search for information spacer
search birth defects
search environmental factors
search geographic areas
birth defects the solution is research discoveries and data serving the public visitor type
home page

discoveries and data center
all birth defects
specific conditions
exposures and risk factors
geographic data

take our survey

Look up in our Glossary

cleft lip
cleft palate
folic acid
neural tube defects

reference informationReferences

PDF file Downloadable
study summary
(requires Acrobat

get acrobat reader!


Past studies hinted that smokers' babies may be more likely to have cleft lip and/or cleft palate, but results were mixed. Are some infants genetically more susceptible to mothers' smoking? We looked at a gene normally involved in development of the palate and mouththe transforming growth factoralpha gene (TGFa).

bullet Women who smoke during pregnancy are 1.5 to 2 times as likely to have babies with oral clefts. The more cigarettes the mother smokes, the higher the risk.
bullet The hazards of smoking are even greater for the 1 in 7 babies who carry a cleft-susceptiblity gene (the A2 form of TGFa). They were 8 times as likely to have oral clefts if their mothers smoked. Those born to nonsmoking mothers were at no greater risk.

reference information PDF file


Taking vitamins does not eliminate the risk for neural tube defectswhy do some pregnancies benefit while others do not? The search to understand how supplements alter risk has focused on a number of genes that influence the developing baby's folic acid metabolism. Variant forms of these genes can lower folic acid levels, particularly if the mother does not take multivitamins containing folic acid. Among babies who inherited variant genes and whose mothers did not use multivitamins, we found:

bullet MTHFR: About 1 in 6 babies has the genetic type "TT" of methylenetetrahydrofolate reductase (MTHFR); this variant is more common in Latino infants. Babies with type "TT" had a modest increase in spina bifida risk.
bullet Methionine synthase: The 15% of babies who carry an altered form of this gene did not have a higher risk for spina bifida.
bullet FR-: We found no variation in the folate receptor alpha (FR-a) gene, responsible for folic acid transport into cells.
bullet BHMT: Babies who have variants of the BHMT/BHMT2 gene do not have a higher risk for oral clefts. reference information

reference information


contact information