The fetal placental hypothalamic-pituitary-adrenal (HPA) axis, parturition and post natal health

Glucocorticoid exposure and tissue gene expression of 11beta HSD-1, 11beta HSD-2, and glucocorticoid receptor in a porcine model of differential fetal growth

Glucocorticoids play a critical role in fetal development, but inappropriate exposure is associated with reduced fetal growth. We investigated cortisol exposure and supply in a porcine model of differential fetal growth. This model compares the smallest fetus of a litter with an average-sized sibling at three stages of gestation. At day 45, small fetuses had reduced plasma cortisol (16.8 +/- 3.4 ng/ml) relative to average fetuses (34.4 +/- 3.4 ng/ml, P < 0.001). At day 65 levels had reduced in small and average fetuses to similar concentrations (5.7 +/- 1.0 vs 4.8 +/- 0.5 ng/ml, P = 0.128). By day 100, elevated levels were found in small fetuses (10.7 +/- 1.5 vs 7.6 +/- 0.7 ng/ml, P < 0.001). Maternal plasma cortisol was unchanged over gestation (day 45, 56.7 +/- 21.6 ng/ml; day 65, 57.8 +/- 14.4 ng/ml; day 100, 55.7 +/- 6.5 ng/ml). We examined the cause of altered cortisol by investigating the fetal hypothalamic-pituitary-adrenal axis through the measurement of adrenocorticotropic hormone and assessing exposure to maternal cortisol by quantifying placental 11beta-hydroxysteroid dehydrogenase-isoform 2 (11beta HSD-2) gene expression. These data suggest that altered cortisol supply was of fetal origin. We examined organ glucocorticoid (GC) metabolism by the measurement of GC receptor (GR) and 11beta-hydroxysteroid dehydrogenase-isoform 1 (11beta HSD-1) gene expression. We found that fetal organs have different temporal patterns of 11beta HSD-1 and GR expression, with the liver particularly sensitive to cortisol in late gestation. This study examines GC exposure in naturally occurring differential growth and simultaneously explores tissue GC sensitivity and handling, at three key stages of gestation.

Depression and anxiety during pregnancy: a risk factor for obstetric, fetal and neonatal outcome? A critical review of the literature

OBJECTIVE

Research from the past two decades has suggested a link between prenatal maternal psychological distress and adverse obstetric, fetal and neonatal outcome. Comparability of study results, however, is complicated by a diversity of definitions and measurements of prenatal maternal stress and different time points of assessment. Our aim was to critically review studies assessing maternal anxiety and depression during pregnancy and their impact on obstetric, fetal and neonatal outcome.

METHODS

We carried out a computerized literature search of PubMed, PsycLIT and EMBASE (1990-2005) and a manual search of bibliographies of pertinent articles. In total 35 studies were identified that fulfilled the inclusion criteria.

RESULTS

Elevated levels of depression and anxiety were found to be associated with obstetric outcome (obstetric complications, pregnancy symptoms, preterm labor and pain relief under labor), and had implications for fetal and neonatal well-being and behavior. However, prediction of the impact of mood and anxiety disorders during pregnancy is very limited due to methodological problems. Most notably, the majority of the studies included pregnant women with elevated symptoms of depressed mood and anxiety and did diagnose mood and anxiety disorders. Also, potentially confounding and protecting factors as well as biological mechanisms with a possible role in adverse outcome in pregnant women with depression and anxiety disorders have received little attention.

CONCLUSIONS

Enhanced levels of depression and anxiety symptoms during pregnancy contribute independently of other biomedical risk factors to adverse obstetric, fetal and neonatal outcome. However, conclusions for women with mood or anxiety disorders are limited.

Simultaneously reduced gene expression of cortisol-activating and cortisol-inactivating enzymes in placentas of small-for-gestational-age neonates

OBJECTIVE

The enzyme 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2) converts cortisol into cortisone. Reduced placental activity of 11beta-HSD2 in small-for-gestational-age (SGA) neonates results in fetal cortisol excess. In the present study, we examined the yet unknown gene expression of 11beta-HSD1, which primarily synthesizes cortisol in SGA placenta.

STUDY DESIGN

In placentas taken from 24 women with normal-weight newborns and 16 women with SGA neonates, expression of 11beta-HSD1 and 11beta-HSD2 messenger ribonucleic acid (mRNA) was determined using reverse transcription-polymerase chain reaction.

RESULTS

Placental mRNA expression of 11beta-HSD1 and 11beta-HSD2 was significantly reduced in the SGA group (P = .006 and P < .0001). Both enzymes showed a significant correlation to birthweight SD score and placental weight. Also, levels of both enzymes were significantly correlated.

CONCLUSION

In placental tissue of SGA neonates 11beta-HSD2 and 11beta-HSD1 gene expression is reduced. Adapted levels of 11beta-HSD1 might result in a counterregulatory mechanism limiting transplacental passage of elevated cortisol levels.

Cord blood cortisol level is lower in growth-restricted newborns

AIM

To establish the difference in plasma cortisol concentrations between newborns with intrauterine growth-restricted (IUGR) and appropriate for gestational age (AGA) birthweights.

SUBJECTS AND METHODS

We measured plasma cortisol concentrations in the umbilical venous cord blood of 68 IUGR newborns and 71 AGA birthweight newborns. All newborns were delivered in term, vaginally, in the morning, within 8 hours and had APGAR scores greater or equal to eight.

RESULTS

There was no significant difference between compared groups according to maternal age, parity, gestational age and neonatal gender. Neonatal plasma cortisol levels were significantly lower in the IUGR (median: 312.3 mmol/L, min-max: 158.9-588.1 mmol/L) compared to the AGA group (median: 458.7 mmol/L, min-max: 314.5-718.5 mmol/L) (Mann-Whitney U-test; P<0000). The probability of having a cortisol plasma level greater than or equal to 458.7 mmol/L for IUGR newborns was only 1:12, and to have cortisol plasma level less than or equal to 312.3 mmol/L for AGA newborns was much lower (0:34). In the range of plasma cortisol level between 312.3 mmol/L and 458.7 mmol/L, no statistically significant difference in the plasma cortisol level between IUGR and AGA newborns was found.

CONCLUSIONS

Neonatal plasma cortisol level is lower in the IUGR compared to the AGA group. Our results suggest that endocrine relationships seem to be lost in a specific group of the IUGR newborns. Although we usually tend to simplify the problem and declare only one cause, this time it is impossible. It is probable that the cause is hidden in small and insufficient placenta with deranged auto-regulation of placental 11beta-HSD-2 mechanism.

Prenatal exposure to maternal depression and cortisol influences infant temperament

BACKGROUND

Accumulating evidence indicates that prenatal maternal and fetal processes can have a lasting influence on infant and child development. Results from animal models indicate that prenatal exposure to maternal stress and stress hormones has lasting consequences for development of the offspring. Few prospective studies of human pregnancy have examined the consequences of prenatal exposure to stress and stress hormones.

METHOD

In this study the effects of prenatal maternal psychosocial (anxiety, depression, and perceived stress) and endocrine (cortisol) indicators of stress on infant temperament were examined in a sample of 247 full-term infants. Maternal salivary cortisol and psychological state were evaluated at 18-20, 24-26, and 30-32 weeks of gestation and at 2 months postpartum. Infant temperament was assessed with a measure of negative reactivity (the fear subscale of the Infant Temperament Questionnaire) at 2 months of age.

RESULTS

Elevated maternal cortisol at 30-32 weeks of gestation, but not earlier in pregnancy, was significantly associated with greater maternal report of infant negative reactivity. Prenatal maternal anxiety and depression additionally predicted infant temperament. The associations between maternal cortisol and maternal depression remained after controlling for postnatal maternal psychological state.

CONCLUSIONS

These data suggest that prenatal exposure to maternal stress has consequences for the development of infant temperament.

Effect of maternal dexamethasone and alpha-ketoglutarate administration on skeletal development during the last three weeks of prenatal life in pigs

BACKGROUND

The effect of dexamethasone (Dex) on postnatal bone formation processes is known to decrease the synthesis of collagen and bone matrix, but the effect of alpha-ketoglutarate (AKG) is to induce positive effects on growth and skeletal development during postnatal life. However, the effects of Dex and AKG treatment on the prenatal processes of skeletal development have not been investigated so far.

OBJECTIVE

The aim of this study was to determine the effect of Dex and AKG administered separately or simultaneously to sows during the last three weeks of pregnancy on the skeletal development in fetuses.

METHODS

Immediately after birth blood samples were collected from non-suckling piglets for alkaline phosphatase and osteocalcin determinations, and the humeri were isolated. Bone mineral density (BMD) and bone mineral content (BMC) of humeri and the geometric and mechanical properties were evaluated.

RESULTS

Dex and AKG administered separately to pregnant sows during the last 24 days of prenatal life decreased BMD, BMC, and geometric and mechanical parameters of humeri in the newborns. Simultaneous administration of Dex and AKG significantly increased the analyzed properties of humeri.

CONCLUSION

The bone mineral density and mechanical and geometric properties of humeri indicate an inverse effect of maternal separate or simultaneous administration of AKG and Dex to sows on bone development during the last 24 days of prenatal life.

Cloning of Chicken Glucocorticoid Receptor (GR) and Characterization of its Expression in Pituitary and Extrapituitary Tissues

Substantial evidence suggests that glucocorticoids play critical roles in the differentiation of somatotroph and lactotroph in embryonic pituitaries of birds. However, the basic information on the expression of glucocorticoid receptor (GR) in avian species is limited. In this study, the full-length cDNA for chicken GR was cloned from the chicken kidney. It encodes 772 amino acids and shares high homology with that of the human (73%), mouse (73%), rat (71%), rabbit (72%), and trout (51%) sequences. Similar to mammals, chicken GR is widely expressed in all adult tissues being investigated. Among the 12 tissues investigated, relatively high expression of GR was detected in pituitary, muscle, ovary, and kidney using reverse transcription-PCR assay. Using semiquantitative reverse transcription-PCR, GR is shown to be abundantly expressed at a more or less constant level during embryonic pituitary development (from d 8 to 20), supporting the hypothesis that the expression of GR is unlikely to be a limiting factor in initiating the differentiation of somatotroph and lactotroph in embryonic pituitary of birds. Moreover, an abundant expression of GR in the whole embryos at earlier developmental stages (from d 2 to 5) was also detected in the present study, though its physiological relevance remains to be determined.

Large maternal weight loss from obesity surgery prevents transmission of obesity to children who were followed for 2 to 18 years

OBJECTIVE

Our aim was to compare the prevalence of obesity in 172 children who were aged 2 to 18 years and born to 113 obese mothers (BMI: 31 +/- 9 kg/m2) with substantial weight loss after biliopancreatic bypass surgery with 45 same-age siblings who were born before maternal surgery (mothers' BMI: 48 +/- 8 kg/m2) and with current population standards.

METHODS

In this case series, with >88% follow-up in a tertiary referral center, cross sectional office chart and telephone data on childhood and adolescent weights were transformed to z scores.

RESULTS

After maternal surgery, the prevalence of obesity in the offspring decreased by 52% and severe obesity by 45.1%, with no increase in the prevalence of underweight. The z score reduction in obesity was gender specific, with boys reducing from 1.4 +/- 1.3 before to 0.57 +/- 1.7 after maternal surgery, corrected for birth order. The difference was not significant in girls (0.8 +/- 1.3 vs 0.8 +/- 1.2). Among children of both genders who were aged 6 to 18 years of age and born after maternal surgery, the prevalence of overweight was reduced to population levels.

CONCLUSIONS

Contrary to outcomes after intrauterine under- and overnutrition, the prevalence of overweight and obesity in children of mothers with large voluntary postsurgical weight loss was similar to that in the general population, with no increase in underweight. The results demonstrate the importance of potentially modifiable epigenetic factors in the cause of obesity.

Changes in ovine maternal temperature, and serum cortisol and interleukin-6 concentrations after challenge with Escherichia coli lipopolysaccharide during pregnancy and early lactation

Major changes in maternal physiology during pregnancy and lactation can have a large impact on the immune and neuroendocrine systems. One of the most significant changes, observed in rats and mice, is hyporesponsiveness of the hypothalamic pituitary adrenal axis (HPAA) in response to inflammation, restraint, and other psychological stressors during late pregnancy and lactation. This attenuation, however, has not been well characterized in ruminant animals and may be relevant to their susceptibility to inflammatory diseases during these periods. Thus, the intent of this study was to characterize responsiveness of the ovine HPAA to inflammatory challenge during pregnancy and lactation. Ewes from early (33 d), middle (55 d), and late (138 d) pregnancy, as well as early lactation (10 d), were challenged i.v. with a bolus dose of 400 ng of Escherichia coli lipopolysaccharide (LPS)/kg of BW or saline. A corresponding group of nonpregnant ewes was also challenged with LPS to serve as positive control animals for each pregnancy and lactation study. Responsiveness of the HPAA was assessed by measuring the 4-h change in serum cortisol concentration after LPS challenge. The cortisol increase after LPS challenge was elevated (P < 0.01) in pregnant ewes during late pregnancy over that of nonpregnant animals. In contrast, the characteristic temperature response associated with systemic LPS challenge was decreased (P < 0.01) during early pregnancy and lactation compared with nonpregnant or nonlactating animals. Serum IL-6 concentrations were measured to assess whether changes in HPAA responsiveness during pregnancy or lactation were attributed to changes in proinflammatory signaling to the HPAA. Interestingly, enhanced cortisol responsiveness during late pregnancy was correlated with increased (P < 0.01) serum IL-6 concentrations, indicating that IL-6 may contribute to enhanced HPAA responsiveness during this period. Serum IL-6 concentrations during early and midpregnancy did not increase in response to LPS challenge, indicating that HPAA activation during periods of pregnancy may be independent of IL-6 production.

Cortisol stimulates system A amino acid transport and SNAT2 expression in a human placental cell line (BeWo)

Both placental system A activity and fetal plasma cortisol concentrations are associated with intrauterine growth retardation, but it is not known if these factors are mechanistically related. Previous functional studies using hepatoma cells and fibroblasts produced conflicting results regarding the regulation of system A by cortisol. Using the b30 BeWo choriocarcinoma cell line, we investigated the regulation of system A by cortisol. System A function was analyzed using methyl amino isobutyric acid (MeAIB) transcellular transport studies. Transporter expression [system A transporter (SNAT)1/2] was studied at the mRNA and protein levels using Northern and Western blotting, respectively. Localization was carried out using immunocytochemistry. The [(14)C]MeAIB transfer rate across BeWo monolayers after preincubation with cortisol for 24 h was significantly increased compared with control. This was associated with a relocalization of the SNAT2 transporter at lower cortisol levels and significant upregulation of mRNA and protein expression levels at cortisol levels >1 microM. This is the first study to show functional and molecular regulation of system A by cortisol in BeWo cells. It is also the first study to identify which system A isoform is regulated. These results suggest that cortisol may be involved in upregulation of system A in the placenta to ensure sufficient amino acid supply to the developing fetus.

Fetal fornix transection and gestation length in sheep

Experiments in several species indicate that the hippocampus influences hypothalamo-pituitary-adrenal (HPA) axis function. In fetal sheep, simultaneous ACTH and cortisol rises over the last 30 days of gestation peak at term and are necessary for birth. We hypothesized that if the fetal hippocampal formation is functional in late gestation, loss of hippocampal input to the HPA axis following fetal fornix transection would change gestation length in comparison to controls. At 118-121 days of gestation (dG), stereotaxic technique was used in fetal sheep to sham transect (SHAM; n = 8) or transect (FXTX; n = 6) the dorsal fornix at the level of the hippocampal commissure. No differences were found between SHAM and FXTX fetuses in daily hormone profiles over the last week of gestation or in gestation length (148.0 +/- 1.2 vs. 149.0 +/- 0.4 dG, respectively). We conclude that the fetal hippocampus is immature in late gestation and we speculate that an immature hippocampus is necessary for the loss of negative feedback control that gives rise to the long term, simultaneous increases in ACTH and cortisol that are indispensable for labor and delivery at term in sheep.

Urocortin 2 and urocortin 3 are expressed by the human placenta, deciduas, and fetal membranes

OBJECTIVE

Urocortin 2 (UCN2) and urocortin 3 (UCN 3) are recently identified neuropeptides showing homology to corticotropin-releasing factor (CRF). In the present study, we evaluated their expression and localization in gestational tissues (placenta, decidua, fetal membranes), and their effect on placental adrenocorticotropic hormone secretion.

STUDY DESIGN

The study was performed in a tertiary clinical care center. Tissues were obtained at first (n = 8; 8-11 weeks of pregnancy) and third (n = 8; 38-40 gestational weeks) trimester. The mRNA expression was evaluated by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR); the cellular localization by immunohistochemistry; ACTH levels were measured in media collected from cultured placental villi.

RESULTS

All tissues analyzed expressed UCN2 and UCN3 mRNA. UCN2 and UCN3 were localized in cytotrophoblast and syncytiotrophoblast cells; UCN2 was present in maternal and fetal vessels and in amniotic cells, while UCN3 was absent. Finally, UCN2 and UCN3 did not stimulate ACTH secretion.

CONCLUSION

Gestational tissues differentially express UCN2 and UCN3 and, despite their homology to CRF, they did not stimulate placental ACTH secretion.

Corticosterone transfer and metabolism in the dually perfused rat placenta: effect of 11beta-hydroxysteroid dehydrogenase type 2

Although rat is the most widely used model of glucocorticoid programming of the fetus, the role of rat placental 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2) in the transplacental pharmacokinetics of the naturally occurring glucocorticoid, corticosterone, has not yet been fully elucidated. In this study, expression of 11beta-HSD2 in the rat placenta on two different gestation days (16 and 22) was examined using quantitative RT-PCR and Western blotting, and dually perfused rat term placenta was employed to evaluate its functional capacity to transfer and metabolize corticosterone. Marked decrease in placental expression of 11beta-HSD2 toward term was observed on both mRNA and protein levels. In perfusion studies, increasing maternal corticosterone concentration from 3 to 200 nM resulted in the fall of 11beta-HSD2 conversion capacity from 64.3 to 16.3%, respectively. Enzyme saturation occurred at about 50 nM substrate concentration. When delivering corticosterone (3 or 100 nM) from the fetal side, a similar decline of 11beta-HSD2 conversion capacity was observed (66.5% and 48.5%, respectively). Addition of carbenoxolone (10 or 100 microM), a non-specific 11beta-HSD inhibitor, to maternal perfusate decreased conversion capacity from 66.7 to 12.6 or 8.1%, respectively. Similarly potent inhibitory effect was observed in feto-maternal studies. Neither saturation nor inhibition of 11beta-HSD2 was associated with transformation of corticosterone in metabolites other than 11-dehydrocorticosterone. These data suggest that 11beta-HSD2 is the principal enzyme controlling transplacental passage of corticosterone in rats and is able to eliminate corticosterone in both maternal and fetal circulations.

Proinflammatory cytokines inhibit human placental 11beta-hydroxysteroid dehydrogenase type 2 activity through Ca2+ and cAMP pathways

Excessive fetal exposure to glucocorticoids has been implicated in the etiology of adult metabolic and cardiovascular disease. Placental 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2) may protect the fetus from excessive glucocorticoid exposure. Maternal stress may be accompanied by elevated levels of cortisol and increased proinflammatory cytokines [interleukin (IL)-1beta, IL-6, and tumor necrosis factor-alpha (TNF-alpha)]. We hypothesize that proinflammatory cytokines inhibit human placental 11beta-HSD activity. We incubated explant cultures of term human placental villi in the presence or absence of 10 ng/ml IL-1beta, IL-6, or TNF-alpha, with or without agonists or antagonists of intracellular Ca2+ and adenylyl cyclase. Activity for 11beta-HSD2 was estimated using a radioisotope assay, and mRNA was measured using quantitative RT-PCR. All cytokines significantly (P < or = 0.05) reduced 11beta-HSD2 activity (>75% suppression); maximal inhibition occurred within 2 h and was maintained for at least 24 h. The IL-1beta-induced inhibitory activity was attenuated using a Ca2+ channel blocker (nifedipine), an intracellular Ca2+ antagonist [8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate], or the adenylyl cyclase stimulant forskolin. Conversely, 11beta-HSD2 activity was diminished in the presence of the Ca2+ ionophore A-23187 or the adenylyl cyclase inhibitor SQ-22536. mRNA levels for 11beta-HSD2 were not changed by any of the treatments. Proinflammatory cytokines inhibit human placental 11beta-HSD2 activity through a mechanism that involves increased intracellular Ca2+ and inhibition of adenylyl cyclase. This could result in excessive fetal exposure to maternal cortisol. This mechanism might mediate part of the increased risk of metabolic and cardiovascular disease in adult offspring.

Chronic fetal hypoxia increases activin A concentrations in the late-pregnant sheep

OBJECTIVE

To determine whether activin A concentrations are altered in chronic fetal hypoxemia and intrauterine fetal growth restriction (IUGR).

DESIGN

In vivo animal experimental model.

SETTING

Department of Physiology, Monash University.

POPULATION

Chronically catherised fetal sheep in late pregnancy.

METHODS

Chronic fetal hypoxia and IUGR were experimentally induced by single umbilical artery ligation (SUAL) in catheterised fetal sheep. Maternal and fetal blood samples and amniotic fluid (AF) samples were collected during surgery and thereafter on alternate days, until the time of delivery for analyte measurement. Fetal blood gas parameters were measured daily.

MAIN OUTCOME MEASURES

Plasma and AF was used to analyse activin A, prostaglandin E2 (PGE2) and cortisol and fetal blood gas analysis was undertaken in whole blood.

RESULTS

SUAL produced asymmetric IUGR and non-acidaemic chronic fetal hypoxia and resulted in preterm labour (129 [3] days). AF activin A concentrations were 10-fold higher in the SUAL group than in controls whereas levels in the fetal and maternal circulations were similar between groups.

CONCLUSIONS

SUAL-induced IUGR and fetal hypoxaemia increases AF activin A. This may be an important adaptive or protective response to IUGR.

Endocrine and metabolic programming during intrauterine development

In humans, low birth weight is associated with an increased risk of metabolic dysfunction in adult life. Many of these metabolic disorders have an endocrine origin and are accompanied by abnormal hormone concentrations. This has led to the hypothesis that adult metabolic disease arises in utero as a result of programming of key endocrine systems during suboptimal intrauterine conditions associated with fetal growth retardation. This review examines the experimental evidence for prenatal endocrine programming with particular emphasis on endocrine axes involved in growth and metabolism, namely, the hypothalamic-pituitary-adrenal axis, the endocrine pancreas and the somatotrophic axis. It also considers how changes in these endocrine systems contribute to the programming of metabolism in later life.

Stress and salivary cortisol during pregnancy

The purpose of this study was to determine whether exposure to stressful life events was associated with changes in levels of circulating cortisol during pregnancy in a population of 603 pregnant women. The participating pregnant women filled out a questionnaire and collected a morning and evening sample of saliva in early pregnancy (median 14th gestational week) and in late pregnancy (median and 30th gestational week). They were asked to report the number of life events experienced during first and second trimester, respectively, and were asked to rate the intensity of the experienced events. Complications related to the pregnancy such as vaginal bleeding and suspected growth retardation were registered and the women were asked about concerns about their pregnancy. The salivary samples were analyzed for cortisol and the levels were higher in late than in early pregnancy. In late pregnancy women exposed to more than one life event or were concerned about pregnancy complications during second trimester had a higher evening cortisol level, whereas morning values were unaffected. After adjustment for smoking women who experienced more than one very stressful life event had 27% higher evening cortisol concentrations (95% confidence intervals: 1-59%). Women with worries about pregnancy complications had 27% (95% confidence intervals: 2-57%) higher levels. In early pregnancy women reporting stressful life events did not have higher evening cortisol levels, but tended to have a blunted morning HPA response. In conclusion, we found differences in the associations between chronic stress in early and late pregnancy and cortisol levels indicating that the response to chronic stress is dependent on the stage of the pregnancy.

Maturity of the Neonatal Foal

The immature foal frequently represents a significant management challenge to even the most experienced clinician. The clinical course typically involves complications to a range of body systems,including the musculoskeletal, respiratory, and gastrointestinal systems. Before the commencement of treatment, it is important to provide the owner with an estimation of short-term and long-term survival, expected costs, and possible complications. Formulation of an accurate prognosis can be a difficult task but is aided by knowledge not only of normal maturation but of the factors that affect this process.

Antenatal maternal anxiety and stress and the neurobehavioural development of the fetus and child: links and possible mechanisms. A review

A direct link between antenatal maternal mood and fetal behaviour, as observed by ultrasound from 27 to 28 weeks of gestation onwards, is well established. Moreover, 14 independent prospective studies have shown a link between antenatal maternal anxiety/stress and cognitive, behavioural, and emotional problems in the child. This link generally persisted after controlling for post-natal maternal mood and other relevant confounders in the pre- and post-natal periods. Although some inconsistencies remain, the results in general support a fetal programming hypothesis. Several gestational ages have been reported to be vulnerable to the long-term effects of antenatal anxiety/stress and different mechanisms are likely to operate at different stages. Possible underlying mechanisms are just starting to be explored. Cortisol appears to cross the placenta and thus may affect the fetus and disturb ongoing developmental processes. The development of the HPA-axis, limbic system, and the prefrontal cortex are likely to be affected by antenatal maternal stress and anxiety. The magnitude of the long-term effects of antenatal maternal anxiety/stress on the child is substantial. Programs to reduce maternal stress in pregnancy are therefore warranted.

Morning cortisol does not mediate the association of size at birth with blood pressure in children born from full-term pregnancies

OBJECTIVE

It had been suggested that programming of the hypothalamo-pituitary-adrenal axis may underlie the associations of reduced size at birth with raised blood pressure in later life. We investigated whether morning salivary cortisol mediates the inverse association of birthweight with systolic blood pressure in children.

DESIGN

Subjects and measurements--a historical cohort study involving 1152 Swedish children aged 5-14 years, who took part in a family study comprised of mother, father, and two full-sibs delivered in 1987-1995 after 38-41 weeks gestation within 36 months of each other. Birthweight and gestational age were available from obstetric records. Blood pressure, weight, height and puberty stage were measured at a clinic. Cortisol was measured by radioimmunoassay in morning salivary samples taken at home, within 30 min of waking.

RESULTS

Morning cortisol showed a weak negative association with length of gestation in siblings, was not related to birthweight or to systolic or diastolic blood pressure. There was no change in the strength of the negative association between birthweight and systolic blood pressure on adjustment for cortisol (-1.4 mmHg/kg, 95% CI -2.7, -0.2; adjusted for age, sex, puberty stage, weight and height, and cortisol).

CONCLUSIONS

Morning cortisol was not associated with size at birth, and did not mediate the birthweight-blood pressure association in children born from full-term pregnancies. It is possible that basal cortisol levels are of more importance in explaining associations of size at birth with later blood pressure in older subjects, or in populations with more varied length of gestation. Alternatively, our results may be caused by misclassification of the hypothalamo-pituitary-adrenal activity.

Ancient origins of human developmental plasticity

Animals have the ability to alter development, physiology, growth, and behavior in response to different environmental conditions. These responses represent critical assessments of both external and internal factors. For example, the timing of metamorphosis, hatching, or birth depends on the trade-offs between growth opportunity and mortality risk in the developmental habitat. Physiological sensors compute these trade-offs as a function of energy balance and environmental stress, and effectors initiate physiological, developmental, and behavioral responses to these determinations. The neuroendocrine stress axis provides a means for animals to integrate information from multiple sources and to respond accordingly. Considerable evidence now supports the view that the secretion of hormones critical to development (corticosteroid and thyroid hormones) is controlled by a common neuroendocrine stress pathway involving corticotropin-releasing factor (CRF) and related peptides. CRF produced in the hypothalamus stimulates the biosynthesis and secretion of both thyroid and corticosteroid hormones, leading to accelerated tadpole metamorphosis. Similarly, in mammals CRF of fetal and placental origin has been shown to influence the timing of birth. Studies in several experimental animal models and in humans show that early life experience can have long-term phenotypic consequences. Furthermore, there is evidence that phenotypic expression is strongly influenced by the actions of stress hormones produced during development. The integrated neuroendocrine response to stress, and its role in timing critical life history transitions and establishing long-term phenotypic expression, arose early in the evolution of vertebrates.

Maternal stress and fetal responses: evolutionary perspectives on preterm delivery

New epidemiological and neurohormonal evidence provides insights into the persistent public health issue of preterm delivery and its long-term health consequences for the newborn. Mechanisms linked to preterm delivery may originate early in gestation as a result of maternal cues signaling a stressful intrauterine environment. When these signals are present, the fetus responds with a series of facultative responses, including accelerated organ maturation. If these responses are unsuccessful and the environment remains insufficient, a series of feed-forward mechanisms initiate the hormonal cascade that leads to parturition, and thus, early expulsion from a stressful environment. The internal environmental cues are delivered via glucocorticoids (stress hormones) in the circulatory system, but fetal responses and the initiation of the final terminal pathway to parturition are regulated by placentally derived corticotropin-releasing hormone (CRH). The potential costs of early expulsion from a stressful intrauterine environment are high and include an increased likelihood of perinatal and infant mortality. Permanent alterations in organ and metabolic functioning may occur, suggesting considerable fitness trade-offs. There is some evidence that preterm parturition is a maternal adaptation to limit the energetic costs of individual pregnancies in the face of poor condition at the time of conception. Moreover, nutritional stress is not the only indicator that signals a stressful environment: maternal psychosocial stress, and thus her response to an assessment of the social environment, also signal an insufficient internal environment to the fetus. The epidemiological and neurohormonal evidence for these relationships and mechanisms responsible for regulating such delicate negotiations are explored. In turn, the implications of such findings are examined from life history and public health perspectives.

Gestational programming: population survival effects of drought and famine during pregnancy

The process whereby a stimulus or stress at a critical or sensitive period of development has long-term effects is termed "programming." Studies in humans and animals convincingly demonstrate that environmental perturbations in utero may permanently change organ structure and metabolism and/or alter homeostatic regulatory mechanisms among the offspring. These programmed changes may be the origins of adult diseases, including cardiovascular disease, obesity, and diabetes. Throughout evolution and development, humans and animals have been exposed to two common environmental stresses, drought and famine. Notably, drought-induced water deprivation is associated with dehydration anorexia and thus a concomitant potential nutrient stress. Our laboratory has performed studies among pregnant rat and sheep in which we simulate drought conditions via maternal dehydration and famine conditions via nutrient restriction. Maternal dehydration results in low-birth-weight offspring, which demonstrate gender-specific plasma hypernatremia and hypertonicity and arterial hypertension. Gestational nutrient restriction also resulted in low-birth-weight offspring. If permitted rapid catch-up growth by nutrient availability, these offspring demonstrate evidence of increased body weight and body fat, and leptin resistance as adults. Conversely, if the catch-up growth is delayed by nutrition restriction, the offspring exhibit normal body weight, body fat, and plasma leptin levels as adults. These studies indicate that osmoregulatory and cardiovascular homeostasis and phenotypic predisposition to obesity may be programmed in utero. Importantly, these results suggest that programming effects may be either potentiated or prevented by interventions during the neonatal period.

Effects of butylated hydroxyanisole on the development and functions of reproductive system in rats

Butylated hydroxyanisol (BHA) is a widely used antioxidant for long preservation of food products, cosmetics and pharmaceuticals. Although BHA is generally recognized as safe, it is classified as a suspected endocrine-disrupting compound. We investigated the effects of BHA on reproductive function and development by the treatment of mature male and female SD rats (F0) through pre-gestation, gestation and lactation period and of their offspring (F1) until 13 weeks old via gavage with BHA 0 (corn oil, vehicle control), 10, 100 and 500 mg/kg bw/day. Organ weights of liver, adrenal gland and thyroid gland of F0 rats were increased by BHA 500 mg/kg but those of spleen and ventral prostate were decreased without significant difference in terminal body weight. Reduced serum testosterone and thyroxine (T4) were observed with dose-dependent manner in F0 male rats. Mating rate was decreased and cohabitation duration for conception was longer without differences in the number, motility and morphology of sperm by BHA 500 mg/kg. Body weight of F1 offspring was significantly decreased with change of relative weight of liver and brain by BHA 500 mg/kg at PND21. Sexual maturation indicated by vaginal opening and preputial separation was delayed by BHA 500 mg/kg. The weights of liver and adrenal gland were increased while those of spleen, vagina, testes and ventral prostate were decreased in F1 rats exposed to BHA 100 or 500 mg/kg for 13 weeks. Also, BHA 500 mg/kg reduced the velocity of sperm motion and number with smaller-sized sperm head in F1 male rats and slightly shortened estrous cycle length with higher frequency of estrus and lower frequency of diestrus stages in F1 female rats. Lower serum T4 and testosterone contents with higher serum cholesterol levels were also observed by BHA 500 mg/kg. Increased follicular cell height, and exfoliated and vacuolated follicular epithelial cells were observed in thyroids of F1 female and males rats exposed to BHA 500 mg/kg. This study elucidates that high dose of BHA induce weak dysfunction and underdevelopment of reproductive system of male and female rats with the change of T4 and testosterone levels, sex organ weights and sexual maturation and histological lesions of thyroid gland.

Effects of cortisol on cardiac myocytes and on expression of cardiac genes in fetal sheep

In 17 fetal sheep aged 129 days, the effects of large-dose infusions of cortisol (72.1 mg/day for 2–3 days) on proliferation, binucleation, and hypertrophy of cardiac myocytes, cardiac expression of angiotensinogen, angiotensin receptor subtypes 1 and 2, Glut-1, glucocorticoid and mineralocorticoid receptors, proteins of the MAPK pathways and calcineurin were studied. Cortisol levels were 8.7 ± 2.3 nM (SE) in 8 control and 1,028 ± 189 nM in 9 treated fetuses ( P < 0.001). Cortisol had no effect on myocyte binucleation. Left ventricular free wall (LVFW) uni- and binucleated myocytes were larger in cortisol-treated fetuses ( P < 0.001, P < 0.05). Cortisol-treated fetuses had higher right ventricular free wall (RVFW) and LVFW angiotensinogen (Aogen) mRNA levels (treated: 2.30 ± 0.37, n = 8 and 2.05 ± 0.45, n = 7 vs. control: 0.94 ± 0.12, n = 8 and 0.67 ± 0.09, n = 7, P < 0.02). Levels of the glucose transporter Glut-1 mRNA were lower in the LVFW of treated fetuses (0.83 ± 0.23 vs. 1.47 ± 0.30 in control, P < 0.05, n = 7, 8). The higher the cortisol level, the greater the Aogen mRNA level (RVFW, r = 0.61, P < 0.01, n = 16; LVFW, r = 0.83, P < 0.0003, n = 14). There were no other changes in mRNA levels nor in levels of extracellular kinase, JNK, p38, their phosphorylated forms, and calcineurin. Thus high levels of cortisol such as occur after birth do not affect fetal cardiac myocyte binucleation or number but are associated with higher levels of ventricular Aogen mRNA, lower levels of Glut-1 mRNA, and hypertrophy of LVFW myocytes. These effects could impact on postnatal cardiac development.

Temporal profiling of the transcriptional basis for the development of corticosteroid-induced insulin resistance in rat muscle

Elevated systemic levels of glucocorticoids are causally related to peripheral insulin resistance. The pharmacological use of synthetic glucocorticoids (corticosteroids) often results in insulin resistance/type II diabetes. Skeletal muscle is responsible for close to 80% of the insulin-induced systemic disposal of glucose and is a major target for glucocorticoid-induced insulin resistance. We used Affymetrix gene chips to profile the dynamic changes in mRNA expression in rat skeletal muscle in response to a single bolus dose of the synthetic glucocorticoid methyl-prednisolone. Temporal expression profiles (analyzed on individual chips) were obtained from tissues of 48 drug-treated animals encompassing 16 time points over 72 h following drug administration along with four vehicle-treated controls. Data mining identified 653 regulated probe sets out of 8799 present on the chip. Of these 653 probe sets we identified 29, which represented 22 gene transcripts, that were associated with the development of insulin resistance. These 29 probe sets were regulated in three fundamental temporal patterns. 16 probe sets coding for 12 different genes had a profile of enhanced expression. 10 probe sets coding for eight different genes showed decreased expression and three probe sets coding for two genes showed biphasic temporal signatures. These transcripts were grouped into four general functional categories: signal transduction, transcription regulation, carbohydrate/fat metabolism, and regulation of blood flow to the muscle. The results demonstrate the polygenic nature of transcriptional changes associated with insulin resistance that can provide a temporal scaffolding for translational and post-translational data as they become available.

Placental corticotropin-releasing hormone (CRH), spontaneous preterm birth, and fetal growth restriction: a prospective investigation

OBJECTIVES

Recent advances in the physiology of human pregnancy have implicated placental corticotropin-releasing hormone (CRH) as one of the primary endocrine mediators of parturition and possibly also of fetal development. The aim of this study was (1) to prospectively assess the relationship of maternal plasma concentrations of CRH in the early third trimester of gestation with two prematurity-related outcomes-spontaneous preterm birth (PTB), and small-for-gestational age birth (SGA), and (2) to determine whether the effects of CRH on each of these outcomes are independent from those of other established obstetric risk factors.

STUDY DESIGN

In a sample of 232 women with a singleton, intrauterine pregnancy, maternal plasma was collected at 33 weeks' gestation and CRH concentrations were determined by radioimmunoassay. Each pregnancy was dated on the basis of last menstrual period and early ultrasonography. Parity, obstetric risk conditions for prematurity, mode of delivery, and birth outcomes were abstracted from the medical record.

RESULTS

After adjusting for the effects of established obstetric risk factors, elevated CRH levels at 33 weeks' gestation were significantly associated with a 3.3-fold increase in the adjusted relative risk (RR) for spontaneous preterm birth and with a 3.6-fold increase in the adjusted relative risk for fetal growth restriction. Women who delivered postterm had significantly lower CRH levels in the early third trimester than those who delivered at term. When outcomes were stratified by gestational length and birth weight, the lowest CRH levels at 33 weeks' gestation were associated with the term non-SGA births, intermediate and approximately equal CRH levels were associated with the preterm non-SGA and term SGA births, and the highest CRH levels were associated with the preterm SGA births.

CONCLUSION

For deliveries occurring after 33 weeks' gestation (the time of CRH sampling in this study), our findings support the notion that in humans placental CRH may play an impending, direct role in not only the physiology of parturition but also in processes related to fetal growth and maturation. Our results also support the notion that the timing of onset of parturition may be determined or influenced by events occurring earlier in gestation rather than those close to the time of actual onset of labor (ie, the notion of a "placental clock").

Prematurity and intrauterine growth retardation--double jeopardy?

Premature infants born with IUGR are at a several-fold increased risk for mortality and major neonatal morbidities, including RDS, BPD, ROP, and NEC. These severe complications of prematurity are intensified by the effect of suboptimal fetal growth. The possible pathophysiologic processes initiated in utero and continuing after birth have been discussed. Recently reported data suggest that IUGR is a risk factor in programming for the later development of cardiovascular diseases, hypertension, and diabetes mellitus in adult life. Experimental research related to the pathophysiology and etiology of these conditions may enable appropriate intervention directed at reducing the excess risk associated with the short- and long-term mortality and morbidity among premature SGA infants.

Prenatal and postnatal steroid therapy and child neurodevelopment

In recent years, scientific evidence has accumulated on the potential neuro-toxic effects of perinatal steroid therapy on the incompletely developed brain; therefore, much effort has been directed toward finding the optimal regimen that may reduce lung disease without incurring significant brain injury in fetuses and preterm infants. Current recommendations of the NIH endorse a single course of prenatal steroids in cases of imminent preterm delivery. Postnatal steroid therapy should be limited, according to the American Association of Pediatrics Guide-lines, to selected clinical cases after the first week of life. These cautions aim to decrease possible harmful effects that could affect short- and long-term neuro-developmental outcome in this high-risk population.

Endocrine mechanisms of intrauterine programming

Epidemiological findings and experimental studies in animals have shown that individual tissues and whole organ systems can be programmed in utero during critical periods of development with adverse consequences for their function in later life. Detailed morphometric analyses of the data have shown that certain patterns of intrauterine growth, particularly growth retardation, can be related to specific postnatal outcomes. Since hormones regulate fetal growth and the development of individual fetal tissues, they have a central role in intrauterine programming. Hormones such as insulin, insulin-like growth factors, thyroxine and the glucocorticoids act as nutritional and maturational signals and adapt fetal development to prevailing intrauterine conditions, thereby maximizing the chances of survival both in utero and at birth. However, these adaptations may have long-term sequelae. Of the hormones known to control fetal development, it is the glucocorticoids that are most likely to cause tissue programming in utero. They are growth inhibitory and affect the development of all the tissues and organ systems most at risk of postnatal pathophysiology when fetal growth is impaired. Their concentrations in utero are also elevated by all the nutritional and other challenges known to have programming effects. Glucocorticoids act at cellular and molecular levels to alter cell function by changing the expression of receptors, enzymes, ion channels and transporters. They also alter various growth factors, cytoarchitectural proteins, binding proteins and components of the intracellular signalling pathways. Glucocorticoids act, directly, on genes and, indirectly, through changes in the bioavailability of other hormones. These glucocorticoid-induced endocrine changes may be transient or persist into postnatal life with consequences for tissue growth and development both before and after birth. In the long term, prenatal glucocorticoid exposure can permanently reset endocrine systems, such as the somatotrophic and hypothalamic-pituitary-adrenal axes, which, in turn, may contribute to the pathogenesis of adult disease. Endocrine changes may, therefore, be both the cause and the consequence of intrauterine programming.

ACTH-producing cells of 21-day-old rat fetuses after maternal dexamethasone exposure

Adrenocorticotrophic hormone (ACTH) is essential for developmental maturation of numerous organ systems during the fetal period and for adaptation to environmental challenges. Immunocytochemical and stereological methods were used in the present study to examine the effects of dexamethasone (Dx) administration during pregnancy on fetal rat pituitary ACTH-producing cells. Doses of 0.5, 0.5 and 1.0 mg Dx/kg body weight/day were given to the dams on 3 consecutive days starting on day 16 of gestation. Morphometric analysis of the ACTH-producing cells of fetuses at 21 days of gestation revealed significant inhibition by 24% and 27%, respectively, of cell volume and cell number after maternal Dx administration, whereas the volume of cell nuclei and volume density of ACTH-stained cells were insignificantly decreased. Immunocytochemical analysis showed reduced numbers, sizes and immunopositivity of ACTH cells of 21-day-old fetuses from Dx-treated dams as compared with the control group. Maternal Dx treatment in the period of intense differentiation of the hypothalamo-hypophyseal-adrenal system had an inhibitory effect on fetal function and proliferative activity of ACTH-producing cells at 21 days of gestation. Thus, inhibition of activity of fetal ACTH-producing cells may lead to adrenal suppression, modified activity of the hypothalamo-pituitary-adrenal axis and reduced body weight possibly causing lasting functional abnormalities.

Effects of three courses of maternally administered dexamethasone at 0.7, 0.75, and 0.8 of gestation on prenatal and postnatal growth in sheep

OBJECTIVES

To evaluate the effects of repeated low doses of maternally administered dexamethasone (DM) on growth in sheep during fetal life and the first 2 years of postnatal life.

METHODS

Ewes received 3 courses of DM (1 course: four 2-mg intramuscular injections at 12-hour intervals) or saline beginning at 103, 110, and 117 days of gestation (dGA). At 119 dGA, fetal BW and organ weight were recorded. Total placentome number, weight, and morphologic distributions were recorded. Placentome glucocorticoid receptor expression was determined by immunocytochemistry. Newborn BW and organ weight were recorded within 12 hours of birth. Duration of gestation was recorded. Measurements were collected on body weight (BW), biparietal diameter (BPD), crown-to-rump length, thoracic girth circumference, abdominal girth circumference, and radial bone length for 2 months. Maternal estradiol and progesterone levels were measured daily from 135 dGA.

RESULTS

At 119 dGA, DM significantly decreased BW. Placentome glucocorticoid receptor expression increased after DM exposure. DM did not significantly decrease BW at birth but did prolong gestation length. DM decreased maternal estradiol before lambing. DM decreased newborn brain weight and BPD. After 2 weeks of age, no effect of DM on postnatal growth could be found.

CONCLUSIONS

This study shows that repeated maternal DM treatment at doses threefold lower than what women in preterm labor receive results in decreased fetal BW, prolonged gestation length, decreased newborn brain weight, and BPD.

Thyroid hormone, glucocorticoids, and prolactin at the nexus of physiology, reproduction, and toxicology

A symposium at the 2003 Annual Meeting of the Society of Toxicology brought together an expert group of endocrinologists to review how non-reproductive hormones can affect the endocrine system. This publication captures the essence of those presentations. Paul Cooke and Denise Holsberger recapitulate the evidence of how thyroid hormones affect male and female reproduction, and reproductive development. Ray Witorsch summarizes the many effects of glucocorticoids on the reproductive system. Finally, Paul Sylvester reviews the mechanism of action of prolactin, and reminds us that this ancient hormone has many functions beyond lactation.

Long-term hypoxia changes myometrial responsiveness and oxytocin receptors in the pregnant ewe: differential effects on longitudinal versus circular smooth muscle

Previous studies from our laboratory demonstrated that long-term hypoxia (LTH) altered in vitro contractile responses to oxytocin in full-thickness myometrial strips from pregnant sheep. The present study was designed to determine, first, if the reduced contractile response to oxytocin following LTH is the result of combined effects on longitudinal and circular smooth muscle or if the effect is specific to a single muscle layer and, second, if the reduced contractile response to oxytocin following LTH is caused by changes in oxytocin-receptor protein. Pregnant ewes were maintained at high altitude (3820 m) from Day 30 to Days 137-142 of gestation, when the ewes were killed for collection of myometrial tissue. Tissue was also collected from age-matched, normoxic controls. Longitudinal and circular layers were separated, length-tension curves generated to determine optimal resting tension, and all strips exposed to increasing half-log doses of oxytocin ranging from 10-12 to 10-6.5 M. The expression of oxytocin-receptor protein was measured using Western blot analysis. We found that LTH did not affect KCl-induced contraction of either smooth muscle layer, whereas the sensitivity of both myometrial layers to oxytocin was altered. A decreased maximum contractile response of the circular layer to oxytocin was also observed. Additionally, LTH decreased expression of oxytocin-receptor protein in the circular layer and increased levels in the longitudinal layer. Results from the present study indicate that LTH alters contractile responses and oxytocin-receptor protein expression in a layer-specific manner in the pregnant sheep myometrium.

Ectopic adrenocorticotropin (ACTH) and corticotropin-releasing hormone (CRH) production in the adrenal gland: basic and clinical aspects

The hypothalamic-pituitary-adrenal (HPA) axis is integrated in the human stress system and controls the metabolism of many cell systems in the body. Therefore, hypofunction or hyperfunction of the HPA axis potentially threatens the life of the whole organism. Noncontrolled overproduction of its key regulators, CRH and ACTH, causes dysfunction of the stress system. Ectopic secretion of these compounds may be part of extraadrenal paraneoplastic syndromes caused by various benign or malignant tumors. However, ectopic ACTH and CRH may originate from the adrenal itself. A local CRH/ACTH system exists in the normal human adrenal medulla. Overproduction of CRH and ACTH has been documented in pheochromocytomas causing Cushing's syndrome. Finally, ectopic production of ACTH causing Cushing's syndrome has also been demonstrated in adrenocortical cells. This suggests a marked plasticity within the HPA axis and the neuroendocrine cell system.

Antenatal corticosteroids: the good, the bad and the unknown

PURPOSE OF REVIEW

The purpose of this review was to summarize recently published clinical and animal-based studies of antenatal corticosteroids, describe current recommendations for practice, and suggest priority areas for future research.

RECENT FINDINGS

A single course of antenatal corticosteroids is known to improve newborn lung function after preterm birth and to reduce the risk of newborn death. Current evidence from animal and clinical studies suggests that additional numbers of courses do not further improve lung function and are associated with risks of adverse consequences. These risks principally include restricted intrauterine growth, altered brain development, postnatal insulin resistance and changes to the hypothalamic-pituitary-adrenal axis.

SUMMARY

The research challenges in this field are now centred on uncovering the mechanisms by which cortisol is involved in programming the fetus for its future metabolic life, and discovering ways in which the effectiveness and safety of antenatal glucocorticoids can be enhanced.

The role of prenatal stress in the etiology of developmental behavioural disorders

Substantial evidence from preclinical laboratory studies indicates that prenatal stress (PS) affects the hormonal and behavioural development of offspring. In the following review, the effects of PS in rodents and non-human primates on hypothalamic-pituitary-adrenal (HPA) reactivity to stress, morphological changes in the brain, motor behaviour and learning are surveyed. PS has been found to alter baseline and stress-induced responsivity of the HPA axis and levels and distribution of regulatory neurotransmitters, such as norepinepherine, dopamine, serotonin and acetylcholine and to modify key limbic structures. In rodents and non-human primates, PS affected learning, anxiety and social behaviour. The relevance of these findings to humans is discussed with respect to (a) the effect of administration of exogenous corticosteroids in pregnancy and (b) maternal state and trait anxiety during gestation and its relation to foetal autonomic regulation as putative predisposing factors in the pathogenesis of behavioural developmental delays in children.