To investigate whether null variants of Glutathione S-transferase Mu 1 (GSTM1) and GST Theta 1 (GSTT1) in infants and mothers, as well as maternal exposures to environmental factors, contribute to the risk of non-syndromic cleft lip with or without palate (NSCL/P) in a Mexican population.
We performed a matched pair case-control study, including 98 cases and 98 controls and their mothers. Sociodemographic information and environmental exposures were collected by a questionnaire. Null variants of GSTM1 and GSTT1 were assessed by multiplex Polymerase Chain Reaction (PCR). Odds ratios (OR) and their 95 % confidence intervals (CI) were calculated to estimate risks. The interaction of genetic variables with smoking and adjusted ORs were evaluated by binary logistic regression.
Homozygous null GSTM1 was associated with the risk of NSCL/P when present in mothers (OR = 2.45, 95 % CI 1.23-4.86) or infants (OR = 2.98, 95 % CI 1.45-6.14). A higher risk was also found when children carried the homozygous null GSTT1 (OR = 4.89, 95 % CI 2.42-9.87). In mothers, this variant showed a crude risk of 9.17 (95 % CI 3.95-21.29), which increased to OR = 13.81 (95 % CI 1.63-117.09) upon interaction with frequent passive smoking (5-7 days/week). Sociodemographic and other environmental exposures were not significantly associated with the risk of NSCL/P.
Maternal and infant GSTT1 and GSTM1 homozygous null genotypes were associated with a higher risk of NSCL/P, and the results suggest an interaction of the maternal GSTT1-null/null genotype with frequent passive smoking.

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