title: First-trimester screening.
abstract: Screening for fetal chromosome abnormalities, particularly for trisomy 21, has made dramatic advances. Better screening demonstrates that "high-risk" patients--particularly over age 35--can have lower risk of defects than younger unscreened women. This has caused reduction of amniocentesis for older patients and made screening available for younger patients who have the universal 2% to 3% risk. This means lower procedural-related losses of normal fetuses, and better resource allocation. The trend toward first-trimester detection of structural defects continues; a normal survey is reassuring and helps exclude major defects. Based on screening results, patients can be triaged into early follow-up and possible amniocentesis as 14 to 16 weeks, or a later detailed anatomic survey at 18 to 20 weeks.
authors.affiliation: Fetal and Women's Center of Arizona, 9440 E. Ironwood Square Drive, Scottsdale, AZ 85258, USA. nyberg@u.washington.edu
authors.forename: David A
authors.initials: DA
authors.lastname: Nyberg
authors.forename: Jon
authors.initials: J
authors.lastname: Hyett
authors.forename: Jo-Ann
authors.initials: JA
authors.lastname: Johnson
authors.forename: Vivienne
authors.initials: V
authors.lastname: Souter
mesh_terms: D005260:Female; D005315:Fetal Diseases / Q000000981:diagnostic imaging*; D006801:Humans; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D016216:Ultrasonography, Prenatal / Q000379:methods*