Special Feature

Work During Pregnancy: Potential Risks and Benefits

By Steven G. Gabbe, MD

Today, most women work during pregnancy. This article examines the issues commonly raised by women concerned about the potential risks associated with working while pregnant: Does work during pregnancy increase adverse perinatal outcomes? Are there identifiable risk factors associated with particular jobs that increase the likelihood of poor perinatal outcome? Are there particularly hazardous behaviors or exposures that the pregnant worker should avoid? What guidance should the obstetrician-gynecologist give the pregnant woman who works?

Today, most pregnant women work. Recent data indicate that nearly two-thirds of women worked for pay for at least six months during their pregnancies, and most worked full time.1 In fact, more than half of working women continue their employment during the month before birth. Women are most commonly employed in technical, sales, and administrative occupations (44%), followed by managerial and professional positions (26%), service (18%), and employment in manufacturing and as laborers (9%).1 Working women might be expected to have better pregnancy outcomes than those who are not employed. Working women usually have a higher income and have health insurance, are better educated, have a more stable home situation, and are less likely to drink and smoke. It could be argued that women who continue to work are able to do so because they are infertile or have had pregnancy losses. In these workers, adverse pregnancy outcome might be increased.

Most studies examining the impact of work during pregnancy have been retrospective questionnaire surveys, usually completed after delivery. The size of the populations studied has been small and many confounding variables, such as the patient’s past obstetrical history, smoking, and substance and alcohol abuse have not been examined. Clearly, there is great need for better data on pregnancy outcomes for working women. A classic retrospective study conducted by Mamelle and colleagues examined the impact of a variety of behaviors at work on the likelihood of preterm birth in French women.2 Mamelle et al considered the effects of standing for three or more hours a day, working on an industrial machine, repeated heavy lifting, jobs requiring little attention, and adverse environmental factors, such as cold and damp conditions, on pregnancy outcome. Mamelle et al developed a point system for each of these risks and created a "fatigue score." they found that working more than nine hours a day, more than 40 hours per week, or more than six days per week significantly increased the risk of preterm birth. In Mamelle’s study and others that followed, prolonged standing emerged as an important risk factor. Luke studied preterm birth in women who were members of the Association of Women’s Health, Obstetric and Neonatal Nurses.3 Working more than 36 hours a week, more than 10 hours a shift, or standing for more than 4-6 hours increased the rate of preterm birth. Of course, pregnant women work not only at their place of employment, but at home as well. Luke has expanded her studies to combine both a "work score" with a "home score," which includes a variety of housekeeping activities.4 She concluded that fatigue from paid employment and work at home contributed significantly to hospitalizations as well as visits to the Emergency Room and Labor and Delivery.

Is residency training associated with poor pregnancy outcome? Klebanoff and colleagues performed a large questionnaire study of women residents and, as a control group, the wives of male residents.5 House officers in obstetrics and gynecology composed approximately 10% of the study population. Klebanoff et al reported that female residents experienced no increase in spontaneous abortion, ectopic pregnancy, stillbirths, preterm births, or intrauterine growth restriction (IUGR). Preterm labor was likely to be diagnosed more often in women residents, as was preeclampsia, but there was no increase in adverse outcomes associated with these problems. The rate of preterm birth was increased in female residents who worked 100 or more hours per week.

Healthcare workers, including residents, are at greater risk for a variety of potentially dangerous exposures.6 Anesthetic gases, if not properly scavenged, increase the risk of spontaneous abortion and infertility. An association between exposure to antineoplastic drugs with pregnancy loss and fetal malformations has been observed. A recent prospective study demonstrated an association between exposure to organic solvents and an increased risk for fetal malformations, particularly in symptomatic women, that is, women who described irritation of the eyes or respiratory system, breathing difficulties, or headache.7 Of course, healthcare workers experience a greater likelihood of exposure to a variety of infectious agents, including hepatitis B, hepatitis C, and HIV.6 Exposure to ionizing radiation must also be carefully monitored. The National Council on Radiation Protection recommends that exposure during pregnancy be limited to a total of 0.5 rads or 0.05 rads per month. For nonpregnant workers, the Occupational Safety and Health Administration recommends that radiation exposure be limited to 1.25 rads per quarter or 5 rads per year. Many pregnant women, including healthcare professionals, commonly use video display terminals (VDTs). While early reports associated VDT use with spontaneous abortion and malformation, these adverse outcomes have not been supported by prospective studies.

In summary, most pregnant women are working outside the home in a wide variety of occupations. Overall, working while pregnant has not been associated with an increased risk of adverse perinatal outcomes such as preterm delivery and IUGR. While most women can continue working during the third trimester, attention should be paid to those occupations that require prolonged periods of standing and long working hours, as these risk factors have been associated with an increased likelihood of preterm birth and IUGR. Consideration should be given to modifying the workplace to allow women to take rest breaks, especially if they are at increased risk for adverse pregnancy outcomes. Residency training itself has not been associated with a greater likelihood of poor pregnancy outcome. Women should be counseled about the potential reproductive hazards of work before pregnancy. Patients should be asked about their employment and risk factors identified. The obstetrician may want to speak with a physician or nurse at the place of employment who has expertise in occupational safety. If specific hazardous exposures are of concern, a Material Safety Data Sheet can be obtained from OSHA. Questions should also be asked if the patient is working at home.

References

1. Centers for Disease Control and Prevention, National Survey of Family Growth, Cycle IV, 1988.

2. Mamelle N, et al. Am J Epidemiol 1984;119:309-322.

3. Luke B, et al. Am J Obstet Gynecol 1995;173:849-862.

4. Luke B, et al. Am J Obstet Gynecol 1999;180:S67.

5. Klebanoff MA, et al. N Engl J Med 1990;323: 1040-1045.

6. Frattarelli JL, Moore GR. Prim Care Update Ob/Gyns 1998;5:54-59.

7. Khattak S, et al. JAMA 1999;281:1106-1109.

Which of the following exposures at work has been associated with an increased risk for preterm birth?
a. Prolonged standing
b. Anesthetic gases
c. Organic solvents
d. Antineoplastic drugs
e. Video display terminals