title: Risk factors for procedure-related fetal losses after mid-trimester genetic amniocentesis.
abstract: BACKGROUND
  The objective of this study was to determine the institutional pregnancy loss rate following second-trimester genetic amniocentesis and to ascertain whether factors exist which would identify pregnancies at increased risk of having a procedure-related fetal loss.
  
  
  METHODS
  University Teaching Hospital
  
  
  METHODS
  Details of the procedure and pregnancy outcome of all patients who had amniocentesis planned or performed between 15-22 gestational weeks between January 1997 and June 2004 were extracted from our clinical audit database. The procedure-related fetal loss rate, defined as all unintended abortions, stillbirths and neonatal deaths without major fetal abnormalities or obvious obstetric causes, was determined and compared to a presumed background fetal loss rate of 0.8% based on a cohort of women who did not undergo the procedure.
  
  
  RESULTS
  A total of 3468 consecutive amniocentesis were performed in 3440 patients with 3498 fetuses. The mean gestational age at amniocentesis was 17.6 +/- 1.2 weeks. The majority (98.6%) required only one puncture and a transplacental procedure was required in 2.7% cases. A total of 3465 chromosomal studies were performed. Sixty six cases (1.9%) of major chromosomal abnormalities were detected. Pregnancy outcome was ascertained in all except 26 singleton pregnancies (0.74%). There were 3285 (93.9%) livebirths, 103 (2.9%) termination of pregnancies (TOP), 6 (0.17%) fetal demises before the procedure, and 20 (0.61%) unintended fetal losses due to significant fetal abnormalities or obstetric complications. The remaining 58 fetal losses (1.66%) were classified as potentially procedure-related, which could be either background fetal losses or procedure-related. The procedure-related fetal loss rate after correcting for the background loss rate was 0.86%.Potentially procedure-related fetal losses were found to be significantly associated with a procedure at 18 weeks or beyond (odds ratio OR = 1.97), a procedure performed for abnormal second-trimester biochemical screening test (OR = 3.08), a bloody tap (OR = 6.48), and a female fetus (OR = 2.39); but not to the number of punctures (p = 0.66) nor transplacental amniocentesis (p = 0.104).
  
  
  CONCLUSIONS
  Mid-trimester amniocentesis is associated with a small but significant risk of fetal loss of 0.86%.
authors.affiliation: Fetal Medicine Unit, Department of Obstetrics and Gynaecology, Prince of Wales Hospital, The Chinese University of Hong Kong Shatin, Hong Kong SAR, China.
authors.forename: Choy Wah
authors.initials: CW
authors.lastname: Kong
authors.forename: Tse Ngong
authors.initials: TN
authors.lastname: Leung
authors.forename: Tak Yeung
authors.initials: TY
authors.lastname: Leung
authors.forename: Lin Wai
authors.initials: LW
authors.lastname: Chan
authors.forename: Daljit Singh
authors.initials: DS
authors.lastname: Sahota
authors.forename: Tak Yuen
authors.initials: TY
authors.lastname: Fung
authors.forename: Tze Kin
authors.initials: TK
authors.lastname: Lau
mesh_terms: D000022:Abortion, Spontaneous / Q000453:epidemiology*; D000649:Amniocentesis / Q000009:adverse effects*; D002869:Chromosome Aberrations; D025063:Chromosome Disorders / Q000175:diagnosis*; D005260:Female; D005313:Fetal Death / Q000209:etiology*; D046689:Fetal Mortality; D005865:Gestational Age; D006801:Humans; D011247:Pregnancy; D011256:Pregnancy Outcome; D011262:Pregnancy Trimester, Second; D012307:Risk Factors