title: Pregnant after assisted reproduction: a risk pregnancy is born! 18-years perinatal outcome results from a population-based registry in Flanders, Belgium.
abstract: BACKGROUND
  Although the increased risk for perinatal morbidity and mortality of babies born after ART is largely attributed to a higher rate of multiple gestations, a significantly worse perinatal outcome for singleton pregnancies following ART compared to pregnancies after natural conception has been reported as well. Most studies only include IVF/ICSI pregnancies; studies describing the perinatal outcome of pregnancies after non-IVF assisted reproduction are scarce.
  
  
  METHODS
  Population-based cohort study with three exposure groups: a study group of pregnancies (1) after ovarian stimulation (OS), with or without artificial insemination (AI), (2) after IFV or ICSI and (3) a naturally conceived (NC) comparison group. Data from the regional registry of all hospital deliveries in the Dutch-speaking part of Belgium during an 18-years period from January 1993 until December 2010 were used. The perinatal outcome parameters were prematurity, low birth weight, perinatal mortality and morbidity including neonatal intracranial bleeding and need for intubation. Logistic regression analysis was used including mode of conception, female age, foetal sex, parity and year of delivery.
  
  
  RESULTS
  Data on 1 079 814 births were studied: 1 039 415 singletons (19 896 IVF/ICSI, 20 469 OS and 999 050 NC) and 39 041 twins (9 353 IVF/ICSI, 4812 OS and 24 876 NC) were available for analysis. IVF/ICSI singletons had a significantly worse outcome when compared to OS and NC for almost all investigated perinatal parameters. Non-IVF/OS singletons were also significantly disadvantaged for prematurity and low birth weight when compared to NC. The outcome of twin pregnancies was similar for the three groups unless only unlike-sex twins were studied separately. Among this subgroup, IVF/ICSI carried a higher risk for low birth weight when compared to NC. OS unlike-sex twins were at increased risk for low birth weight, intra uterine death and perinatal mortality when compared to NC.
  
  
  CONCLUSIONS
  According to our results all ART pregnancies, whether due to IVF/ICSI or non-IVF treatment, have to be considered as risk pregnancies, irrespective of the number of foetuses.
  
  
  CONCLUSIONS
  Although our logistic regression analysis included co-variables with a potential impact on perinatal outcome such as mode of conception, female age, foetal sex, parity and year of delivery, we couldn't correct for other prominent confounders such as the use of fresh or frozen embryos, use of homologous or donor gametes, smoking, obesity, socio-economic status, occupation exposures and pre-existing disease.
authors.affiliation: Genk Institute for Fertility Technology, Department of Obstetrics and Gynaecology, Schiepse Bos 6, 3600 Genk, Belgium; Faculty of Medicine and Life Sciences, Hasselt University, Martelarenlaan 42, Hasselt, Belgium.
authors.forename: W
authors.initials: W
authors.lastname: Ombelet
authors.affiliation: SPE (Study Center for Perinatal Epidemiology), Brussels, Belgium.
authors.forename: G
authors.initials: G
authors.lastname: Martens
authors.affiliation: Center for Statistics (CENSTAT), Agoralaan building D, 3590 Diepenbeek, Belgium.
authors.forename: L
authors.initials: L
authors.lastname: Bruckers
keywords: ART; ICSI; IUI; IVF; assisted reproduction; perinatal outcome; pregnancy; pregnancy outcome; singleton; twin