The Effects of Stress During Pregnancy: First of a Series

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A significant amount of research over the years has been conducted in an effort to determine the effects of stress during pregnancy. While it would be helpful to have a straight forward answer to this question, conflicting results, weaknesses in research methodologies, and the intricate nature of the relationship between pregnancy and stress, make easy answers difficult. The general hypothesis of those who believe that stress can negatively affect pregnancy is that difficult life events produce increased levels of the stress hormone cortisol. Since studies have shown that persistently high levels of cortisol in adults have been linked to negative health effects such as increased blood pressure and heart disease, the exposure of the fetus to high levels of cortisol must also have a detrimental effect. The belief is that too much cortisol in amniotic fluid affects the developing brains of foetuses. There are certainly studies that have shown that increased stress leads to premature birth and lowered birth weight. Other studies have also shown that increased stress during pregnancy is related to ADHD, learning problems and even schizophrenia later in life. One study even linked severe stress in the six months prior to conception to preterm birth. Given all this research and the headlines they generate, one begins to wonder whether the stress related to exposure to this research is having a negative effect!

However, as stated above, there are several things to consider when deciding how much to worry about the effects of worry. First, not all studies have demonstrated negative effects. In fact, an American study from 2006 found that moderate levels of stress were linked to more advanced mental ability in children by the age of two. There is certainly a competing hypothesis here related to the fact that cortisol, in an evolutionary sense, is critical to health and well-being. Its release in the brain is related to the fight or flight response which protects us from dangerous threats in the environment. Cortisol helps us focus our energies thereby leading to engagement, and perhaps improved competence, in the face of challenges. Psychologists have known for some time that there are optimal levels of "good" stress that can increase performance, while too little or too much stress have the opposite effect.

Second, critics also point to methodological problems with many of these studies. For instance, studies are often done retrospectively. That is, women are asked after their children have been born to rate their stress during pregnancy. The problem here is that women who have had a worrying low birth weight or premature birth experience are more likely to recall stressful life events during the pregnancy. Some have called into question the subjective nature of these studies. Other critics question the robustness of the results since the studies typically involved relatively small groups of women. Still others note that if the stress event is, for instance wife abuse during pregnancy, how can one rule out the detrimental role of the continued abuse in the months or even years following birth?

Third, the number of different variables involved in the stress and pregnancy equation is much larger than it may at first appear. Consider the following questions. If stress is harmful to the developing fetus, does it matter if the stress occurs during the first, second or third trimester? Is is only severe stress that leads to negative consequences, while more moderate stress has no effect, or as mentioned above, a positive effect? Is the social support one receives during pregnancy, or lack of it,  a more powerful predictor of post-natal outcomes than stress levels? In addition, is it the stressful life event itself that leads to negative consequences or the interpretation given to that event by the particular person involved, that is related to positive versus more problematic outcomes? How about the effects of acute versus chronic stress? As can be seen, the relationship between stress, pregnancy and outcome is quite complex.

What has your experience taught you? What conclusions have you reached? Let us know what you think.

Visit us tomorrow for the second part of our series on Stress and Pregnancy.

You can read more here and here and here and here and here.

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