Background Congenital anomaly diagnoses, and the subsequent discussions around termination of pregnancy, are associated with significant emotional distress. Families who have previously lost a child or pregnancy to a congenital anomaly are hence often particularly concerned about the risks of recurrence, but limited data exist for all but a few familial conditions.

This study used unique data from the UKs longest running register of congenital anomalies to estimate the absolute and relative risks of recurrent congenital anomaly in the second pregnancy for mothers who experienced congenital anomaly in their first pregnancy.

Methods Data on 18,524 singleton pregnancies affected by major congenital anomaly occurring in 872,500 singleton stillbirths, live births and terminations of pregnancy for fetal anomaly (TOPFA) were obtained from the Northern Congenital Abnormality Survey for 1985–2010. Absolute risks and relative risks (RR) for recurrent congenital anomaly in the second pregnancy (overall, in the same organ system, in a different organ system) were estimated by history of congenital anomaly in the first pregnancy. Predictors of recurrence were examined by logistic regression with missing data (most notably parity) supplemented using multivariate imputation of chained equations.

Results The estimated prevalence proportions for congenital anomaly in first and second pregnancies were respectively 276 (95% CI: 270–281) and 163 (95% CI: 159–168) per 10,000 singleton births and TOFPA. For women whose first pregnancies were affected by congenital anomaly, the absolute risk of recurrent congenital anomaly in the second pregnancy was 378 (95% CI: 336–420) per 10,000, 2.4 (95% CI: 2.2–2.7, p < 0.0001) times higher than for those with unaffected first pregnancies.

There was a considerable increase in the relative risk of a congenital anomaly from the same organ system (RR = 21.6, 95% CI: 18.1–25.1, p < 0.0001) but only a modest increase for anomalies from different organ systems (RR = 1.2, 95% CI: 1.1–1.4, p = 0.007), such that the absolute risks of both were around 2%.

More deprived socio-economic circumstances were also associated with higher risks of recurrence, independent of maternal age (conditional OR, for most deprived vs least deprived tertile = 1.35, 95% CI: 1.01–1.85, p = 0.046).

Conclusion For most congenital anomaly groups, the absolute risk of a woman experiencing a recurrent congenital anomaly in their second pregnancy is between 1 in 20 and 1 in 30. This information will be helpful to women and families during antenatal and pre-conception counselling. It may be particularly reassuring that despite high relative risks, the absolute risks of recurrence are generally relatively low.