Abstract
Background. An increased risk of cerebral palsy (CP) after in-vitro fertilisation (IVF) has previously been reported from a Swedish cohort including all children born after IVF in 1982-1995. The background CP prevalence of 0.15% was increased to 0.55%. Children born after IVF had a 3.7-fold increased risk of cerebral palsy compared with non IVF children. An increased risk (2.8 fold), of CP was also found in the IVF singletons. The aim of this study was to further describe background factors and morbidity details regarding children with CP born after IVF. Methods. In the previous report 31 cases of CP were identified among children born after IVF (n = 5680), compared to the expected number, nine. In this study we compared the type and severity of CP and maternal and perinatal characteristics of the 31 children with CP born after IVF with 44 non-IVF children with CP. Data were collected from four different sources. Data concerning treatment details were collected from all Swedish IVF clinics and data concerning maternal background factors, pregnancy complications, delivery and immediate post-natal outcome from the Swedish Medical Birth Registry. All Swedish habilitation centres provided data concerning the CP syndromes. Finally, data were collected from the Swedish Hospital Discharge Registry, which covers all public in-patient care in Sweden, on whether these children, in addition to CP, had been treated for mental retardation (MR) or epilepsy (EP). Using the specific personal identification number given to every Swede, data were cross-linked. Singletons were matched for sex, year of birth and birth hospital, whereas twins were just matched for year of birth. Findings. The method of conception was conventional IVF in 29/31 children, intracytoplasmic sperm injection in one IVF twin and conventional IVF with frozen embryos in one IVF triplet. All twins except one non-IVF twin pair and all IVF triplets were from different sets. The median maternal age and range were 30 (21-42) years. IVF mothers were more likely to be over 35 years of age and primiparous than non-IVF mothers, although the differences were not statistically significant (OR 2.6; 95% CI 0.8-8.4 and OR 1.4; 95% CI 0.5-4.9, respectively). No specific antepartum risk factor could be identified. Most children with CP were of male sex, were born preterm or were the result of a multiple pregnancy. Very preterm birth was seen more often among IVF singletons than among non-IVF singletons (OR 6.5; 95% CI 1.0-42.2). Spastic/ataxic diplegia, followed by spastic hemiplegia, were the most commonly seen CP syndromes both among the IVF and non-IVF children, irrespective of single or twin birth. As expected, most children with spastic/ataxic diplegia were born preterm and term infants were in majority in the spastic hemiplegia group. Both these CP syndromes were seen more often among twins. Four IVF singletons and four IVF twins had CP + MR compared to three and seven non-IVF singletons or twins respectively. The corresponding numbers of IVF children with CP + EP were five singletons and four twins compared to four non-IVF singletons and three non-IVF twins. No statistically significant differences between IVF and non-IVF children were found in respect to type of CP or concerning CP in combination with MR or EP. Interpretations. No differences in type, severity of CP or background characteristics were found between children born after IVF and non-IVF children. Our interpretation is that aetiological factors for CP do not differ, but that the increased prevalence of CP seen after IVF is due to the high multiple pregnancy rate and prematurity.