Reduced monoamine oxidase A activity in pregnant smokers and in their newborns

Tobacco smoking is associated with reduced monoamine oxidase A (MAOA) activity. Smoking-associated low MAOA activities in pregnancy and in newborns may have negative perinatal and postnatal consequences. We aimed to compare, in everyday clinical conditions, biomarkers of MAOA activity in smoking (SPW) and lifetime nonsmoking pregnant women (NSPW) and in cord blood and to assess the newborns' behavior during the first 48 hours of life.

Thirty SPW and 29 NSPW in their second trimester of pregnancy were included. Plasma MAOA dependent metabolites of norepinephrine: dihydroxyphenylglycol; dopamine: homovanillic and dihydroxyphenylacetic acid; and serotonin: 5-hydroxy-indol acetic acid were measured at the end of the second trimester, at delivery, and in arterial cord blood along with plasma cotinine. The newborns' discomfort was evaluated every 8 hours by a standardized questionnaire.

The SPW smoked, on average, 73 cigarettes per week at the end of second trimester and 80 cigarettes per week at delivery. Mean plasma cotinine was 84 ng/mL, 105 ng/mL, and 95 ng/mL at the end of second trimester, at delivery, and in cord blood, respectively (NSPW < 10 ng/mL). Plasma markers of MAOA activity, in particular those reflecting dopamine's catabolism, were significantly lower in SPW and in the arterial cord blood of their newborns than in NSPW and their newborns. Newborns of SPW showed significantly more facial discomfort than those of NSPW.

Smoking is associated with MAOA inhibition in pregnant women and in their newborns at birth. Further studies are needed to estimate the behavioral significance of these findings.