Occupational physical activities, working hours and outcome of pregnancy: findings from the Southampton Women's Survey.

OBJECTIVES To investigate risks of physical activity at work by pregnancy trimester, including the effects on head and abdominal circumference. METHOD At 34 weeks of gestation we interviewed 1327 mothers from the prospective Southampton Women's Survey (SWS); we asked about their activities (working hours, standing/walking, kneeling/squatting, trunk bending, lifting and night shifts) in jobs held at each of 11, 19 and 34 weeks of gestation, and subsequently ascertained four birth outcomes (preterm delivery, small for gestational age (SGA) and reduced head or abdominal circumference) blinded to employment history. RESULTS Risk of preterm delivery was elevated nearly threefold in women whose work at 34 weeks entailed trunk bending for >1 h/day. Small head circumference was more common in babies born to women who worked for >40 h/week. However, no statistically significant associations were found with SGA or small abdominal circumference, and preterm delivery showed little association with long working hours, lifting, standing or shift work. CONCLUSIONS There is a need for more research on trunk bending late in pregnancy, and on the relationship of work to reduced head circumference. Our findings on several other occupational exposures common among pregnant workers are reassuring.