About 22 percent of facial clefting has a genetic origin. Again, most cleft lips with or without cleft palate are produced by environmental insults (teratogens such as alcohol, retinoic acid, maternal illness, protein/calorie malnutrition during pregnancy) interacting with one or more genes.
Additional risk factors include lack of prenatal care during pregnancy, cigarette smoking, lack of a balanced diet and the chronic use of non- prescribed drugs or substance abuse.
If either parent has a cleft, the relative risks become about four to five percent for having a baby with a cleft.
My suggestion is that you look after yourself before and during your pregnancy, good diet, correct nutrients, limit stress, no smoking or drinking. You should have a high level scan during the pregnancy to exclude the diagnosis. The chances are small and the corrective surgery for a cleft is advanced if the problem occurs.