Consanguinity (parents being first cousins or otherwise blood‐related) was a strong factor: in the Pakistani subgroup, a high proportion (≈37%) of parents were first cousins; consanguinity more than doubled the risk of anomalies (multivariate RR ~ 2.19) in the study population.
In the UK, particularly in studies like Born in Bradford (which is often referenced because Bradford has one of the largest Pakistani heritage populations), the majority of people of Pakistani and Bangladeshi origin are Muslim.