Study question: Is the risk of stillbirth and perinatal deaths increased after assisted reproductive technology (ART) compared with pregnancies established by spontaneous conception (SC)?
Summary answer: A significantly increased risk of stillbirth in ART singletons was only observed before 28 + 0 gestational weeks.
What is known already: The current literature indicates that children born after ART have an increased risk of perinatal death. The knowledge on stillbirth in ART pregnancies is limited.
Study design, size, duration: A population based case-control study.
Participants/materials, setting and methods: A total of 62 485 singletons and 29 793 twins born after ART in Denmark, Finland, Norway and Sweden, from 1982 to 2007, were compared with 362 798 spontaneously conceived (SC) singletons and 132 181 twins.
Main results and the role of chance: The adjusted rate ratio for stillbirth at gestational weeks 22 + 0 to 27 + 6 was 2.08 [95% confidence interval (CI) 1.55-2.78] for ART versus SC singletons. After 28 + 0 gestational weeks there was no significant difference in the risk of stillbirth between ART and SC singletons. ART twins had a lower risk of stillbirth compared with SC twins, but when restricting the analysis to opposite-sex twins and excluding all monozygotic twins, there was no significant difference between the groups. Singletons conceived by ART had an overall increased risk of early neonatal death (adjusted odds ratio 1.54, 95% CI 1.28-1.85) and death within the first year after birth (1.45, 1.26-1.68). No difference regarding these two parameters was found when further adjusting for the gestational age [(0.97, 0.80-1.18) and (0.99, 0.85-1.16), respectively]. ART twins had a lower risk of early neonatal and infant deaths than SC twins, but no difference was found when restricting the analyses to opposite-sex twins.
Limitations, reason for caution: We were not able to adjust for potential confounders, such as a prior history of stillbirth, induction of labour, body mass index or smoking.
Wider implications of the findings: The risk of stillbirth in ART versus SC singletons was only increased for very early gestational ages (before 28 weeks). This might indicate that the current clinical management of ART pregnancies is sufficient regarding prevention of stillbirth during the third trimester.
Study funding/competing interest(s): No conflict of interest was reported. The European Society for Human Reproduction and Embryology (ESHRE), the University of Copenhagen, Denmark, the Danish Agency for Science, Technology and Innovation and Sahlgrenska University Hospital, Gothenburg, Sweden supported the project. The CoNARTaS group has received travel and meeting funding from the Nordic Society of Obstetrics and Gynecology (NFOG).
Keywords: assisted reproductive technology; infant death; preterm birth; small-for-gestational age; stillbirth.