Stress Deprivation in the Perinatal Period
Editor’s note: This article first appeared in Midwifery Today, Issue 116, Winter 2015.
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In the framework of our cultural conditioning, stress has a negative connotation: we must avoid stressful situations. Meanwhile, in the current scientific context, it appears that stress hormones have multiple roles to play and the concept of “stress deprivation” has recently emerged in scholarly articles. We’ll look at birth by pre-labor cesarean as an extreme example of stress deprivation.
It has been understood for a long time that pre-labor cesarean is a risk factor for respiratory difficulties in the neonatal period and that the risks are dependent on the gestational age. Differences in the quality of the respiratory functions are detectable when comparing pre-labor births at 38 and 39 weeks (Glavind and Uldbjerg 2015). One of the interpretations is that the fetus participates in the initiation of labor, probably through the release of surfactant, when its lungs have reached a certain degree of maturity (Condon et al. 2004). Furthermore, the roles of maternal and fetal stress hormones are well-known. The effect of maternal corticosteroids on fetal lung maturation has had practical implications for several decades. Labor implies the action of beta-endorphins—releasers of prolactin, which participate in lung maturation (Hauth 1978). Labor also implies the release of the fetal noradrenaline, which is probably one of the main factors participating in lung maturation.
Recent Human Studies
The important point is that the multiple negative effects of stress deprivation among babies born by pre-labor c-section have been underestimated until recently. For example, it has been demonstrated that, under the effect of noradrenaline, the sense of smell has reached a high degree of maturity at birth among babies born by in-labor c-section or via the vaginal route. The principle of a Swedish experiment was to expose babies to an odor for 30 minutes shortly after birth and then to test them for their response to this odor (and also to another odor) at the age of 3 or 4 days (Varendi, Porter and Winberg 2002). Since the concentrations of noradrenaline had been evaluated, it was possible to conclude that fetal noradrenaline released during labor is involved in the maturation of the sense of smell. We must emphasize the paramount role of the sense of smell immediately after birth. I had already mentioned in the 1970s that the sense of smell is the main guide towards the nipple as early as during the hour following birth (Odent 1977; Odent 1978). It has been demonstrated that it is mostly through the sense of smell that the newborn baby can identify its mother (and, to a certain extent, that the mother can identify her baby).
There has been recently an accumulation of data regarding the effects of cesarean births according to their timing. Among such studies, we must mention the evaluation of adiponectin concentration in cord blood of healthy babies born at term. The concentration of this agent involved in fat metabolism is significantly lower after pre-labor cesarean compared with in-labor cesarean or birth via the vaginal route (Hermansson, Hoppu and Isolauri 2014). This data suggests a mechanism according to which stress deprivation at birth might be a risk factor for obesity in childhood and adulthood.
We must also give great importance to data regarding the milk microbiome. There are significant differences between the milk of mothers who gave birth by pre-labor cesarean and those who gave birth by in-labor cesarean or via the vaginal route (Cabrera-Rubio et al. 2012). These results suggest that there are other factors than the operation per se that can alter the process of microbial transmission to milk. Similar differences were found by a Canadian study of the gut flora of 4-month-old babies (Azad et al. 2013). Joanna Holbrook and her team, in Singapore, suggest interpretations for these surprising data. They collected fecal samples from 75 babies at the age of 3 days, 3 weeks, 3 months and 6 months (and they evaluated the degree of adiposity at 18 months). It appears that, apart from the route of birth and exposure to antibiotics, a shortened duration of pregnancy tends to delay the maturation of the gut flora. One week more or less in the duration of pregnancy is associated with significant differences; a pre-labor cesarean implies the association of all the known factors that can delay the maturation of the gut flora. This study is all the more important since it also reveals that a delayed maturation of the gut flora is a risk factor for increased adiposity at the age of 18 months (Dogra et al. 2015).
In the framework of human studies, we may include also evaluations of the concentrations of melatonin in the cord blood. It is low after pre-labor births (Bagci et al. 2012). This is an important point, since melatonin has protective anti-oxidative properties. Furthermore, it confirms that the “darkness hormone” is involved in the birth process. This is one of the reasons why the role of melatonin during labor is topical, at a time when we are learning about a synergy between its uterine receptors and oxytocin receptors.
In general, a baby born after a pre-labor cesarean is physiologically different from the others. For example, babies born pre-labor tend to have a lower body temperature than the others during the first 90 minutes following birth (Christensson et al. 1993).
In spite of possible inter-species differences, we must seriously consider animal experiments that suggest the stress of labor influences brain development. Such is the case of studies demonstrating that the birth process in mice triggers the expression of a protein (uncoupled protein 2) that is important for development of the hippocampus (Simon-Areces et al. 2012). Let us recall that, among humans, the hippocampus is a major component of the limbic system. It has been compared to an “orchestra conductor” directing brain activity. It has also been presented as a kind of physiological GPS system, helping us navigate while also storing memories in space and time. The work of three scientists who studied this important function of the hippocampus has been recognized by the award of the 2014 Nobel Prize in physiology and medicine. This is also the case of studies with rats suggesting that oxytocin-induced uterine contractions reverse the effects of the important neurotransmitter GABA; this primary excitatory neurotransmitter becomes inhibitory (Tyzio et al. 2006). If uterine contractions affect the neurotransmitter systems of rats during an important phase of brain development, why would the same not occur in humans?
Other effects of pre-labor cesareans will probably appear in the near future. It seems that the prevalence of placenta previa is significantly increased only in the case of a pregnancy following a pre-labor cesarean (Downes et al. 2015). There is already an accumulation of data confirming the negative effect of pre-labor cesarean on breastfeeding, particularly at the phase of the initiation of lactation (Prior et al. 2012; Zanardo et al. 2012).
We must also keep in mind that cesareans performed in a real situation of emergency are associated with comparatively bad short-term outcomes. This well-known fact is easily interpreted. We must first notice that such cesareans are often performed when there are already signs of fetal distress, after a long period of pharmacological assistance. We must also take into account that emergency cesareans are often performed hurriedly and therefore in poor technical conditions. Furthermore, they are associated with negative long-term outcomes. For example, according to an American study, women with a full-term second stage cesarean have a spectacular increased rate of subsequent premature births (13.5%) compared to a first-stage cesarean (2.3%) and to the overall national rate (7–8%) (Levine et al. 2014).
This overview of the multiple effects of pre-labor cesareans—associated with a reminder of the particularities of last-minute emergency cesareans—suggests that the ideal kind of cesarean is the one performed during labor, before the stage of a real emergency.
Until now, the concepts of “planned in-labor cesareans” and “in-labor non-emergency cesareans” have not been introduced in epidemiological studies. For example, in the well-known multicentered, randomized controlled trial about breech presentation at term, only two options were considered: planned pre-labor cesarean and planned vaginal route (Hannah et al. 2000).
On the day when the concept of “in-labor non-emergency cesarean” becomes familiar, the doors will be open towards simplified binary strategies, with two basic scenarios: either the birth process is straightforward by the vaginal route, or it appears difficult, and an in-labor cesarean before the stage of emergency is considered the best option. Before such simplified strategies become realistic, the history of midwifery and obstetrics will have to go through several steps.
The main step will be to challenge the effects of thousands of years of tradition and cultural conditioning. This is becoming realistic in the light of the concept of neocortical inhibition. The key will be to study how some human physiological functions, such as the birth process, are obscured by the activity of a powerful neocortex and to understand the solution nature found to adapt to the human particularities.
- Azad, MB, et al. 2013. “Gut Microbiota of Healthy Canadian Infants: Profiles by Mode of Delivery and Infant Diet at 4 Months.” CMAJ 185 (5): 385–94.
- Bagci, S, et al. 2012. “Melatonin Concentration in Umbilical Cord Blood Depends on Mode of Delivery.” Early Hum Dev 88 (6): 369–73.
- Cabrera-Rubio, R, et al. 2012. “The Human Milk Microbiome Changes over Lactation and Is Shaped by Maternal Weight and Mode of Delivery.” Am J Clin Nutr 96 (3): 544–51.
- Christensson, K, et al. 1993. “Lower Body Temperature in Infants Delivered by Caesarean Section Than in Vaginally Delivered Infants.” Acta Paediatr 82 (2):128–31.
- Condon, JC, et al. 2004. “Surfactant Protein Secreted by the Maturing Mouse Fetal Lung Acts as a Hormone That Signals the Initiation of Parturition.” Proc Natl Acad Sci USA 101 (14): 4978–83.
- Dogra S, et al. 2015. “Dynamics of Infant Gut Microbiota Are Influenced by Delivery Mode and Gestational Duration and Are Associated with Subsequent Adiposity.” MBio 6 (1): e02419–514.
- Downes, KL, et al. 2015. “Previous Prelabor or Intrapartum Cesarean Delivery and Risk of Placenta Previa.” Am J Obstet Gynecol 212 (5): 669.
- Glavind, J, and N Uldbjerg. 2015. “Elective Cesarean Delivery at 38 and 39 Weeks: Neonatal and Maternal Risks.” Curr Opin Obstet Gynecol 27 (2): 121–27.
- Hannah, ME, et al. 2000. “Planned Caesarean Section Versus Planned Vaginal Birth for Breech Presentation at Term: A Randomised Multicentre Trial.” Lancet 356 (9239): 1375–83.
- Hauth, JC, et al. 1978. “A Role of Fetal Prolactin in Lung Maturation.” Obstet Gynecol 51 (1): 81–88.
- Hermansson, H, U Hoppu and E Isolauri. 2014. “Elective Caesarean Section Is Associated with Low Adiponectin Levels in Cord Blood.” Neonatology 105 (3): 172–74.
- Levine, LD, et al. 2014. “Does Stage of Labor at Time of Cesarean Affect Risk of Subsequent Preterm Birth?” Am J Obstet Gynecol 212 (3): 160.
- Odent, Michel. 1977. “The Early Expression of the Rooting Reflex.” In Proceedings of the 5th International Congress of Psychosomatic Obstetrics and Gynaecology. London: Academic Press, 1117–19.
- Odent, Michel. 1978. “L’expression précoce du réflexe de fouissement.” In Les cahiers du nouveau-né vol. 1–2, edited by E Herbinet, 169–85. Paris: Stock.
- Prior, E, et al. 2012. “Breastfeeding after Cesarean Delivery: A Systematic Review and Meta-Analysis of World Literature.” Am J Clin Nutr 95 (5): 1113–35.
- Simon-Areces, J, et al. 2012. “UCP2 Induced by Natural Birth Regulates Neuronal Differentiation of the Hippocampus and Related Adult Behavior.” PLoS ONE 7 (8): e42911.
- Tyzio, R, et al. 2006. “Maternal Oxytocin Triggers a Transient Inhibitory Switch in Gaba Signaling in the Fetal Brain During Delivery.” Science 314 (5806): 1788–92.
- Varendi, H, RH Porter and J Winberg. 2002. “The Effect of Labor on Olfactory Exposure Learning within the First Postnatal Hour.” Behav Neurosci 116 (2): 206–11.
- Zanardo, V, et al. 2012. “Impaired Lactation Performance Following Elective Cesarean Delivery at Term: Role of Maternal Levels of Cortisol and Prolactin.” J Matern Fetal Neonatal Med 25 (9): 1595–98.