In considering documented developmental toxicity and teratogenicity found in earlier research, maternal betel quid chewing may very well be linked to a higher risk of adverse birth outcomes. The aim of this study was to investigate the significance of betel quid chewing, together with the use of cigarettes or alcohol, either independently or combined, on birth-related outcomes. A total of 1264 aboriginal women who had just given birth in 10 hospitals in Southern and Eastern Taiwan were recruited. Information on their maternal and newborn characteristics was obtained from medical charts and by performing personal interviews using a validated questionnaire. Maternal areca nut chewing during pregnancy was found to be significantly associated with both birth weight loss (-89.54 g) and birth length reduction (-0.43 cm). A significantly lower male newborn rate (aOR = 0.62) was observed among aboriginal women with a habit of betel quid chewing during pregnancy. The use of this substance conveyed a 2.40- and 3.67-fold independent risk of low birth weight and full-term low birth weight, respectively. An enhanced risk (aOR = 3.26-5.99) of low birth weight was observed among women concomitantly using betel quid, cigarette and alcohol during gestation. Our findings suggest that betel quid chewing during pregnancy has a substantial effect on a number of birth outcomes, including sex ratio at birth, lower birth weight and reduced birth length. (c) 2008 Elsevier Ireland Ltd. All rights reserved.