Research Summary

The Women’s Health Group—headed by Donna D. Baird, Ph.D.—uses the tools of reproductive epidemiology to address women's reproductive health issues. It combines epidemiologic methods development with research of public health concern. This research has focused on:

• fertility and early pregnancy
• epidemiology of uterine fibroids

The Early Pregnancy Study, a longstanding collaboration between Baird, Clarice Weinberg, Ph.D., and Allen Wilcox, M.D., Ph.D., was a prospective cohort study conducted in the 1980s that was designed to determine the risk of early loss of pregnancy among healthy women. Participants collected daily urine specimens during the menstrual cycles when they were trying to conceive and also during the first eight weeks of gestation for those who became pregnant. Urine was analyzed for human chorionic gonadotropin (hCG), estrogen and progesterone metabolites and luteinizing hormone (LH) to identify ovulation and implantation. These markers served as benchmarks for studying fertility and corpus luteum rescue, and length of pregnancy. The researchers have collaborated with the Centers for Disease Control to measure urinary biomarkers of exposure to bisphenol A and phthalates in order to investigate associations with fertility and the reproductive events of early pregnancy as well as pregnancy outcomes.

We conducted the NIEHS Uterine Fibroid Study (UFS) which screened randomly selected participants, 35-49 years of age, for fibroids using transvaginal ultrasound. We described the prevalence of these benign tumors in black and white women (Baird et al., 2003) and have analyzed the data to identify risk factors. As in laboratory animal studies of fibroids (Walker et al., 2001), parity is protective. As an explanation, we hypothesized that postpartum uterine remodeling could clear existing lesions from the myometrium (Baird et al, 2003). To test this hypothesis, a collaborative study was designed with Right From The Start, a prospective pregnancy study that screens for fibroids in very early pregnancy; findings are consistent with the hypothesized mechanism. Also, confirming laboratory animal studies, the UFS data revealed an increased risk associated with prenatal diethystilbestrol (DES) exposure (Baird and Newbold, 2005). Study participants were followed to assess the health consequences of fibroids, with a final follow-up completed in 2005, and the initial ultrasound data on size of fibroid(s) was associated with surgical treatment during follow-up, suggesting that a single ultrasound exam is strongly predictive of adverse health consequences of fibroids.

We collaborated with other NIEHS researchers and clinicians at the University of North Carolina to describe fibroid growth using magnetic resonance imaging at 3-6 month intervals over a year. Though most fibroids grew slowly on average, a small minority grew very rapidly while others shrank; individual tumors within a woman were highly variable in their growth dynamics with no evidence of synchrony among tumors.

We are currently conducting a large prospective study of uterine fibroids, the Study of Environment, Lifestyle & Fibroids (SELF). African-American women in the Detroit, Michigan area, aged 23-34, who have not been diagnosed with fibroids are being enrolled. Ultrasound is used to determine their fibroid status at enrollment. Further ultrasound examinations at 20-month intervals over a 5-year follow-up identify new fibroids and provide measures of fibroid growth. Risk factors for fibroid incidence and growth are being identified.

Baird received a B.A. from Macalester College, a Ph.D. in evolutionary ecology from the University of Minnesota and an M.P.H. in epidemiology from the School of Public Health, University of North Carolina at Chapel Hill. She did a postdoctoral fellowship at the Center for Biopolitical Research at Northern Illinois University and a year at the Biological Sciences Curriculum Study before coming to NIEHS in 1983. Baird currently serves as a Principal Investigator at NIEHS.

Studies

• Study of Environment, Lifestyle & Fibroids
  SELF is designed to prospectively identify risk factors for fibroid development including both new tumorigenesis and fibroid growth.

• NIEHS Uterine Fibroid Study
  The Uterine Fibroid Study was designed to determine the prevalence of fibroids, identify risk factors for fibroids, identify biological changes in tumor tissue and describe women's experience of symptoms and their change over time.

• Early Pregnancy Study 
  The Early Pregnancy Study provides a detailed look at ovulation, conception and early pregnancy for a group of 221 women who collected daily diary and urine specimens before and during early pregnancy. A recent follow-up study of participants was conducted to examine accuracy of long-term recall of time to pregnancy and early pregnancy exposures.

• Fibroid Growth Study
  The Fibroid Growth Study examines the variation in fibroid growth, the biological differences between growing and non-growing fibroids and the relationship between fibroid growth and symptom severity.

• Postpartum Uterine Regression Study
  The Postpartum Uterine Regression Study documents any fibroids present in early to mid-pregnancy and measures fibroid size after postpartum uterine regression. Investigators hypothesized that small fibroids will have disappeared, and large fibroids will remain essentially unchanged in size.

• Dietary Soy Study
  This study was an unblinded trial to test the hypothesis that dietary soy would have estrogenic effects on post-menopausal women.

• Minnesota Time-To-Pregnancy Study
  Smokers were found to have a longer time to pregnancy in a study of over 600 pregnant women. This study, as well as subsequent NIEHS time-to-pregnancy studies, were used to evaluate the feasibility of measuring time-to-pregnancy as a marker of fertility for epidemiologic studies.