External influences on development including prenatal nutrition are said to constitute:

Abstract

The prenatal period reflects a time when the embryo or fetus is particularly sensitive to environmental insult from maternal experiences. It is imperative that pregnant women be informed of possible teratogens and the risk to fetal health. Unfortunately, many teratogens lurk in food and water supplies. Methylmercury (MeHg), polychlorinated biphenyls (PCBs), and bisphenol-A (BPA) are disguised in seemingly healthy foods like fish or canned peaches. The safety of nicotine, caffeine, and alcohol is disputed among physicians and in the media. This article highlights several disguised and disputed teratogens, and describes how they may impact brain development and mental health.

Prenatal Nutritional Needs

The prenatal period is the period of time before birth. A woman’s nutritional needs are high during this time. Because a woman may not know that she is pregnant, she may be poorly nourished. She may also consume alcohol or caffeine in excess, which may affect the growing embryo or fetus.

A woman should be at nutritional readiness for pregnancy during her childbearing years. Her body weight should be at a desirable level. She should consume a wide range of foods and beverages that contain a variety of nutrients, including an assortment of fruits and vegetables—particularly those that are rich in iron and folate to help prevent anemia and neural tube defects—and calcium for growth, development and repair. She should be at her peak of physical fitness to handle the tremendous physical stresses of pregnancy. Yet, even nutritional and physical readiness does not ensure a healthy, risk-free pregnancy or birth.

The risk factors of pregnancy include alcohol intake, chronic disease such as diabetes or hypertension, drug intake, eating disorders, excessive dieting, folic acid deficiency, iron deficiency, lack of health care, multiple pregnancies, nicotine use, overweight, poor education, poor pregnancy outcomes, poverty, previous abortions, teenage pregnancy and/or underweight.

2.2.1 Prenatal Exposures

The prenatal period is critical for fetal development and is particularly critical to brain development in the context of psychiatric disorders. Neurogenesis, neuron migration, maturation, and networking, as well as synaptic pruning, all require precise procedures that could be affected by environmental factors.

The fetus is, in general, well protected by the mother's body from biological and physical insults, though viral infection, malnutrition, and maternal substance and medication use pose potential biological threats. Many of these factors have been shown to increase risk of the fetus developing psychiatric disorders, and DNA methylation may play an important role in the process.66 Even though a causal relationship has not been established,67 much evidence connecting prenatal factors to DNA methylation changes are present in animal models.68

At least two studies have connected maternal malnutrition to the risk of schizophrenia.69,70 Perinatal malnutrition was found to be linked to changes in DNA methylation, which may further lead to growth and metabolic disease.71,72 DNA methylation is at its most dynamic period during early embryonic development; maternal intake of methyl-group donors such as folate, betaine, and folic acid was found to be associated with infant buccal cell DNA methylation, though only in the periconception period.73

Prenatal alcohol exposure was found to be associated with DNA methylation changes in genes related to protocadherins, glutamatergic synapses, and hippo signaling.74

Psychological stress experienced by the mothers may have an impact on the well-being of the fetus as well, possibly by affecting DNA methylation. A small study on pregnancy during the 1998 Quebec ice storm identified altered DNA methylation in blood and saliva of children 8 and 11 years old; the DNA methylation changes were correlated with objective maternal stress.75 A new study of 121 subjects showed that even grand-maternal exposure to psychosocial stress during pregnancy had an effect on DNA methylation of the grandchildren.76

It is unlikely that DNA methylation is the only change maternal malnutrition and other stressors impose on fetal development and consequent risk of psychiatric and other disorders. Fetal neuroendocrine alteration77 and inflammation reaction78 could also lead to pathology risk.

Early Development

The prenatal period and early postnatal life are precarious times. Cell duplication and the formation of a diverse number of different cells progresses rapidly, dictated by DNA and mRNA functioning. This process is dynamic in the sense that various endogenous substrates are added as part of the instruction for the developing fetus, and then removed at appropriate times. These modifications necessarily require that particular genes be turned on and off in a well-orchestrated sequence.

Gene transcription that occurs early in embryonic development can instill a stable epigenetic state that has implications for later physiological functioning (Greenberg et al., 2017). Yet, with so many changes occurring during the course of prenatal development, especially those stemming from multiple rounds of cell multiplication, the risk for chance mutations and those that are instigated by toxicants is considerable, and should such an outcome occur, it will be amplified with cell multiplication. At the same time, dynamic epigenetic processes are thought to be important in the regulation of developmental processes, and here again, there is ample room for problems to occur owing to environmental challenges and stressors. During this time, immune system functioning is blunted so that the fetus isn’t swarmed by the maternal immune system, and to some extent, components of the immune system are functional by the second trimester (McGovern et al., 2017). Indeed, during pregnancy a mother’s immune functioning may be down-regulated, which may account for the alleviation of autoimmune symptoms women may experience during this period, but this may also leave her at risk for infection, which could impact the developing fetus. In addition to variations of peripheral immune functioning, cytokine changes are diminished in the maternal brain (Sherer, Posillico, & Schwarz, 2017), which can have profound behavioral consequences that are apparent during the postpartum period.

In the context of developmental problems, there was a time when the focus of teratogenic effects involved drugs and environmental chemicals, and to some extent immunologically related illnesses (e.g. Rubella). But, it has become clear that a wide range of factors, including moderate stressors, may affect the developing brain. It also appears that prenatal stressors may interact with genetic factors in determining the occurrence of developmental disorders as well as pathologies that emerge in adulthood. As we’ll see in Chapter 8, Depressive Disorders, individuals carrying the short variants of the gene for the 5-HT transporter (5-HTT) may be at increased risk for the development of mood disorders, provided that they also experienced strong early life or adult stressors (although there have been indications that these actions might be less straight forward than initially thought). It likewise seems that in mice, prenatal stressors were more likely to promote depressive-like features among female offspring carrying the short allele of the 5-HTT promoter gene (Van den Hove et al., 2011). Moreover, behavioral effects of prenatal immune challenge could develop through epigenetic actions on the gene coding for the 5-HTT transporter (Reisinger et al., 2016).

Placental Cellular Populations and Extraction Process

The antenatal and perinatal periods can provide a high yield of progenitor cells. These can be isolated from a variety of regions, including the amniotic fluid, placenta, yolk sac, umbilical cord, and the umbilical cord blood. In this chapter, we have focused on the cardiogenic potential of stem cells isolated from the placenta and the amniotic fluid. Other perinatal cell sources have been extensively reviewed elsewhere [10,11].

The amniotic fluid is mainly composed of water, and it provides a nutritive and a cushion support for the fetus throughout the embryonic development. Amniotic fluid stem cells (AFSCs) can be easily collected by amniocentesis during a routine prenatal diagnosis or an amnioreduction for the treatment of twin–twin transfusion syndrome. The amniotic fluid is then centrifuged and the cells are seeded and incubated at 37°C for several days to adhere and proliferate in their appropriate culture medium. On confluency, the cells are passaged and the subcultures are cryopreserved for future experimentation. Other isolation variants based on immune selection or a two-stage culture protocol are also reported [12].

The term placenta contains different cellular populations, which can be isolated from four distinct layers. The amnion is the innermost part of the placenta in direct contact with the amniotic fluid. Externally situated, the chorion surrounds the amnion and is separated from the maternal decidua basalis by a rich network of fetomaternal vasculature, constituting the chorion villi. In the 2007 First International Workshop on the placenta-derived stem cells, it was agreed that four different cell populations of multipotent potential can be isolated from the placenta. Two of them can be extracted from the amnion: the amniotic epithelial stem cells (AESCs) and the amniotic mesenchymal stromal cells (AMSCs). The two other cell populations are derived from the chorionic membrane: the chorionic mesenchymal stromal cells (CMSCs) and the chorionic trophoblastic stem cells (CTSCs) [13]. However, as later discussed in this chapter, additional reports in cellular cardiomyoplasty have indicated the isolation of progenitor cells from other placental layers such as the chorionic villi, the decidua basalis, and the complete placental tissue (Fig. 7.2).

To harvest stem cells from the human term placenta, umbilical cord blood is first allowed to drain from the placenta, which is then dissected carefully. Isolation protocols of the various cellular populations in the placenta resemble to a certain extent. The extraction procedure begins with the dissection of the anatomical region of interest followed by its enzymatic digestion. Subsequently, samples are filtered and centrifuged, and the pellets are resuspended in the corresponding medium. Stem cells are then seeded in culture plates and incubated at 37°C for several days. Adherent cells are identified as the placenta-derived stem cells. The culture medium is refreshed, and the cells are allowed to expand for subsequent passages and cryopreservation. It is noteworthy to indicate that isolation protocols differ among investigators. However, the sequential steps are similar to a large extent. The different isolation procedures are detailed in Parolini et al. [14].

Preparation of the Breasts

The prenatal period is a time for a couple to prepare for their new role as parents and to learn as much as possible about breastfeeding. Most mothers do no special preparation and are successful. Carefully controlled studies do not support the contention that fair-skinned women, especially redheads, are more prone to developing cracked, sore nipples than are others. Mothers who have had trouble with tender, cracked nipples when nursing a previous infant will need extra assistance in putting the infant to breast properly in the first few days, but elaborate rituals prenatally may actually cause problems. Nipple preparation has a negative effect on some women who are not ready to handle their breasts for these preparations during pregnancy.

Bathing should be as usual, with minimal or no soap directly on the nipples and thorough rinsing. Some recommend patting the nipple dry with a soft towel, but this should not be done except after a shower or bath. Persistent removal of natural oils of the nipple and areola actually predisposes the skin to irritation. Montgomery glands in the areola secrete a sebaceous material for the cleansing and lubrication of the areola and nipple. This should not be removed by soaps or chemicals. Tincture of benzoin, alcohol, and other drying agents are contraindicated because they predispose the nipples to cracking during early lactation.114 Wearing protective brassieres, modern women do not experience the friction to the nipples that looser clothing causes, which may be why cracked nipples are a common problem in modern society but almost unheard of in developing countries and among other mammals. In Scandinavia, it is suggested that pregnant women get as much air and sunshine as possible directly on the breasts before delivery. Wearing a nursing brassiere with the flaps down to expose the nipples under loose clothing will serve the same purpose. However, aggressive and abrasive treatment of the nipples does not prevent nipple pain postpartum and may aggravate it. Gentle love making involving the breasts is usually safe and is the most effective preparation.68

The use of lanolin, which is miscible with water and thus allows normal evaporation from the skin, does no apparent harm but in controlled studies also made no difference prenatally. Women allergic to wool will also be allergic to lanolin. Use of vitamin A and D ointment prophylactically also makes no difference, having an effect only in the treatment of fissures later.146 In climates with average to high humidity, ointments are not routinely recommended for breasts and may interfere with Montgomery gland secretion. In extremely dry climates, using ointments sparingly is often necessary.

Some believe gentle traction to the point of discomfort, but not pain, reduces perception of pain in the first week of lactation. A study carefully controlled to eliminate subjective discrepancies of interpretation revealed no significant difference in nipple sensitivity or trauma in those who practiced prenatal nipple rolling, application of breast cream, or expression of colostrum compared with those who had untreated breasts.68 No increased pain or trauma was reported among fair-skinned participants in the study, treated or untreated. Because many women are not inclined to manipulate their breasts before delivery and might be discouraged from breastfeeding if it is implied that this must be done, physicians should prescribe treatment only when an indication exists.186

Early life immune regulation

The prenatal period is instrumental in shaping a child’s immune system (“programming”) influenced by a wide variety of factors elucidated below, including microbiome, nutrition, smoke exposure, and infection, among many others (Figure 1). This window of opportunity is thus critical for a wide range of risk and protective influences discussed in more detail below. Multifaceted effects on early immune programming can occur prenatally that are critical for effects on local tissues and relevant for risk for or protection from immune-mediated diseases, which may occur only several years later. Thus, an efficient interplay between innate and adaptive immune regulation can shape the maturing immune system, keeping it balanced over numerous years during childhood. Any default regulation affecting solely parts of the system or even cells can result in different immune-mediated diseases such as infections, more chronic diseases such as, for example, allergies, autoimmune diseases, or lack of tolerance.

Whereas bidirectional interactions between the fetus and mother seem critical for postnatal immune regulation, human studies on causal effects are complex because of multifaceted influences that are difficult to study at this time of maturation.

In addition to genetic factors such as “immutable footprints”, epigenetics, the environment, and their interactions influence early immune programming, subsequently affecting anatomical structures such as the mucosa and epithelium, and influencing barrier function.

The exact nature underpinning intrauterine modulatory mechanisms may be composed of the following: Although the amniotic fluid has been shown not to be sterile, direct and indirect modulation via fetoplacental transfer may occur. Decidual tissue maternal immune cells including macrophages, CD8+ and γδ-T cells, and large granulated lymphocyte cells are able to induce rejection of paternal histocompatibility antigens. Maternal–fetal tolerance to paternal alloantigens is actively mediated, involving pTregs (peripheral Tregs) distinctly responding to paternal antigens for tolerance induction.11 Generally, maturation of the infant adaptive immune system occurs from the 15th to 20th week of gestation and can be Ag-specific.

Postnatal immune maturation influences are comparable to before birth, with the major difference in the absence of direct maternal environment. Whereas effects on immune programming most likely happen continuously with different thresholds on several types of immune cells, numerous factors induce changes directly in the organs subsequently affected by later disease. For allergic diseases, for example, airway antigen-presenting cells are most likely involved in local damage during airway inflammation and are critical to programming of adaptive T cell responses after migration to the lymph nodes.

Regarding innate priming, children during the first year of life are not present in the airways without an inflammatory trigger.12 During respiratory infection, mature DCs are revealed,13 indicating that local pulmonary inflammation can influence DC maturation followed by T cell activation.

Although early respiratory tract infections (e.g., rhinovirus-induced) are linked to allergic inflammation, this early priming in the airways seems to be specific to the infectious agent.14 Taken together, early childhood exposure to infectious agents affects immune programming, locally and systemically, inducing immune networks and subsequently influencing Tregs and Th2/Th2 cell fate that is important for healthy immune balance. It is still unknown which type of infections in the skin and upper and lower respiratory tract are important for immune programming. Different viruses or bacteria in close interaction with genetic, epigenetic, and environmental factors may influence early immune maturation in distinct ways, either predisposing for disease development or protecting against it.

1 Stress

The prenatal period is an interesting period to study to understand our twin data, since the environmental factors experienced by the twins in utero are hypothetically shared. One of the possible environmental factors that are experienced in utero and can influence both the immune system as well as the brain is prenatally experienced stress. The literature describes that the effect of prenatal stress on the immune system mostly leads to a reduction of immune function (Merlot et al., 2008). However, a few studies report on an exaggeration of inflammatory function after prenatal stress. (Hashimoto et al. (2001) showed that prenatal stress in rats led to an increased fever response to LPS. In addition, Laviola et al. (2004) demonstrated an increase of spleen and brain frontal cortex levels of IL-1β in prenatally stressed rats. Possible mechanisms behind prenatal-stress-induced immune alterations are thought to be (1) a direct influence of maternal hormones and neurotransmitters on the ontogeny of immune cells, (2) an indirect effect via deregulation of the hypothalamic pituitary adrenal (HPA)-axis in the prenatally stressed offspring, and (3) via stress mediator induced change in placental function (Merlot et al., 2008).

With regard to the effect of prenatal stress on the brain, there is increasing evidence suggesting that exposure to prenatal stress is a risk factor for psychopathology. Prenatally stressed rats, for instance, show higher emotional reactivity, higher levels of anxiety, and a depressive-like behavior (Abe et al., 2007). In humans, a low birth weight is considered an index of prenatal stress, and indeed this has also been shown to be a risk factor for later development of mood symptoms (Costello et al., 2007). Also, the amount of stress experienced by the mother during pregnancy was positively correlated to emotional, cognitive, and behavioral problems of the offspring (Van den Bergh et al., 2005). It is suggested that stress exposure at critical time points during fetal development may (1) influence the HPA-axis (Lin et al., 1998), leading to glucocorticoid resistance and hypercortisolism, (2) alter brain development, and (3) change neurotransmitter systems (Abe et al., 2007; Austin et al., 2005; Maccari and Morley-Fletcher, 2007; Van den Bergh et al., 2005). All these events have been implicated in the pathogenesis of mood disorders (Fig. 4).

Stress experienced later in life is able to induce mood symptoms. In rats, it was shown that chronic mild stress experienced during adulthood elicited depressive-like behavior (Willner, 2005). And, in children of bipolar patients, major life events increased the risk to develop a mood disorder (Hillegers et al., 2004). The impact of stress on the immune system in adulthood has also extensively been researched. It is a complex interaction in which the HPA-axis and the sympathetic nervous system play pivotal roles, especially with regards to their neuroendocrine products cortisol and catecholamines. These two main mediators of stress effects can regulate a variety of immune functions such as cytokine and chemokine production, the trafficking of immune cells and their proliferation, differentiation, and effector functions. The final outcome is, although dependent on the quantity and quality of stress and on coping strategies, an increased susceptibility to infection and inflammatory and autoimmune diseases (Leonard, 2006; Padgett and Glaser, 2003).

1.1 Physical and Cognitive Development

The ‘prenatal period’ extends from conception to birth. During the ‘germinal stage’ (fertilization–2 weeks) and ‘embryonic stage’ (2–8 weeks), the fertilized egg rapidly divides and attaches to the uterine wall, the major organs and systems of the body differentiate, and interconnections form between the developing components of the central and peripheral nervous systems. During the fetal stage (8 weeks–birth), the organism grows rapidly and the physical features that identify it as human become increasingly apparent.

During the prenatal period, the mechanisms that will facilitate the organism's adaptation postnatally become functionally mature. Infants born prematurely, for example, who readily learn responses that increase the amount of quiet sleep, reveal this anticipatory maturation. The characteristics of the mother's voice are also learned during the prenatal period. After birth, hungry infants orient and root in the direction of their mother's voice, thereby increasing their efficiency of breast-feeding irrespective of whether the mother is holding them on the left or right. Newborns will also learn to activate a tape-recording of their mother's voice—but not of another woman's voice—by sucking non-nutritively on a modified nipple. Moreover, ‘prenatal learning’ is highly specific: newborns will suck harder to listen to their mother reading a Dr. Seuss passage that she had read aloud daily during the last 6 weeks of gestation than to hear her reading a novel Dr. Seuss passage (DeCasper and Spence 1986). This specificity continues postnatally throughout the first half year. Similar learning pre-natally familiarizes organisms with the linguistic environment into which they eventually will be born.

Cranial Ultrasound

In the prenatal and perinatal period, real-time sonography is currently the most frequently used neuroimaging modality. The various methods of acquiring ultrasound images are discussed in the online chapter.

In newborns, the open anterior fontanel provides an excellent window for the evaluation of the infant brain. Postnatally, sonography is helpful in the evaluation of hypoxic-ischemic encephalopathy, including complications of hemorrhage into the germinal matrix, ventricles, or surrounding parenchyma. For infants younger than 30 weeks' gestation, routine cranial ultrasonography screening should be performed once between 7 and 14 days of age, and should be repeated optimally between 36 and 40 weeks' postmenstrual age to detect lesions such as intraventricular hemorrhage, periventricular leukomalacia, ventriculomegaly, and intrauterine infections. Major migrational anomalies, such as agyria-pachygyria and lissencephaly, or tuberous sclerosis may be delineated; however, smaller heterotopias or other subcortical dysplasias may be overlooked. Sonography can be used to screen for myelodysplasia (see Chapter 19). It can also reveal the presence or absence of cord pulsations, a sign of tethering as well as other dysraphic lesions, such as meningocele, lipoma, hydromyelia, Arnold–Chiari II malformation, diastematomyelia, and lipomyelomeningocele.

Intraoperative sonography is an important modality for the safe and specific guidance of neurosurgical biopsy or lesion resection, for the accurate placement of ventricular shunts, drainage of intraparenchymal fluid collections, localization of brain or cord tumors, drainage of hydrosyringomyelias, delineation of posttraumatic intraspinal bone fragments, and for monitoring resection of arteriovenous malformations.