A few years ago, while in that happy but anxious limbo of expecting my first baby, I dutifully read up on labor–its stages, birth plans, and the best ways to “achieve” a natural childbirth.
On this last point—achieving a natural childbirth—a theme quickly emerged: My mental state was key. Without the proper level of mindfulness, my labor was likely to stall.
Statements emphasizing the importance of remaining calm were anything but stress-reducing:
“Once labor has begun, fear can cause labor to progress more slowly and painfully… relaxation is the key to natural childbirth.”
Nothing short of Zen-like transcendence seemed to be the goal. Any anxiety, any worry could initiate the dreaded cascade of interventions—oxytocin, epidural, and possibly an otherwise avoidable C-section.
Even well-respected sources like the American Pregnancy Association seem to buttress these claims, noting that “research has linked prolonged labor or failure to progress to psychological factors, such as worry, stress, or fear.”
But, don’t panic. These descriptions of stress and labor are inaccurate.
Given how widespread these claims are, I was surprised to learn that there’s actually no evidence that normal levels of worry, stress or anxiety stall labor. None.
There’s no evidence that normal levels of worry, stress or anxiety stall labor.
None.
Here’s how researchers summarize the role of stress during labor (a far cry from popular natural birth websites):
“A reasonable amount of stress is harmless to the mother and to labor progress, and actually benefits the fetus by promoting adaptation to labor and birth. Excessive stress (as yet undefined in Perinatal medicine)… may be related to dysfunctional labor and fetal and neonatal distress and illness”
—Simkin, 1986[1]
In other words, giving birth is an inherently stressful experience, regardless of whether you approach it with a positive attitude.
And let’s tackle the first part first: Stress is a normal, often beneficial part of labor.
A surge in stress hormones is a normal during an unmedicated labor.
This is not detrimental. It is adaptive.
For one, stress hormones actually help initiate labor (in direct contrast to the blanket claims that stress derails labor). Women whose labor begins spontaneously have about 3 times the levels of the stress hormone, cortisol, at the outset of labor as compared to levels in women whose labor was induced[2].
As labor progresses, stress hormones continue to rise. The pain and physical strain of active labor floods your body with stress hormones like cortisol and adrenaline. Again, contrary to the claims of some natural birth advocates, high levels of stress are a hallmark of an unmedicated labor. Women who deliver vaginally have twice as much cortisol in their blood after giving birth as women who deliver by C-section[3,4]. Cortisol is also higher among women who don’t receive epidurals[5].
The surge of stress hormones is not detrimental. It is adaptive: Stress hormones help you handle the physical strain of labor by boosting your energy and keeping your blood sugar from plummeting.
But what about your baby?
During labor, your baby will experience a significant amount of stress and high cortisol levels. The stress hormones are not from you AND they are a good thing. Labor itself stresses the fetus. And this helps ensure your baby’s survival.
Labor itself stresses the fetus and helps ensure baby’s survival in the outside world.
Why is labor stressful for your baby? Each time your uterus contracts, it squeezes your baby’s placenta. This briefly throttles the flow of blood across the placenta, cutting off your baby’s blood supply, and dropping their oxygen levels.
In response to this precipitous drop in available oxygen, your fetus releases stress hormones. These hormones shunt blood away from your baby’s arms and legs to her brain and heart. The extra blood helps protect these critical organs[1].
Stress hormones released during labor also help your fetus maintain her body temperature and dry out her lungs, preparing them to take that first breath outside the womb.
Okay, so what about “extreme stress”?
How excessive does stress have to be to delay labor?
Short answer: We don’t know.
Longer answer: we will probably never know, because it’s too hard to study extreme stress in laboring women. For ethical reasons, researchers can’t induce extreme stress in laboring women.
So instead, researchers have turned to animals to study how extreme stress (e.g., being chased by a lion) can impact labor. These studies suggest that severe stress may slow down progress during early labor[6]. However, extreme stress does not appear to slow down active labor. If anything, extreme stress during active labor–at least in animals–accelerates labor (get that baby out so you can flee!)
Extreme stress does not slow down active labor. If anything, extreme stress in active labor may accelerate labor.
So while in theory extreme stress could derail early labor[1], nothing we know suggests ordinary stressors – normal pre-labor jitters, discomfort with your delivery team, or anxiety about how your labor is going – affect labor progress. Stress hormone levels during normal labor are simply too high for minor worries to have a physiological impact.
Want to know what might actually stall labor? Those glaring hospital lights!
REferences:
[1] Simkin P. Stress, pain, and catecholamines in labor: Part 1. A review. Birth. 1986;13: 227–233.
[2] Benfield RD, Newton ER, Tanner CJ, Heitkemper MM. Cortisol as a Biomarker of Stress in Term Human Labor: Physiological and Methodological Issues. Biol Res Nurs. NIH Public Access; 2014;16: 64.
[3] Talbert LM, Pearlman WH, Potter HD. Maternal and fetal serum levels of total cortisol and cortisone, unbound cortisol, and corticosteroid-binding globulin in vaginal delivery and cesarean section. Am J Obstet Gynecol. 1977;129: 781–787.
[4] Dickens MJ, Pawluski JL. The HPA Axis During the Perinatal Period: Implications for Perinatal Depression. Endocrinology. Oxford University Press; 2018;159: 3737–3746.
[5] Maltau JM, Eielsen OV, Stokke KT. Effect of stress during labor on the concentration of cortisol and estriol in maternal plasma. Am J Obstet Gynecol. 1979;134: 681–684.
[6] Lothian JA. Do Not Disturb: The Importance of Privacy in Labor. J Perinat Educ. 2004;13: 4–6.
