title: Pregnancy loss after chorionic villus sampling and genetic amniocentesis in twin pregnancies: a systematic review.
abstract: OBJECTIVE
  To review the available evidence regarding pregnancy loss following first-trimester chorionic villus sampling (CVS) and mid-trimester genetic amniocentesis in twins.
  
  
  METHODS
  We searched the MEDLINE database from January 1990 to May 2011 for randomized and cohort studies reporting on the risk of pregnancy loss after first-trimester CVS performed between 9 and 14 weeks and after genetic amniocentesis performed between 14 and 22 weeks. Where appropriate, we calculated pooled proportions and relative risks with 95% CI.
  
  
  RESULTS
  No randomized studies were found. For CVS, nine studies fulfilled the inclusion criteria. The overall pregnancy-loss rate was 3.84% (95% CI, 2.48-5.47; n = 4). The rate of pregnancy loss before 20 weeks was 2.75% (95% CI, 1.28-4.75; n = 3) and before 28 weeks was 3.44% (95% CI, 1.67-5.81; n = 3). For amniocentesis, the overall pregnancy-loss rate was 3.07% (95% CI, 1.83-4.61; n = 4). The rate of pregnancy loss before 20 weeks was 2.25% (95% CI, 1.23-3.57; n = 2), before 24 weeks was 2.54% (95% CI, 1.43-3.96; n = 9) and before 28 weeks was 1.70% (95% CI, 0.37-3.97; n = 5). Pooled data from four case-control studies showed a higher risk (2.59% vs. 1.53%) of pregnancy loss before 24 weeks following amniocentesis (relative risk = 1.81; 95% CI, 1.02-3.19). There were no statistically significant differences in reported pregnancy loss between transabdominal and transcervical approaches, use of a single-needle system vs. a double-needle system and single uterine entry vs. double uterine entry in the CVS group. Similarly, in the amniocentesis group, there was no statistically significant difference in fetal loss between the single uterine entry vs. the double uterine entry.
  
  
  CONCLUSIONS
  In the absence of randomized studies, it is not possible to estimate accurately the excess risk following invasive procedures in twins. Currently available data show similar overall pregnancy-loss rates for both amniocentesis and CVS with the excess risk of around 1% above the background risk.
authors: Department of Obstetrics & Gynecology, Maulana Azad Medical College, New Delhi, India.
authors: K
authors: K
authors: Agarwal
authors: Z
authors: Z
authors: Alfirevic
mesh_terms: D000649:Amniocentesis / Q000009:adverse effects*; D015193:Chorionic Villi Sampling / Q000009:adverse effects*; D020964:Embryo Loss / Q000453:epidemiology / Q000209:etiology*; D005260:Female; D006801:Humans; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011262:Pregnancy Trimester, Second; D059285:Pregnancy, Twin