Clefts affect approximately 1 in every 700 babies in Ireland.

There has been no national register of infants born with a cleft lip and/or palate in Ireland. The compilation of such a register for the purposes of clinical audit and strategic planning has only recently (2000) been made possible with the appointment of a Cleft Co-ordinator in the Eastern Regional Health Authority area.
Consequent on the lack of record-keeping, any figure given of the number of babies born with a cleft lip and/or palate in Ireland can only be an approximation. The figure of (‘approximately’) 75 children quoted in the report ((Eastern Health Board. Development of Oral & Maxillofacial Surgery Services in the Eastern Health Board Region. February 1999)) of a review into the development of oral and maxillofacial surgery services in the Eastern Health Board region (February 1999) is probably based on the often given estimation of 1:700. Based on the (provisional) number of live births in 1998 of 53,551 (Source: Central Statistics Office), this figure calculates correctly.

However, as can be seen from the varied research reports into the incidence of cleft throughout the world (and reported here), there would seem to be quite a variance in reported figures. Ratios have gone as high as 1:481 and as low as 1:1000. Most reported studies we have examined indicate a figure of around 1:700 or higher. The figures from Denmark where records have been kept since 1937 consistently show a higher ratio. The average for the years 1976-81 was 1:529, with a high of 1:481 in 1981. Analysis of the various research reports would seem to suggest that 1:700 may be a conservative figure. Many figures (one exception being Denmark) are based on voluntary disclosure and not accurate record-keeping. Based on the Danish figure of 1:529, this would give an Irish total of 121 such births in 2006 (1:700 = 92).
A fair conclusion would be that the figure of 92 per annum may be conservative, and it could theoretically be as much as 30% higher, particularly allowing for year to year variation.
American figures indicate that the incidence of cleft lip/palate varies between different races; among Asians it is 1.7 per 1000 births, while among African-Americans it is approximately 1 per 2500 births. The risk of isolated cleft palate seems to be the same across all racial groups. ((March of Dimes Birth Defects Foundation.

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The incidence of cleft palate occuring alone is about 1 in 2000 births. More than 70% of babies with cleft lip also have cleft palate. ((REF:2))
Combined cleft lip and palate (CLP) represents approximately 50% of incidents, cleft palate alone c.30%, and cleft lip alone c.20%. ((Young, Greg, M.D. (1998).
Cleft Lip and Palate. [Online] 28 January 1998. Available from http://www2.utmb.edu/otoref/Grnds/Cleft-lip-palate-9801/Cleft-lip-palate-9801.htm [verified 26 Mar 2001])) (These ratios are at slight variance with figures reported from Denmark and the UK and referred to below. Other reports have also given slightly variant figures).
According to Dr. John Mulliken, Director of the Craniofacial Centre, Children’s Hospital, Boston, Massachusetts, less than 10% of cleft lips are bilateral. ((Mulliken, John B., M.D. (2000). Repair of bilateral complete cleft lip and nasal deformity – state of the art. [Online] American Cleft Palate-Craniofacial Association Journal 37:342-347 2000. Available at http://cpcj.allenpress.com/ [verified 26 March 2001]))
Where a child is born with a cleft, there is a 5% chance of the next born also having a cleft – that is a 1 in 20 chance. If a second child is born with a cleft, the likelihood increases further for any subsequent child.
The chances of a parent who was born with a cleft having a cleft baby is approximately seven in one hundred.
Cleft lip and palate are what are known as congenital or birth defects, and are the fourth most common birth defect, being the most common of the head and neck region.
Clefts of the lip and combined lip and palate are twice as common in males. Isolated cleft palates are twice as common in females. This may be explained by the fact that the secondary palate closes one week later in females. ((REF:4))
According to the UK Craniofacial Anomalies Register (CARE), patients with cleft lip only account for 22% of total cases, with cleft lip and palate 34%, and cleft palate only 44%. The sex distribution is reported as 59% male and 40% female, with 1% unknown.Statistics from Denmark, where there is a compulsory reporting code, indicate that the reported incidence of cleft lip and/or palate is higher than the widely accepted figure of 1:700. Danish figures indicated a rise from 1:667 to 1:529 between 1942 and 1981 (Jensen et al 1988). ((Jensen, B. L. et al, (1998). Cleft lip and palate in Denmark, 1976-1981. Epidemiology, variability, and early somatic development. Cleft Palate Journal, 25:258-269)) It is thought that the Danish figure may be due to better reporting, decreased neonatal mortality, increased levels of environmental teratogens and increased frequency of marriage and childbirth in cleft patients because of better care. ((UK Craniofacial Anomalies Register (CARE). Available at http://www.cfsgb.org.uk/care/ [accessed 25 June 2000])) The sex distribution among Danish cases according to the Jensen report was 61% male and 39% female. Cleft lip accounted for 34% of cases, cleft lip and palate 39% and cleft palate 27%. The ratios of CL, CLP and CP among the sexes mirrors the ratios reported above.
According to statistical data from Brian Sommerlad, ((Sommerlad, Brian C. (1994) Management of cleft lip and palate. Current Paediatrics, 4:189-195)) Consultant Plastic Surgeon, North East Thames Cleft Service, unilateral cleft lip and palate accounted for 24.1% of clefts among 522 patients (excluding submucous cleft palate), bilateral cleft lip and palate 9.4%, isolated cleft palate 41%, and cleft lip 25.5%. These figures further highlight the discrepencies in the reported statistical data from different sources.
During the period 1975-1992, 616 children (367 boys, 249 girls) with cleft lip and palate were born in greater Stockholm, Sweden (pop. 1.3m). ((Milerad, J., et al. (1997) Duarte, R., Leal, M.J. (1999). Associated Malformations in Infants with Cleft Lip and Palate: A Prospective, Population-based Study. Pediatrics, August 1997, 100(2): 180-186.)) The number varied from 20 in 1977 to 51 in 1992. Related to the number of live births, this gave a range of 1.2/1000 (1 per 833) to 2/100 (1 per 500) live births and a mean incidence of 1.7/1000 (1 per 588) live births.
Of the total 616 infants, 163 (26%) had cleft lip, 239 cases (39%) had isolated cleft palate, and 214 cases (35%) had both cleft lip and palate. Of these 214 infants with complete clefts, 143 were unilateral and 71 were bilateral cleft lip and palate.