Cleft lip is congenital condition (meaning it is present from birth) where there is a split or gap in the upper lip. This split can be on the left side of the upper lip, on the right side, or straight down the middle. The gap can also extend up to the base of the nose, or extend inward toward the bones of the upper jaw (called the maxilla). Cleft lip occurs when the sides of the upper lip don’t fuse properly during pregnancy, leaving a gap there. Cleft lip is similar to cleft palate – a condition where a gap or split is present in the roof of the mouth, due to improper fusion – and the two often occur together.
Cleft lip is one of the most common congenital disorders. About 2 out of every 1000 people worldwide are born with cleft lip and/or palate, but the exact number differs significantly between country and ethnic group. In South Africa, about 0.3 out of 1000 people are born with cleft lip or palate.
Cleft lip is usually discovered at birth, in brand new babies. Besides the visible gap in the upper lip, other symptoms of cleft lip include:
Some symptoms of cleft lip, such as difficulty vocalizing, are present immediately. Other symptoms, such as hearing loss and social anxiety, take time to develop or get worse with time. It is important for cleft lip to be treated early in life, so that the time-dependent symptoms do not occur.
Cleft lip does not have one specific cause. Instead, it is a polygenic condition that also is affected by environmental factors. This means cleft lip is formed from the input of multiple genes in combination with things like nutrients, exposure to toxins, and more. This polygenic, multifactorial inheritance is seen in things like cleft lip and human height, but it differs from the inheritance pattern in things like ABO blood type (which is determined by a single gene).
About 25 – 50% of the factors that decide cleft lip are genetic, while the rest are environmental. A major environmental cause of cleft lip is exposure to teratogens, which are substances that can alter and damage a developing foetus. Teratogens range from cigarette smoke and alcohol, to pesticides and certain blood pressure medicines.
Certain syndromes are associated with cleft lip, like Pierre Robin syndrome or Patau syndrome. Babies with these syndromes will often have cleft lip, alongside several other severe issues like microcephaly (a tiny head) in Patau syndrome, and glossoptosis (a retracted tongue) in Pierre Robin syndrome.
Risk factors for cleft lip include:
Historically, cleft lip was diagnosed at birth, by a doctor’s examination. More recently, some cleft lip can be seen while a baby is still in the uterus. This is usually done via ultrasound of the pregnant mothers abdomen.
The treatment for cleft lip is surgery to close the gap. Ideally this surgery should occur when the baby is 3 months old. Cleft-lip repair surgeries done at this early age help to avoid some of the time-dependent symptoms of cleft lip.