Enzyme polymorphisms, smoking, and human reproduction. A study of human placental alkaline phosphatase

We investigated the possible effects of placental alkaline phosphatase (PLAP) genotype on the deleterious action of maternal smoke on intrauterine survival and birthweight. PLAP is a highly polymorphic enzyme with several alleles associated with different enzymatic activities. PLAP is produced by the embryo and is found in maternal blood, where it is responsible for the rise of serum alkaline phosphatase during pregnancy. Two hundred and fourteen Caucasian consecutive newborn infants delivered in the Maternity Department of the University of Rome La Sapienza Hospital were studied. Infants from smoking women 28 years or older show a strong decrease of both PLAP*1/*1 and *2/*2 homozygous types and a marked deviation from Hardy-Weinberg expectation, thus suggesting a different lethal effect of smoke depending on PLAP genotype and maternal age. In infants from smoking mothers there is a decrease of birthweight that is much less evident and statistically not significant in infants carrying the PLAP*1/*1 genotype as compared to other genotypes. The difference between PLAP genotypes concerning birthweight is more marked in women older than 28 years than in younger ones. This suggests that the effects of smoke on birthweight are also dependent on PLAP and maternal age.