recent data from population-based registries indicate an NTD prevalence of 1.0 to 1. The risk for these defects is also increased in certain racial or ethnic groups as well as in populations from selected geographical regions. Although the exact mechanism by which diabetes causes these anomalies is unknown, rodent studies have found that oxidative stress from embryonic hyperglycemia is associated with apoptosis in the developing neural tube (Li, 2012 Sugimura, 2009 Yang, 2008). Multiple-marker screening can be used not only for the detection of fetal anomalies and aneu-ploidy but also for detection of high-risk pregnancies.Other risk factors for NTDs include hyperthermia, medications that disturb folic acid metabolism, and hyperglycemia from insulin-dependent diabetes. These are most likely attributed to placental dysfunction. As with increased second-trimester maternal serum alpha-fetoprotein levels, increased serum beta-human chorionic gonadotropin and low unconjugated estriol levels are significantly associated with adverse pregnancy outcomes. Finally, decreased unconjugated estriol levels (<0.5 MoM) were found to be significantly associated with pregnancy-induced hypertension, miscarriage, intrauterine growth restriction, and intrauterine fetal death. Increased beta-human chorionic gonadotropin levels (>2.5 multiples of the median ) were significantly associated with pregnancy-induced hypertension, miscarriage, preterm delivery, and intrauterine fetal death. In confirmation of previous observations, increased maternal serum alpha-fetoprotein levels (>2.5 multiples of the median) were found to be significantly associated with pregnancy-induced hypertension, miscarriage, preterm delivery, intrauterine growth restriction, intrauterine fetal death, oligohydramnios, and abruptio placentae. The incidences of various pregnancy outcomes were evaluated according to the serum marker levels by using clinically applied cutoff points. All patients had maternal serum alpha-fetoprotein measurements beta-human chorionic gonadotropin was measured in 45,565 patients, and 24,504 patients had determination of all 3 markers, including unconjugated estriol. We evaluated the value of all 3 common biochemical serum markers, maternal serum alpha-fetoprotein, beta-human chorionic gonadotropin, and unconjugated estriol, and combinations thereof as predictors of pregnancy outcome.Ī total of 60,040 patients underwent maternal serum screening.
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