Search

Several studies suggest that toxic chemicals in hair products may be absorbed through the scalp in sufficient amounts to increase the risks of adverse health effects in women or their infants. This case-control study of 525 Black women from three counties in North Carolina who had delivered a singleton, liveborn infant examined whether exposure to chemicals used in hair straightening and curling increased the odds that the infant was preterm or low birth weight. Cases consisted of 188 preterm and 156 low birth weight births (for 123 women, their infant was both low birth weight and preterm). Controls were 304 women who delivered term and normal birth weight infants. Women who used a chemical hair straightener at any time during pregnancy or within 3 months prior to conception had an adjusted odds ratios (OR) of 0.7 (95% confidence interval (Cl) 0.4−1.1) for preterm birth and 0.6 (95% Cl 0.4−1.1) for low birth weight. Exposure to chemical curl products was also not associated with preterm delivery (adjusted OR = 0.9, 95% Cl 0.5−1.8) or low birth weight (adjusted OR = 1.0, 95% Cl 0.5−1.9). Despite this failure to find an association, continued search for risk factors to which Black women are uniquely exposed is warranted. Am J Epidemiol 1999; 149: 712−16. [ABSTRACT FROM PUBLISHER]

Biologic evidence suggests that the hormones activated by stress affect gestational length, but the results of epidemiologic investigations are inconsistent. The authors of this paper know of no threshold models that have been studied; these models assume that stress does not affect preterm delivery until a certain amount of stress has been experienced but that each unit of stress above the threshold adds to the risk of preterm delivery. By using standard logistic regression, the authors compared threshold and nonthreshold models of the relation between number of stressful life events and preterm delivery in 11 US states. They used data on 1990–1995 births from the Pregnancy Risk Assessment Monitoring System. The risk of preterm delivery among multiparas who gave birth in 1990–1993 increased 7% for each event over five they experienced, but no relation was found for 1994–1995 births. Among primiparas who gave birth in 1994–1995, the risk increased 5% for each event over two, but no relation was found for 1990–1993 births. These results suggest that a threshold model may fit the relation between stress and preterm delivery better than one with no threshold. However, the inconsistent results are difficult to reconcile with a biologic threshold in the relation between stress and preterm delivery. [ABSTRACT FROM PUBLISHER]