Objective To determine the prevalence and the timing of pregnancy termination relative to the type of central nervous system (CNS) malformations.

Design Retrospective cohort study.

Setting Multidisciplinary centre for prenatal diagnosis in the Languedoc-Roussillon region, France.

Population A cohort of 481 pregnancy terminations performed between 2005 and 2009.

Methods Detailed post-termination fetal and neuropathological analyses were carried out to identify the CNS malformations. Then, the prevalence and timing of pregnancy termination were assessed relative to the identified malformations.

Results About one-third of pregnancy terminations (143/481) were performed for severe CNS malformations. Up to 24 weeks of gestation (WG), pregnancy terminations (56.6%) were carried out mainly for defects occurring during the two major first steps of CNS development (neurulation and differentiation of cerebral vesicles). After 24 WG, pregnancy terminations (43.3%) were mainly performed for corpus callosum agenesis (16/17), vermian agenesis (10/12) and gyral anomalies (13/15). For hindbrain malformations and gyral anomalies, there was a significant relationship between the timing of pregnancy termination and the presence of a severe ventriculomegaly at prenatal diagnosis (p=0.002 and p=0.02, respectively).

Conclusion By classifying CNS malformations according to the neuropathological analysis, the authors show that the timing and prevalence of pregnancy termination are distributed in a manner that is consistent with what is currently known on the development of brain. They are also influenced by the French prenatal screening policy and the variable expressivity of the brain malformations and associated lesions.