title: Dating the early pregnancy by sequential appearance of embryonic structures.
abstract: A total of 97 transvaginal scans were performed from 4 to 12 weeks' gestation in normal and accurately dated gestations. The sequential appearance of six structures were examined: (1) the gestational sac only was present during week 4; (2) the yolk sac appeared in week 5; (3) the fetal pole with detectable heart motion was first seen in week 6; (4) the single unpartitioned ventricle in the brain marked week 7; (5) the falx cerebri appeared during week 9; and (6) the appearance and the disappearance of the physiologic midgut herniation were seen in week 8 and week 11, respectively. Inasmuch as the time in gestation at which these structures appear characterizes the gestational age more than any measurement at this age, we propose a practical method to determine the correct gestational age in early first-trimester pregnancy.
authors.affiliation: Department of Obstetrics and Gynecology, Columbia University College of Physicians and Surgeons, New York, NY.
authors.forename: W B
authors.initials: WB
authors.lastname: Warren
authors.forename: I
authors.initials: I
authors.lastname: Timor-Tritsch
authors.forename: D B
authors.initials: DB
authors.lastname: Peisner
authors.forename: S
authors.initials: S
authors.lastname: Raju
authors.forename: M G
authors.initials: MG
authors.lastname: Rosen
mesh_terms: D001921:Brain / Q000196:embryology; D005314:Embryonic and Fetal Development; D005260:Female; D005318:Fetal Heart / Q000196:embryology; D005323:Fetal Monitoring; D005865:Gestational Age; D006801:Humans; D011247:Pregnancy; D014463:Ultrasonography; D014470:Umbilical Cord / Q000032:analysis; D015017:Yolk Sac / Q000032:analysis