Deliveries and children born after in-vitro fertilisation in Sweden 1982-95: a retrospective cohort study

Abstract

Background: In-vitro fertilisation is an effective treatment for infertility, but there is concern about the health of children. We investigated, in a retrospective registry study, malformations, cancers, and deaths in the complete Swedish in-vitro-fertilisation birth cohort compared with the general population.

Methods: We collected data from all in-vitro-fertilisation clinics in Sweden and compared the obstetric outcomes of babies (n=5856) born between 1982 and 1995 with all babies born in the general population (n=1,505,724) during the same period, according to data from the Swedish Medical Birth Registry and the Registry of Congenital Malformations. We investigated the incidence of childhood cancer through the Swedish Cancer Registry. Data were stratified for maternal age, parity, previous subfertility, year of birth, and multiple of pregnancies.

Findings: Multiple births occurred in 27% of pregnancies compared with 1% in the control group. In the in-vitro-fertilisation group, more babies were born preterm (<37 weeks) than controls (30.3 vs 6.3%) and more had low birthweights (<2500 g, 27.4 vs 4.6%). The perinatal mortality was 1.9% in the in-vitro fertilisation group and 1.1% in the controls. For in-vitro-fertilisation singletons, the risk ratios, adjusted for year of birth, for very preterm birth (<32 weeks) and very low birthweight (<1500 g) were 3.54 (95% CI 2.90-4.32) and 4.39 (3.62-5.32), respectively. Malformations occurred in 5.4% of all babies in the in-vitro-fertilisation group (1.39 [1.25-1.54]), and the rates of neural-tube defects and oesophageal atresia were higher than those in the controls. There was no increase in childhood cancer in the in-vitro-fertilisation group.

Interpretation: A high frequency of multiple births and maternal characteristics were the main factors that led to adverse outcomes, and not the in-vitro-fertilisation technique itself. The clinical practice of in-vitro-fertilisation needs to be changed to lower the rate of multiple pregnancy.