Collectively, orofacial clefts, which include cleft lip with or without cleft palate or cleft palate alone, are the most common craniofacial birth defects in humans and affect nearly 1 in 700 individuals. Newborns with cleft lip and palate commonly exhibit feeding difficulties as well as develop speech, hearing, and dental anomalies. The complications of cleft lip and palate in early life are particularly noteworthy in resource-poor regions without access to comprehensive healthcare. Clefting impacts not only the psychosocial and financial needs of patients and their families, but it also contributes significantly to societal healthcare costs with a lifetime cost of treatment estimated at $200,000.
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In large series, the distribution of clefts is about 50% cleft lip and palate, 30% cleft palate only, and 20% cleft lip only. Cleft lip occurs most often on the left side; the distribution of left to right to bilateral cleft lip is approximately 6:3:1. Right-sided clefts are more commonly associated with syndromes and there is a slightly higher incidence in males.
Modern ultrasound can identify cleft lip by the absence of muscle fibers crossing the lip. Specific efforts must be made to obtain a frontal view to make a prenatal diagnosis. Newer ultrasounds have increasing accuracy. Although fetal surgery for clefts is not yet feasible in humans, prenatal diagnosis makes it possible to counsel parents earlier and prepare them for the care that their new child will require (Figure 20–1).
(A) Ultrasound of a child with bilateral cleft, incomplete on the left. (B) Photo of the same child postnatally before lip repair.
It is important to remember the embryology of clefting; the primary palate includes the lip and premaxilla, whereas the secondary palate extends from the incisive foramen back. The lip and alveolus are formed by the fusion of the frontonasal process with the lateral maxillary processes; this fusion is reinforced by the migration of mesenchymal tissue derived from neuroectoderm (Figure 20–2). The stabilization of neuroectoderm by folate during the first trimester of pregnancy has been shown to reduce the incidence of clefting as well as that of other neural crest defects such as myelomeningocele.