Reply: Implication of the liberal use of ART in Nordic countries: should stricter guidelines be created to prevent unnecessary stillbirth and preterm delivery?

Sir, With interest we read the article of Henningsen et al., who compared pregnancy outcomes in singleton pregnancies after ART to singleton pregnancies that were conceived naturally. The authors report a significantly increased risk of stillbirth after ART before a gestational age of 28 weeks. They conclude that in view of the fact that the increased stillbirth risk was observed before 28 weeks only, prevention of stillbirth in the third trimester might be sufficient. We have two comments. First, the authors have acknowledged that a proportion of the cohort of women with ART singleton pregnancies (estimating background rate 1 in 10 (Henningsen et al., 2014)) initially might have had a vanishing twin. They have also acknowledged the subsequent possible implications for early stillbirths in this group. It would be crucial to know what proportion of the singletons after ARTwould be the result from single embryo transfer (SET) or from double embryo transfer (DET). This information is not provided, but may be available to the authors. Moreover, as SET in Scandinavia was introduced well before the end of the study period, the authors might be able to look at trends over this time. Secondly, when the increased perinatal mortality rate before 28 weeks indeed can be linked to the use of ART, we would like to challenge the opinion of the authors on the liberal use of ART in Nordic countries, where .3% of the babies are conceived after ART, with Denmark leading the way with 4.5% of infants born through ART (Ferraretti et al., 2013). Considering the fact that many couples would conceived naturally when allowed a longer expectant management period we could imagine stricter guidelines around use of ART in Scandinavia to prevent unnecessary stillbirth and preterm delivery.