title: Procedure-related risk of miscarriage following amniocentesis and chorionic villus sampling: a systematic review and meta-analysis.
abstract: OBJECTIVE
  To estimate procedure-related risks of miscarriage following amniocentesis and chorionic villus sampling (CVS) based on a systematic review of the literature and a meta-analysis.
  
  
  METHODS
  A search of MEDLINE, EMBASE, CINHAL and The Cochrane Library (2000-2014) was performed to review relevant citations reporting procedure-related complications of amniocentesis and CVS. Only studies reporting data on more than 1000 procedures were included in this review to minimize the effect of bias from smaller studies. Heterogeneity between studies was estimated using Cochran's Q, the I(2) statistic and Egger bias. Meta-analysis of proportions was used to derive weighted pooled estimates for the risk of miscarriage before 24 weeks' gestation. Incidence-rate difference meta-analysis was used to estimate pooled procedure-related risks.
  
  
  RESULTS
  The weighted pooled risks of miscarriage following invasive procedures were estimated from analysis of controlled studies including 324 losses in 42 716 women who underwent amniocentesis and 207 losses in 8899 women who underwent CVS. The risk of miscarriage prior to 24 weeks in women who underwent amniocentesis and CVS was 0.81% (95% CI, 0.58-1.08%) and 2.18% (95% CI, 1.61-2.82%), respectively. The background rates of miscarriage in women from the control group that did not undergo any procedures were 0.67% (95% CI, 0.46-0.91%) for amniocentesis and 1.79% (95% CI, 0.61-3.58%) for CVS. The weighted pooled procedure-related risks of miscarriage for amniocentesis and CVS were 0.11% (95% CI, -0.04 to 0.26%) and 0.22% (95% CI, -0.71 to 1.16%), respectively.
  
  
  CONCLUSIONS
  The procedure-related risks of miscarriage following amniocentesis and CVS are much lower than are currently quoted.
authors.affiliation: Fetal Medicine Unit, Medway Maritime Hospital, Gillingham, Kent, UK; Harris Birthright Research Centre, King's College Hospital, London, UK.
authors.forename: R
authors.initials: R
authors.lastname: Akolekar
authors.forename: J
authors.initials: J
authors.lastname: Beta
authors.forename: G
authors.initials: G
authors.lastname: Picciarelli
authors.forename: C
authors.initials: C
authors.lastname: Ogilvie
authors.forename: F
authors.initials: F
authors.lastname: D'Antonio
mesh_terms: D000022:Abortion, Spontaneous / Q000453:epidemiology / Q000209:etiology*; D000649:Amniocentesis / Q000009:adverse effects*; D000782:Aneuploidy; D015193:Chorionic Villi Sampling / Q000009:adverse effects*; D003657:Decision Making; D005260:Female; D005865:Gestational Age; D006801:Humans; D016017:Odds Ratio; D010353:Patient Education as Topic; D011247:Pregnancy; D011296:Prenatal Diagnosis / Q000009:adverse effects*; D012307:Risk Factors
keywords: CVS; amniocentesis; chorionic villus sampling; fetal loss; invasive diagnostic procedure; miscarriage; pregnancy loss; prenatal diagnosis; procedure-related loss