Well first of all I am sorry to hear that your child was born with a cleft lip. The term "cleft" simply means that there is a fissure or opening. Thus a "cleft lip" (or cheiloschisis) is a fissure within the lip. As the palate and lip form during gestation (pregnancy), there are three different prominences that form (frontonasal, maxillary, and mandibular prominences). Failure of any one of these to form completely can result in a cleft.
The maxillary and mandibular prominences are formed by two symmetric lobes that come from laterally to medial and fuse in the midline. If the maxillary priminences fail to form the embryo can get an upper lip cleft. Cleft lip can be partial (only through the lip), or complete (through the lip and into the nostril), and can be unilateral or bilateral. The treatment for any type of cleft is surgery
, which can be very successful. There has been some research into cleft formation, and the theory is that anything that can potentially disrupt the fusion or migration process of the "prominences" (that I mentioned above) can result in a cleft.
Things like prescription drugs, illicit drugs, vitamin deficiencies, and dietary deficiencies have been looked at, but no direct correlation has been found. Thus it is hard to tell you that there is anything that you should have done differently. I recommend that you discuss your concerns with a facial plastics or pediatric ENT surgeon
. Hope this helps.