Stress deprivation and Caesarean birth

Is birth by pre-labour Caesarean an extreme example of stress deprivation?

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.

It has been understood for a long time that pre-labour Caesarean 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.¹

One of the interpretations is that the foetus participates in the initiation of labour, probably through the release of surfactant, when its lungs have reached a certain degree of maturity.² Furthermore the roles of maternal and foetal stress hormones are well-known. The effects of maternal corticosteroids on foetal lungs maturation has had practical implications for several decades. Labour implies the action of beta-endorphin (releasers of prolactin, which participate in lung maturation).³ Labour also implies the release of  the foetal noradrenaline, 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-labour 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-labour C-section or via the vaginal route. The principle of a Swedish experiment was to expose babies to an odour for thirty minutes shortly after birth and then to test them for their response to this odour (and also to another odour) at the age of three or four days.⁴ Since the concentrations of noradrenaline had been evaluated, it was possible to conclude that foetal noradrenaline released during labour is involved in the maturation of the sense of smell. We must emphasize the paramount role of the sense of smell immediately after birth. In the 1970s, the sense of smell was found to be the main guide towards the nipple as early as during the hour following birth.^{,5, 6} 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 Caesarean 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-labour Caesarean compared with in-labour Caesarean or vaginal route.⁷ These data suggest 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-labour Caesarean and those who gave birth by in-labour Caesarean or the vaginal route.⁸These 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 four-month-old babies.⁹   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-labour Caesarean 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.¹⁰

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-labour births.¹¹ 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 labour 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-labour Caesarean is physiologically different from the others. For example, babies born pre-labour tend to have a lower body temperature than the others during the first 90 minutes following birth.¹²

Animal experiments

In spite of possible inter-species differences, we must seriously consider animal experiments suggesting that the stress of labour 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 the hippocampus development.¹³ 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.¹⁴ If uterine contractions affect the neurotransmitter systems of rats during an important phase of brain development, why would not the same occur in humans?

The future

Other effects of pre-labour Caesareans will probably appear in the near future. It seems that the prevalence of placenta praevia is significantly increased only in the case of a pregnancy following a pre-labour Caesarean.¹⁵ There is already an accumulation of data confirming the negative effect of pre-labour Caesarean on breastfeeding, particularly at the phase of initiation of lactation.^16,17

We must also keep in mind that Caesareans 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 in a hurry and therefore 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 Caesarean have a spectacular increased rate of subsequent premature births (13.5%) compared to a first stage Caesarean (2.3%) and to the overall national rate (7-8%).¹⁸

This overview of the multiple effects of pre-labour Caesareans – associated with a reminder of the particularities of last minute emergency cesareans – suggests that the ideal kind of Caesarean is the one performed during labor, before the stage of a real emergency.

Until now, the concepts of ”planned in-labour Caesareans” 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-labour Caesarean and planned vaginal route.¹⁹

On the day when the concept of ”in-labour non emergency Caesarean” 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-labour Caesarean 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.

References:

1-Glavind J, Uldbjerg N. Elective cesarean delivery at 38 and 39 weeks: neonatal and maternal risks. Curr Opin Obstet Gynecol 2015 Apr;27(2):121-7. doi: 10.1097/GCO.0000000000000158.

2-Condon JC¹, Jeyasuria P, Faust JM, Mendelson CR. Surfactant protein secreted by the maturing mouse fetal lung acts as a hormone that signals the initiation of parturition. Proc Natl Acad Sci U S A. 2004 Apr 6;101(14):4978-83. Epub 2004 Mar 25.

3-Hauth JC, Parker CR Jr, MacDonald PC, Porter JC, Johnston JM. A role of fetal prolactin in lung maturation. Obstet Gynecol. 1978 Jan;51(1):81-8.

4- Varendi H, Porter RH, Winberg J. The effect of labor on olfactory exposure learning within the first postnatal hour. Behav Neurosci. 2002 Apr;116(2):206-11

5-Odent M. The early expression of the rooting reflex. Proceedings of the 5^th  International Congress of Psychosomatic Obstetrics and Gynaecology, Rome 1977. London: Academic Press, 1977: 1117-19.

6-Odent M. L’expression précoce du réflexe de fouissement. In : Les cahiers du nouveau-né 1978 ; 1-2 : 169-185

7-Hermansson H. · Hoppu U. · Isolauri E. Elective Caesarean Section Is Associated with Low Adiponectin Levels in Cord Blood. Neonatology 2014;105:172-174 (DOI:10.1159/000357178).

8-Cabrera-Rubio R, Collado MC, Laitinen K, et al. The human milk microbiome changes over lactation and is shaped by maternal weight and mode of delivery. Am J Clin Nutr. 2012 Sep;96(3):544-51. doi: 10.3945/ajcn.112.037382. Epub 2012 Jul 25.