Reducing the need for amniocentesis in XXXX 35 years of age or older with serum markers for screening.

@entity1 @entity11111 @entity160 @entity1467 @entity2008
BACKGROUND: As maternal age advances, the risk of fetal @entity1467 increases. Pregnant @entity1 35 years of age or older are routinely offered amniocentesis because of this risk. Recently, maternal serum markers have been reported to be useful in screening for @entity1467 , primarily in younger @entity1 . We therefore investigated whether offering amniocentesis only to selected @entity1 35 years of age or older who were identified by screening measurements in serum might prove a useful alternative to the current practice. METHODS: We studied 5385 @entity1 with singleton pregnancies who were 35 years of age or older and were undergoing routine amniocentesis. Along with information about the pregnancy, we obtained a serum sample for measurement of @entity160 , unconjugated @entity11111 , and @entity1 chorionic gonadotropin. Individual estimates of the risk of @entity1467 in the fetus were calculated for each pregnancy before the karyotype was known. RESULTS: If amniocentesis had been reserved for the @entity1 calculated to have a risk greater than 1 in 200 of having a fetus with @entity1467 , 48 of the 54 cases of @entity1467 (89 percent) would have been identified, 25 percent of the unaffected pregnancies would also have been identified as being at high risk for @entity1467 (false positives). Seven of 15 fetuses (47 percent) with other trisomies, 11 of 25 (44 percent) with sex aneuploidy, and 1 of 9 (11 percent) with miscellaneous @entity2008 would also have been detected. In practice, such screening would have made 75 percent of the amniocentesis unnecessary, along with a proportion of the amniocentesis-associated fetal losses. If the cutoff for the risk of @entity1467 were set higher than 1 in 200, both the rate of detection and the false positive rate would be lower. Conversely, these rates would be higher if the cutoff were set lower. CONCLUSIONS: Prenatal screening of serum to generate individual estimates of the risk of @entity1467 in the fetus can provide a basis for decision making in the cases of @entity1 35 years of age or older, as it does in younger pregnant @entity1 , and is an alternative to current testing practices.
