title: Neonatal outcome in pregnancies from ovarian stimulation.
abstract: OBJECTIVE
  To study the neonatal outcome in pregnancies after ovarian stimulation, not including in vitro fertilization. The outcomes studied were multiple birth, preterm birth, and low birth weight among singletons, congenital malformations, and infant death.
  
  
  METHODS
  We identified 4029 women who delivered between 1995-1999 after ovarian stimulation alone and compared them with 438,582 women who neither had ovarian stimulation nor in vitro fertilization. We controlled for the confounding effect of year of birth, maternal age, parity, and length of subfertility before the pregnancy.
  
  
  RESULTS
  The twinning rate was 5.9% in the study group and 1.2% in the control group. The triplet rate was 0.5% in the study group and 0.02% in the control group. A nearly doubling of the rate of monozygotic twinning was indicated in the study group compared with the control group. There was an excess of singleton preterm births and low birth weight infants in the study group, but this was mainly explainable by confounding of maternal age, parity, and subfertility. The rates of congenital malformations and perinatal deaths were increased, also mainly explainable by maternal characteristics. No increase in specific types of congenital malformations was seen.
  
  
  CONCLUSIONS
  As the deviations in neonatal outcome after ovarian stimulation alone were reduced or disappeared when the confounding of maternal age, parity, and subfertility was taken into consideration, there is probably little direct effect of the stimulation procedure as such.
authors.affiliation: Tornblad Institute, University of Lund, Sweden. embryol@embryol.lu.se
authors.forename: B
authors.initials: B
authors.lastname: Källén
authors.forename: P Otterblad
authors.initials: PO
authors.lastname: Olausson
authors.forename: K G
authors.initials: KG
authors.lastname: Nygren
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D016001:Confidence Intervals; D000013:Congenital Abnormalities / Q000175:diagnosis / Q000453:epidemiology*; D005260:Female; D006801:Humans; D007226:Infant Mortality / Q000639:trends*; D007231:Infant, Newborn; D007234:Infant, Premature; D019102:Infant, Very Low Birth Weight; D008875:Middle Aged; D010062:Ovulation Induction / Q000009:adverse effects* / Q000379:methods; D016012:Poisson Distribution; D011247:Pregnancy; D011256:Pregnancy Outcome; D011272:Pregnancy, Multiple / Q000706:statistics & numerical data*; D012042:Registries; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D014310:Triplets; D014427:Twins