Physical exertion at work during pregnancy did not increase risk of preterm delivery or fetal growth restriction

March of Dimes Birth Defects Foundation; National Institute of Child Health and Human Development; Centers for Disease Control and Prevention; American Association of Occupational Health Nurses Foundation. 2 Although her prior history of preterm delivery increases the risk of recurrence, Maria should be advised (based on combined evidence from good quality studies) that the possible effects of physical exertion in her work (and unpaid work) need to be balanced with those that could be associated with a drop in income (and change in socioeconomic status) if she stopped doing her regular work. 3