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Gender‐adjusted multiples of the median in amniotic fluid alpha‐fetoprotein‐screening for neural‐tube defects halve false‐positive rate without affecting detection rate
Author(s) -
Kozlowski P.,
Knippel A. J.,
Stressig R.
Publication year - 2001
Publication title -
ultrasound in obstetrics and gynecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.202
H-Index - 141
eISSN - 1469-0705
pISSN - 0960-7692
DOI - 10.1046/j.1469-0705.2001.abs23-4.x
Subject(s) - medicine , fetus , amniocentesis , amniotic fluid , pregnancy , obstetrics , alpha fetoprotein , gestation , false positive rate , gynecology , prenatal diagnosis , statistics , genetics , mathematics , hepatocellular carcinoma , biology
Previous studies have shown that fetal gender had influence on various pregnancy complications and prenatal diagnostic biochemical markers. We have evaluated, whether elevation of amniotic fluid alpha‐fetoprotein (AF‐AFP) is associated with fetal sex and whether a sex‐related difference can help to identify pregnancies with AFP‐associated malformations or poor pregnancy outcome. Material and methods: From our database, we obtained 6461 singleton gestations with absolute values and corresponding multiples of the median (MoM) for AF‐AFP for the period database April 1997–March 1999. In all instances high‐resolution ultrasonography was performed before amniocentesis to measure biparietal diameter. Patients with AF‐AFP ≥2 MoM were identified, details of pregnancy outcome were obtained and compared to matched‐pair‐controls having AF‐AFP <2 MoM. Results: A total of 262 patients showed AF‐AFP levels ≥2 MoM. Outcome information was available in 232 cases (88.6%) including all cases with fetal anomalies recorded at ultrasonographic examination. Of these fetuses significantly more had male gender (147 male fetuses vs. 85 female, P < 0005). Having a positive screen result in the risk of AFP‐associated malformations was significantly higher for female fetuses (25 female fetuses (29.4%) vs. 22 male fetuses (15%) with AFP‐associated malformations, P < 0025). Pregnancies with false positive AF‐AFP had a significantly higher risk for poor pregnancy outcome compared with pregnancies having normal AF‐AFP (11 fetal losses (59%) from 185 vs. two fetal losses (0.9%) from 232, P < 0025) but fetal gender had no significant influence. Conclusions: Measuring AF‐AFP routinely in amniotic fluid obtained for cytogenetic evaluation is a cheap method to identify fetuses, on which high‐resolution ultrasonography in a level 3 center should be focused. Adjusting the cut‐off MoM to 2.5 for male and to 2.0 for female fetuses halves the false‐positive rate from 3.4 to 1.7 without affecting the detection rate of 95% in our population. Larger studies are required to determine suitable sex‐adjusted cut‐off values.