Background Congenital heart disease (CHD) is a diverse group of birth defects of the cardiovascular system. In the UK, 0.7% of births are affected, equating to approximately 6000 cases per year. Several studies have reported that advanced maternal age, generally defined as ≥35, is a risk factor for CHD. However, this association has never been investigated in the UK. The aim of this study is to examine the association between maternal age at delivery and CHD prevalence in the North of England.

Methods Singleton cases of CHD notified to the population-based Northern Congenital Abnormality Survey and born between 1^st Jan 1998–31^st Dec 2013 were included. Cases occurring with chromosomal anomalies were excluded. The yearly number of births in the North of England, aggregated by maternal age, were available from the ONS. While we had information on socioeconomic deprivation for cases, we did not have this information for the population births. The relative risk (RR) of CHD according to maternal age at delivery (categorised as <20, 20–24, 25–29, 30–34 and ≥35) was estimated using Poisson regression adjusted for year of delivery. RRs were estimated for CHD overall and according to CHD severity.

Results There were 4,024 singleton cases of non-chromosomal CHD, giving a prevalence of 8.1 (95% confidence interval (CI): 7.8–8.3) per 1000 live and stillbirths. Altogether, 9.6% of cases were born to mothers aged <20, 22.3% to mothers aged 20–24, 27.9% to mothers aged 25–29, 25.0% to mothers aged 30–34, 13.8% to mothers aged ≥35 and 1.4% cases with missing maternal age. Compared to case mothers aged 25–29, mothers aged ≥35 were significantly less likely to reside in the most deprived areas of the North of England (43.4% vs 28.5%, p < 0.001). There was no overall association between maternal age at delivery and CHD prevalence (p = 0.97), with no evidence of an increased risk of CHD in mothers aged ≥35 compared to aged 25–29 (RR = 0.99, 95% CI: 0.89–1.09). There were no significant associations between maternal age at delivery and mild CHD (p = 0.84), moderate CHD (p = 0.74) or severe CHD (p = 0.66), although there was a slight increased risk of severe CHD associated with maternal age ≥35 (RR = 1.27, 95% CI: 0.83–1.95).

Conclusion We found little evidence that advanced maternal age is a risk factor for CHD. We could not adjust for socioeconomic deprivation, which is a potential risk factor for CHD. Therefore, we cannot rule out that the lack of association with maternal age is a result of confounding.