Time trends, geographic variation and risk factors for gastroschisis in Canada: A population-based cohort study 2006-2017.

BACKGROUND: Previous studies showed increases in rates of gastroschisis in Canada in the first decade of the 21st century. OBJECTIVE: We sought to examine the epidemiologic characteristics of gastroschisis in Canada in recent years. METHODS: We conducted a retrospective population-based cohort study of all livebirths and stillbirths delivered in Canada (excluding Quebec) from 2006 to 2017, with information obtained from the Canadian Institute for Health Information. Gastroschisis rates by maternal age, region of residence, and maternal and infant characteristics were quantified using prevalence rate ratios (RR) and 95% confidence intervals (CI). Log-binomial regression was used to quantify the associations between risk factors and gastroschisis. RESULTS: There were 1314 gastroschisis cases among 3 364 116 births. The prevalence rate was 3.7 per 10 000 total births in 2006 and 3.4 per 10 000 total births in 2017, with substantial annual variation in rates. The proportion of mothers aged 20-24 years decreased from 16.5% in 2006 to 11.3% in 2017, while the proportion of mothers aged <20 years halved from 4.8% to 2.3%. The prevalence of gastroschisis at birth remained unchanged among mothers aged <20, 20-24 and 30-49 years but increased among mothers aged 25-29 years. The age-adjusted prevalence rate of gastroschisis increased across the period (for 2016-2017 versus 2006-2007 rate ratio [RR] 1.28, 95% CI 1.05, 1.56), and there was substantial regional variation. Risk factors included problematic use of substances (RR 2.61, 95% CI 2.01, 3.39) and hypothyroidism (RR 2.76, 95% CI 1.56, 4.88). There was a North-to-South difference in gastroschisis prevalence (adjusted RR Far North compared with South 1.54, 95% CI 1.11, 2.15). CONCLUSION: Gastroschisis birth prevalence rates in Canada have stabilised in recent years compared with the increase documented previously. The substantial geographic variation and North-to-South difference in gastroschisis prevalence may indicate variation in socio-economic status, lifestyle and nutritional patterns.