The forming of clefts lips and palates
Development deficits during pregnancy
Actually, the term cleft involves two different development disorders: lip clefts and palate clefts. What they share is that during the fourth to eighth week of pregnancy parts of the baby's mouth do not fully develop.
Normally the separate pairs of placodes close to form the lips and the palate.
"Normally," explains Prof. Sailer, "during this time the separate pairs of placodes close to form the lips and the palate. If this closure does not take place or only takes place incompletely, we have these visible defects: the so-called clefts." Depending upon the severity and the exact time of the development disorder, different forms of clefts can occur in different degrees.
Sometimes it is only the upper lip (cleft lip), or only the soft palate, others are a combination of lips, the entire jaw and the palate (lip-maxilla-palate cleft) and beyond that the entire face. Overall one differentiates between 13 different forms of cleft including the lower jaw cleft (mandible cleft).