Prediction of birth weight by cotinine levels during pregnancy in a population of black smokers.

OBJECTIVE

The goal was to investigate the association between maternal salivary cotinine levels (SCLs) and pregnancy outcomes among black smokers.

METHODS

In a randomized, controlled trial conducted in 2001-2004 in Washington, DC, 714 women (126 active smokers [18%]) were tested for SCLs at the time of recruitment and later in pregnancy. Sociodemographic health risks and pregnancy outcomes were recorded.

RESULTS

Birth weights were significantly lower for infants born to mothers with baseline SCLs of > or =20 ng/mL in comparison with <20 ng/mL (P = .024), > or =50 ng/mL in comparison with <50 ng/mL (P = .002), and > or =100 ng/mL in comparison with <100 ng/mL (P = .002), in bivariate analyses. In linear regression analyses adjusting for sociodemographic and medical factors, SCLs of > or =20 ng/mL were associated with a reduction in birth weight of 88 g when SCLs were measured at baseline (P = .042) and 205 g when SCLs were measured immediately before delivery (P < .001). Corresponding results were 129 g (P = .006) and 202 g (P < .001) for > or =50 ng/mL and 139 g (P = .007) and 205 g (P < .001) for > or =100 ng/mL. Gestational age was not affected significantly at any SCL, regardless of when SCLs were measured.

CONCLUSIONS

Elevated SCLs early in pregnancy or before delivery were associated with reductions in birth weight. At any cutoff level, birth weight reduction was more significant for the same SCL measured in late pregnancy. Maintaining lower levels of smoking for women who are unable to quit may be beneficial.