BACKGROUND: Hairdressers and cosmetologists are commonly exposed to chemicals, poor posture and psychological stress that may increase the risk of adverse pregnancy outcomes. AIM: To assess whether work as a hairdresser and cosmetologist during pregnancy increases the risk of low birth weight, preterm delivery, small for gestational age (SGA) and perinatal death. METHODS: The 1990-2004 Finnish Medical Birth Registry was used to identify all singletons of hairdressers (n = 10 622) and cosmetologists (n = 2490) and those of teachers (n = 18 594) as the reference group. The main outcomes were sexual differentiation measured as the probability of female gender, low birth weight, preterm delivery, SGA and perinatal death. Logistic regression analysis was used to estimate odds ratios (ORs) adjusted for maternal age, parity, marital status and maternal smoking during pregnancy. RESULTS: In logistic regression, the risk of low birth weight (adjusted OR 1.44, 95% CI 1.23-1.69), preterm delivery (adjusted OR 1.21, 95% CI 1.07-1.38), SGA (adjusted OR 1.65, 95% CI 1.38-2.07) and perinatal death (adjusted OR 1.62, 95% CI 1.01-1.60) was higher in hairdressers than in teachers. In cosmetologists, the risk of SGA (adjusted OR 1.53, 95% CI 1.10-2.12) and perinatal death (adjusted OR 1.36, 95% CI 0.62-2.98) was elevated. There were no substantial differences in the sex distribution. CONCLUSIONS: This study provides evidence that work as a hairdresser or cosmetologist may reduce foetal growth. Work as a hairdresser may also increase the risk of preterm delivery and perinatal death.