Laura Swift—lauraswiftphotography.com

Editor’s note: This article first appeared in Midwifery Today, Issue 129, Spring 2019.
Join Midwifery Today Online Membership

For a long time, many women have noticed that they are not as mentally sharp as usual at the end of their pregnancies. They mention anecdotes of memory loss and, occasionally, poor concentration. Their topics of interest become different. Their need for socialization may be reduced and reoriented.

This deep-rooted empirical knowledge is convincingly supported by imaging techniques. As early as 2003, an American study had observed that in late pregnancy there is a significant reduction in blood flow in the large arteries going to the brain (Zeeman, Hatab, and Twickler 2003). Significant decreases occur in both the middle and posterior cerebral arteries between 36 and 38 weeks of gestation. (Unfortunately, no data regarding brain blood flow during the last days of pregnancy are available.) According to a complementary study by the same authors, there is no reduction in blood flow in the case of preeclampsia (Zeeman, Hatab, and Twickler 2004). More recently, a Spanish and Dutch team demonstrated that during pregnancy there are gradual reductions in grey matter volumes (Hoekzema et al. 2016). The observed volume reductions are not distributed randomly across the brain but are located in areas of the cortex that play a key role in sociability. It is as if the need for privacy is already increasing before the process of parturition starts. There were no changes in the grey matter volumes of the fathers—evidence for the selectivity of the changes for women undergoing pregnancy. Furthermore, brain changes were similarly affected regardless of means of conception (natural or medically assisted).

Rising rates of melatonin (the “darkness hormone”) might also be presented as a component of this preliminary phase since its release tends to reduce neocortical activity: the synergy between melatonin and gamma-Aminobutyric acid (GABA), the main inhibitory neurotransmitter, is an established fact (Kivelä 1991; Tamura et al. 2008). We even know about the kind of light that has the most powerful inhibitory effect on melatonin release: it is the blue part of the spectrum (Nakamura et al. 2001; Bagci et al. 2012). This kind of knowledge is of paramount importance, since modern lifestyle is characterized by the widespread use of a new generation of artificial light (light emitting diodes [LEDs]). This kind of light is rich in the blue spectrum.

When I studied medicine in Paris in the middle of the twentieth century, the term first stage was not used: this is why I am not supposed to understand it. At that time, midwives evaluated “dilation of the cervix” through comparisons. French midwives were comparing the degree of dilation with the size of coins or palms of hands. For example, the dilation could be “one franc,” “five francs,” “petite paume” (like the palm of the hand of a child), or “grande paume” (like the palm of the hand of an adult).

Because I am not the prisoner of the modern technical language, I feel free to smash the limits of the concept of first stage and to focus on the little-known preliminary phase of human parturition, as it may be understood in a renewed scientific context.

We must also keep in mind that the role of melatonin during the birth process is confirmed by its comparatively high concentration in the blood of babies “born with labour” (Bagci et al. 2012). It is roughly twice the level among babies born by the vaginal route or caesarean during labour, compared with babies born by “pre-labour caesarean.” Let us open a parenthesis to underline the paramount importance of these findings: the protective anti-oxidative properties of melatonin are widely documented.

The peak production of allopregnanolone (ALLO) by the placenta during the days preceding birth might also be considered an important aspect of the preliminary phase. ALLO is a positive modulator of GABA (Children’s National Health System 2018).

We must add that altered memory and absentmindedness in pregnancy have been the topic of publications in a great diversity of scientific and medical journals. The common point among such studies is a widespread tendency to consider physiological changes during pregnancy only in the framework of preparation for motherhood. As long as there is a lack of interest in birth physiology, it is commonplace to forget that, between the time when a woman is pregnant and the phase of mother-infant interaction, there is an acute and critical event—giving birth—and that this event needs to be physiologically prepared.  

It is notable that the countless descriptions of what we present as symptoms and signs of this preliminary phase have attracted the attention of a diverse public. Some of them have directly reached health professionals involved in obstetrics (Sharp et al. 1993; Keenan et al. 1998), others have reached psychiatrists (Christensen, Leach, and Mackinnon 2010), others have reached mostly general practitioners (Davies et al. 2018), and still others specialized physiologists (Henry and Sherwin 2012). Many have reached psychologists and psychotherapists and had echoes in the media and the general public.

One may wonder why, in many such studies, it was difficult to confirm facts considered obvious and even established. The main reason undoubtedly is that researchers are not thinking in terms of the preliminary phase of parturition. This is why they are vague about the phases of pregnancy they are exploring. For example, in a huge study published in an authoritative journal of obstetrics, a period as long as the last four months is presented as “late stage of pregnancy” (Keenan et al. 1998). There are reasons to be more curious about the last four weeks and even the last four days! Another reason for discrepancies between the results is that memory has often been the main criterion explored by researchers. The point is that there are many kinds of memory: retrospective, prospective, short term, long term, spatial, verbal, visual, emotional, and also priming memory and working memory. When taking into account the point of view of mothers and the results of one particular study, it seems that an altered prospective memory (remembering to perform an act at the right time) is a frequent aspect of what is commonly called “baby brain” (Rendell and Henry 2008).

Some aspects of pre-labour behavior are not easily measured and, therefore, evaluated through scientific methods. The high incidence of lost objects is still in the framework of empiric knowledge: there are countless anecdotes of women in late pregnancy who lost their keys, their mobile telephone, or their credit card. Some aspects of maternal behavior in the preliminary phase of parturition justify the term “nesting instinct,” since a nest is a protective structure built by certain animals to hold either eggs or offspring or, occasionally, the animal itself. The content of a nest is cut off from the rest of the world. In humans, the urge to clean, tidy, and organize the environment has been traditionally interpreted as a sign that labour and delivery are imminent. From an overview of what we learn from tradition, empiric knowledge, and scientific knowledge, we can summarize a simple conclusion about the period of transition preceding the process of parturition: it is a phase of human life when down-to-earth preoccupations prevail over all the others.

From a practical perspective, the main question is: Who must understand that before giving birth women need to live in peace and be protected against unnecessary intellectual stimulations? The answer is that everybody is concerned, since everybody may have an occasional opportunity to communicate with pregnant women. In other words, we are studying the evolution of cultural conditioning. However, in the context of the twenty-first century, we must consider in particular several aspects of a radically renewed social environment, such as small modern family structures and the medicalization of pregnancies.  

The point is to realize the importance of the topic and to phrase urgent questions at a time when this phase of human life is frequently altered, shortened, or eliminated, not only through labour induction or pre-labour cesarean, but also through many aspects of modern lifestyle.   

References:

• Bagci, S, et al. 2012. “Melatonin concentration in umbilical cord blood depends on mode of delivery.” Early Hum Dev 88(6): 369–73.
• Children’s National Health System. “Placental ALLO levels rise during pregnancy and peak as fetuses approach full term: Study is largest neonatal sample to date in which multiple steroid hormones were measured.” Science Daily. Accessed December 4, 2018. sciencedaily.com/releases/2018/05/180505091803.htm.
• Christensen, H, LS Leach, and A Mackinnon. 2010. “Cognition in pregnancy and motherhood: prospective cohort study.” Br J Psychiatry 196(2): 126–32. doi: 10.1192/bjp.bp.109.068635.
• Davies, SJ, et al. 2018. “Cognitive impairment during pregnancy: a meta-analysis.” Med J Aust 208(1): 35–40.
• Henry, JF, and BB Sherwin. 2012. “Hormones and cognitive functioning during late pregnancy and postpartum: a longitudinal study.” Behav Neurosci 126(1): 73–85. doi: 10.1037/a0025540. Epub 2011 Sep 19.
• Hoekzema, E, et al. 2016. “Pregnancy leads to long-lasting changes in human brain structure.” Nat Neurosci 20(2): 287–96. doi: 10.1038/nn.4458. Epub 2016 Dec 19.
• Keenan, PA, et al. 1998. “Explicit memory in pregnant women.” Am J Obstet Gynecol 179(3 Pt 1): 731–37.
• Kivelä, A. 1991. “Serum melatonin during human pregnancy.” Acta Endocrinol (Copenh) 124(3): 233–37.
• Nakamura, Y, et al. 2001. “Changes of serum melatonin level and its relationship to feto-placental unit during pregnancy.” J Pineal Res 30(1): 29–33.
• Rendell, PG, and JD Henry. 2008. “Prospective-memory functioning is affected during pregnancy and postpartum.” J Clin Exp Neuropsychol 30(8): 913–19. doi: 10.1080/13803390701874379. Epub 2008 Mar 14.
• Sharp, K, et al. 1993. “Memory loss during pregnancy.” Br J Obstet Gynaecol 100(3): 209–15.
• Tamura, H, et al. 2008. “Melatonin and pregnancy in the human.” Reprod Toxicol 25(3): 291–303. doi: 10.1016/j.reprotox.2008.03.005. Epub 2008 Apr 1.
• Zeeman, GG, M Hatab, and DM Twickler. 2003. “Maternal cerebral blood flow changes in pregnancy.” Am J Obstet Gynecol 189(4): 968–72.
• ———. 2004. “Increased cerebral blood flow in preeclampsia with magnetic resonance imaging.” Am J Obstet Gynecol 191(4): 1425–29.