title: Assisted reproductive technology and risk of adverse obstetric outcomes in dichorionic twin pregnancies: a systematic review and meta-analysis.
abstract: OBJECTIVE
  To examine whether dichorionic twin pregnancies after assisted reproductive technology (ART) were at higher risk of adverse obstetric outcomes compared with those conceived naturally.
  
  
  METHODS
  Meta-analysis.
  
  
  METHODS
  University-affiliated teaching hospital.
  
  
  METHODS
  Dichorionic twin pregnancies conceived with ART and naturally.
  
  
  METHODS
  Studies comparing obstetric outcomes in dichorionic twin pregnancies conceived by ART and naturally were identified by searching PubMed, Google Scholar, Cochrane Libraries, and Chinese databases through July 2015 with no restrictions. Either a fixed-effects or a random-effects model was used to calculate the overall combined risk estimates. Subgroup analysis was performed to explore potential heterogeneity moderators.
  
  
  METHODS
  Maternal complications and adverse pregnancy outcomes.
  
  
  RESULTS
  Fifteen cohort studies involving 6,420 dichorionic twins after ART and 13,650 dichorionic twins conceived naturally were included. Most of maternal complications were similar in both groups, but placenta previa (relative risk [RR] = 2.99, 95% confidence interval [CI] 1.51-5.92; I(2) = 0) was significantly more common in the ART group. For neonatal outcomes, the ART group experienced higher risk of preterm birth (RR = 1.13, 95% CI 1.00-1.29; I(2) = 75%), very preterm birth (RR = 1.39, 95% CI 1.07-1.82; I(2) = 71%), low birth weight (RR = 1.11, 95% CI 1.00-1.23; I(2) = 61%), and congenital malformations (RR = 1.26, 95% CI 1.09-1.46; I(2) = 26%). In addition, the ART group had a higher proportion of elective cesarean sections (RR = 1.79, 95% CI 1.49-2.16; I(2) = 60%), but had a similar proportion for emergency cesarean sections. Relevant heterogeneity moderators have been identified by subgroup analysis. No evidence of publication bias was observed.
  
  
  CONCLUSIONS
  The rates of placenta previa, elective cesarean section, preterm birth, very preterm birth, low birth weight, and congenital malformations were significantly higher in dichorionic twin pregnancies after ART.
authors.affiliation: Division of Medical Genetics, Maternal and Child Health Hospital of Hunan province, Hunan, People's Republic of China; State Key Laboratory of Medical Genetics, Central South University, Hunan, People's Republic of China. Electronic address: qinjiabi123@hotmail.com.
authors.forename: Jiabi B
authors.initials: JB
authors.lastname: Qin
authors.affiliation: Division of Medical Genetics, Maternal and Child Health Hospital of Hunan province, Hunan, People's Republic of China.
authors.forename: Hua
authors.initials: H
authors.lastname: Wang
authors.affiliation: Pediatric Rehabilitation, Maternal and Child Health Hospital of Hunan province, Hunan, People's Republic of China.
authors.forename: Xiaoqi
authors.initials: X
authors.lastname: Sheng
authors.affiliation: Division of Medical Genetics, Maternal and Child Health Hospital of Hunan province, Hunan, People's Republic of China.
authors.forename: Qiong
authors.initials: Q
authors.lastname: Xie
authors.affiliation: Reproductive Center, Maternal and Child Health Hospital of Hunan province, Hunan, People's Republic of China.
authors.forename: Shiyou
authors.initials: S
authors.lastname: Gao
mesh_terms: D002823:Chorion / Q000502:physiology; D036861:Delivery, Obstetric / Q000009:adverse effects* / Q000639:trends; D005260:Female; D006801:Humans; D011247:Pregnancy; D011248:Pregnancy Complications / Q000175:diagnosis / Q000453:epidemiology*; D011256:Pregnancy Outcome / Q000453:epidemiology*; D059285:Pregnancy, Twin / Q000502:physiology; D027724:Reproductive Techniques, Assisted / Q000009:adverse effects* / Q000639:trends
keywords: In vitro fertilization; dichorionic twins; intracytoplasmic sperm injection; neonatal outcomes; obstetric outcomes