Of 11,396 babies for whom questionnaire data were available, 386 (3%) had a congenital anomaly. Rates for congenital anomaly were 305·74 per 10,000 livebirths, compared with a national rate of 165·90 per 10,000. The risk was greater for mothers of Pakistani origin than for those of white British origin (univariate RR 1·96, 95% CI 1·56-2·46). Overall, 2013 (18%) babies were the offspring of first-cousin unions. These babies were mainly of Pakistani origin--1922 (37%) of 5127 babies of Pakistani origin had parents in first-cousin unions
Sheridan E, Wright J, Small N, Corry PC, Oddie S, Whibley C, Petherick ES, Malik T, Pawson N, McKinney PA, Parslow RC. Risk factors for congenital anomaly in a multiethnic birth cohort: an analysis of the Born in Bradford study. Lancet. 2013 Oct 19;382(9901):1350-9. doi: 10.1016/S0140-6736(13)61132-0. Epub 2013 Jul 4. PMID: 23830354.
pubmed.ncbi.nlm.nih.gov/23830354/
Participating families live predominantly in three health districts of Birmingham, and were recruited in three local maternity hospitals. PARTICIPANTS--Babies of 2432 European mothers, 509 Afro-Caribbean mothers, 625 Indian mothers, 956 Pakistani mothers, and 216 Bangladeshi mothers have been enrolled in the study…The highest prevalence of parental consanguinity was in Pakistani Muslims (69%), whereas in Muslims from other countries it was 23%, and it was less than 1% in non-Muslims.
Bundey S, Alam H, Kaur A, Mir S, Lancashire RJ. Race, consanguinity and social features in Birmingham babies: a basis for prospective study. J Epidemiol Community Health. 1990 Jun;44(2):130-5. doi: 10.1136/jech.44.2.130. PMID: 2370500; PMCID: PMC1060620.
www.ncbi.nlm.nih.gov/pmc/articles/PMC1060620/
There's reference to a TV programme here.
Dyer O. MP is criticised for saying that marriage of first cousins is a health problem. BMJ. 2005 Dec 3;331(7528):1292. PMCID: PMC1298844.
www.ncbi.nlm.nih.gov/pmc/articles/PMC1298844/