Researchers in the making:
Stress and preterm birth
AHFMR Student Inge Christiaens examines how chronic stress affects women who deliver their babies early.
Story by Tara Narwani/Photos by Trudie Lee and Dustin Delfs
Medical science has focused considerable attention on understanding the extraordinary process of childbirth. But, despite these efforts, the how and when of birth remains somewhat of a mystery. "We don't have a clock or a specific signal saying 'Boom, this triggers birth,'" explains Inge Christiaens, an AHFMR Student and Ph.D. candidate in the Department of Physiology at the University of Alberta.
She explains that these gaps in our knowledge of childbirth pose a particular challenge. Her specific interest is in why some women deliver their babies preterm (early). "When you don't know how normal birth is completely regulated, it makes it even harder to know why sometimes it goes wrong."
Normally, full-term babies are born between 37 and 42 weeks of pregnancy. Preterm babies are born before 37 weeks. Due to the shortened time in the protected environment of the womb, these babies have a higher risk of future medical problems such as cerebral palsy, or learning and behavioural issues. Finding medical treatments to prevent preterm births in the first place could help avoid these complications.
Some risk factors for preterm birth are already known: Women over the age of 35 are more likely to deliver babies early. Women with medical conditions such as high blood pressure or diabetes are at greater risk, as are women who smoke. But these risk factors account for less than half of preterm births, and researchers still cannot explain the remaining 60%. Moreover, preterm birth rates differ by region in Canada. "In Alberta, we have the highest preterm birth rate [at 9%], and we don't know why," Christiaens notes.
Christiaens studies how innate genetic factors interact with environmental factors, and how this relationship in turn affects preterm birth. "We consider preterm birth a complex disease, comparable to heart disease or diabetes. There are genetic factors involved, but also many environmental factors, and those interact," she explains. Christiaens examines one of those environmental factors: chronic stress. She wants to know whether the higher levels of stress over the course of a woman's life, in combination with particular genetic traits, predispose a woman to giving birth early.
To find out, Christiaens has been recruiting new mothers from Edmonton hospitals to take part in a stress questionnaire (to investigate the environmental side of the equation), as well as an analysis of their genes. By the end of 2009, she will have interviewed 600 mothers—half of whom delivered preterm, and half of whom were full-term. Comparing the information from the two groups will allow her to identify the significant differences.
The stress questionnaire was developed to evaluate chronic (repeated or long-term) stress, instead of acute (sudden) stress. During stressful events, the body's physiology changes to help individuals cope. In the long term, however, these physiological changes can actually damage the body's normal functions. Christiaens wonders whether the physiological changes due to stress are an important factor in women who deliver preterm: "The more things you put in the bucket, in the end it overflows."
Christiaens interviews the participants in her study by telephone six to twelve weeks after they have given birth. The 25-minute questionnaire investigates many different kinds of stress. She asks whether the women experienced stress during pregnancy (such as financial or work-related stress), whether they have experienced previous traumatic events (such as car accidents, fire, or war), and whether they had a difficult childhood (for example, whether they had close contact, as children, with anyone who had substance abuse problems). Christiaens also looks for factors that reduce stress, assessing, for instance, the women's coping strategies, as well as the availability of support networks.
For the genetic part of the project, Christiaens collects DNA samples from the participant's saliva. Each woman's genes will be analyzed to look for small changes in the gene sequences. Christiaens will contribute this information to the Preterm Birth Genome Project, an international collaboration to find genetic factors for preterm birth. She is also working closely with investigators on the Preterm Birth and Healthy Outcomes Team (PreHOT), funded by AHFMR's Interdisciplinary Team Grant Program.
By looking at the genetic and environmental data together, Christiaens expects to see patterns in the data. She hopes to identify genes not previously associated with preterm birth, which will open up new arenas for research. "In the last decade," Christiaens points out, "we haven't found anything to treat or prevent preterm birth. Any new hypotheses are welcome."