title: Assisted reproductive technology and the risk of pregnancy-related complications and adverse pregnancy outcomes in singleton pregnancies: a meta-analysis of cohort studies.
abstract: OBJECTIVE
  To determine whether there are any increases in pregnancy-related complications and adverse pregnancy outcomes in singleton pregnancies after assisted reproductive technology (ART) compared with those conceived naturally.
  
  
  METHODS
  Meta-analysis.
  
  
  METHODS
  University-affiliated teaching hospital.
  
  
  METHODS
  Singleton pregnancies conceived with ART and naturally.
  
  
  METHODS
  PubMed, Google Scholar, Cochrane Libraries and Chinese database were searched through March 2015 to identify studies that met pre-stated inclusion criteria. Either a fixed- or a random-effects model was used to calculate the overall combined risk estimates. Subgroup analysis was performed to explore potential heterogeneity moderators.
  
  
  METHODS
  Pregnancy-related complications and adverse pregnancy outcomes.
  
  
  RESULTS
  Fifty cohort studies comprising 161,370 ART and 2,280,241 spontaneously conceived singleton pregnancies were identified. The ART singleton pregnancies had a significantly increased risk of pregnancy-induced hypertension (relative risk [RR] 1.30, 95% confidence interval [CI] 1.04-1.62; I(2) = 79%), gestational diabetes mellitus (RR 1.31, 95% CI 1.13-1.53; I(2) = 6%), placenta previa (RR 3.71, 95% CI 2.67-5.16; I(2) = 72%), placental abruption (RR 1.83, 95% CI 1.49-2.24; I(2) = 22%), antepartum hemorrhage (RR 2.11, 95% CI 1.86-2.38; I(2) = 47%), postpartum hemorrhage (RR 1.29, 95% CI 1.06-1.57; I(2) = 65%), polyhydramnios (RR 1.74, 95% CI 1.24-2.45; I(2) = 0%), oligohydramnios (RR 2.14, 95% CI 1.53-3.01; I(2) = 0%), cesarean sections (RR 1.58, 95% CI 1.48-1.70; I(2) = 92%), preterm birth (RR 1.71, 95% CI 1.59-1.83; I(2)=80%), very preterm birth (RR 2.12, 95% CI 1.73-2.59; I(2) = 90%), low birth weight (RR 1.61, 95% CI 1.49-1.75; I(2) = 80%), very low birth weight (RR 2.12, 95% CI 1.84-2.43; I(2) = 67%), small for gestational age (RR 1.35, 95% CI 1.20-1.52; I(2) = 82%), perinatal mortality (RR 1.64, 95% CI 1.41-1.90; I(2)=45%), and congenital malformation (RR 1.37, 95% CI 1.29-1.45; I(2)=41%). Relevant heterogeneity moderators have been identified by subgroup analysis. Sensitivity analysis yielded consistent results. No evidence of publication bias was observed.
  
  
  CONCLUSIONS
  The ART singleton pregnancies are associated with higher risks of adverse obstetric outcomes. Obstetricians should manage these pregnancies as high risk.
authors.affiliation: Division of Medical Genetics, Maternal and Child Health Hospital of Hunan Province, Hunan, People's Republic of China; Department of Epidemiology and Health Statistics, School of Public Health, Central South University, Hunan, People's Republic of China. Electronic address: qinjiabi123@hotmail.com.
authors.forename: Jiabi
authors.initials: J
authors.lastname: Qin
authors.affiliation: Department of Epidemiology and Health Statistics, School of Public Health, Central South University, Hunan, People's Republic of China.
authors.forename: Xiaoying
authors.initials: X
authors.lastname: Liu
authors.affiliation: Division of Medical Genetics, 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: Hua
authors.initials: H
authors.lastname: Wang
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: D016009:Chi-Square Distribution; D005260:Female; D005298:Fertility; D006801:Humans; D007246:Infertility / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*; D016014:Linear Models; D016017:Odds Ratio; D011247:Pregnancy; D011248:Pregnancy Complications / Q000175:diagnosis / Q000209:etiology*; D027724:Reproductive Techniques, Assisted / Q000009:adverse effects*; D018570:Risk Assessment; D012307:Risk Factors
keywords: Adverse pregnancy outcomes; assisted reproductive technology; meta-analysis; pregnancy-related complications; singleton pregnancies