Introduction: Anorectal malformations (ARMs) represent the most common form of congenital gastrointestinal malformations. ARMs range from mild anal stenosis to complex abnormalities involving the rectum, genitals, and urinary tract. The aim of this study is to investigate prevalence, mortality, and associated anomalies of ARMs in the Finnish population. This study offers comprehensive updated population-based estimates on stillbirths and terminations of pregnancy due to fetal anomalies (TOPFA).

Materials and methods: The data were obtained on all live births, TOPFA, and stillbirths from registers maintained by the Finnish Institute for Health and Welfare and Statistics Finland. All individuals diagnosed with ARM between January 1, 2004 and December 31, 2017, were included in the study.

Results: This population-based study identified 646 ARM cases, including 545 (84.4%) live births, 8 (1.2%) stillbirths, and 93 (14.4%) TOPFA. The total prevalence for ARM in Finland was 8.00 per 10,000 births, without significant variation in prevalence between 2004 and 2017. Neonatal mortality was 4.6% (n = 25), and infant mortality was 6.0% (n = 33). Neonatal and infant mortality were both associated with very low birth weight (p = 0.0001), prematurity (p = 0.0001), congenital heart defects (p = 0.02 and p < 0.001), and VACTERL (vertebral, anal, cardiac, tracheoesophageal, renal, limb; p = 0.0002 and p < 0.001, respectively). Postnatal survival rate for isolated ARM was 100%. Most commonly associated anomalies were urinary tract, heart, and limb malformations.

Conclusion: The overall prevalence of ARMs has remained stable in the Finnish population. Neonatal and infant mortality remains a significant concern, particularly among patients with severe associated anomalies, highlighting the importance of systematic screening for co-occurring malformations.