Ketty Mobed, MSPH PhD

PhD Dissertation

Reproductive health and its relationship to occupational exposures and activities are a growing area of epidemiologic research interest, but have rarely been studied in female migrant farmworkers. Women who are agricultural fieldworkers are simultaneously exposed to such factors as ergonomic strain, psychological stress, agricultural chemicals, and extreme climatic conditions, which potentially can influence pregnancy outcomes and menstrual cycle patterns. The purpose of this investigation was three-fold: 1) to compare pregnancy outcomes of migrant farmworkers to migrant non-fieldworkers and non employed women, 2) to compare interview-based menstrual cycle characteristics in these 3 groups of women, and 3) to compare prospectively collected menstrual cycle data from daily diaries among these three work groups of women.

Of 386 women contacted who were aged 18 to 45 years and living in 5 county- and state-run Migrant Housing Centers (MHC) in northern California, 336 (87%) of them participated in the interview and 310 (92%) completed a daily menstrual calendar over the 1994 summer growing season. At the time of the interview, 194 (58%) of the participating women were employed in the fields, 36 (11%) were doing work other than fieldwork, and 106 (31%) were not employed. From all pregnancies, one pregnancy that had occurred in the last 5 years was randomly selected from all parous women. Of 180 randomly selected recent pregnancies the following adverse pregnancy outcomes occurred: 9 (5%) ended in spontaneous abortion (SAB), 4 (2%) ended in stillbirth, and 8 (5%) were low birth weight (LBW). In addition, the following delivery complications were reported: 20 (12%) pregnancies ended in premature labor; 35 (21%) ended in a Caesarian Section; and 8 (5%) breech births. Forty-one (23%) of the live births were high birth weight (HBW). Compared to non-employed women, the adjusted odds ratio (OR) for combined adverse pregnancy outcomes in fieldworkers was 1.2 (95% confidence limit (95% CL) 0.3, 4.4); the adjusted OR for combined delivery complications was 1.8 (95% CL 0.7, 4.2) in fieldworkers and the adjusted OR was 1.5 (95% CL 0.3, 7.3) in non-fieldworkers; adjusted OR for HBW was 0.7 (95% CL 0.3, 1.7) in fieldworkers.

For usual menstrual cycle characteristics reported on the baseline interview, the adjusted mean menstrual bleeding length (MBL) for fieldworkers was 4.0 days, for non fieldworkers 4.5 days, and for unemployed women 4.7 days (p=0.05); the adjusted mean menstrual cycle length (MCL) was 29.3 days, 29.1 days, and 28.0 days (p=0.01), respectively for the 3 different work groups. The adjusted OR of short cycle (<24 days) (SC) of fieldworkers compared to unemployed women was 0.66 (95% CL 0.2, 2.8), and OR of variable cycle (VC) was 1.11 (95% CL 0.5, 2.3) for fieldworkers and 1.72 (95% CL 0.5, 6.1) for non-fieldworkers. In the analysis of the diary-based prospective data, the adjusted mean MBL was 4.1 days, 4.8 days, and 5.1 days (p=0.03) for fieldworkers, non fieldworkers, and non-employed women, respectively. The adjusted mean MCL was 29.5 days, 30.4 days, and 33.8 days (p=0.02), respectively. When compared to non-employed women, the adjusted OR for SC in fieldworkers was 0.27 (95% CL 0.03, 2.24). For long cycle (>35 days) (LC) the adjusted OR was 1.77 (95% CL 0.65, 4.82) for fieldworkers, and the adjusted OR was 1.32 (95% CL 0.28, 6.26) for non-fieldworkers.

A notable success of the present study was its ability to contact and follow female Mexican migrant agricultural workers over a harvesting season with good participation rates. This study has not only been able to confirm some of the results of previous studies in observing shorter bleeding length in heavier or more physically active women, but also detected significant differences in menstrual bleeding length, menstrual cycle length and cycle variability in women in different occupational groups. However, due to the limitation of the study population size, the results remain inconclusive for the interpretation of the influence of occupation and environment on pregnancy outcomes. Further expanded and detailed studies of migrant and seasonal farmworker women are needed to determine the influence of occupational conditions, environmental characteristics and chemical exposures on reproductive health outcomes.

Copyright released by Ketty Mobed, 1997.
Photographs by Ketty Mobed showing women in the workplace.