Introduction: The incidence of congenital anomalies of the central nervous system (CNS) in Iceland during 1992-2016 was examined along with timing of diagnosis, maternal residence, known risk factors and perinatal outcomes.

Material and methods: This was a retrospective study of all fe­tuses and newborns diagnosed with a CNS anomaly during the study period and their mothers. Information was obtained from the Icelandic Birth Registry and from maternal and neonatal medical records. Descriptive and inferential statistics were used in data analyzing.

Results: Annually, 3-12 cases of congenital CNS anomalies were diagnosed. Five year period incidence ranged from 1.4-2.4/1000 newborns, highest in 2012-2016. Over 89% were diagnosed ­prenatally, of those 80% were terminated. The average gestational age at diagnosis of anencephaly was 19,3 weeks 1992-1996 vs. 11.6 weeks 2012-2016 (p=0,006). Urban area prenatal diagnosis was higher (94%) than rural (80%) (p=0.006). Known risk factors among mothers were uncommon, except for maternal obesity during the period 2012-2016 (23%). Of 57 live born children with CNS anomalies 37 (65%) were alive at the time of the study.

Conclusion: The incidence of congenital anomalies of the CNS is stable and maternal risk factors are infrequent. Around 90% were diagnosed prenatally. Fetal anencephaly was diagnosed earlier at the end of the study period, after the introduction of a 11-14 week ultrasound scan in 2003, along with increased training among ­healthcare professionals and improved ultrasound equipment. Higher prenatal detection rate in urban areas compared with rural may be explained by fewer ultrasound examinations being performed in less populated health districts, staff consequently receiving less training and experience and also with less advanced equipment.

Table I   Incidence of congenital CNS* anomalies, five year period

Table II   Prenatal detection rate for each category of CNS anomalie

Table III Mean gestational age in weeks at diagnosis of a CNS anomalies, five year period

Table IV   Birthweight of live born children with CNS abnormality, NICU stay, surgery and number of survivors, five year periods

Table V Results of genetic studies performed when fetal congenital central nervous system anomalies were diagnosed