Fetal swallowing: relation to amniotic fluid regulation

Afterbirth oral fluid secretory leukocyte protease inhibitor decreased in acute histologic chorioamnionitis in preterm birth

BACKGROUND

Secretory leukocyte protease inhibitor (SLPI) is an innate anti-inflammatory and anti-microbial peptide and produced in amnion of fetal membranes during pregnancy. However, studies on the association between SLPI levels in amniotic fluid and acute chorioamnionitis are limited. Afterbirth oral fluid (AOF) of the baby could be useful for representing the intra-amniotic environment precisely just before delivery. This study aimed to determine the relationship between SLPI levels in AOF and acute histologic chorioamnionitis (HC).

METHODS

AOF of the baby was obtained during delivery from 24(0/7) to 36(6/7) weeks of gestational age (preterm group, n = 94) and from 37(0/7) to 41(6/7) weeks of gestational age (term group, n = 27) just after birth. SLPI expression levels among five classifications were compared to the intensity of acute HC as follows: no inflammation, acute subchorionitis, acute chorionitis, acute chorioamnionitis, and funisits. The SLPI and matrix metalloproteinase-8 (MMP-8) concentrations of AOF were determined using Enzyme Linked Immunosorbent Assay. Histologic examination of the placenta and membranes was performed after delivery.

RESULTS

SLPI concentrations in AOF inversely decreased according to the intensity of acute HC (161.62 ng/mL in funisitis, 134.83 ng/mL in acute chorioamnionitis, 749.35 ng/mL in acute chorionitis, 953.05 ng/mL in acute subchorionitis, and 1126.77 ng/mL in no inflammation [p = .021]). The MMP-8 concentrations in AOF and maternal serum C-reactive protein were the highest in funisitis. The SLPI/ MMP-8 ratio was low in subgroup with acute chorioamnionitis and funisitis.

CONCLUSION

Along with increased MMP-8 levels, decreased SLPI levels in AOF of the baby could be an additional factor in predicting acute HC immediately after birth.

Cerebral control of swallowing: An update on neurobehavioral evidence

This review aims to update the current knowledge on the cerebral control of swallowing. We review data from both animal and human studies spanning across the fields of neuroanatomy, neurophysiology and neuroimaging to evaluate advancements in our understanding in the brain's role in swallowing. Studies have collectively shown that swallowing is mediated by multiple distinct cortical and subcortical regions and that lesions to these regions can result in dysphagia. These regions are functionally connected in separate groups within and between the two hemispheres. While hemispheric dominance for swallowing has been reported in most human studies, the laterality is inconsistent across individuals. Moreover, there is a shift in activation location and laterality between swallowing preparation and execution, although such activation changes are less well-defined than that for limb motor control. Finally, we discussed recent neurostimulation treatments that may be beneficial for dysphagia after brain injury through promoting the reorganization of the swallowing neural network.

Transcriptome Dynamics in the Developing Larynx, Trachea, and Esophagus

The larynx, trachea, and esophagus share origin and proximity during embryonic development. Clinical and experimental evidence support the existence of neurophysiological, structural, and functional interdependencies before birth. This investigation provides the first comprehensive transcriptional profile of all three organs during embryonic organogenesis, where differential gene expression gradually assembles the identity and complexity of these proximal organs from a shared origin in the anterior foregut. By applying bulk RNA sequencing and gene network analysis of differentially expressed genes (DEGs) within and across developing embryonic mouse larynx, esophagus, and trachea, we identified co-expressed modules of genes enriched for key biological processes. Organ-specific temporal patterns of gene activity corresponding to gene modules within and across shared tissues during embryonic development (E10.5-E18.5) are described, and the laryngeal transcriptome during vocal fold development and maturation from birth to adulthood is characterized in the context of laryngeal organogenesis. The findings of this study provide new insights into interrelated gene sets governing the organogenesis of this tripartite organ system within the aerodigestive tract. They are relevant to multiple families of disorders defined by cardiocraniofacial syndromes.

Advances in Swallowing Neurophysiology across Pediatric Development: Current Evidence and Insights

Purpose of Review

This review article analyzes current evidence on the neurophysiology of swallowing during development and offers expert opinion on clinical implications and future research directions.

Recent Findings

In the past five years, basic and clinical research has offered advances in our understanding of pediatric swallowing neurophysiology. Animal models have elucidated the role of brainstem circuits and the peripheral and central nervous system in neonatal swallowing. Recent human studies have further showcased that fetal and infant swallowing require cerebral inputs in order to develop functionally. Finally, neurophysiological and neuroimaging studies are starting to better define these cerebral inputs, as well as neuroplastic adaptations that may be needed for optimal feeding development.

Summary

The neural development of swallowing is a complex and dynamic process. Continued research is needed to better understand influences on swallowing neural development, which can be essential for improving prevention, diagnosis, and interventions for pediatric dysphagia.

First Bites-Why, When, and What Solid Foods to Feed Infants

Humans are the only mammals who feed our young special complementary foods before weaning and we are the only primates that wean our young before they can forage independently. There appears to be a sensitive period in the first several months of life when infants readily accept a wide variety of tastes and this period overlaps with a critical window for oral tolerance. As a result, infants should be exposed to a wide variety of flavors while mother is pregnant, while mother is nursing and beginning at an early age. There also appears to be a sensitive period between 4 and 9 months when infants are most receptive to different food textures. There remains debate about when it is best to begin introducing solid foods into an infant's diet however, the available evidence suggests that provided the water and food supply are free of contamination, and the infant is provided adequate nutrition, there are no clear contraindications to feeding infants complementary foods at any age. There is emerging evidence that introduction of solid foods into an infant's diet by 4 months may increase their willingness to eat a variety of fruits and vegetables later in life, decrease their risk of having feeding problems later in life, and decrease their risk of developing food allergies, and the early introduction of solid foods into an infant's diet does not appear to increase their risk of obesity later in childhood.

The meconium microbiota shares more features with the amniotic fluid microbiota than the maternal fecal and vaginal microbiota

The early-life gut microbiota is associated with potential development of diseases in adulthood. The sterile womb paradigm has been challenged by recent reports that revealed the presence of the meconium, amniotic fluid, and placenta microbiome. This study aimed to explore the maternal origin of the microbiota of neonate meconium by using the PacBio single-molecule real-time circular consensus sequencing technology. Such technology could produce high fidelity reads of full-length 16S rRNA genes, improving the sensitivity and specificity of taxonomic profiling. It also reduced the risk of false positives. This study analyzed the full-length 16S rRNA-based microbiota of maternal samples (amniotic fluid, feces, vaginal fluid, saliva) and first-pass meconium of 39 maternal-neonate pairs. Alpha- and beta-diversity analyses revealed sample type-specific microbiota features. Most sample types were dominated by sequences representing different genera (Lactobacillus and Curvibacter in the amniotic fluid and vaginal fluid microbiota; Bacillus and Escherichia/Shigella in the meconium microbiota; Bacteroides and Faecalibacterium in the maternal fecal microbiota; Streptococcus and Prevotella in the maternal saliva microbiota). Moreover, specific operational taxonomic units (OTUs) were identified in all sample types. Dyad analysis revealed common OTUs between the meconium microbiota and microbiota of multiple maternal samples. The meconium microbiota shared more features with the amniotic fluid microbiota than the maternal fecal and vaginal microbiota. Our results strongly suggested that the meconium microbiota was seeded from multiple maternal body sites, and the amniotic fluid microbiota contributed most to the seeding of the meconium microbiota among the investigated maternal body sites.

Cystic Crypt Changes in Midgestational Human Vermiform Appendix: An Unrecognized Transient Histologic Feature

INTRODUCTION

Lewis and Huff briefly described the presence of "microcystic cryptitis" in some of fetal vermiform appendices (VA) at autopsy. We further characterized these crypt changes (CC), their timing of occurrence, and tested their association with infection/inflammatory conditions.

METHODS

Hematoxylin and eosin-stained slides of 345 VA were evaluated for the presence or absence of CC and their different morphologies. Autopsy reports were reviewed for evidence of amniotic fluid or fetal systemic infection and placental inflammatory conditions.

RESULTS

Crypt dilatation with or without irregularity of the lumen, crypt dilatation with semiattenuated epithelium, intraluminal apoptotic debris and inflammatory cells, especially eosinophils, and foci of swirled spindled cells with calcifications or multinucleated giant cells were observed, either alone or in combination, in at least 58.5% (202/345) of the VA. CC began to appear at 17 weeks, peaked at 20 to 25 weeks (with up to 82% of VA exhibiting CC during this time), and followed by a steady decline beyond 28 weeks gestation. χ² test of independence showed no significant association (P = .435; >0.05) between the presence and absence of CC and infection status of the fetus or placenta.

CONCLUSION

The underrecognized CC of the developing fetal vermiform appendix (VA) showed distinct temporal pattern of occurrence and did not seem to be affected by the presence or absence of infection, which so far favored their being a part of the normal gut developmental process.

Preparing for Life After Birth: Introducing the Concepts of Intrauterine and Extrauterine Sensory Entrainment in Mammalian Young

Presented is an updated understanding of the development of sensory systems in the offspring of a wide range of terrestrial mammals, the prenatal exposure of those systems to salient stimuli, and the mechanisms by which that exposure can embed particular sensory capabilities that prepare newborns to respond appropriately to similar stimuli they may encounter after birth. Taken together, these are the constituents of the phenomenon of "trans-natal sensory continuity" where the embedded sensory capabilities are considered to have been "learnt" and, when accessed subsequently, they are said to have been "remembered". An alternative explanation of trans-natal sensory continuity is provided here in order to focus on the mechanisms of "embedding" and "accessing" instead of the potentially more subjectively conceived outcomes of "learning" and "memory". Thus, the mechanistic concept of "intrauterine sensory entrainment" has been introduced, its foundation being the well-established neuroplastic capability of nervous systems to respond to sensory inputs by reorganising their neural structures, functions, and connections. Five conditions need to be met before "trans-natal sensory continuity" can occur. They are (1) sufficient neurological maturity to support minimal functional activity in specific sensory receptor systems in utero; (2) the presence of sensory stimuli that activate their aligned receptors before birth; (3) the neurological capability for entrained functions within specific sensory modalities to be retained beyond birth; (4) specific sensory stimuli that are effective both before and after birth; and (5) a capability to detect those stimuli when or if they are presented after birth in ways that differ (e.g., in air) from their presentation via fluid media before birth. Numerous beneficial outcomes of this process have been reported for mammalian newborns, but the range of benefits depends on how many of the full set of sensory modalities are functional at the time of birth. Thus, the breadth of sensory capabilities may be extensive, somewhat restricted, or minimal in offspring that are, respectively, neurologically mature, moderately immature, or exceptionally immature at birth. It is noted that birth marks a transition from intrauterine sensory entrainment to extrauterine sensory entrainment in all mammalian young. Depending on their neurological maturity, extrauterine entrainment contributes to the continuing maturation of the different sensory systems that are operational at birth, the later development and maturation of the systems that are absent at birth, and the combined impact of those factors on the behaviour of newborn and young mammals. Intrauterine sensory entrainment helps to prepare mammalian young for life immediately after birth, and extrauterine sensory entrainment continues this process until all sensory modalities develop full functionality. It is apparent that, overall, extrauterine sensory entrainment and its aligned neuroplastic responses underlie numerous postnatal learning and memory events which contribute to the maturation of all sensory capabilities that eventually enable mammalian young to live autonomously.

Neonatal oral fluid as a transmission route for bifidobacteria to the infant gut immediately after birth

Bifidobacteria are one of the most abundant bacterial groups in the infant gut microbiota and are closely associated with infant health and can potentially affect health in later life. However, the details regarding the source of bifidobacteria have yet to be completely elucidated. This study aimed to assess neonatal oral fluid (OF) as a transmission route for bifidobacteria to the infant gut during delivery. Neonatal OF and infant feces (IF) were collected immediately and one month after birth from 15 healthy vaginally delivered newborns. Bifidobacterium strains were isolated from OF and IF samples, and the similarity of strains between the OF-IF pairs was evaluated based on the average nucleotide identity (ANI) value. The 16S rRNA gene sequencing results revealed the presence of Bifidobacteriaceae at >1% relative abundance in all OF samples. Bifidobacterium strains were isolated from OF (9/15) and IF (11/15) samples, and those sharing high genomic homology (ANI values >99.5%) between the neonatal OF and IF samples were present in one-third of the OF-IF pairs. The results of this study indicate that viable bifidobacteria are present in neonatal OF and that OF at birth is a possible transmission route of bifidobacteria to the infant gut.

Assessment of the effects of repeated doses of potassium iodide intake during pregnancy on male and female rat offspring using metabolomics and lipidomics

Preparedness for nuclear accident responsiveness includes interventions to protect pregnancies against prolonged exposure to radioactive iodine. The aim of this study was to investigate a new design consisting of repeated administration of potassium iodide (KI, 1 mg/kg) for 8 days in late pregnancy gestational day 9-16 (GD9-GD16) in rats. The later-life effects of this early-life iodine thyroid blocking (ITB) strategy were assessed in offspring two months afterbirth. Functional behavioral tests including forced swimming test (FST) and rotarod test (RRT) in rats of both genders showed lower FST performance in KI-treated females and lower RRT performance in KI-treated male pups. This performance decline was associated with metabolic disruptions in cortex involving amino acid metabolism, tyrosine metabolism, as well as docosahexaenoic acid (DHA) lipids and signaling lipids in males and females. Beyond these behavior-associated metabolic changes, a portion of the captured metabolome (17-25%) and lipidome (3.7-7.35%) remained sensitive to in utero KI prophylactic treatment in both cortex and plasma of post-weaning rats, with some gender-related variance. Only part of these disruptions was attributed to lower levels of TSH and T4 (males only). The KI-induced metabolic shifts involved a broad spectrum of functions encompassing metabolic and cell homeostasis and cell signaling functions. Irrespective Regardless of gender and tissues, the predominant effects of KI affected neurotransmitters, amino acid metabolism, and omega-3 DHA metabolism. Taken together, data demonstrated that repeated daily KI administration at 1 mg/kg/day for 8 days during late pregnancy failed to protect the mother-fetus against nuclear accident radiation. Abbreviations: CV-ANOVA: Cross-validation analysis of variance; DHA: Docosahexaenoic acid; FST: Forced swimming test; FT3: plasma free triiodothyronine; FT4: plasma free thyroxine; GD: Gestational day; ITB: Iodine thyroid blocking; KI: potassium iodide; LC/MS: Liquid chromatography coupled with mass spectrometry; MTBE: Methyl tert-butyl ether; m/z: mass-to-charge ratio; PLS-DA: Partial least squares-discriminant analysis; PRIODAC: Repeated stable iodide prophylaxis in accidental radioactive releases; RRT: Rotarod test; TSH: Thyroid-stimulating hormone; VIP: Variable importance in projection.

Effect of maternal metabolism on fetal supply: Glucose, non-esterified fatty acids and beta-hydroxybutyrate concentrations in canine maternal serum and fetal fluids at term pregnancy

The progressive adaptations in carbohydrate and lipid metabolism during canine pregnancy are reflected in the concentrations of glucose, non-esterified fatty acids (NEFA) and β-hydroxybutyrate (BHB). The levels of these metabolites in the bitch likely affect fetal concentrations and the composition of amniotic and allantoic fluids (AMF and ALF, respectively). We studied 31 canine parturitions (Cesarean sections) and found that glucose, NEFA and BHB concentrations were significantly higher in maternal serum than in AMF or ALF. Glucose levels in maternal serum, AMF and ALF were closely related (R² ≥ 0.821, P < 0.0001) as well as serum and AMF BHB levels (R² = 0.661, P < 0.0001). In maternal serum, increases in NEFA were associated with increased BHB, and both were negatively related to glucose (P ≤ 0.010). To estimate the effect of the metabolic burden of pregnancy, we evaluated these variables in relation to the dam's body weight and to the ratio of litter weight to the dam's body weight (LW/BW). Maternal serum glucose was not influenced by LW/BW, but it was lower in small than in large/giant bitches. Small breed dogs and those with >10% LW/BW had significantly higher serum NEFA and BHB concentrations. Glucose in AMF and ALF was independent of LW/BW (P ≥ 0.399). AMF NEFA was lower and BHB higher, if LW/BW was >10% (P ≤ 0.048). In conclusion, the extent of the metabolic load of pregnancy in bitches depends on breed size and on the ratio of litter weight to dam's body weight. Maternal concentrations of glucose, BHB and NEFA determine the concentrations of these metabolites in fetal fluids.

Upper gastrointestinal motility: prenatal development and problems in infancy

Deglutition, or swallowing, refers to the process of propulsion of a food bolus from the mouth into the stomach and involves the highly coordinated interplay of swallowing and breathing. At 34 weeks gestational age most neonates are capable of successful oral feeding if born at this time; however, the maturation of respiration is still in progress at this stage. Infants can experience congenital and developmental pharyngeal and/or gastrointestinal motility disorders, which might manifest clinically as gastro-oesophageal reflux (GER) symptoms, feeding difficulties and/or refusal, choking episodes and airway changes secondary to micro or overt aspiration. These problems might lead to impaired nutritional intake and failure to thrive. These gastrointestinal motility disorders are mostly classified according to the phase of swallowing in which they occur, that is, the oral preparatory, oral, pharyngeal and oesophageal phases. GER is a common phenomenon in infancy and is referred to as GERD when it causes troublesome complications. GER is predominantly caused by transient relaxation of the lower oesophageal sphincter. In oesophageal atresia, oesophageal motility disorders develop in almost all patients after surgery; however, a congenital origin of disordered motility has also been proposed. This Review highlights the prenatal development of upper gastrointestinal motility and describes the most common motility disorders that occur in early infancy.

Congenital feeding and swallowing disorders

Although poorly recognized and studied, congenital sucking, swallowing, and/or feeding disorders are common. They can be the symptoms that reveal a neuromuscular disease, or that complicate a neuromuscular disease. It is essential to know feeding physiology during fetal and infant development in order to understand the variety of its disorders and to direct correctly diagnostic and therapeutic processes. A good semiological analysis will identify the symptoms. Several investigations help to determine the mechanism of the trouble (fiber endoscopy, videofluoroscopy, facial and swallowing electromyography, esophageal manometry, etc.). Other investigations, in addition to clinical assessments, help to identify the cause of the whole picture (peripheral electromyography, brain MRI, genetic or metabolic investigations, etc.). The main causes of sucking, swallowing, and feeding disorders are lesions of the brainstem (malformations of the posterior fossa, neonatal brainstem tumors, agenesis of cranial nerves, clastic lesion of the posterior brain, craniovertebral anomalies, syndromes that involve the rhombencephalic development such as Pierre Robin sequence, CHARGE syndrome, etc.). Suprabulbar lesions, neuromuscular disorders, peripheral esophageal, digestive, and laryngeal anomalies and dysfunctions can also be involved. The main principles of the management of congenital sucking, swallowing, and feeding disorders are the following: cure the cause if possible, facilitate the sucking reflex, preventing deleterious consequences of aspiration, preventing malnutrition, and preventing posttraumatic anorexia. Advice can be given to caregivers and physiotherapists who take charge of these children.

Fetal swallowing as a protective mechanism against oligohydramnios and polyhydramnios in late gestation sheep

Our objectives were to (1) quantify the relationship between daily swallowed volume and amniotic fluid volume (AF volume) in late gestation ovine fetuses and (2) use the resulting regression equation to explore the role of swallowing in regulating AF volume. Daily swallowed volume ranged from 36 to 1963 mL/d while experimental AF volume ranged from 160 to 6150 mL (n = 115). Swallowed volume was near zero when AF volume was far below normal, a maximum of 635 ± 41 (standard error) mL/d when AF volume was 1682 ± 31 mL and did not increase further with higher AF volumes. Computer simulations predicted that fetal swallowing would (1) return AF volume to normal in 5 to 6 days following an acute volume change in the absence of changes in other amniotic inflows or outflows and (2) stabilize AF volume in 4 to 8 days following sustained alterations in amniotic inflows or outflows other than swallowing.

CONCLUSIONS

The volume of AF swallowed each day by the fetus is a strong function of AF volume and reaches a maximum when mild polyhydramnios develops. With deviations in AF volume from normal, changes in fetal swallowing protect against oligohydramnios and polyhydramnios because the changes in swallowing over time reduce the extent of the AF volume change. However, with experimental changes in AF volume stabilizing in 1 to 2 days, it appears that swallowing is not the major regulator of AF volume.

Amniotic fluid and the clinical relevance of the sonographically estimated amniotic fluid volume: oligohydramnios

The amniotic fluid volume (AFV) is regulated by several systems, including the in-tramembranous pathway, fetal production (fetal urine and lung fluid) and uptake (fetal swallowing), and the balance of fluid movement via osmotic gradients. The normal AFV across gestation has not been clearly defined; consequently, abnormal volumes are also poorly defined. Actual AFVs can be measured by dye dilution techniques and directly measured at cesarean delivery; however, these techniques are time-consuming, are invasive, and require laboratory support, and direct measurement can only be done at cesarean delivery. As a result of these limitations, the AFV is estimated by the amniotic fluid index (AFI), the single deepest pocket, and subjective assessment of the AFV. Unfortunately, sonographic estimates of the AFV correlate poorly with dye-determined or directly measured amniotic fluid. The recent use of color Doppler sonography has not improved the diagnostic accuracy of sonographic estimates of the AFV but instead has led to overdiagnosis of oligohydramnios. The relationship between the fixed cutoffs of an AFI of 5 cm or less and a single deepest pocket of 2 cm or less for identifying adverse pregnancy outcomes is uncertain. The use of the single deepest pocket compared to the AFI to identify oligohydramnios in at-risk pregnancies seems to be a better choice because the use of the AFI leads to an increase in the diagnosis of oligohydramnios, resulting in more labor inductions and cesarean deliveries without any improvement in peripartum outcomes.

Gustation

Much has been discovered over the last few decades about the anatomy and physiology of the human taste system, most notably its receptor mechanisms and intermodal factors that influence its function. While the taste system works in concert with the olfactory, somatosensory, auditory, and visual sensory systems to establish the overall gestalt of flavor, its primary specialization is to ensure that the organism obtains energy, maintains proper electrolyte balance, and avoids ingestion of toxic substances. Despite its focus on inborn functions, taste-like its sister sense of smell-is remarkably malleable, reflecting the need to adapt to changing circumstances and general nutrient availability. It is now widely appreciated that taste dysfunction is common in many diseases and disorders, and is a frequent side effect of a number of medications. This interdisciplinary review examines salient aspects of the human gustatory system, including its anatomy, physiology, and pathophysiology. WIREs Cogn Sci 2012, 3:29-46. doi: 10.1002/wcs.156 For further resources related to this article, please visit the WIREs website.

Opioid mediation of amniotic fluid effects on chemosensory responsiveness in the neonatal rat

The present study investigated if oral exposure to milk or amniotic fluid (AF) alters responsiveness to sensory stimulation in the neonatal rat, and whether these effects are mediated by the opioid system. Facial wiping evoked by intraoral lemon infusion was used as a measure of sensory responsiveness. Pups were tested in a supine posture, because they showed more paw-face strokes during facial wiping than pups tested prone (Experiment 1). Moreover, pups orally exposed to milk (Experiment 2) or AF (Experiment 3) showed a diminished wiping response to lemon compared to controls exposed to water. Blockade of opioid receptors with the nonselective antagonist naltrexone (Experiment 4) or the kappa antagonist nor-binaltorphimine (Experiment 5) reinstated higher levels of facial wiping after AF exposure. These findings confirm developmental continuity between fetal and neonatal behavioral responses to AF and the ability of AF to induce activity at kappa receptors of the endogenous opioid system.

Measurement of fetal urine production to differentiate causes of increased amniotic fluid volume

OBJECTIVES

In polyhydramnios, amniotic fluid (AF) volume can be increased not only as a result of increased fetal urine production, but also due to several other factors, including impairment of both fetal swallowing and gastrointestinal (GI) absorption of AF. Our aim was to evaluate whether measurement of the fetal urine production rate (UPR) can be used to differentiate the causes of increased AF volume.

METHODS

This cross-sectional study included 54 pregnant women with an increased amniotic fluid index (AFI), defined as AFI > or = 18 cm, divided into two groups according to the presence of fetal anomalies that are associated with impairment of fetal swallowing or decreased GI absorption of AF (Group 1, n = 14) or the absence of fetal anomalies (Group 2, n = 40). The control group included 96 normal pregnancies with normal AFI (8 < or = AFI < 18 cm) (Group 3). Fetal UPR was obtained by serial bladder volume measurements (two to four times, with a median interval of 5 min between each) using the rotational method of Virtual Organ Computer-aided AnaLysis (VOCAL()) with three-dimensional ultrasound. To adjust for fetal weight (Wt) and gestational age (GA), UPR_Wt and UPR_SD were calculated using the following formulae: UPR_Wt = measured UPR/estimated fetal weight and UPR_SD = (measured UPR - mean UPR for each GA)/SD of UPR for each GA.

RESULTS

The AFI was increased significantly in Groups 1 and 2 compared with Group 3. However, the median fetal UPR in Group 1 did not differ from that of Group 3, in contrast to the higher median fetal UPR in Group 2 compared with Groups 1 and 3; this difference remained significant after adjusting for GA and estimated fetal weight in terms of UPR_SD and UPR_Wt. In Groups 2 and 3, AFI and UPR had a positive correlation in terms of UPR, UPR_SD and UPR_Wt.

CONCLUSIONS

Our findings that fetal UPR is significantly increased in cases with increased AFI without fetal anomalies, but not in those with increased AFI and fetal anomalies involving decreased GI absorption of AF, might be used to differentiate causes of increased AF volume. In the absence of fetal anomalies, AFI and fetal UPR correlate positively.

Nutrition and its contribution to obesity and diabetes: a life-course approach to disease prevention?

Whilst previously type 2 diabetes occurred in older adults, its incidence, together with obesity, has increased rapidly in children. An improved understanding of this disease pathway from a developmental view point is critical. It is likely that subtle changes in dietary patterns over an extended period of time contribute to diabetes, although this type of rationale is largely ignored in animal studies aimed at determining the mechanisms involved. Small-animal studies in which large, and often extreme, changes in the diet are imposed at different stages of the life cycle can have substantial effects on fat mass and/or pancreatic functions. These responses are not representative of the much more gradual changes seen in the human population. An increasing number of studies indicate that it is growth rate per se, rather than the type of dietary intervention that determines pancreatic function during development. Epigenetic mechanisms that regulate insulin secretion by the pancreas can be re-set by more extreme changes in dietary supply in early life. The extent to which these changes may contribute to more subtle modulations in glucose homeostasis that can accompany excess fat growth in childhood remains to be established. For human subjects there is much less information as to whether specific dietary components determine disease onset. Indeed, it is highly likely that genotype has a major influence, although recent data relating early diet to physical activity and the FTO gene indicate the difficulty of establishing the relative contribution of diet and changes in body mass to diabetes.

Dietary lipids in early development and intestinal inflammatory disease

Inflammatory bowel diseases are life-long reoccurring inflammatory disorders of the gastrointestinal tract and have been increasing in incidence in recent decades, notably in the pediatric population. Although genetic predisposition remains an important factor, this increased incidence most likely reflects an environmental change. One potential contributor to this is the change in dietary fat intake, with dietary intake of n-6 polyunsaturated fatty acids (PUFAs) following a similar temporal pattern to the change in inflammatory bowel disease incidence. Dietary n-6 PUFAs comprise a major, modifiable, environmental factor known to promote a heightened inflammatory response through a number of pathways, including their role as precursors for synthesis of eicosanoids and their inhibitory effect on the synthesis of the n-3 PUFAs eicosapentanoic acid and docosahexanoic acid. The increase in n-6 PUFA intake affects individuals of all ages, with fetal PUFA accretion and infant dietary PUFA intake from breast milk reflecting maternal dietary intake. A high level of n-6 PUFA in milk results in increased n-6 PUFA in colonic phospholipids and an exaggerated inflammatory response to chemically induced colitis. Conversely, during development, a diet low in n-6 PUFAs and high in n-3 PUFAs increases colonic n-3 fatty acids, attenuates the inflammatory response, and lowers colonic damage. High dietary n-6 PUFA intake may be an important environmental modifier that contributes to inflammatory bowel diseases.

Amniotic fluid can act as an appetitive unconditioned stimulus in preweanling rats

Studies in humans and animals indicate that exposure to flavors in the amniotic fluid during the later gestational period may induce preferences for those flavors. Considering that during the last prenatal period the amniotic fluid contains substances that activate the opioid system, and that this system plays a critical role in the acquisition of olfactory preferences early in life, it has been hypothesized that the amniotic fluid may acquire appetitive unconditioned properties during this period. This has been tested in an experiment in which preweanling rats were exposed to alcohol odor (CS) paired or unpaired with the intraoral infusion of amniotic fluid (US) collected on gestational day 20. The pairing of these two stimuli induced an enhanced palatability of alcohol's flavor as well an increased intake of the drug. These results support the idea that amniotic fluid acquires appetitive unconditioned properties during the last days of gestation and suggest that associative mechanisms involving the amniotic fluid could be underlying odor and taste preferences acquired through fetal exposure.

A phase 1 trial testing an enteral solution patterned after human amniotic fluid to treat feeding intolerance

OBJECTIVE

Feeding intolerance is a common problem in neonates; in some cases it may be related to atrophic changes in the small bowel mucosa. In these infants, feeding tolerance might improve after oral administration of enterocyte growth factors in a sterile, isotonic, noncaloric solution patterned after human amniotic fluid.

STUDY DESIGN

Ten infants who met the study criteria for feeding intolerance were enrolled in this pilot trial. The test solution was administered, 2.5 mL/kg every 3 hours, until 80 mL/kg/day of milk feedings were tolerated, or for a maximum of 7 days. When milk feedings were prescribed, they were mixed with the test solution. Volumes of milk feedings were increased in amounts determined by the attending neonatologist and neonatal nurse practitioner. The outcome was the net average enteral kilocalories per kilogram of body weight per day (kcal/kg/day) for 3 periods: (1) the 3 days before the test treatment was begun, (2) the days the test treatment was administered, and (3) the 7 days following cessation of the test treatment.

RESULTS

At study entry the infants' chronological ages ranged from 3 to 65 days. All infants tolerated the test solution, which was given for a mean of 5 days (range 3 to 7 days). During that period, the infants received more enteral calories (mean 18 kcal/kg/day, range 1 to 32) than during the preceding 3 day period (mean 3 kcal/kg/day, range 0 to 7, P < 0.05). During the 7 days following the test treatment the infants received 87 enteral kcal/kg/day (range 11 to 109, P < 0.02 compared to the treatment period).

CONCLUSIONS

In this Phase 1 pilot trial, 10 heterogeneous infants in the neonatal intensive care unit with feeding intolerance had a significant increase in milk feedings after treatment with a sterile, isotonic, noncaloric solution patterned after human amniotic fluid.

Maternal dietary fat alters amniotic fluid and fetal intestinal membrane essential n-6 and n-3 fatty acids in the rat

We investigated whether maternal fat intake alters amniotic fluid and fetal intestine phospholipid n-6 and n-3 fatty acids. Female rats were fed a 20% by weight diet from fat with 20% linoleic acid (LA; 18:2n-6) and 8% alpha-linolenic acid (ALA; 18:3n-3) (control diet, n = 8) or 72% LA and 0.2% ALA (n-3 deficient diet, n = 7) from 2 wk before and then throughout gestation. Amniotic fluid and fetal intestine phospholipid fatty acids were analyzed at day 19 gestation using HPLC and gas-liquid chromotography. Amniotic fluid had significantly lower docosahexaenoic acid (DHA; 22:6n-3) and higher docosapentaenoic acid (DPA; 22:5n-6) levels in the n-3-deficient group than in the control group (DHA: 1.29 +/- 0.10 and 6.29 +/- 0.33 g/100 g fatty acid; DPA: 4.01 +/- 0.35 and 0.73 +/- 0.15 g/100 g fatty acid, respectively); these differences in DHA and DPA were present in amniotic fluid cholesterol esters and phosphatidylcholine (PC). Fetal intestines in the n-3-deficient group had significantly higher LA, arachidonic acid (20:4n-6), and DPA levels; lower eicosapentaenoic acid (EPA; 20:5n-3) and DHA levels in PC; and significantly higher DPA and lower EPA and DHA levels in phosphatidylethanolamine (PE) than in the control group; the n-6-to-n-3 fatty acid ratio was 4.9 +/- 0.2 and 32.2 +/- 2.1 in PC and 2.4 +/- 0.03 and 17.1 +/- 0.21 in PE in n-3-deficient and control group intestines, respectively. We demonstrate that maternal dietary fat influences amniotic fluid and fetal intestinal membrane structural lipid essential fatty acids. Maternal dietary fat can influence tissue composition by manipulation of amniotic fluid that is swallowed by the fetus or by transport across the placenta.

Fetal abdominal magnetic resonance imaging

This review deals with the in vivo magnetic resonance imaging (MRI) appearance of the human fetal abdomen. Imaging findings are correlated with current knowledge of human fetal anatomy and physiology, which are crucial to understand and interpret fetal abdominal MRI scans. As fetal MRI covers a period of more than 20 weeks, which is characterized not only by organ growth, but also by changes and maturation of organ function, a different MR appearance of the fetal abdomen results. This not only applies to the fetal intestines, but also to the fetal liver, spleen, and adrenal glands. Choosing the appropriate sequences, various aspects of age-related and organ-specific function can be visualized with fetal MRI, as these are mirrored by changes in signal intensities. Knowledge of normal development is essential to delineate normal from pathological findings in the respective developmental stages.

Repeatability of the sonographic assessment of fetal sucking and swallowing movements

OBJECTIVE

To test the repeatability of sonography in the assessment of fetal sucking and swallowing movements.

METHODS

Eighty normal fetuses of pregnant women with no systemic abnormalities were examined sonographically at 30-38 weeks of gestation. Sucking and swallowing movements were observed for 15 min and the face was visualized in frontal and lateral views. The examinations were recorded for later analysis by two independent observers and the 95% limits of agreement (Bland and Altman) method was used for inter- and intraobserver comparison.

RESULTS

The mean +/- SD number of swallowing movements, sucking bursts and total sucking movements recorded by Observer 1 were 8.3 +/- 4.7, 9.9 +/- 9.3 and 35.8 +/- 48.0 and the equivalent values for Observer 2 were 8.2 +/- 4.8, 9.8 +/- 9.3 and 36.4 +/- 49.0, respectively. The mean (95% limits of agreement) interobserver difference was 0.1 (-1.4; 1.6), 0.1 (-2.2; 2.3) and -0.6 (-9.0; 7.9), and the mean (95% limits of agreement) intraobserver difference was 0.4 (-3.1; 3.9), 0.1 (-2.0; 2.2) and 1.0 (-10.7; 12.7) for swallowing movements, sucking bursts and total sucking movements, respectively.

CONCLUSIONS

The high degree of intra- and interobserver repeatability disclosed in the sonographic analysis of fetal sucking and swallowing movements supports the applicability of sonographic assessment in normal fetuses.

Gastric emptying cycles in the human fetus

OBJECTIVE

Fetal swallowing contributes greatly to amniotic fluid homeostasis and fetal somatic development. Despite the absorption and recirculation of significant volumes of amniotic fluid, little is known about the rates of fetal gastric emptying or gastrointestinal absorption. We sought to determine the patterns of human fetal gastric emptying cycles across gestation.

STUDY DESIGN

The gastric emptying cycle of 80 normal human fetuses at 12 to 39 weeks of gestation was studied. Real-time ultrasound examination of the fetal stomach (defined as the largest gastric area inclusive of the pylorus) was recorded continuously for a minimum of 1 hour (60-112 minutes). Images were replayed with measurements of gastric size every minute. The gastric area ratio was defined as the ratio of the fetal gastric area divided by the area of the fetal abdominal transverse section. The changes in gastric area ratio of all subjects were analyzed with the discrete Fourier transform method. The calculable maximum cycle was 60 or 112 minutes, and the minimum cycle was 2 minutes. The highest and second highest peaks of all power spectrum were recorded, and each cycle was converted from frequency of each peak.

RESULTS

The gastric emptying cycles of the highest peak before 24 weeks of gestation were scattered between 30 and 100 minutes with low power. At 32 to 35 weeks of gestation, cycles were focused at approximately 40 minutes with increased power. At term, the cycles increased to >80 minutes. The gastric emptying cycles of the second highest peak were constant at 20 minutes, with stronger power after 24 weeks of gestation.

CONCLUSION

Fetal gastric emptying cycles normalize during the early third trimester. The near-term evidence of delayed emptying may contribute to newborn infant feeding satiation.

Function curve of the membranes that regulate amniotic fluid volume in sheep

Seven singleton 120-day fetal lambs were prepared with a shunt from the lung to the gastric end of the esophagus, a bladder catheter, and multiple amniotic fluid and vascular catheters. The urachus was ligated. Beginning 7 days later, amniotic fluid volumes were determined by drainage, followed by replacement with 1 liter of lactated Ringer (LR) solution. Urine flow into the amnion was measured continuously. In 14 of 27 experiments, amniotic fluid volumes were determined again 2 days after the inflow into the amnion had consisted of urine only and in 13 experiments after the inflow of urine had been supplemented by an intraamniotic infusion of LR solution. Intramembranous absorption was calculated from the inflows and the changes in volume between the beginning and end of each experiment. The relations between absorption rate and amniotic fluid volume, the “function curves,” were highly individual. Urine production during the infusion of LR solution did not decrease, fetal plasma renin activity decreased ( P < 0.001), and amniotic fluid volume increased by 140% [SE (27%), P < 0.005], but the increase in the amniochorionic absorption rate of 411% [SE (48%), P < 0.001] was greater ( P < 0.005) than the increase in volume. Each of the seven fetuses was proven capable of an average intramembranous absorption rate that exceeded 4.5 liters of amniotic fluid per day. During the infusion of LR solution, the increase in the rate of absorption matched the rate of infusion (both in ml/h), with a regression coefficient of 0.75 ( P < 0.001). Thus, even for large amniotic fluid volumes, volume is not limited by the absorptive capacity of the amniochorion, and, at least in these preparations, the position of the function curve and not the natural rate of inflow was the major determinant of resting amniotic fluid volume.

Intramembranous absorption rate is unaffected by changes in amniotic fluid composition

Experiments were performed to determine the effect of amniotic fluid dilution on the rate of intramembranous absorption. Seven fetal sheep at 118 days gestation were instrumented with a shunt between the trachea and esophagus and arterial and venous vascular catheters. In addition, the urachus of the fetal bladder was ligated, and a catheter was placed in the bladder. Ligation of the urachus does not interfere with urine flow into the amnion. After 5 days of recovery, fetuses were randomly assigned to one of two protocols; all fetuses completed both protocols. In the fetuses in the control period, continuous urine flow measurement was begun. In the fetuses assigned to the isovolumic dilution protocol, continuous urine flow measurement was also begun and, in addition, amniotic fluid was continually exchanged with lactated Ringer solution on an isovolumic basis. After 3–4 days, fetal blood pressures and amniotic fluid volumes were determined. Amniotic fluid volumes were determined by drainage. Each fetus was then assigned to the remaining protocol. The presence of the tracheal-esophageal shunt and the ligation of the urachus allowed the rate of intramembranous absorption to be calculated. Isovolumic exchange showed no effect on fetal vascular pressures, blood-gas values, or urine production. We could demonstrate no effect of isovolumic dilution of amniotic fluid on its volume. However, we were able to demonstrate an inverse relationship between amniotic fluid volume and intramembranous absorption ( P < 0.02).

Hematopoietic growth factors in neonatal medicine: the use of enterally administered hematopoietic growth factors in the neonatal intensive care unit

The practice of complete bowel rest in prematurely delivered neonates and those who have undergone surgery for congenital anomalies of the gastrointestinal (GI) tract is common in neonatal intensive care units (NICU). However, increased recognition of the critical role of growth factors in GI development suggests that this practice might be modified to include the administration of synthetic amniotic fluid-like solutions designed to bridge the neonate between their intra-uterine environment and that of the NICU. This article reviews advances in administering synthetic amniotic fluid-like solutions in the NICU.

Tolerance of simulated amniotic fluid in premature neonates

OBJECTIVE

To assess the tolerance of simulated amniotic fluid enterally administered in premature neonates.

DESIGN

A multicentered, Phase I, dose-escalation trial was accomplished among 30 preterm neonates. Groups of 10 patients received 5, 10, or 20 mL/kg/d enterally of the amniotic fluid solution, divided into every-3-hour dosing, for 3 days.

MAIN OUTCOME MEASURES

Amount and character of emesis, stools, and gastric residuals; changes in abdominal girth; presence of a skin rash; blood pressure instability; the diagnosis of necrotizing enterocolitis (NEC) or intestinal perforation.

RESULTS

Thirty patients were studied: 10 received 5 mL/kg/d, 10 received 10 mL/kg/d, and 10 received 20 mL/kg/d of amniotic solution. Gestational ages ranged from 25 to 31 weeks. The Data Safety and Monitoring Board met after each group of 10 patients completed the study, reviewed the outcome measurements, and recommended continuance of the study. Dosing was discontinued for 3 patients prior to receiving all 24 doses because of gastric residuals (n = 1; 5 mL/kg), stage I NEC (n = 1; 10 mL/kg), or symptomatic patent ductus arteriosus (n = 1; 20 mL/kg). The remaining patients completed the doses with no evidence of intolerance: specifically, no increased gastric residuals, increased abdominal girth, diarrhea, blood pressure change, rash, NEC, or intestinal perforation.

CONCLUSIONS

Enteral administration of an amniotic fluid-like solution to preterm neonates is well tolerated in doses <or=20 mL/kg/d.

Enteral administration of hematopoietic growth factors in the neonatal intensive care unit

By 20 wk of gestation, the human fetal gastrointestinal (GI) tract morphologically resembles that of the term infant, but functional development is limited before 26 wk. By 30 wk of gestation, the fetus has the capacity for limited digestion and enteral absorption. GI growth and development continue postnatally. Trophic factors, including nutrients, peptides, hormones and growth factors, are recognized as having important influences on the morphology and histology of the developing GI tract. Other trophic factors are important in adaptation and repair following injury. Many such factors are provided in utero via amniotic fluid swallowing and later by human colostrum and milk.

CONCLUSION

This review discusses cytokines with known GI trophic effects, either in vitro or in vivo, and focuses on those cytokines that have been used in the neonatal intensive care unit.

Reversal of pregnancy-mediated plasma hypotonicity in the near-term rat

OBJECTIVE

Maternal plasma hypotonicity occurs early in rat and human pregnancy with resetting of the plasma osmolality threshold for vasopressin secretion and thirst. In humans, amniotic fluid volume reaches maximum levels in the mid-third trimester and decreases thereafter. We hypothesized that a reversal of maternal plasma hypotonicity occurs near term, contributing to reduced fetal and amniotic fluid water content.

METHODS

Maternal plasma and amniotic fluid osmolality and sodium levels, including amniotic fluid volume, were measured at 16, 18 and 20 days of rat gestation. Additionally, maternal and fetal brains were analyzed for water and electrolyte content. Non-pregnant adult female rats represented controls.

RESULTS

Compared to non-pregnant adults, 16-day and 18-day pregnant rats had significantly lower plasma osmolality (301.0 +/- 2.3 vs. 295.4 +/- 2.8 and 289.7 +/- 3.3 mOsm/kg, respectively) and sodium levels (140.3 +/- 1.0 vs. 135.7 +/- 0.8 and 133.4 +/- 1.4 mEq/l, respectively). Conversely, 20-day pregnant rats showed no significant difference in plasma osmolality (298.4 +/- 3.1 mOsm/kg) or sodium levels (137.6 +/- 1.0 mEq/l) from non-pregnant adults. With advancing gestation, the amniotic fluid volume decreased whereas the osmolality and sodium levels increased significantly. Maternal brain water content was significantly higher in 16-day and 18-day pregnant rats compared to control rats (78.7 +/- 0.1 and 78.1 +/- 0.2 vs. 76.9 +/- 0.2% wet weight) and returned to non-pregnant values in the 20-day pregnant rats (76.6 +/- 0.2%). In association with the maternal changes, fetal brain water and electrolyte content significantly decreased from 16-day to 18-day to 20-day fetuses.

CONCLUSION

These findings indicate a reversal of maternal plasma hypotonicity and reduced maternal brain water content in the near-term pregnant rat. We speculate that relative maternal plasma hypertonicity near term may contribute to reduced amniotic fluid volume.

Emergence of oropharyngeal, laryngeal and swallowing activity in the developing fetal upper aerodigestive tract: an ultrasound evaluation

The developing fetal upper aerodigestive system provides the structural support for respiratory and ingestive functions necessary to sustain life at birth. This study investigated prenatal development of upper aerodigestive anatomy and the association of emerging functions as predictors of postnatal feeding skills. Biometric measures of oral, lingual, pharyngeal and laryngeal structures were obtained in fetuses 15-38 weeks gestational age using a four-plane sonographic technique. Accompanying ingestive behaviors were tallied across development. The data from 62 healthy controls were compared to seven cases at risk for postnatal feeding and swallowing dysfunction (Type II Arnold Chiari Malformation, trisomy 18, polyhydramnios, intrauterine growth restriction, Brachmann-de Lange Syndrome). Significant (p<0.001) linear regressions occurred in pharyngeal and lingual growth across gestation while ingestive behavior such as suckling emerged in a sequence of basic to complex movement patterns. Jaw and lip movements progressed from simple mouth opening to repetitive open-close movements important for postnatal suckling. Lingual movements increased in complexity from simple forward thrusting and cupping to anterior-posterior motions necessary for successful suckling at term. Laryngeal movements varied from shallow flutter-like movements along the lumen to more complex and complete adduction-abduction patterns. Fetal swallowing primarily occurred in the presence of concomitant oral-facial stimulatory activity. Significant variations (p<0.01) in the form and function of the ingestive system occurred in comparisons of gestational age-matched controls to at-risk cases. We postulate that prenatal developmental indices of emerging aerodigestive skills may guide postnatal decisions for feeding readiness and, ultimately, advance the care of the premature, medically fragile neonate.

Substance abuse and polyhydramnios

OBJECTIVE

Maternal drug use is known to have fetal central nervous system depressive effects as manifested by decreased biophysical profile scores. Drug effects on the amniotic fluid index (AFI), one variable of the biophysical profile, are not well documented. Our objective was to determine the effects of maternal drug use on the AFI.

STUDY DESIGN

Over an 18-month period from July 1997 to December 1998, consecutive cases of women with toxicology-proven drug use during pregnancy were identified. AFI values and the rate of polyhydramnios in substance users were compared with those observed at our institution in more than 6400 patients undergoing ultrasound testing during the same period as the cases.

RESULTS

Sixty-three toxicology-positive cases were identified. Although there was no significant difference between mean AFI values, the incidence of polyhydramnios (AFI >24 cm) was significantly higher in substance users (28.6%) than in control patients (3.9%) (P <.005).

CONCLUSION

Maternal substance abuse is associated with a significantly higher incidence of polyhydramnios and should be considered a possible etiologic factor in women with apparent idiopathic polyhydramnios.

Absorption of amniotic fluid by amniochorion in sheep

Swallowing of amniotic fluid and lung fluid inflow were eliminated in 10 chronically instrumented fetuses. The urachus was ligated, and fetal was urine drained to the outside. At the beginning and the end of 21 experiments of 66 +/- 5 (SE) h duration, all amniotic fluid was temporarily drained to the outside for volume measurement and sampling. Amniotic fluid osmolalities and oncotic pressures were experimentally controlled. Amniochorionic absorption of amniotic fluid depended strongly on the osmolality difference between amniotic fluid and fetal plasma (P < 0.001), but at zero osmolality difference there still was a mean absorption rate of 23.8 +/- 4.7 (SE) ml/h (P < 0.001). Absorption was unaffected by the protein concentration difference between amniotic fluid and fetal plasma, but infused bovine albumin in the amniotic fluid was absorbed at a rate of 1.8 8 +/- 0.4 g/h (P < 0.001), corresponding to a volume flow of fluid of 33.8 8 +/- 6.1 ml/h (P < 0.001). Fluid absorption in the amniochorion is driven in part by crystalloid osmotic pressure, but about 25 ml/h is absorbed by a path that is permeable to protein. That path has the physiological characteristics of lymphatic drainage, although no anatomic basis is known to exist for a lymphatic system in the amniochorion.

Ontogeny of fetal rabbit upper gastrointestinal motility

BACKGROUND

The gastrointestinal (GI) tract performs the digestion, propulsion, and absorption of nutrients both pre- and postnatally, although little is known about the development of fetal motility. We evaluated the development of GI motility using a novel fetal rabbit model.

METHODS

Nine pregnant rabbits were obtained and three litters were studied at day 24 (n = 24), 27 (n = 29), and 30 (n = 24) of their 31-day gestation. Under ultrasound guidance fetal position was identified, a spinal needle was percutaneously inserted into each fetal stomach, and fluorescein, labeled with color-coded microspheres, was injected. Two hours later, fetuses were delivered and weighed, and the small intestine was harvested. The absolute length of fluorescein traveled was measured by ultraviolet light optical density and the percentage motility was calculated by dividing the absolute length of fluorescein traveled by the total small intestinal length.

RESULTS

All injected fetuses survived. The length of fluorescein traveled significantly increased from day 24 (8.1 +/- 2.1 cm) to day 27 (18.8 +/- 4.6 cm) and 30 (22.6 +/- 5.2 cm). The length of fluorescein traveled significantly correlated with body weight on day 27 and 30. Calculated percentage motility significantly increased from day 24 to 30. However, percentage motility showed no correlation with fetal weight.

CONCLUSIONS

This study describes a novel rabbit model for the assessment of in vivo fetal GI motility. Motility matured during the last third of gestation when assessed by the absolute length of fluorescein travel and the percentage motility. These results confirm that late-gestation fetuses have developed sufficient motility to propel potential nutrients, drugs, or gene therapy vectors to the small intestinal absorptive surface area.

Ovine hourly fetal urine production: relation to fetal electrocortical activity

OBJECTIVE

Ultrasound studies of hourly urine production rate in human fetuses have suggested that a fall in urine production occurs in state 2F (fetal quiet sleep) secondary to a state-dependent decrease in renal blood flow. We sought to ascertain the relationship between fetal hourly urine production rate and behavioral state in the near-term ovine fetus, a model in which urine production and fetal brain activity can be directly measured.

METHODS

Six ewes with singleton pregnancies were prepared with vascular and amniotic fluid catheters. Fetuses were prepared with hindlimb vascular catheters, a bladder catheter, and biparietal ECoG electrodes. After at least 5 days of recovery (ga 130 +/- 2 days; term = 145-150 days), each animal was monitored for a 6-h period. Urine production was measured by draining the bladder catheter through a drop counter and fetal ECoG was continuously recorded (sampling rate of 50 Hz). ECoG activity was analyzed using power spectral analysis and periods of active and quiet sleep identified using both signal amplitude and corresponding 85% spectral edge frequency.

RESULTS

Basal fetal arterial pH (7.36 +/- 0.01), pO2 (22.0 +/- 1.2 mmHg) and pCO2 (47.0 +/- 1.6 mmHg) and plasma (295 +/- 2 mOsm/kg) and urine (179 +/- 3 mOsm/kg) osmolalities were within normal ranges. Active and quiet sleep comprised 50 +/- 2 and 43 +/- 1% time, respectively. There was no difference in hourly urine production rate in active sleep (21.4 +/- 9.7 ml/h) and quiet sleep (18.8 +/- 7.7 ml/h).

CONCLUSIONS

1) Hourly fetal urine production rate is independent of ECoG activity state in the near-term ovine fetus. 2) Assuming only minor species differences, ultrasound measurement of human fetal hourly urine production rate can be performed without concern for fetal neurobehavioral state changes.

Postnatal changes in the types of muscle fibre in the canine inferior pharyngeal constrictor

Deglutition is considered to be immature in infants and to mature postnatally. We evaluated postnatal changes in muscle fibre type composition in the canine inferior pharyngeal constrictor muscle, which consists of the thyropharyngeal (TP) and cricopharyngeal (CP) muscles, using ATPase staining with respect to the maturation of deglutition. In the TP muscle type IIA and type IIB fibres, the main components in the adult, were already predominant at 1 week postnatally. The percentage of primitive type IIC fibre showed a rapid reduction and reached the adult level within 6 weeks. In the CP muscle, the majority of fibres were type IIC at 2 weeks. At 2 months, more than 20% of the fibres were still type IIC and the proportion of type I fibres as a main component in the adult was smaller than that of the adult. None of the puppies younger than 9 weeks old had a fibre type composition similar to that of the adult. In the extensor digitorum longus and flexor digitorum superficialis, the compositions of muscle fibre types became similar to that of the adult at 6 and 9 weeks of age, respectively. Thus, the TP muscle matured more rapidly than the limb muscles, while the CP muscle matured more slowly. We speculated that the TP and CP muscles have specific individual differentiation patterns associated with their functional roles before and after birth, compared with the limb muscles.

Prediction of oligohydramnios in prolonged pregnancy

A decrease in amniotic fluid in prolonged pregnancy is associated with increased fetal morbidity. However, few investigations have been reported on the prediction of this condition. Fetal renal arterial pulsatility index (PI), hourly fetal urine production rate (HFUPR) and amniotic fluid index (AFI) at 39 weeks were studied in 51 singleton pregnancies with (n = 14) and without oligohydramnios (AFI < 5, n = 37) in prolonged pregnancy. There was no difference in the average fetal renal arterial PI and HFUPR between the oligohydramnios group and the normal group. However, the average AFI in the oligohydramnios group was 7.5 +/- 0.9, which was lower than that in the normal group (p < 0.05). We speculated that AFI value at 39 weeks is useful for predicting the incidence of oligohydramnios in prolonged pregnancy.

Regulatory response of intramembranous absorption of amniotic fluid to infusion of exogenous fluid in sheep

Six fetal sheep were operated on at 118 to 121 days of gestation. The pulmonary end of the trachea was connected to the gastric end of the esophagus with a section of tubing. This left urine as the only source of amniotic fluid and intramembranous absorption as sole exit. Multiple indwelling fetal vascular, intra-amniotic, allantoic, and a fetal bladder catheter were placed. Beginning 5 days after surgery, all urine was drained from the bladder and immediately reinfused into the amniotic sac to monitor urine production rate. After 4 days of urine infusion alone, the urine infusion was augmented for 6 days with an intra-amniotic infusion of Ringer solution. Amniotic and allantoic fluid volumes were measured at autopsy. During the period of Ringer infusion, intramembranous absorption of amniotic fluid increased by more than 1,191 +/- 186 (SE) ml/day (P < 0.002) and the rates of Na(+) and Cl(-) absorption increased to more than five times (P < 0.005) and eight times (P < 0.005) their initial values. Only one of six fetuses had polyhydramnios. It is concluded that intramembranous absorption of amniotic fluid makes a strong regulatory adjustment in response to an abnormal increase in inflow of exogenous fluid.

Clinical utility of amniotic fluid volume assessment

Abnormal amniotic fluid volume is associated with increased maternal risk and perinatal morbidity and mortality. Until the advent of ultrasonography, the invasive nature of amniotic fluid volume assessment limited its clinical utility. Refinements in quantifying the noninvasive sonographic assessment of oligohydramnios and hydramnios have improved the ability of clinicians to identify at-risk pregnancies. This article reviews the available methods of amniotic fluid volume assessment and outlines a comprehensive approach to sonographic screening and monitoring.

Development of ingestive behavior

Swallowing represents a primary physiological function that provides for the ingestion of food and fluid. In precocial species, swallowing activity likely develops in utero to provide for a functional system during the neonatal period. The chronically instrumented ovine fetal preparation has provided the opportunity for recent advances in understanding the regulation of in utero swallowing activity. The near-term ovine fetus swallows fluid volumes (100-300 ml/kg) that are markedly greater, per body weight, than that of the adult (40-60 ml/kg). Spontaneous in utero swallowing and ingestive behavior contribute importantly to the regulation of amniotic fluid volume and composition, the acquisition and potential recirculation of solutes from the fetal environment, and the maturation of the fetal gastrointestinal tract. Fetal swallowing activity is influenced by fetal maturation, neurobehavioral state alterations, and the volume of amniotic fluid. Furthermore, intact dipsogenic mechanisms (osmolality, angiotensin II) have been demonstrated in the near-term ovine fetus. It remains unknown to what degree, if any, fetal swallowing may be influenced by nutrient appetite, salt appetite, or taste. Nevertheless, the development of dipsogenic and additional regulatory mechanisms for ingestive behavior occurs during fetal life and may be susceptible to changes in the pregnancy environment. This review describes what is currently known regarding the in utero development of ingestive behavior and the importance of this activity for fetal and perhaps ultimately adult fluid homeostasis.