Physical hazards in employment and pregnancy outcome

The past century has seen an enormous improvement in the political, social, and economic status of women, of which employment is an integral part. Women workers require special protection while pregnant because of the following reasons:(1) The developing embryo may be more susceptible to noxious agents than the exposed mother. Females may be less suited for some work tasks than males. Pregnancy may decrease the capacity to cope with many work factors. Women tend to feed themselves less substantially than men. The Physiology of Work During Pregnancy Physical exertion has often been suggested as a risk factor for adverse pregnancy outcomes,(2–21) which may occur due to various factors.(4,22–24) Work involves muscle action, causing an increase of sympathetic vasomotor activity in working muscles proportional to the severity of work. Hence, when cardiac output increases rapidly during muscular activity, most blood goes to the working muscles and proportionately less arrives in the other viscera, which during pregnancy, includes the placental bed. With hard work there is an increased release of catecholamines with resultant arteriolar constriction. With chronic hard work, lactate accumulates making any unloading of lactate from the fetus more difficult. Sweating reduces plasma volume, which is an important determinant of uteroplacental blood flow. Circulatory blood flow in the uterus and placenta decreases in the standing position. Pronounced physical exercise may lead to hormonal disturbances, hypothermia, and nutritional deficits. Shift work and irregular work schedules could lead to a change in the circadian rhythm, which affects regulation of the ovulatory cycle with resultant menstrual irregularities. Whether such shifts also influence pregnancy outcome is unknown. Heavy lifting increases intra-abdominal pressure and this may provoke uterine contractions. Heat stress causes dehydration resulting in the release of the anti-diuretic hormone and oxytocin, which stimulates the uterus to contract. Due to the combined effects of vasoconstriction, myometrial contraction, reduced plasma volume, and diversion of blood flow away from the placental bed, there is diminution of uteroplacental blood flow and resultant fetal hypoxia. This, along with possible hormonal imbalance, may have deleterious effects on the fetus.