Blood chemistry of normal human fetuses at midtrimester of pregnancy

Physiologically Based Pharmacokinetics Modeling in the Neonatal Population-Current Advances, Challenges, and Opportunities

Physiologically based pharmacokinetic (PBPK) modeling is an approach to predicting drug pharmacokinetics, using knowledge of the human physiology involved and drug physiochemical properties. This approach is useful when predicting drug pharmacokinetics in under-studied populations, such as pediatrics. PBPK modeling is a particularly important tool for dose optimization for the neonatal population, given that clinical trials rarely include this patient population. However, important knowledge gaps exist for neonates, resulting in uncertainty with the model predictions. This review aims to outline the sources of variability that should be considered with developing a neonatal PBPK model, the data that are currently available for the neonatal ontogeny, and lastly to highlight the data gaps where further research would be needed.

Early Life Programming of Skeletal Health

PURPOSE OF REVIEW

Increasing bone mineral accrual during childhood might delay the onset of osteoporosis. We discuss the scientific evidence for early life approaches to optimising skeletal health.

RECENT FINDINGS

There is an ever-growing body of evidence from observational studies suggesting associations between early life exposures, particularly during foetal development, and bone mineral density (BMD). The findings of such studies are often heterogeneous, and for some exposures, for example, maternal smoking and alcohol intake in pregnancy or age at conception, intervention studies are not feasible. The most frequently studied exposures in intervention studies are calcium or vitamin D supplementation in pregnancy, which overall suggest positive effects on offspring childhood BMD. Maternal calcium and/or vitamin D supplementation during pregnancy appear to have positive effects on offspring BMD during early childhood, but further long-term follow-up is required to demonstrate persistence of the effect into later life.

Developmental changes in the extent of drug binding to rat plasma proteins

Binding of therapeutics to proteins in blood plasma is important in influencing their distribution as it is their free (unbound) form that is able to cross cellular membranes to enter tissues and exert their actions. The concentration and composition of plasma proteins vary during pregnancy and development, resulting in potential changes to drug protein binding. Here, we describe an ultrafiltration method to investigate the extent of protein binding of six drugs (digoxin, paracetamol, olanzapine, ivacaftor, valproate and lamotrigine) and two water soluble inert markers (sucrose and glycerol) to plasma proteins from pregnant and developing rats. Results showed that the free fraction of most drugs was lower in the non-pregnant adult plasma where protein concentration is the highest. However, plasma of equivalent protein concentration to younger pups obtained by diluting adult plasma did not always exhibit the same extent of drug binding, reinforcing the likelihood that both concentration and composition of proteins in plasma influence drug binding. Comparison between protein binding and brain drug accumulation in vivo revealed a correlation for some drugs, but not others. Results suggests that plasma protein concentration should be considered when using medications in pregnant and paediatric patients to minimise potential for fetal and neonatal drug exposure.

Quantification of Fetal Renal Function Using Fetal Urine Production Rate and Its Reflection on the Amniotic and Fetal Creatinine Levels During Pregnancy

Adequate prediction of fetal exposure of drugs excreted by the kidney requires the incorporation of time-varying renal function parameters into a pharmacokinetic model. Published data on measurements of fetal urinary production rate (FUPR) and creatinine at various gestational ages were collected and integrated for prediction of the fetal glomerular filtration rate (GFR). The predicted GFR values were then compared to neonatal values recorded at birth. Collected data for FUPR across different gestational ages using both 3D (N = 517) and 2D (N = 845) ultrasound methods showed that 2D techniques yield significantly lower estimates of FUPR than 3D (p < 0.0001). A power law function was shown to best capture the change in FUPR with fetal age (FA) for both 2D ( F U P R 2 D ( m L min ) = 0 . 000169     FA 2 . 19 ); and 3D ( F U P R 3 D   ( m L min ) =   3 . 21 × 1 0 - 7   FA 4 . 21 ) data. The predicted FUPR based on the observed 3D data was shown to be strongly linearly related (R ² = 0.95) to measured values of amniotic creatinine concentration (N = 664). The FUPR_3D data together with creatinine levels in the fetal urine and serum resulted in median predicted fetal GFR values of 0.47, 1.2, 2.5, and 4.9 ml/min at 23, 28, 33, and 38 weeks of fetal age (50% CV), respectively. These values are in good agreement with neonatal values observed immediately at birth. The derived FUPR and creatinine functions can be utilized to assess fetal renal maturation and predict fetal renal clearance.

A Preterm Physiologically Based Pharmacokinetic Model. Part I: Physiological Parameters and Model Building

BACKGROUND

Developmental physiology can alter pharmacotherapy in preterm populations. Because of ethical and clinical constraints in studying this vulnerable age group, physiologically based pharmacokinetic models offer a viable alternative approach to predicting drug pharmacokinetics and pharmacodynamics in this population. However, such models require comprehensive information on the changes of anatomical, physiological and biochemical variables, where such data are not available in a single source.

OBJECTIVE

The objective of this study was to integrate the relevant physiological parameters required to build a physiologically based pharmacokinetic model for the preterm population.

METHODS

Published information on developmental preterm physiology and some drug-metabolising enzymes were collated and analysed. Equations were generated to describe the changes in parameter values during growth.

RESULTS

Data on organ size show different growth patterns that were quantified as functions of bodyweight to retain physiological variability and correlation. Protein binding data were quantified as functions of age as the body weight was not reported in the original articles. Ontogeny functions were derived for cytochrome P450 1A2, 3A4 and 2C9. Tissue composition values and how they change with age are limited.

CONCLUSIONS

Despite the limitations identified in the availability of some tissue composition values, the data presented in this article provide an integrated resource of system parameters needed for building a preterm physiologically based pharmacokinetic model.

The importance of maternal pregnancy vitamin D for offspring bone health: learnings from the MAVIDOS trial

Optimisation of skeletal mineralisation in childhood is important to reduce childhood fracture and the long-term risk of osteoporosis and fracture in later life. One approach to achieving this is antenatal vitamin D supplementation. The Maternal Vitamin D Osteoporosis Study is a randomised placebo-controlled trial, the aim of which was to assess the effect of antenatal vitamin D supplementation (1000 IU/day cholecalciferol) on offspring bone mass at birth. The study has since extended the follow up into childhood and diversified to assess demographic, lifestyle and genetic factors that determine the biochemical response to antenatal vitamin D supplementation, and to understand the mechanisms underpinning the effects of vitamin D supplementation on offspring bone development, including epigenetics. The demonstration of positive effects of maternal pregnancy vitamin D supplementation on offspring bone development and the delineation of underlying biological mechanisms inform clinical care and future public-health policies.

Fetal Physiologically Based Pharmacokinetic Models: Systems Information on Fetal Blood Components and Binding Proteins

BACKGROUND

Fetal blood and plasma volume and binding components are critical parameters in a fetal physiologically based pharmacokinetic model. To date, a comprehensive review of their changes during fetal development has not been reported.

OBJECTIVE

The objective of this work was to collate and analyze physiological information on fetal blood and plasma volume and binding component data during development and to provide a mathematical description of these parameters that can be integrated within a fetal physiologically based pharmacokinetic model.

METHODS

A comprehensive literature search was conducted on fetal blood and plasma volume and binding component parameters and their changes during growth from apparently healthy fetuses from uncomplicated pregnancies. Collated data were assessed, integrated, and analyzed to establish continuous mathematical functions describing their growth trends with fetal age and weight.

RESULTS

Data were available from 14 studies for blood, ten studies for hematocrit, 12 studies for albumin, and four studies for alpha-1-acid glycoprotein, while plasma and red blood cell volumes were described based on blood and hematocrit data. Fetal physiologically based pharmacokinetic parameters, including blood, plasma and red blood cell volumes, hematocrit, serum albumin, and acid glycoprotein were quantified as a function of fetal age and weight. Variability around the mean parameters at different fetal ages was also investigated. The growth of each of these parameters was different (with respect to direction and monotonicity).

CONCLUSIONS

Despite the limitations identified in the availability of some values, the collected data presented in this article provide a useful resource for fetal physiologically based pharmacokinetic modeling. Potential applications include predicting xenobiotic exposure and risk assessment in the fetus following maternally administered drugs or unintended exposure to environmental toxicants.

Managing the Unusual Causes of Fetal Anemia

BACKGROUND

Rare causes of fetal anemia requiring intrauterine transfusion (IUT) are challenging for fetal medicine specialists.

OBJECTIVES

The aim of this study was to describe the perinatal patterns and prognosis in a consecutive series of fetuses transfused for fetal anemia of rare or unknown etiology, and to propose a protocol of investigation for fetal anemia of undetermined cause and for the management of subsequent pregnancies.

METHOD

We conducted a retrospective descriptive study on fetuses transfused for severe anemia of rare or unknown etiology managed in our national referral center (Centre National de Référence d'Hémobiologie Périnatale) and born between 2010 and 2017.

RESULTS

During the study period, 584 IUT were performed in 253 fetuses. Among those IUT, 23 (3.9%) were performed for a rare or unknown cause of anemia in 13 fetuses (5.1% of transfused fetuses). The median gestational age at diagnosis was 26 weeks of gestation (WG; range 21-33). Hemoglobin levels ranged from 1.6 to 9.1 g/dL (0.18-0.83 multiples of median) before the first IUT. The fetuses received between 1 and 6 IUT (39% received at least 2 IUT). The definitive etiologies for central anemia were: congenital syphilis, neonatal poikilocytosis, type II congenital dyserythropoietic anemia (CDA), and neonatal hemochromatosis. There was 1 case with suspected type I CDA and 1 with suspected Diamond-Blackfan anemia. There was 1 case of peripheral anemia, secondary to cerebral hemorrhages of different ages, related to a variant of the COL4A1 gene. In 6 fetuses corresponding to 4 mothers, no precise diagnosis was found despite a complete workup. In our series, there were 8 live births, 4 terminations of pregnancy, and 1 intrauterine fetal death.

CONCLUSIONS

Fetal anemia of rare or unknown diagnosis represents 5% of all transfused fetuses in our cohort. Fetal and neonatal anemias can be recurrent in further pregnancies, with variable expressivity.

Prenatal influences on bone health in children

INTRODUCTION

Optimising bone health might reduce the burden of both fractures in childhood and fragility fractures in later life. A number of maternal dietary and non-dietary factors have been identified that might influence offspring bone health and represent targets for intervention.

AREAS COVERED

This article will outline the accrual of bone mineral throughout the life course and how observational and intervention studies have shown that maternal diet, in particular maternal calcium and 25-hydroxyvitamin D [25(OH)D] status, and lifestyle are associated with offspring bone mineralization. Studies examining the effects of maternal micronutrient supplementation on offspring bone mineral density (BMD) will also be discussed.

EXPERT COMMENTARY

There is a wealth of observational evidence relating maternal diet to offspring BMD. However, high quality randomized controlled trials, such as the ongoing MAVIDOS study, are needed before these findings can be definitively translated into public health advice.

EXPOSURE TO FAMINE IN EARLY LIFE AND THE RISK OF OSTEOPOROSIS IN ADULTHOOD: A PROSPECTIVE STUDY

Objective: To assess the association between famine exposure in early life and osteoporosis in adulthood. Methods: A total of 2,292 participants born between 1955 and 1965 in Fujian Province were selected; after 3 years, 1,378 participants attended a follow-up research visit. Calcaneus bone mineral density and bone quality were measured by quantitative ultrasound. The T-score was used to assess bone mineral density, and the parameters quantitative ultrasound index (QUI), speed of sound (SOS), and broadband ultrasonic attenuation (BUA) were used to assess bone quality. A T-score threshold of -1.8 was defined as osteoporosis, and a possible vertebral fracture was considered as a prospective height loss of 0.8 inches or more. Results: Compared with the nonexposed cohort, risks of osteoporosis for fetal-, early childhood, and mid-childhood famine-exposed cohorts in postmenopausal women were adjusted odds ratio (OR), 3.741 (95% confidence interval [CI], 1.233, 11.44) versus OR 2.894 (95% CI, 0.997, 8.571) versus OR 4.699 (95% CI, 1.622, 13.612) by logistic regression but not significant in men. Moreover, the fetal-exposed cohort had a weak negative relation with QUI (β, -5.07 [-10.226, 0.127]) and BUA (β, -4.321 [-0.88, 0.238]). The early- and mid-childhood-exposed cohorts had significantly lower QUI (β, -7.085 [-11.799, -2.372] versus β, -10.845 [-15.68, -6.01]) and BUA (β, -6.381 [-10.515, -2.246] versus β, -8.573 [-12.815, -4.331]) than the nonexposed cohort by linear regression. None of the famine-exposed cohorts had a significant relationship with SOS. Conclusion: Famine exposure during early life is associated with higher risk of osteoporosis in adulthood, which is most obvious in postmenopausal women. Furthermore, famine exposure in early life has adverse effects on bone quality. Abbreviations: BMD = bone mineral density; BUA = broadband ultrasonic attenuation; CI = confidence interval; OR = odds ratio; QUI = quantitative ultrasound index; QUS = quantitative ultrasound; SOS = speed of sound.

Relationship of maternal creatinine to first neonatal creatinine in infants <30 weeks gestation

OBJECTIVE

To examine the relationship between maternal and neonatal creatinine (Cr) in preterm infants in the context of antenatal and intrapartum maternal and neonatal factors.

STUDY DESIGN

In this 5½-year, single-center, retrospective study, paired maternal and neonatal Cr were compared by t-test. Linear regression for correlated outcomes employing generalized estimating equations was used to examine neonatal Cr as a function of antenatal maternal Cr and potential confounders.

RESULT

A total of 157 neonates of 124 mothers met study criteria. Neonatal Cr values in the first 24 h of life were significantly higher than antenatal maternal values. Linear regression modeling showed that maternal Cr, neonatal lactate, hypoxic-ischemic villous changes on placental pathology and multiple gestation were each significant determinants of the first neonatal Cr.

CONCLUSION

No neonatal Cr was less than its paired maternal value. Maternal Cr, neonatal lactate, hypoxic-ischemic villous changes in the placenta and multiple gestation were each significantly associated with neonatal Cr.

Early development and osteoporosis and bone health

Osteoporosis is a skeletal disorder characterized by low bone mass and micro-architectural deterioration of bone tissue with a consequent increase in bone fragility and susceptibility to fracture. Evidence is now accumulating from human studies that programming of bone growth might be an important contributor to the later risk of osteoporotic fracture. Body weight in infancy is a determinant of adult bone mineral content, as well as of the basal levels of activity of the growth hormone/insulin-like growth factor-1 (GH/IGF-1) and hypothalamo-pituitary-adrenal (HPA) axes, and recent work has suggested a central role for vitamin D. Epidemiological studies have shown that maternal smoking and nutrition during pregnancy influence intrauterine skeletal mineralization. Childhood growth rates have been directly linked to the risk of hip fracture many decades later, and now evidence is emerging from experimental animal studies that support these observational data. Recent studies have also highlighted epigenetic phenomena as potential mechanisms underlying the findings from epidemiological studies.

Prenatal calcium and vitamin D intake, and bone mass in later life

The aging population will result in an increasing burden of osteoporotic fractures, necessitating the identification of novel strategies for prevention. There is increasing recognition that factors in utero may influence bone mineral accrual, and, thus, osteoporosis risk. The role of calcium and vitamin D has received much attention in recent years, and in this review, we will survey available studies relating maternal calcium and vitamin D status during pregnancy to offspring bone development. The evidence base supporting a positive influence on intrauterine skeletal growth appears somewhat stronger for maternal 25(OH)-vitamin D concentration than for calcium intake, and the available data point toward the need for high-quality randomized controlled trials in order to inform public health policy. It is only with such a rigorous approach that it will be possible to delineate the optimal strategy for vitamin D supplementation in pregnancy in relation to offspring bone health.

Fetal Laboratory Medicine: On the Frontier of Maternal–Fetal Medicine

BACKGROUND

Emerging antenatal interventions and care delivery to the fetus require diagnostic support, including laboratory technologies, appropriate methodologies, establishment of special algorithms, and interpretative guidelines for clinical decision-making.

CONTENT

Fetal diagnostic and therapeutic interventions vary in invasiveness and are associated with a spectrum of risks and benefits. Fetal laboratory assessments are well served by miniaturized diagnostic methods for blood analysis. Expedited turnaround times are mandatory to support invasive interventions such as cordocentesis and intrauterine transfusions. Health-associated reference intervals are required for fetal test interpretation. Fetal blood sampling by cordocentesis carries substantial risk and is therefore performed only when fetal health is impaired, or at risk. When the suspected pathology is not confirmed, however, normative fetal data can be collected. Strategies for assurance of sample integrity from cordocenteses and confirmation of fetal origin are described. After birth, definitive assessment of prenatal environmental and/or drug exposures to the fetus can be retrospectively assessed by analysis of meconium, hair, and other alternative matrices. A rapidly advancing technology for fetal assessment is the use of fetal laboratory diagnostic techniques that use cell-free fetal DNA collected from maternal plasma, and genetic analysis based on molecular counting techniques.

SUMMARY

Developmental changes in fetal biochemical and hematologic parameters in health and disease are continually delineated by analysis of our collective outcome-based experience. Noninvasive technologies for fetal evaluation are realizing the promise of lower risk yet robust diagnostics; examples include sampling and analysis of free fetal DNA from maternal blood, and analysis of fetal products accessible at maternal sites. Application of diagnostic technologies for nonmedical purposes (e.g., sex selection) underscores the importance of ethical guidelines for new technology implementation.

Cord blood calcium, phosphate, magnesium, and alkaline phosphatase gestational age-specific reference intervals for preterm infants

Background

The objective was to determine the influence of gestational age, maternal, and neonatal variables on reference intervals for cord blood bone minerals (calcium, phosphate, magnesium) and related laboratory tests (alkaline phosphatase, and albumin-adjusted calcium), and to develop gestational age specific reference intervals based on infants without influential pathological conditions.

Methods

Cross-sectional study. 702 babies were identified as candidates for this study in a regional referral neonatal unit. After exclusions (for anomalies, asphyxia, maternal magnesium sulfate administration, and death), relationships were examined between cord blood serum laboratory analytes (calcium, phosphate, magnesium, alkaline phosphatase, and albumin-adjusted calcium) with gestation age and also with maternal and neonatal variables using multiple linear regression. Infants with influential pathological conditions were omitted from the development of gestational age specific reference intervals for the following categories: 23-27, 28-31, 32-34, 35-36 and > 36 weeks.

Results

Among the 506 preterm and 54 terms infants included in the sample. Phosphate, magnesium, and alkaline phosphatase in cord blood serum decreased with gestational age, calcium increased with gestational age. Those who were triplets, small for gestational age, and those whose mother had pregnancy-induced hypertension were influential for most of the analytes. The reference ranges for the preterm infants ≥ 36 weeks were: phosphate 1.5 to 2.6 mmol/L (4.5 to 8.0 mg/dL), calcium: 2.1 to 3.1 mmol/L (8.3 to 12.4 mg/dL); albumin-adjusted calcium: 2.3 to 3.2 mmol/L (9.1 to 12.9 mg/dL); magnesium 0.6 to 1.0 mmol/L (1.4 to 2.3 mg/dL), and alkaline phosphatase 60 to 301 units/L.

Conclusions

These data suggest that gestational age, as well as potentially pathogenic maternal and neonatal variables should be considered in the development of reference intervals for preterm infants.

Regulation of placental calcium transport and offspring bone health

Osteoporosis causes considerable morbidity and mortality in later life, and the risk of the disease is strongly determined by peak bone mass, which is achieved in early adulthood. Poor intrauterine and early childhood growth are associated with reduced peak bone mass, and increased risk of osteoporotic fracture in older age. In this review we describe the regulatory aspects of intrauterine bone development, and then summarize the evidence relating early growth to later fracture risk. Physiological systems include vitamin D, parathyroid hormone, leptin, GH/IGF-1; finally the potential role of epigenetic processes in the underlying mechanisms will be explored. Thus factors such as maternal lifestyle, diet, body build, physical activity, and vitamin D status in pregnancy all appear to influence offspring bone mineral accrual. These data demonstrate a likely interaction between environmental factors and gene expression, a phenomenon ubiquitous in the natural world (developmental plasticity), as the potential key process. Intervention studies are now required to test the hypotheses generated by these epidemiological and physiological findings, to inform potential novel public health interventions aimed at improving childhood bone health and reducing the burden of osteoporotic fracture in future generations.

The prognostic value of ultrasound abnormalities and biological parameters in blood of fetuses infected with cytomegalovirus

OBJECTIVE

To evaluate the prognostic value of ultrasound abnormalities and of selected biological parameters in blood of fetuses infected with cytomegalovirus (CMV).

DESIGN

Retrospective observational study.

SETTING

Two fetal medicine units in Paris, France.

POPULATION

All fetuses infected with CMV referred between 1998 and 2006.

METHODS

We retrospectively analysed data collected prospectively in 73 fetuses infected by CMV with a positive CMV polymerase chain reaction in amniotic fluid. Fetal blood sampling (FBS) was performed for evaluation of platelet count, plasma levels of aminotransferases and gamma-glutamyl transpeptidases (GGT), presence of viraemia and specific fetal immunoglobulin M. Targeted ultrasound examination was performed every fortnight. Ultrasound findings were categorised into normal examination and any ultrasound abnormality, which was further grouped as ultrasound abnormality of the fetal brain and noncerebral ultrasound abnormality.

MAIN OUTCOME MEASURES

A combination of histological findings after termination of pregnancy and evidence of cytomegalic inclusion disease at birth when pregnancies were continued. Clinical symptoms at birth or histological lesions attributable to CMV were considered as poor outcome. Statistical analysis was conducted to determine the value of each parameter to predict outcome. Logistic regression was used to build up a multivariate model combining the relevant parameters.

RESULTS

In univariate analysis, only thrombocytopenia and the presence of any ultrasound abnormality were associated with a poor outcome (P < 10(-4) for both abnormalities). In the multivariate analysis, both thrombocytopenia and the presence of ultrasound abnormalities remained significant independent predictors of a poor outcome. Based on univariate logistic regression, odds ratio for a poor outcome were 1.24, 7.2, 22.5 and 25.5 for each 10,000/mm(3) decrease in platelet count, the presence of noncerebral, any ultrasound and cerebral ultrasound abnormalities, respectively.

CONCLUSIONS

The prognosis of CMV-infected fetuses relies independently on both targeted ultrasound examination and fetal platelet count. FBS for platelet count may therefore justify FBS in infected fetuses even in the absence of ultrasound. features of brain involvement.

Review: developmental origins of osteoporotic fracture

Osteoporosis is a major cause of morbidity and mortality through its association with age-related fractures. Although most effort in fracture prevention has been directed at retarding the rate of age-related bone loss and reducing the frequency and severity of trauma among elderly people, evidence is growing that peak bone mass is an important contributor to bone strength during later life. The normal patterns of skeletal growth have been well characterised in cross-sectional and longitudinal studies. It has been confirmed that boys have higher bone mineral content (BMC), but not volumetric bone density, than girls. Furthermore, there is a dissociation between the peak velocities for height gain and bone mineral accrual in both genders. Puberty is the period during which volumetric density appears to increase in both axial and appendicular sites. Many factors influence the accumulation of bone mineral during childhood and adolescence, including heredity, gender, diet, physical activity, endocrine status, and sporadic risk factors such as cigarette smoking. In addition to these modifiable factors during childhood, evidence has also accrued that fracture risk might be programmed during intrauterine life. Epidemiological studies have demonstrated a relationship between birth weight, weight in infancy, and adult bone mass. This appears to be mediated through modulation of the set-point for basal activity of pituitary-dependent endocrine systems such as the HPA and GH/IGF-1 axes. Maternal smoking, diet (particularly vitamin D deficiency), and physical activity also appear to modulate bone mineral acquisition during intrauterine life; furthermore, both low birth size and poor childhood growth are directly linked to the later risk of hip fracture. The optimisation of maternal nutrition and intrauterine growth should also be included within preventive strategies against osteoporotic fracture, albeit for future generations.

Ontogeny of hematological cell and biochemical profiles in maternal and fetal baboons (Papio species)

The normal ranges of hematological cell profiles and biochemistry are documented in adult non-pregnant, pregnant, juvenile, and neonatal baboons. Despite the extensive use of the baboon as a model for the study of various aspects of pregnancy, there is no data from paired mothers and their fetuses at different stages of gestation. Hematologic and biochemical profile data were obtained from eight non-pregnant female baboons, 37 mothers and 38 fetal baboons at 30 +/- 2, 90 +/- 2, 125 +/- 2, and 175 +/- 2 days of gestation (mean +/- range; dGA; term, 180 dGA). Changes observed in fetal and maternal blood during normal baboon pregnancy were similar to those reported in human pregnancy. The level of alkaline phosphatase was two times higher in fetal blood circulation than that reported in human pregnancy.

Amniotic Fluid and Maternal Blood Characteristics in Severe Mid-Trimester Twin–Twin Transfusion Syndrome

OBJECTIVE

To investigate the concentrations of metabolic variables in the amniotic fluid of the recipient twin and maternal blood and to correlate them with clinical features, which are characteristic for the course of pregnancies with twin-twin transfusion syndrome (TTS).

MATERIALS AND METHODS

In 109 pregnancies with severe mid-trimester TTS, we measured the concentrations of interleukin-6 (IL-6), alpha-fetoprotein (AFP), sodium, potassium, total protein, beta2-microglobulin and osmolality in the amniotic fluid of the recipient twin prior to laser coagulation of the vascular anastomoses and compared them to a control group of 92 singleton pregnancies. We measured the pulsatility index (PI) of ductus venosus flow velocity waveforms in the recipient twin and performed a retrospective chart analysis for complete maternal blood count before and after the procedure.

RESULTS

All variables, except osmolality, IL-6 and AFP were significantly lower in the TTS group. There was a significant positive correlation between PI in the ductus venosus and the amniotic fluid AFP concentrations (r = 0.355; p < 0.001). There was a significant fall in complete maternal blood count after laser therapy (p < 0.001) and a significant correlation between the amount of amniotic fluid drained and the fall of maternal Hb (r = -0.261; p = 0.03) and hematocrit (r = -0.212; p = 0.01).

CONCLUSION

Pathophysiologic changes in TTS do not only occur at the inter-twin level of placental vascular anastomoses but also at the materno-fetal level of fluid exchanges. AFP is correlated to the severity of congestive heart failure of the recipient twin.

Blood biochemistry and endocrinology in the human fetus between 11 and 17 weeks of gestation

Fetal blood was obtained in 35 normal pregnancies undergoing termination for psychosocial reasons between 11 and 17 weeks of gestation. Biochemical and endocrinological analyses were performed on each sample including concentrations of urea, creatinine, beta-microglobulin total protein, electrolytes, enzymes, alpha-fetoprotein (AFP), human chorionic gonadotrophin (HCG), thyroid stimulating hormone (TSH), thyroxin binding globulin (TBG), total thyroxin (TT4) and free thyroxin (FT4). The results were compared with values in maternal serum obtained at the same time. Fetal serum contained significantly higher concentrations of iron, beta-microglobulin, alkaline phosphatase (ALP), aspartate amniotransferase (AST), AFP, HCG and TSH and lower concentration of total protein, TBG and TT4 than maternal serum. Significant positive linear relationships were found between gestational age and the concentration of fetal serum total protein, ALP, TBG and FT4. Significant negative linear relationships were observed between gestational age and fetal serum beta-microglobulin and iron concentration. There were no significant correlations between fetal and maternal values. These data indicate that fetal blood biochemistry is not directly related to placental transfer and that the proteins and enzymes found inside the gestational sac are essentially of feto-placental origin with minimal contribution from the maternal protein metabolism. The comparison of coelomic fluid composition at 10-13 weeks with that of fetal serum at 11-17 weeks suggests that the anatomical changes in the human materno-fetal interface architecture between the early and late pregnancy periods could have a direct impact on materno-fetal transfer pathways.

Prenatal and childhood influences on osteoporosis

Osteoporosis is a major cause of morbidity and mortality through its association with age-related fractures. Although most effort in fracture prevention has been directed at retarding the rate of age-related bone loss, and reducing the frequency and severity of trauma among elderly people, evidence is growing that peak bone mass is an important contributor to bone strength during later life. The normal patterns of skeletal growth have been well characterized in cross-sectional and longitudinal studies. It has been confirmed that boys have higher bone mineral content, but not volumetric bone density, than girls. Furthermore, in both genders there is a dissociation between the peak velocities for height gain and bone mineral accrual. Puberty is the period during which volumetric density appears to increase in both axial and appendicular sites. Many factors influence the accumulation of bone mineral during childhood and adolescence, including heredity, gender, diet, physical activity, endocrine status and sporadic risk factors such as cigarette smoking. Measures for maximizing bone mineral acquisition, particularly through encouraging physical activity and adequate dietary calcium intake, are likely to affect the risk of fracture in later generations. In addition to these modifiable factors during childhood, evidence has also accrued that the risk of fracture might be programmed during intrauterine life. Epidemiological studies have demonstrated a relationship between birthweight, weight in infancy and adult bone mass. This appears to be mediated through modulation of the set-point for basal activity of pituitary-dependent endocrine systems such as the hypothalamic - pitutiary - adrenal (HPA) and growth hormone/insulin-like growth factor I (GH/IGF-I) axes. Maternal smoking, diet and physical activity levels appear to modulate bone mineral acquisition during intrauterine life; furthermore, both low birth size and poor childhood growth are directly linked to the later risk of hip fracture. The optimization of maternal nutrition and intrauterine growth should also be included within preventive strategies against osteoporotic fracture, albeit for future generations.

Fetal and maternal outcome after administration of tenofovir to gravid rhesus monkeys (Macaca mulatta)

Tenofovir has been shown to cross the placenta in quantities sufficient to sustain reductions in viral load in simian immunodeficiency virus (SIV)-infected fetal monkeys. With chronic exposure (30 mg/kg), however, significant bone-related toxicity has been shown in approximately 25% of infants studied. Further investigations were conducted to determine whether the bone-related toxicity observed was initiated during fetal life. Gravid rhesus monkeys (n = 4) were administered tenofovir subcutaneously once daily from 20 to 150 days of gestation (30 mg/kg; term: 165 +/- 10 days). Fetuses were monitored sonographically, and maternal and fetal blood and urine samples were collected to assess hematologic parameters, clinical chemistry, insulin-like growth factor (IGF) levels, and bone biomarkers. Fetuses were delivered by hysterotomy near term for necropsy and evaluation of bone-related mechanical properties. Results of these studies have shown 1) normal fetal development, although overall body weights and crown-rump lengths were less than those for age-matched controls (p < or = .03); 2) a significant reduction in circulating IGF-I (p <.001); 3) a small reduction in fetal bone porosity (p < or = .03); and 4) transient alterations in maternal body weights and bone-related biomarkers during the treatment period. The results of these studies suggest that chronic fetal exposure to tenofovir at the maternal dose of 30 mg/kg throughout gestation can alter select fetal parameters and transiently affect maternal bone biomarkers.

Plasma creatinine rises dramatically in the first 48 hours of life in preterm infants

OBJECTIVE

Published data show that plasma creatinine falls steadily during the first 28 days of life and that creatinine levels in the neonatal period are higher in more premature infants. However, the best reference data commence on day 2 of life. The objective of this study was to document how plasma creatinine changes in the first 48 hours of life and to examine the reason for the apparently high levels of creatinine in preterm infants, compared with maternal levels.

DESIGN

A prospective observational study on a regional neonatal intensive care unit.

PATIENTS

A total of 42 preterm infants, mean gestational age of 29.4 weeks (range: 23-35), mean birth weight of 1.42 kg (.55-2.77), divided into 4 gestation groups: 23 to 26 weeks (n = 9), 27 to 29 weeks (n = 13), 30 to 32 weeks (n = 12), and 33 to 35 weeks (n = 8).

INTERVENTIONS

Measurement of plasma creatinine and urea concentration in cord blood and in serial samples taken for routine arterial blood gas analysis.

OUTCOME MEASUREMENTS

Changes in creatinine concentration with time and relationship to gestational age, birth weight, and illness severity.

RESULTS

Mean creatinine at birth was 73 micromol/L (95% confidence interval [CI]: 68-79 micromol/L). Plasma creatinine rose significantly over the first 48 hours. Mean peak creatinine in the most preterm infants (23-26 weeks) was 221 micromol/L (CI: 195-247 micromol/L). Peak plasma creatinine was inversely related to gestation (Spearman's coefficient: -.73) and birth weight (Spearman's coefficient: -.76). Significant differences in creatinine concentration were seen among different gestational groups at 24 and 48 hours of life. Peak creatinine correlated with a high Clinical Risk Index for Babies score (Spearman's coefficient:. 64). The fall in creatinine began later in more premature infants. All 38 surviving infants had normal renal function; their mean plasma creatinine at discharge was 52 micromol/L (CI: 46-58 micromol/L).

CONCLUSIONS

Rather than falling steadily from birth, creatinine rises dramatically in the first 48 hours of life, especially in infants of <30 weeks' gestation. Even large rises in creatinine in the first 48 hours may be expected and should not be used in isolation to diagnose renal failure.

Assessing fluid and electrolyte status in the newborn

Fluid and electrolyte assessment during the first week of life is complicated by rapid changes in fluid and electrolyte balance during the transition from fetal to neonatal life and by the newborn’s small size. A physiologic decrease in extracellular water volume, as well as a transient increase in serum potassium and transient decreases in plasma glucose and total plasma ionized calcium concentrations must be taken into account. In general, the more immature the newborn, the greater the changes that can be expected. The use of plasma creatinine as an indicator of glomerular filtration rate is limited because it is a function of maternal renal function at birth and because of non-steady-state conditions in the immediate postnatal period. Guidelines for monitoring schedules are provided on the basis of these physiologic considerations and the author’s experience. Method of blood sampling and time to separation of serum are important considerations in interpreting results. Minimization of sample volume is critical to minimize blood transfusion requirements. Clinicians should be aware of the analytical error associated with these measurements in their own institutions. Reference ranges are provided.

Serum lipid, apolipoprotein and lipoparticle levels in the human fetus

Blood collected from 62 fetuses aged 20-38 weeks of gestation was studied. The values of ten lipid parameters were determined: cholesterol (TC), triglycerides (TGs), apolipoprotein A1 (apo A1), apolipoprotein B (apo B), apolipoprotein E (apo E), total apolipoprotein CIII (apo CIII), apolipoprotein CIII present in particles containing apo B (apo CIII LpB) or not (apo CIII Lp non-B), lipoparticles A1 (LpA1), and lipoprotein a (Lp(a)). The results show that, except for apo E, all the studied parameters were present in lower concentrations than in adults and newborns, and that Lp(a) is not detectable at that stage in life.

Plasma protein levels in normal human fetuses: 13 to 41 weeks' gestation

OBJECTIVES

To establish reference ranges for the levels of alpha-fetoprotein, albumin, prealbumin (transthyretin) alpha-1-antitrypsin, transferrin, ceruloplasmin and total protein in the plasma of normal human fetuses and newborn babies.

DESIGN

Prospective study of individual normal cases to fulfil objectives.

SETTING

Pathology laboratories of the University of Edinburgh and the biochemistry laboratories of the University of Keele.

SUBJECTS

Twenty-two normal fetuses 13 to 22 weeks of gestation and 66 babies born between 24 and 41 weeks gestation.

RESULTS

Albumin is the predominant plasma protein throughout gestation. The levels of alpha-fetoprotein and prealbumin fell significantly with increasing gestation, whereas the concentrations of the other proteins studied increased. The ratios of individual proteins to total protein demonstrated similar trends.

CONCLUSIONS

This study provides developmental profiles of normal human fetal plasma proteins to serve as possible reference data for abnormal fetuses. Declining levels of prealbumin (transthyretin) were unexpected and suggest a functional role for this protein in early pregnancy.

Renal function in sick very low birthweight infants: 2. Urea and creatinine excretion

Plasma urea and creatinine concentrations and urea and creatinine clearances and excretion were measured in a sample of 40 infants of 25.5-33 weeks' gestation, birth weight 720-2000 g, between the ages of 0.5 and 33 days. Creatinine excretion rate was between 60 and 120 mumol/kg/day in the first five postnatal weeks (mean 90.5) and was independent of sex or growth retardation. This can be used in clinical practice to estimate instantaneous urine flow rate V, if the creatinine concentration is measured in a randomly voided urine sample, from the formula V = 90.5/urine creatinine, with 95% confidence limits +/- 39%. There is a wide range of plasma creatinine at all gestations and ages decreasing from range 75-130 mumol/l in the first two days to 35-80 mumol/l at 3 weeks of age. Plasma urea is a poor indicator of glomerular filtration rate (GFR) in sick preterm infants. GFR (ml/min/kg) can be estimated from plasma creatinine from the formula GFR = 69.2/plasma creatinine but this estimate is imprecise with 95% confidence limits +/- 46%. Urea:creatinine clearance ratio was usually less than 1.0 (range 0.18 to 1.5) and was lower when the urine flow rate was low. Urea excretion was up to 17 mmol/kg/day in the first two weeks, higher in the more immature infants. These high levels were paralleled by a high plasma urea concentration, up to 18 mmol/l. A high plasma urea is not necessarily associated with renal failure or dehydration.

Changes in alpha 1-acid glycoprotein serum concentrations and glycoforms in the developing human fetus

alpha 1-Acid glycoprotein concentrations and reactivity to concanavalin A were measured in maternal and fetal serum and amniotic fluid obtained from 24 women undergoing diagnostic cordocentesis at 20 to 33 wk gestation and in 30 additional fetal sera (19 to 34 weeks gestation). Maternal alpha 1-acid glycoprotein serum levels were five to ten times higher than fetal and amniotic levels. Fetal alpha 1-acid glycoprotein levels were found to increase with advancing gestational age. Using crossed immunoaffino electrophoresis with concanavalin A, alpha 1-acid glycoprotein patterns were identical in maternal serum and amniotic fluid but totally different in fetal serum. The fetal concanavalin A pattern changed progressively during fetal life towards that of the newborn. These data confirm earlier assumptions of fetal synthesis of alpha 1-acid glycoprotein and provide normal reference values for alpha 1-acid glycoprotein in fetal serum. In addition, the specific fetal concanavalin A pattern indicates that the alpha 1-acid glycoprotein glycosylation process during fetal life differs from that in post-natal life.

Developmental profile of plasma proteins in human fetal cerebrospinal fluid and blood

Total protein, alphafetoprotein, albumin, prealbumin, alpha-1-antitrypsin, transferrin and ceruloplasmin levels were measured in samples of human fetal and neonatal cerebrospinal fluid (CSF) (97 cases), obtained between 12 and 41 weeks of gestation. In 39 of these cases (13 to 40 weeks gestation) plasma was also available for comparative analysis. CSF was collected from lateral ventricles in the first half of gestation and from the lumbar region in the second. Since these CSF samples were obtained from different sites, the protein levels in the lateral ventricle (early) samples could not be compared directly with those in the lumbar (later) samples. However, the mean protein levels in the lumbar samples were lower than those in the ventricular samples, which is in accord with the decline in CSF protein levels described in maturing animal fetuses. Despite a wide scatter of results, particularly in the first half of gestation, significant decline in the level of CSF alphafetoprotein was demonstrated during both first and second halves of gestation, and of albumin and prealbumin in the second half. No sex differences were found except for ceruloplasmin in lumbar CSF later in gestation, when males had higher levels than females. In fetal plasma, protein levels increased with increasing gestation apart from alphafetoprotein and prealbumin which both declined progressively. CSF/plasma ratios were dissimilar for different proteins, and changed with increasing gestation. These findings support the concept that the human fetal blood brain barrier matures early.

Blood chemistry of human fetuses in the second and third trimesters

Six biochemical parameters and four enzyme activities were determined from the serum of 76 healthy and 56 pathological human fetuses between the 20th and 38th week of pregnancy. In the normal fetuses studied within that period, creatinine, immunoglobulin M, lactate dehydrogenase, and gamma-glutamyltransferase increased; haemoglobin F and glucose progressively decreased; and alkaline phosphatase was at a peak around the 26th week; cholesterol and triglycerides were always low. The same parameters were also measured in some of the pathological fetuses and compared with their normal counterparts.

Percutaneous umbilical blood sampling

Percutaneous umbilical blood sampling (PUBS), also called cordocentesis, is a newly introduced technique that enables blood samples to be obtained from the fetus in utero for a variety of conditions. The major applications are for the diagnosis of fetal infections, karyotype analysis, fetal growth retardation, diagnosis of hematologic conditions, and metabolic evaluation. This procedure is gaining in popularity, since it provides direct information on fetal blood status. It can be applied to therapeutic manipulations such as in utero transfusions or drug administration. The procedure is remarkably safe and has few technical problems. The applicability of its use in the assessment of fetal thrombocytopenia is also discussed in detail.

Maternal-fetal glucose gradient in normal pregnancies and in pregnancies complicated by alloimmunization and fetal growth retardation

Maternal and fetal glucose concentrations were measured simultaneously in 54 pregnancies in which fetal blood sampling was conducted between 18 and 34 weeks gestation. Twenty-five pregnancies were normal (group 1), 13 were complicated by fetomaternal alloimmunization (group 2), and 16 by intrauterine growth retardation (group 3). The maternal glucose concentration was similar in the three groups. The fetal glucose level was significantly lower in growth-retarded (mean = 2.7 mmol/L) than in normal pregnancies (mean = 3.5 mmol/L). There was a statistically significant gradient between maternal and fetal glucose concentrations in groups 1 and 3, but no gradient was found in group 2. Maternal and fetal glucose concentrations were significantly correlated in all groups, but the correlations were distinct. For a given maternal glucose concentration, fetal glucose was higher in patients with alloimmunization and lower in patients with intrauterine growth retardation than in normal pregnancies. In patients with intrauterine growth retardation, fetal PO2 correlated positively with fetal glucose and inversely with maternal fetal glucose gradient.

Consequences of fetomaternal haemorrhage after intrauterine transfusion

Fetomaternal haemorrhage was studied after 68 consecutive fetal intravascular transfusions performed in 20 patients with Rh isoimmunisation. alpha Fetoprotein concentration was assayed in maternal blood taken before, and immediately after each transfusion and three and 24 hours later. An increase of 50% or more in the concentration in any of the samples after transfusion was considered to indicate fetomaternal haemorrhage. Fetal alpha fetoprotein concentration in blood sampled before transfusion was also assayed and the amount of fetomaternal haemorrhage calculated. Fetomaternal haemorrhage occurred in 21 of 32 patients with an anterior placenta and in six of 36 with a posterior or fundal placenta. The mean estimated volume of haemorrhage was 2.4 ml, which was on average equal to 3.1% of the total fetoplacental blood volume. When the volume of fetomaternal haemorrhage at the first transfusion was greater than 1 ml there was a greater increase in maternal Rh (D) antibody titres and a greater fall in fetal packed cell volume. Sampling of fetal blood should not be routinely done early in patients with Rh isoimmunisation, and intrauterine transfusion should be delayed as long as possible. Sampling sites other than the placental cord insertion reduces the risk of fetomaternal haemorrhage.

Physiology and management of intrauterine growth retardation: a biologic approach with fetal blood sampling

Intrauterine growth retardation is a major contributor to perinatal mortality and morbidity. The most important obstetric problem is to determine which fetuses are well in utero and which are at risk of irreversible damage or severe and prolonged neonatal morbidity. The optimal timing of delivery is at present made by subjective assessment of clinical variables. We present hematologic and biochemical values obtained by fetal blood sampling of 24 idiopathic fetuses with intrauterine growth retardation to give objective information on which to base clinical management. The results show that there is stimulation of erythropoiesis as well as evidence of red blood cell destruction and liver damage. In many cases there is acute decompensation with acid base abnormalities in a setting of chronic hematologic and biochemical changes.

The assessment of fetal blood samples

Fetal blood sampling under ultrasound control is rapidly expanding the study of human fetal biology. Pure fetal blood is required for prenatal diagnosis, establishment of reference ranges for biologic measurements, and assessment of fetal welfare. We present here the methods that we have developed to detect contamination in more than 1500 samples. These include hematologic indexes, blood smear, erythrocyte antigens, beta-human chorionic gonadotropin, and coagulation factor assays. The tests are relatively simple, inexpensive, and widely available. No single test is reliable in all situations, and it is necessary to perform all the tests on each sample of fetal blood. In the clinical setting where irrevocable action may be taken as a consequence of our results, we require absolute assurance of the purity of the sample.

The reversal of hydrops fetalis by intravascular intrauterine transfusion in severe isoimmune fetal anemia

Seventy-two intrauterine intravascular transfusions were performed on 26 patients with severe erythroblastosis fetalis. Twenty of the 26 fetuses were hydropic at the time of referral. Of the 20 hydropic fetuses, 16 (80%) survived. Hydrops was completely reversed in 13 of the 16 fetuses (81%). Total protein of less than 3 gm/dl, albumin less than 2 gm/dl, and a hematocrit level of less than 15% were associated with hydrops fetalis. After hydrops was reversed, total protein greater than 3 gm/dl, albumin greater than 2 gm/dl, along with a sustained hematocrit level of greater than 15%, were found. Only three neonates were born with minimal ascites, two of whom had had intraperitoneal transfusions before intravascular treatments. There were 21 survivors of the total group, giving an overall survival rate of 82%. There was one neonatal death from severe respiratory distress syndrome. Thirty-eight percent of the neonates did not require exchange transfusions in the newborn period. Intrauterine intravascular transfusions appear to be an effective mode of therapy in severe erythroblastosis fetalis and not only increase survival rates but also decrease neonatal morbidity and mortality.