title: Perinatal outcome of singleton siblings born after assisted reproductive technology and spontaneous conception: Danish national sibling-cohort study.
abstract: OBJECTIVE
  To compare the perinatal outcome of singleton siblings conceived differently.
  
  
  METHODS
  National population-based registry study.
  
  
  METHODS
  Denmark, from 1994 to 2008.
  
  
  METHODS
  Pairs of siblings (13,692 pairs; n = 27,384 children) conceived after IVF, intracytoplasmatic sperm injection (ICSI), frozen embryo replacement (FER), or spontaneous conception subcategorized into five groups according to succession: [1] IVF-ICSI vs. spontaneous conception (n = 7,758), [2] IVF-ICSI vs. FER (n = 716), [3] FER vs. FER (n = 34), [4] IVF-ICSI vs. IVF-ICSI (n = 2,876), and [5] spontaneous conception vs. spontaneous conception (n = 16,000).
  
  
  METHODS
  Observations were obtained from national registries.
  
  
  METHODS
  Birth weight, gestational age, low birth weight (<2,500 g), preterm birth (<37 weeks' gestation) and perinatal deaths.
  
  
  RESULTS
  Mean birth weight was 65 g (95% confidence interval [CI], 41-89] lower in all assisted reproductive technology children compared with their spontaneously conceived siblings. FER children were 167 g (95% CI, 90-244] heavier than siblings born after replacement of fresh embryos. The difference in birth weight between firstborn and second born sibling depended on order of conception method. Higher risk of low birth weight with (odds ratio [OR], 1.4; 95%CI, 1.1-1.7] and preterm birth (OR, 1.3; 95% CI, 1.1-1.6] was observed in IVF/ICSI compared with spontaneous conception.
  
  
  CONCLUSIONS
  When differentiating between order and mode of conception, it seems that assisted reproductive technology plays a role in mean birth weight and risk of low birth weight and preterm birth. Birth weight was higher in siblings born after FER compared with fresh embryos replacement.
authors.affiliation: Fertility Clinic, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark. anna-karina.aaris.henningsen@rh.regionh.dk
authors.forename: Anna-Karina Aaris
authors.initials: AK
authors.lastname: Henningsen
authors.forename: Anja
authors.initials: A
authors.lastname: Pinborg
authors.forename: Øjvind
authors.initials: Ø
authors.lastname: Lidegaard
authors.forename: Christina
authors.initials: C
authors.lastname: Vestergaard
authors.forename: Julie Lyng
authors.initials: JL
authors.lastname: Forman
authors.forename: Anders Nyboe
authors.initials: AN
authors.lastname: Andersen
mesh_terms: D000293:Adolescent; D000328:Adult; D015331:Cohort Studies; D003718:Denmark / Q000453:epidemiology; D004624:Embryo Transfer / Q000706:statistics & numerical data; D005260:Female; D005306:Fertilization; D005307:Fertilization in Vitro / Q000706:statistics & numerical data; D005865:Gestational Age; D006801:Humans; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D008297:Male; D011247:Pregnancy; D011256:Pregnancy Outcome / Q000453:epidemiology*; D047928:Premature Birth / Q000401:mortality*; D012042:Registries; D027724:Reproductive Techniques, Assisted / Q000706:statistics & numerical data*; D035781:Siblings; D020554:Sperm Injections, Intracytoplasmic / Q000706:statistics & numerical data; D055815:Young Adult