Practically everyone has heard of a couple who, after fertility treatments fail, adopt a baby and then all of a sudden get pregnant.
Those stories have given rise to the belief that it takes longer for stressed-out women to conceive, a notion for which there has been little scientific evidence.
But a new study in the current issue of the journal Fertility and Sterility lends credence to a link between stress and time to conception, and not just in couples dealing with infertility.
The study involved 274 British women 18 to 40 years old in the Oxford Conception Study, which examined whether information from fertility-monitoring devices would improve their chances of conception.
They were followed for six menstrual cycles or until they got pregnant, whichever came first. On Day 6 of each cycle, they collected saliva samples.
Researchers measured their levels of alpha amylase and cortisol, two substances that serve as barometers of how the body reacts to physical or psychological stress.
After accounting for couples' ages, intercourse frequency and alcohol intake _ all factors that could influence pregnancy chances _ the scientists found that women with highest concentrations of alpha amylase in the first cycle were 12 percent less likely to conceive than women with the lowest. On average, couples have a 30 percent chance of conceiving each cycle. (Few of the women smoked, the lifestyle factor most strongly linked to time to conception.)
Cortisol levels were not associated with the women's chances of conceiving. Alpha amylase and cortisol reflect two different components of the stress response and don't correlate well, explains lead author Germaine Buck Louis of the Eunice Kennedy Shriver National Institute of Child Health and Human Development. Alpha amylase reflects the "fight-or-flight" response to immediate stressors, such as temperature or noise, Buck Louis says.
To confirm the findings, her team is conducting a larger and longer study of women trying to conceive. She says "a handful of very good trials" suggest that stress-reduction techniques can improve pregnancy rates in couples who use in vitro fertilization and related methods.
Meanwhile, Buck Louis says, it can't hurt for women hoping to conceive to try to relax, using whatever approach works for them (except, of course, alcohol or cigarettes). "The beauty is it's such a low-tech solution."