Cleft lip spelled out in alphabet toys with a stethoscope.

Cleft Lip Causes

A cleft lip is a slit in the upper lip. This congenital abnormality appears when a baby’s lip fails to completely fuse together. It can be scary to see your baby has been born with a cleft lip, but the surgeries used to treat cleft abnormalities are quite efficient, leaving minimal scarring. Here’s a look at the causes and risk factors of a cleft lip. 

How Cleft Lip Occurs

Cleft lip is present by the time an infant emerges from the womb. During normal fetal development, the tissue that makes up the baby’s upper lip fuses together. For most babies, this occurs by the end of the first trimester, but babies with a cleft lip never conquer this. 

Why Cleft Lip Occurs

Although doctors can fix cleft lip, they aren’t totally sure why cleft lip occurs. Most experts suspect it is a combination of internal and external factors. It can be caused by genes or an inherited syndrome from the mother or father that particularly cause cleft lip

Teratogens are toxins in the world that affect a pregnant mother. These chemicals can cause an abnormality in unborn fetuses. Taking phenytoin-- an anticonvulsant-- while pregnant seems to make a baby significantly (approximately 10 times) more likely to develop cleft lip. Likewise, smoking cigarettes makes a pregnant mother twice as likely to have a baby with cleft lip. 

Risk Factors for Cleft Lip Development

There are certain factors beyond syndromes and genes that can influence cleft lip development. For example, male children are twice as likely to be born with a cleft lip than females. Based on the causes, it is easily concluded that if the parents have a cleft lip, the baby is more likely to have a cleft lip, because the genes are already there.

If the mother is obese or has diabetes while pregnant, this may also be a risk factor for the developing baby. Another influential factor that cannot be changed is race. According to the Mayo Clinic, cleft lip is most likely to develop in Native Americans and least likely to develop in African Americans. 

Last Updated: January 27, 2017