Labor and catecholaminesIt is axiomatic among "natural" childbirth advocates that fear interferes with labor. This claim originated primarily with Grantly Dick-Read who touted the fact that "primitive" women had painless labors. As we have seen, Dick-Read simply made that up.
As far as I can tell, there has been no basic research that has shown that fear has a dampening effect on human labor. Nonetheless, the claim has persisted among "natural" childbirth advocates and has been elaborated into a sophisticated biochemical argument. Stress hormones (catecholamines) supposedly triggered by fear suppress labor. Consider this paper, Do Not Disturb: The Importance of Privacy in Labor, by Judith Lothian, a board member of Lamaze. Lothian asserts:
In early labor, catecholamines (the stress hormones) have the potential to stop labor. When a woman is very frightened—of pain, of the hospital, of the unknown—labor fails to progress. Contractions can become very strong and difficult to handle or, more typically, they become weaker. In both instances, the contractions become ineffective. Why should this be so? For animals giving birth in the wild, fear of predators in early labor triggers catecholamine release and labor stops, giving the animal time to move out of danger before labor begins again. Catecholamine release and the temporary shutdown of labor protect the animal and her young.There's a serious problem with this claim. It is precisely the opposite of what the scientific evidence shows. Catecholamine release is caused by the pain of labor and increasing levels of pain produce increasing amounts of catecholamines. Fear, pain and stress hormones during childbirth(J Psychosom Obstet Gynaecol. 2005 Sep;26(3):153-65) describes the interaction between pain and catecholamines:
To investigate the course of fear, pain and stress hormones during labor, and the associations between fear, pain, stress hormones and duration of labor in nulliparous women with and without epidural analgesia (EDA). METHOD: One day during gestation weeks 37-39, urinary and salivary samples were collected to measure catecholamines and cortisol. Hourly during labor, the participants answered the Delivery Fear Scale and a pain intensity scale, and urinary and salivary samples were collected to measure stress hormones. RESULTS: The course of fear, pain and stress hormones differed throughout labor in women with and without EDA. Pain and cortisol increased throughout labor in women without EDA. Women who received EDA had more fear, but not more pain, before the administration of the EDA than women who did not receive EDA. Pain, fear and catecholamines decreased when women received EDA, but fear and pain increased again later in labor. Fear and pain correlated, as well as levels of fear in the different phases of labor. During phase one of labor epinephrine and duration of the phase were negatively correlated. CONCLUSION: The course of fear, pain and concentrations of stress hormones differed, highly influenced by the administration of EDA. Fear and pain correlated more pronounced than stress hormones and fear, pain and duration of labor."Natural" childbirth advocates insist that it is critical to keep catecholamine levels low in order for labor to progress. What is most effective at lowering catecholamines during labor? You guessed it: an epidural.
Based on the scientific evidence that I could find, it seems that "natural" childbirth advocates have simply fabricated the claim that stress supresses labor, and fabricated the claim that high levels of catecholamines interfere with labor. The scientific evidence shows exactly the opposite. Interestingly, this is in keeping with the speculations of the bioanthropologists Rosenberg and Trevathan who suggest that fear and pain are evolutionarily favored, not because they are beneficial in and of themselves, but because they cause women to seek out assistance in childbirth, and assistance is more likely to lead to a live baby and a live mother.
When it comes to the claims about fear and catecholamines in labor, "natural" childbirth advocates are wrong about the source of increased catecholamines in labor, wrong about the effects of increased catecholamines, and wrong about the value of increased catecholamines.