title: The quality and size of yolk sac in early pregnancy loss.
abstract: BACKGROUND
  Accurate differentiation between normal pregnancy and pregnancy loss in early gestation remains a clinical challenge.
  
  
  OBJECTIVE
  To determine whether ultrasound findings of yolk sac size and morphology are valuable in relation to pregnancy loss at six to ten weeks gestation.
  
  
  METHODS
  Transvaginal ultrasonography was performed in 111 normal singleton pregnancies, 25 anembryonic gestations, and 18 missed abortions. Mean diameters of gestational sac and yolk sac were measured. The relationship between yolk sacs and gestational sacs in normal pregnancies was depicted. The yolk sacs ultrasound findings in cases of pregnancy loss were recorded.
  
  
  RESULTS
  In normal pregnancies with embryonic heartbeats, a deformed or an absent yolk sac was never detected. Sequential appearance of yolk sac, embryonic heartbeats and amniotic membrane was essential for normal pregnancy. The largest yolk sac in viable pregnancies was 8.1 mm. Findings in anembryonic gestations included an absent yolk sac, an irregular-shaped yolk sac and a relatively large yolk sac (> 95% upper confidence limits, in 11 cases). In cases of missed abortion with prior existing embryonic heartbeats, abnormal findings included a relatively large, a progressively regressing, a relatively small, and a deformed yolk sac (an irregular-shaped yolk sac, an echogenic spot, or a band).
  
  
  CONCLUSIONS
  A very large yolk sac may exist in normal pregnancy. When embryonic heartbeats exist, the poor quality and early regression of a yolk sac are more specific than the large size of a yolk sac in predicting pregnancy loss. When an embryo is undetectable, a relatively large yolk sac, even of normal shape, may be an indicator of miscarriage.
authors.affiliation: Department of Obstetrics and Gynecology, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan. fncho@isca.vghks.gov.tw
authors.forename: Fu-Nan
authors.initials: FN
authors.lastname: Cho
authors.forename: San-Nung
authors.initials: SN
authors.lastname: Chen
authors.forename: Ming-Hong
authors.initials: MH
authors.lastname: Tai
authors.forename: Tsung-Lung
authors.initials: TL
authors.lastname: Yang
mesh_terms: D000030:Abortion, Missed / Q000473:pathology; D000022:Abortion, Spontaneous / Q000473:pathology*; D004622:Embryo, Mammalian / Q000473:pathology*; D005260:Female; D005865:Gestational Age; D006801:Humans; D011247:Pregnancy; D011256:Pregnancy Outcome; D011261:Pregnancy Trimester, First; D016216:Ultrasonography, Prenatal; D015017:Yolk Sac / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000473:pathology