Risk Factors And Pregnancy Outcome

Gestational age is the age from conception to birth as counted from the first day of the last normal menstrual period. Normal gestational age at birth is 37-41 weeks.

   Low birthweight, gestational age before 37 weeks and prematurity are considered to be harmful to the baby.

   Gestational age has been shown to be affected by prolonged standing^12,13 and heavy physical exertion¹. Gestational age is not affected by heavy lifting².

Birthweight is the weight of the baby at birth. Low birthweight is less than 2500 g (5.5 lbs), normal birthweight is 2500-4500g (5.5-10 lbs).

   Women who worked in metal, electrical, clothing and manufacturing industries, in food and drink services, or as janitors or chambermaids tended to have babies born with a lower birthweight⁷. Low birthweight was thought to be related to fatigue, heavy lifting and long work hours in the women who worked in the two service and three manufacturing industries⁷. Low birthweight also tended to occur more frequently when the women were standing for more than 3 hours at a time during the later stages of pregnancy¹⁰. Exposure to high noise levels (over 85 dB) may also cause low birthweight^9,5.

Premature birth is birthweight less than 2500 g or less than 37 weeks gestational age.

Preterm birth is birth before 37 weeks.

   High fatigue, shiftwork, rotating or changing schedules were found to be related to preterm birth^9,11.

   Preterm birth may be caused by noise exposure^9,5, prolonged standing¹³, frequent heavy lifting (more than 50 times per week)² and strenuous working postures¹.

Pregnancy Loss

Spontaneous abortion (miscarriage) is the termination of pregnancy without apparent cause.

   Occupational ergonomic risk factors for spontaneous abortion were shiftwork, piecework, posture, heavy lifting or physical effort⁴. Heavy lifting and physical effort, especially bending movements in early pregnancy was associated with an increase in spontaneous abortion³. An elevated risk of spontaneous abortion was found to be related to shift work⁸. Occupations that may be more at risk for spontaneous abortion include metal and electrical workers^6,8, as well as sales and service occupations⁸.

Stillbirth is the birth of a dead baby.

   An increase in the risk of stillbirth in leather workers and other manufacturing industries was found⁸. There has been an increase in the risk of stillbirth and spontaneous abortion in nursing assistants and aides, saleswomen, and food and beverage service workers, which may be associated with heavy lifting, physical effort and long working hours⁷.