title: Neonatal and maternal outcome after blastocyst transfer: a population-based registry study.
abstract: BACKGROUND
  Previous studies have shown a higher risk of birth defects and preterm birth (PTB) in singletons born after blastocyst transfer as compared to singletons born after cleavage-stage transfer. Few studies have investigated the maternal outcomes.
  
  
  OBJECTIVE
  We sought to analyze the neonatal and maternal outcome after blastocyst transfer (day 5-6) compared to transfer of cleavage-stage embryos (day 2-3) and spontaneous conception.
  
  
  METHODS
  This was a population-based retrospective registry study including all singleton deliveries after blastocyst transfer in Sweden from 2002 through 2013. The in vitro fertilization register was cross-linked with the Swedish Medical Birth Register, the Register of Birth Defects, and the National Patient Register. Deliveries after blastocyst transfer were compared with deliveries after cleavage-stage transfer and deliveries after spontaneous conception. Outcome measures included birth defects, PTB, low birthweight, small for gestational age, large for gestational age, perinatal mortality, placenta previa, placental abruption, and preeclampsia. Crude and adjusted odds ratios (AOR) with 95% confidence interval (CI) were calculated. Adjustment was made for year of birth of child, maternal age, parity, smoking, body mass index, years of involuntary childlessness, and child's sex and, for cleavage stage, also for number of oocytes retrieved, number of embryos transferred, and fresh/frozen embryo transfer.
  
  
  RESULTS
  There were 4819 singletons born after blastocyst transfer, 25,747 after cleavage-stage transfer, and 1,196,394 after spontaneous conception. Singletons born after blastocyst transfer had no increased risk of birth defects compared to singletons born after cleavage-stage transfer (AOR, 0.94; 95% CI, 0.79-1.13) or spontaneous conception (AOR, 1.09; 95% CI, 0.92-1.28). Perinatal mortality was higher in the blastocyst vs the cleavage-stage group (AOR, 1.61; 95% CI, 1.14-2.29). When comparing singletons born after blastocyst transfer to singletons born after spontaneous conception, a higher risk of PTB (<37 weeks) was seen (AOR, 1.17; 95% CI, 1.05-1.31). Singletons born after blastocyst transfer had a lower rate of low birthweight (AOR, 0.83; 95% CI, 0.71-0.97) as compared to cleavage-stage transfer. The rate of being small for gestational age was lower in singletons born after blastocyst transfer as compared to both cleavage-stage and spontaneous conception (AOR, 0.71; 95% CI, 0.56-0.88 and AOR, 0.70; 95% CI, 0.57-0.87, respectively). The risk of placenta previa and placental abruption was higher in pregnancies after blastocyst transfer as compared to pregnancies after cleavage-stage (AOR, 2.08; 95% CI, 1.70-2.55 and AOR, 1.62; 95% CI, 1.15-2.29, respectively) and spontaneous conception (AOR, 6.38; 95% CI, 5.31-7.66 and AOR, 2.31; 95% CI, 1.70-3.13, respectively).
  
  
  CONCLUSIONS
  No increased risk of birth defects was found in singletons born after blastocyst transfer. Perinatal mortality and risk of placental complications were higher in the blastocyst group as compared to the cleavage-stage group, observations that need further investigations.
authors.affiliation: Department of Obstetrics and Gynecology, Institute of Clinical Science, Sahlgrenska Academy, Gothenburg University, Reproductive Medicine, Gothenburg, Sweden.
authors.forename: Erica
authors.initials: E
authors.lastname: Ginström Ernstad
authors.affiliation: Department of Obstetrics and Gynecology, Institute of Clinical Science, Sahlgrenska Academy, Gothenburg University, Reproductive Medicine, Gothenburg, Sweden.
authors.forename: Christina
authors.initials: C
authors.lastname: Bergh
authors.affiliation: Department of Obstetrics and Gynecology, Institute of Clinical Science, Sahlgrenska Academy, Gothenburg University, Reproductive Medicine, Gothenburg, Sweden.
authors.forename: Ali
authors.initials: A
authors.lastname: Khatibi
authors.affiliation: Department of Reproduction Epidemiology, Tornblad Institute, Institution of Clinical Science, Lund University, Lund, Sweden.
authors.forename: Karin B M
authors.initials: KB
authors.lastname: Källén
authors.affiliation: Fertility Center, Carlanderska Hospital, Gothenburg, Sweden.
authors.forename: Göran
authors.initials: G
authors.lastname: Westlander
authors.affiliation: In Vitro Fertilization Clinic, Falun, Sweden.
authors.forename: Staffan
authors.initials: S
authors.lastname: Nilsson
authors.affiliation: East Hospital, Sahlgrenska University Hospital, Gothenburg, Sweden. Electronic address: ulla-britt.wennerholm@vgregion.se.
authors.forename: Ulla-Britt
authors.initials: UB
authors.lastname: Wennerholm
mesh_terms: D000037:Abruptio Placentae / Q000453:epidemiology; D000328:Adult; D001724:Birth Weight; D000013:Congenital Abnormalities / Q000453:epidemiology; D004624:Embryo Transfer / Q000379:methods*; D005260:Female; D005320:Fetal Macrosomia / Q000453:epidemiology; D006801:Humans; D007231:Infant, Newborn; D007236:Infant, Small for Gestational Age; D054238:Perinatal Mortality; D010923:Placenta Previa / Q000453:epidemiology; D011225:Pre-Eclampsia / Q000453:epidemiology; D011247:Pregnancy; D011248:Pregnancy Complications / Q000453:epidemiology*; D047928:Premature Birth / Q000453:epidemiology; D012042:Registries; D012189:Retrospective Studies; D018570:Risk Assessment; D013548:Sweden / Q000453:epidemiology; D055815:Young Adult
keywords: assisted reproductive technology; birth defects; congenital anomalies; malformations; placenta previa; preterm birth