PFAS alters placental arterial vasculature in term human placentae: A prospective pregnancy cohort study

INTRODUCTION

Perfluoroalkyl substances (PFAS) are synthetic chemicals used in industrial and consumer goods that are widely detected in human populations and are associated with adverse health outcomes, including perinatal health risks and child health. One mechanism of influence may be the impact of PFAS exposure on placental structure and function.

OBJECTIVES

The objective of this study is to investigate the relationship between maternal prenatal exposure to PFAS and measures of placental vascularization, and to assess whether changes in vascularization play a role in mediating the impact of PFAS on birth outcomes.

METHODS

Using data from a prospective cohort study, we examined associations between second trimester PFAS (individually and as mixtures using Bayesian kernel machine regression) and placental arterial vasculature in term placentae (N = 158); secondarily we evaluated the degree to which alterations in placental arterial vasculature explained associations between PFAS exposure and birth outcomes. Placental arterial vasculature features were collected from arterial tracings of each placental image.

RESULTS

In both linear regression and mixture models, natural log-transformed perfluorooctanoic acid concentrations were negatively associated with surface vasculature, indexed by the mean distance from arterial end point to perimeter (β = -0.23, 95% CI: -0.41, -0.041); additionally, maximum arterial tortuosity was negatively associated with placental weight (β = -0.19, 95% CI: -0.34, -0.051). There were no reliable differences in effect by fetal sex.

DISCUSSION

The findings provide some of the first evidence of PFAS exposure shaping a key measure of placental vascular function, which may underlie the impact of PFAS on perinatal and child health risks.

Comparison of trace element concentrations in paired formalin-fixed paraffin-embedded and frozen human placentae

INTRODUCTION

There is increasing interest in measuring metals concentrations in human placentas to better understand physiology, disease, and toxic and diagnostic exposures. For these purposes, formalin-fixed paraffin embedded (FFPE) tissues obtained at clinical pathology examination represent a valuable potential store of well-characterized tissues for analysis. However, the limited data that exist comparing metal concentrations in FFPE tissue to recently collected frozen tissues paints a confusing picture, and there is no published data directly comparing frozen and FFPE placental villus tissues.

METHODS

Paired samples of fresh frozen and FFPE tissue from 22 rapidly processed human singleton placentae were weighed and digested using standard clean laboratory procedures and subsequently analyzed for a suite of 13 metals using a PerkinElmer DRC II ICP-MS. The analytical results were compared using either a paired t-test or a sign test depending on data normality.

RESULTS

Concentrations of metals (aluminum (Al), arsenic (As), barium (Ba), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), gadolinium (Gd), mercury (Hg), manganese (Mn), lead (Pb), strontium (Sr), and zinc (Zn)) measured in both types of tissue preparations (frozen and FFPE) displayed a consistent range with other studies and did not display significantly different values from each of the paired specimens for any of the 13 specific metals analyzed.

DISCUSSION

Within placentae, metals concentrations of measured trace, toxic and diagnostic elements (Al, As, Ba, Cd, Cr, Cu, Fe, Gd, Hg, Mn, Pb, Sr, and Zn) are consistent between FFPE and fresh placental villus tissue, without indications of systematic element loss or bias. FFPE from archived pathology specimens may offer an important and convenient alternative for measuring trace metals in human frozen placental tissues.

Criteria for placental examination for obstetrical and neonatal providers

Pathologic examination of the placenta can provide insight into likely (and unlikely) causes of antepartum and intrapartum events, diagnoses with urgent clinical relevance, prognostic information for mother and infant, support for practice evaluation and improvement, and insight into advancing the sciences of obstetrics and neonatology. Although it is true that not all placentas require pathologic examination (although alternative opinions have been expressed), prioritization of placentas for pathologic examination should be based on vetted indications such as maternal comorbidities or pregnancy complications in which placental pathology is thought to be useful for maternal or infant care, understanding pathophysiology, or practice modifications. Herein we provide placental triage criteria for the obstetrical and neonatal provider based on publications and expert opinion of 16 placental pathologists and a pathologists' assistant, formulated using a modified Delphi approach. These criteria include indications in which placental pathology has clinical relevance, such as pregnancy loss, maternal infection, suspected abruption, fetal growth restriction, preterm birth, nonreassuring fetal heart testing requiring urgent delivery, preeclampsia with severe features, or neonates with early evidence of multiorgan system failure including neurologic compromise. We encourage a focused gross examination by the provider or an attendant at delivery for all placentas and provide guidance for this examination. We recommend that any placenta that is abnormal on gross examination undergo a complete pathology examination. In addition, we suggest practice criteria for placental pathology services, including a list of critical values to be used by the relevant provider. We hope that these sets of triage indications, criteria, and practice suggestions will facilitate appropriate submission of placentas for pathologic examination and improve its relevance to clinical care.

Placental morphology in association with autism-related traits in the EARLI study

Background

In prior work we observed differences in morphology features in placentas from an autism-enriched cohort as compared to those from a general population sample. Here we sought to examine whether these differences associate with ASD-related outcomes in the child.

Methods

Participants (n = 101) were drawn from the Early Autism Risk Longitudinal Investigation (EARLI), a cohort following younger siblings of children with autism spectrum disorder (ASD). ASD-related outcomes, including the Social Responsiveness Scale (SRS), Mullen Scales of Early Learning (MSEL) Early Learning Composite, and ASD diagnosis, were assessed at age 3. Crude and adjusted linear regression was used to examine associations between placental morphological features (parametrized continuously and in quartiles) and SRS and MSEL scores; comparisons by ASD case status were explored as secondary analyses due to the small number of cases (n = 20).

Results

In adjusted analyses, we observed a modest positive association between umbilical cord eccentricity, defined as the ratio of the maximum:minimum radius from the cord insertion point, and SRS scores (Beta = 1.68, 95%CI = 0.45, 2.9). Positive associations were also suggested between placental maximum thickness and cord centrality and SRS scores, though these were estimated with little precision. Associations between other placental morphological features and outcomes were not observed.

Conclusions

Our analyses suggested a potential association between umbilical cord features and ASD-related traits, of interest as non-central cord insertion may reflect reduced placenta efficiency. Future studies with larger sample sizes are needed to further examine these and other placental features in association with ASD-related outcomes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-022-04851-4.

Differences in clinical and laboratory biomarkers for short and long-term respiratory outcomes in preterm neonates

BACKGROUND

Pulmonary outcome of premature neonates has focused more on short-term than long-term respiratory morbidities.

OBJECTIVE

Describe risk factors/biomarkers associated with short-term (bronchopulmonary dysplasia [BPD]) (supplemental oxygen use at 36 weeks postmenstrual age [PMA]) and longer-term (chronic respiratory morbidity [CRM]) (respiratory related symptoms, medications, medical/emergency visits, hospitalizations at 6-12 months corrected gestational age [CGA]) respiratory outcomes in a longitudinal cohort.

DESIGN/METHODS

Neonates born at 24-29-week gestation were prospectively followed to 6-12-month CGA. Associations between clinical and laboratory risk factors/biomarkers of BPD and CRM were explored.

RESULTS

Of 86 subjects, 94% survived. Outcomes were available for 89% at 36-week PMA (BPD present in 42% of infants) and 72% at 6-12-month CGA (CRM present in 47% of infants). For the 54 infants with known outcomes for both BPD and CRM, diagnoses were discordant in 41%. BPD was associated with lower birthweight and birthweight Z-score for GA, lower Apgar scores, more surfactant doses, higher SNAPPE-II scores, highest Day 1 inspired oxygen concentration, Day 7 oxygen use, prolonged ventilatory support, bacteremia, necrotizing enterocolitis, and treated patent ductus arteriosus. CRM was associated with lower Apgar scores, Day 7 oxygen use and higher urine vascular endothelial growth factor. Patterns of plasma and urine lipid oxidation products differed in the two outcomes.

CONCLUSION

In this hypothesis generating and exploratory study, BPD and CRM were associated with different risk factors/biomarker patterns. Concordance between these two outcomes was weak. Strategies for reducing CRM should be studied in cohorts identified by appropriate early risk factors/biomarkers.

Ultrasonographic study of umbilical cord twist direction during second trimester

OBJECTIVE

To explore/study/evaluate the relationships among umbilical twist direction, the degree of umbilical twist and differences of umbilical arterial diameters (UAD).

METHODS

All obstetric patients presenting for prenatal care of singleton fetuses between 18 and 25 weeks gestation to a single provider (MN) from 2015 to 2018 had detailed umbilical cord Doppler measurements. Data including the cord twist direction, degree of twist and number of twists per cord segment length, and the diameters of each UA (UAD) and the umbilical vein (UVD) were extracted from the records. UAs were described as right or left depending on their position at the fetal cord insertion. Three groups were identified: Group A: right UAD > left UAD and Group B: left UAD > right UAD Group C: equal UAD. The coiling index was calculated as the inverse of the length of cord required for one complete 360 degrees wrap of the UA around the cord. According to the difference of UADs, the variables of right and left UADs, the coiling index, and frequencies of umbilical twist direction were analyzed using non-parametric methods.

RESULTS

485 singleton fetuses and umbilical cords were examined. The value of the antenatal coiling index in cases with left UAD greater than right was 0.43 ± 0.16, which was significantly higher than 0.38 ± 0.16 with right UAD greater than left (p = .001). There were significant differences between the two groups in the values of right and left UAD, value of right minus left UAD, absolute value between right and left UAD, antenatal coiling index, antenatal coiling index due to umbilical twist direction and frequencies of cord twist direction.

CONCLUSION

The direction of umbilical twist may be in part dependent on differences in diameters of the umbilical arteries, in addition to other fetal characteristics such as fetal movement, or handedness of fetus or mother, fetal hemodynamic forces and structure of muscles of umbilical vessels.

Cohort profile: Understanding Pregnancy Signals and Infant Development (UPSIDE): a pregnancy cohort study on prenatal exposure mechanisms for child health

PURPOSE

Extensive research suggests that maternal prenatal distress is reliably related to perinatal and child health outcomes-which may persist into adulthood. However, basic questions remain regarding mechanisms involved. To better understand these mechanisms, we developed the Understanding Pregnancy Signals and Infant Development (UPSIDE) cohort study, which has several distinguishing features, including repeated assessments across trimesters, analysis of multiple biological pathways of interest, and incorporation of placental structure and function as mediators of child health outcomes.

PARTICIPANTS

Women with normal risk pregnancies were recruited at <14 weeks gestation. Study visits occurred in each trimester and included extensive psychological, sociodemographic, health behaviour and biospecimen collection. Placenta and cord blood were collected at birth. Child visits (ongoing) occur at birth and 1, 6, 12, 24, 36 and 48 months of age and use standard anthropometric, clinical, behavioural, biological and neuroimaging methods to assess child physical and neurodevelopment.

FINDINGS TO DATE

We recruited 326 pregnancies; 294 (90%) were retained through birth. Success rates for prenatal biospecimen collection were high across all trimesters (96%-99% for blood, 94%-97% for urine, 96%-99% for saliva, 96% of placentas, 88% for cord blood and 93% for buccal swab). Ninety-four per cent of eligible babies (n=277) participated in a birth examination; postnatal visits are ongoing.

FUTURE PLANS

The current phase of the study follows children through age 4 to examine child neurodevelopment and physical development. In addition, the cohort participates in the National Institutes of Health's Environmental influences on Child Health Outcomes programme, a national study of 50 000 families examining early environmental influences on perinatal outcomes, neurodevelopment, obesity and airway disease. Future research will leverage the rich repository of biological samples and clinical data to expand research on the mechanisms of child health outcomes in relation to environmental chemical exposures, genetics and the microbiome.

Histopathology of the fetal inflammatory response to intra-amniotic pathogens

Obstetric endorsement of the utility of placental histologic examination remains infrequent, especially from obstetricians who do not have a placental pathologist as part of their own local clinical care team. Placental pathologic examinations are viewed as useless if they do not provide answers to urgent clinical questions. Increasingly, however, it is appreciated that while placental analysis should be considered with regard to its longer term value; results can assess lifelong risks of a wide range of diseases that have been tied to prenatal exposures (e.g., [1]), including distinguishing sex-specific differences in those risks. (e.g., [2]) This review will focus solely on acute fetal (?) inflammation, more specifically, the fetal neutrophil responses in umbilical cord, chorionic plate vessels and to some degree, the fetal system as a whole. This histologic fetal inflammatory response is often the most readily accessible aspect of "FIR" piece of FIRS (the fetal inflammatory response syndrome). Some researchers have defined FIRS by a combination of both cytokine (especially IL-6) levels and the histopathologic FIR (Musilova et al., 2018) [3]. As we and others have noted, many histology based FIR cases, even those associated with neurodevelopmental outcomes such as cerebral palsy, are clinically silent.(e.g., [4]) Current clinical diagnostic criteria may have high specificity as they are very good at identifying non-FIR cases. However, that high specificity is coupled with very low specificity, identifying only 10% of FIR (Doty et al., 2018 Jul) [5]. Our aim is to provide a conceptual framework for the readers of the journal to better understand how to answer the following questions: What is a neutrophil and how is it important in FIR? What is the differential diagnosis for histologic FIR? How long has there been FIR? What secondary processes may have been recruited (and when) to contribute to the final pathology and pathophysiology of the given pregnancy?

Placental infarcts in the collaborative perinatal project: Variable associations infer variable constructs

PURPOSE

Reproducible diagnoses of placental infarcts may permit more accurate assessment of their clinical significance. Using data across the 12 study sites of the National Collaborative Perinatal Project, we investigated the consistency of associations between infarct features with birthweight, placental weight and measures of placental "efficiency."

METHODS

All delivered infants, live or stillborn, single or multiple, regardless of gestational age, were included. Pathologists scored infarcts by color (tan-white or "old" or pink-red "more recent"), size (cm), location (marginal or central), and total number.

RESULTS

Incidence of any infarcts and distributions of specific features such as size, color (indicating age), locations and total numbers of infarcts were highly variable across sites, as were their associations with birthweight and placental efficiency. The most stable associations (consistent results across sites) of placental infarct scores were with placental size and/or other placental shape variables and with birthweight, but the number of significant associations ranged from 13 to 1.

CONCLUSION

Given the extremes of infarct incidence within each site plus the variable correlations of infarct features with other placental and birth outcome measures, CPP infarct scores cannot be used as indicative of an underlying shared pathophysiologic construct. However, given the accumulating evidence that intrauterine stressors have the potential for lifelong impact on health, we propose that the infarct features and distinctions proposed are neither complex nor should they be jettisoned. Rather these measures should be clarified and refined. Only then can we understand the reported associations of placental infarcts with child and adult health outcomes.

Gestational growth trajectories derived from a dynamic fetal-placental scaling law

Fetal trajectories characterizing growth rates in utero have relied primarily on goodness of fit rather than mechanistic properties exhibited in utero. Here, we use a validated fetal-placental allometric scaling law and a first principles differential equations model of placental volume growth to generate biologically meaningful fetal-placental growth curves. The growth curves form the foundation for understanding healthy versus at-risk fetal growth and for identifying the timing of key events in utero.

Urinary Incontinence in Pregnant Young Women and Adolescents: An Unrecognized At-Risk Group

OBJECTIVES

The aims of this study were to determine the prevalence of urinary incontinence (UI) in pregnant young women and adolescents, characterize UI subtype, and identify characteristics associated with UI.

METHODS

This was a cross-sectional study of pregnant females aged 25 years or below, presenting for routine obstetrical care at a New York City community hospital. Subjects were stratified into 2 groups: adolescents (age, ≤19 years) and young adults (age, >19 years). Demographic and obstetric data were collected. The 3 Incontinence Questions questionnaire was used to screen and evaluate UI symptoms.

RESULTS

A total of 98 young females with a mean age of 20.3 ± 2.6 years were enrolled. Most participants were nulliparous (64%). Of parous women, route of previous obstetric delivery was primarily vaginal (83%). Mean gestational age at recruitment was 34.5 ± 7.5 weeks. The prevalence of UI was 52%. Urinary incontinence was associated with the following conditions: strenuous activity, 73%; urinary urgency, 67%; and absence of either, 20%. However, the most predominant UI subtype was with strenuous activity (63%). There was no statistical difference detected in demographic characteristics (such as age, parity, mode of delivery, race, education, and trimester of pregnancy) between continent and incontinent pregnant females (P > 0.18). No differences were appreciated between pregnant adolescents and young adult females with UI (P > 0.18).

CONCLUSIONS

Urinary incontinence was present in 52% of pregnant females aged 25 years or below. By age group, approximately 50% of both adolescents and young adults reported UI during pregnancy. Continent and incontinent patients did not seem to differ demographically. Our study highlights the extent of UI in this segment of the population. This data may support the need for services targeting UI prevention and early intervention in this newly identified at-risk group.

Scaling of the surface vasculature on the human placenta

The networks of veins and arteries on the chorionic plate of the human placenta are analyzed in terms of Voronoi cells derived from these networks. Two groups of placentas from the United States are studied: a population cohort with no prescreening, and a cohort from newborns with an elevated risk of developing autistic spectrum disorder. Scaled distributions of the Voronoi cell areas in the two cohorts collapse onto a single distribution, indicating common mechanisms for the formation of the complete vasculatures, but which have different levels of activity in the two cohorts.

Autism risk classification using placental chorionic surface vascular network features

Background

Autism Spectrum Disorder (ASD) is one of the fastest-growing developmental disorders in the United States. It was hypothesized that variations in the placental chorionic surface vascular network (PCSVN) structure may reflect both the overall effects of genetic and environmentally regulated variations in branching morphogenesis within the conceptus and the fetus’ vital organs. This paper provides sound evidences to support the study of ASD risks with PCSVN through a combination of feature-selection and classification algorithms.

Methods

Twenty eight arterial and 8 shape-based PCSVN attributes from a high-risk ASD cohort of 89 placentas and a population-based cohort of 201 placentas were examined for ranked relevance using a modified version of the random forest algorithm, called the Boruta method. Principal component analysis (PCA) was applied to isolate principal effects of arterial growth on the fetal surface of the placenta. Linear discriminant analysis (LDA) with a 10-fold cross validation was performed to establish error statistics.

Results

The Boruta method selected 15 arterial attributes as relevant, implying the difference in high and low ASD risk can be explained by the arterial features alone. The five principal features obtained through PCA, which accounted for about 88% of the data variability, indicated that PCSVNs associated with placentas of high-risk ASD pregnancies generally had fewer branch points, thicker and less tortuous arteries, better extension to the surface boundary, and smaller branch angles than their population-based counterparts.

Conclusion

We developed a set of methods to explain major PCSVN differences between placentas associated with high risk ASD pregnancies and those selected from the general population. The research paradigm presented can be generalized to study connections between PCSVN features and other maternal and fetal outcomes such as gestational diabetes and hypertension.

Chorionic vascular "fit" in the human placenta: Relationship to fetoplacental outcomes

BACKGROUND

Novel measures of the chorionic plate and vessels are used to test the hypothesis that variation in placental structure is correlated with reduced birth weight (BW) independent of placental weight (PW), suggesting functionally compromised placentas.

METHODS

916 mothers recruited to the Pregnancy, Infection and Nutrition Study delivering singleton live born infants at >30 gestational weeks had placentas collected, digitally photographed and weighed prior to formalin fixation. The fetal-placental weight ratio (FPR) was calculated as birthweight/placental weight. Beta (beta) was calculated as ln(PW)/ln(BW). Chorionic disk perimeter was traced and chorionic surface shape (CS) area was calculated. "Fit" was defined as the ratio of the area of the vascular to the full chorionic surface area. The sites at which chorionic vessels dived beneath the chorionic surface were marked to calculate the chorionic surface vessel (CV) area. The centroids of shapes, the distance between centroids and other measures of shape irregularities were calculated. Principal components analysis (PCA) created three independent factors. Factors were used in regression analyses to explore relations to birth weight, trimmed placental weight, FPR, and beta. Specific measures of shape irregularity were also examined in regression analyses for interrelationships and to predict birth weight, placental weight, FPR, and beta.

RESULTS

Variables related to disk size (CS area, perimeter) were correlated with BW, GA, trimmed PW and beta. "Fit" (the ratio of CV area to CS area), measures of shape irregularities, and the distance between the cord insertion and the centroids of surface and vascular areas were also correlated with one or more of the clinical outcome variables. PCA yielded three factors that had independent effects on birth weight, placental weight, the fetal-placental weight ratio, and beta (each p < 0.0001). Addition of GA did not alter the factors' associations with outcomes. Chorionic "fit" (ratio of areas), also included within the factor analysis, was a positive predictor of birth weight (p = 0.005) and FPR (p = 0.002) and a negative predictor of beta (p = 0.01). Fit was statistically significantly associated with greater distances between the umbilical cord insertion site and the CS (p < 0.001) and CV centroids (p < 0.001), and to lesser displacement between CS and CV centroids (p < 0.001).

CONCLUSIONS

Measures of CS and CV account for variation in placental efficiency defined by beta, independent of GA. Macroscopic placenta measurements can identify suboptimal placental development.

The association between placental histopathology and autism spectrum disorder

INTRODUCTION

Research suggests that autism spectrum disorder (ASD) has its origins in utero. This study examines the association between evidence of placental histopathology and ASD.

METHODS

Administrative claims data and medical records data were used to identify ASD cases (N = 55) and matched controls (N = 199) born at New York Methodist Hospital between 2007 and 2014 and subsequently seen in affiliated pediatrics clinics. Placentas from all births during this time period were reviewed as part of routine care. Data were analyzed using conditional logistic regression to account for the matched (gender, gestational age, and birth weight) design.

RESULTS

Acute placental inflammation, regardless of type was associated with an increased risk of ASD (odds ratio [OR] = 3.14, 95% CI = 1.39, 6.95). Chronic uteroplacental vasculitis (OR = 7.13; 95% CI = 1.17, 43.38), the fetal inflammatory response in the chorionic plate vessels (OR = 5.12; 95% CI = 2.02, 12.96), and maternal vascular malperfusion pathology (OR = 12.29; 95% CI = 1.37, 110.69) were associated with an increased risk of ASD. Placental villous edema was associated with a decreased risk of ASD (OR = 0.05; 95% CI = 0.0005, 0.42). In subanalyses among male placentas acute inflammation overall, fetal inflammatory response in the chorionic plate vessels, and maternal vascular malperfusion pathology remained significantly associated with an increased risk of ASD whereas placental villous edema remained associated with a decreased risk of ASD.

DISCUSSION

Histologic evidence of placental inflammation and maternal vascular malperfusion pathology are associated with ASD.

Hemodynamic analysis of blood flow in umbilical artery using computational modeling

The umbilical cord is the crucial pathway for blood flow between the fetus and the placenta. Umbilical coiling and length have been separately linked to adverse clinical outcomes; however, the effects of variations of these parameters on umbilical arterial blood flow are not well understood. Using 3D computational model, we studied the individual and combined effects of umbilical coiling index, cord length and arterial diameter on umbilical artery hemodynamics. We found that specific combinations of umbilical coiling index, cord length and arterial diameter yielded pressure and flow drops incompatible with fetal life. Such models are useful as hypothesis-developing tools.

Methods to decrease variability in histological scoring in placentas from a cohort of preterm infants

OBJECTIVE

Reliable semiquantitative assessment of histological placental acute inflammation is problematic, even among experts. Tissue samples in histology slides often show variability in the extent and location of neutrophil infiltrates. We sought to determine whether the variability in pathologists' scoring of neutrophil infiltrates in the placenta could be reduced by the use of 'regions of interest' (ROIs) that break the sample into smaller components.

DESIGN

ROIs were identified within stained H&E slides from a cohort of 56 women. ROIs were scored using a semiquantitative scale (0-4) for the average number of neutrophils by at least two independent raters.

SETTING

Preterm singleton births at Yale New Haven Hospital.

PARTICIPANTS

This study used stained H&E placental slides from a cohort of 56 women with singleton pregnancies who had a clinically indicated amniocentesis within 24 hours of delivery.

PRIMARY AND SECONDARY OUTCOME MEASURES

Interrater agreement was assessed with the intraclass correlation coefficient (ICC) and log-linear regression. Predictive validity was assessed using amniotic fluid protein profile scores (neutrophil defensin-2, neutrophil defensin-1, calgranulin C and calgranulin A).

RESULTS

Excellent agreement by the ICC was found for the average neutrophil scores within a region of interest. Log-linear analyses suggest that even where there is disagreement, responses are positively associated along the diagonal. There was also strong evidence of predictive validity comparing pathologists' scores with amniotic fluid protein profile scores.

CONCLUSIONS

Agreement among observers of semiquantitative neutrophil scoring through the use of digitised ROIs was demonstrated to be feasible with high reliability and validity.

Villus packing density and lacunarity: Markers of placental efficiency?

We evaluate, in routine H&E histology slides, villus quantity in a given area (villous packing density, VPD) and the pattern or "gappiness" of villous distribution (lacunarity), and test for correlations with a proxy for fetoplacental metabolic rate, β calculated as (ln (placental weight)/ln (birthweight)) from Kleiber's law [1]. Three ∼4.3 mm² images each were obtained from 88 term placentas. Ranges of VPD and lacunarity were each correlated with β (r = 0.31, p = 0.003, r = 0.23, p = 0.03 and respectively). The relationship between β and within-placenta variation in VPD and lacunarity highlights the need to study not merely the mean but the variance of villous geometries and spatial distributions.

First Trimester Detection of Placental Disease: Challenges and Opportunities

It is generally agreed that placental pathology accounts for the majority of perinatal morbidity and mortality. If a placental prodrome could be diagnosed in vivo, risk for maternal or fetal complications could be estimated and acted upon before clinical symptoms are apparent. This is especially relevant in early diagnoses of gestational diabetes mellitus, which can be controlled through carefully monitored diet and activity changes. To meet this important need, there have been increased efforts to identify early gestation biomarkers of placental dysfunction using innovative imaging technologies. Here we outline innovative quantitative markers of placental shape and their relationship to placental function, clinical implications of these quantifiers, and the most recent mathematical models that utilize placental images to delineate at risk from normal pregnancies. We propose that novel contexts of readily available placental measures and routine collection of in vivo placental images in all pregnancies may be all that are needed to advance the identification of early risk determination of complicated pregnancies from placental images.

Increasing maternal body mass index during pregnancy increases neonatal intensive care unit admission in near and full-term infants

BACKGROUND

Obesity is becoming an increasingly commonplace health problem. Obesity during pregnancy is important because the condition adversely affects not only the mother, but also the developing fetus and the newborn.

OBJECTIVE

The primary objective of this study was to evaluate the association between maternal body mass index (mBMI) at the time of delivery and neonatal intensive care unit (NICU) admission of offspring and to analyze the role of possible confounding variables that are often associated with obesity. Comorbidities, such as gestational diabetes mellitus (DM), hypertension (HT) and/or pre-eclampsia (PEC), are more common in more obese mothers, as is a higher association of obesity among non-Caucasian patients.

METHODS

Using a retrospective cohort design, 1736 mothers and their singleton live-born at  ≥35 weeks' gestation were analyzed for mBMI, maternal conditions of DM, HT and/or PEC, and whether NICU care was required and the reason for NICU admission.

RESULTS

NICU admission rate was significantly associated with maternal obesity. In comparing women with mBMI  < 30 versus mBMI ≥ 30, OR was 1.39 (p = 0.045); OR increased to 1.76 (p = 0.006) in comparing patients with mBMI  ≥ 35. mBMI was significantly associated with an increased rate of maternal DM, HT and PEC (p < 0.05 each); however, NICU admission rate was not correlated with DM, HT or PEC. The relationship between NICU admission and mBMI was significant in Caucasian mothers versus a borderline significance in African-American mothers (p = 0.035 versus p = 0.05). After controlling for neonatal hypoglycemia (NH) as the reason for admission to the NICU, no mBMI-NICU association persisted. The rate of infants with NH increased in higher mBMI groups, independent of maternal DM diagnosis.

CONCLUSION

This study demonstrated a significant association between higher mBMI groups and NICU admissions independent of diagnosis of maternal comorbidities. However, accounting for NH eliminating this association suggests a pre-clinical diabetic pathology in obese women that affects newborn outcome. Despite increased percentage of nonwhite mothers in higher mBMI groups, African-American race does not seem to be a significant contributing factor in the increased rate of NICU admission in our population.

IFPA meeting 2015 workshop report II: mechanistic role of the placenta in fetal programming; biomarkers of placental function and complications of pregnancy

Workshops are an integral component of the annual International Federation of Placenta Association (IFPA) meeting, allowing for networking and focused discussion related to specialized topics on the placenta. At the 2015 IFPA meeting (Brisbane, Australia) twelve themed workshops were held, three of which are summarized in this report. These workshops focused on various aspects of placental function, particularly in cases of placenta-mediated disease. Collectively, these inter-connected workshops highlighted the role of the placenta in fetal programming, the use of various biomarkers to monitor placental function across pregnancy, and the clinical impact of novel diagnostic and surveillance modalities in instances of late onset fetal growth restriction (FGR).

Shape matching algorithm to validate the tracing protocol of placental chorionic surface vessel networks

Variability in placental chorionic surface vessel networks (PCSVNs) may mark developmental and functional changes in fetal health. Here we report a protocol of manually tracing PCSVNs from digital 2D images of post-delivery placentas and its validation by a shape matching method to compare the similarity between paint-injected and unmanipulated (uninjected and deflated vessels) tracings of PCSVNs. We show that tracings of unmanipulated vessels produce networks that are very comparable to the networks obtained by tracing paint-injected PCSVNs. We suggest that manual tracings of unmanipulated PCSVNs can extract features of PCSVN growth and structure that may impact fetal wellbeing.

Analytical theory of oxygen transport in the human placenta

We propose an analytical approach to solving the diffusion-convection equations governing oxygen transport in the human placenta. We show that only two geometrical characteristics of a placental cross-section, villi density and the effective villi radius, are needed to predict fetal oxygen uptake. We also identify two combinations of physiological parameters that determine oxygen uptake in a given placenta: (i) the maximal oxygen inflow of a placentone if there were no tissue blocking the flow and (ii) the ratio of transit time of maternal blood through the intervillous space to oxygen extraction time. We derive analytical formulas for fast and simple calculation of oxygen uptake and provide two diagrams of efficiency of oxygen transport in an arbitrary placental cross-section. We finally show that artificial perfusion experiments with no-hemoglobin blood tend to give a two-orders-of-magnitude underestimation of the in vivo oxygen uptake and that the optimal geometry for such setup alters significantly. The theory allows one to adjust the results of artificial placenta perfusion experiments to account for oxygen-hemoglobin dissociation. Combined with image analysis techniques, the presented model can give an easy-to-use tool for prediction of the human placenta efficiency.

Probability distributions of placental morphological measurements and origins of variability of placental shapes

INTRODUCTION

While the mean shape of human placenta is round with centrally inserted umbilical cord, significant deviations from this ideal are fairly common, and may be clinically meaningful. Traditionally, they are explained by trophotropism. We have proposed a hypothesis explaining typical variations in placental shape by randomly determined fluctuations in the growth process of the vascular tree. It has been recently reported that umbilical cord displacement in a birth cohort has a log-normal probability distribution, which indicates that the displacement between an initial point of origin and the centroid of the mature shape is a result of accumulation of random fluctuations of the dynamic growth of the placenta. To confirm this, we investigate statistical distributions of other features of placental morphology.

METHODS

In a cohort of 1023 births at term digital photographs of placentas were recorded at delivery. Excluding cases with velamentous cord insertion, or missing clinical data left 1001 (97.8%) for which placental surface morphology features were measured. Best-fit statistical distributions for them were obtained using EasyFit.

RESULTS AND DISCUSSION

The best-fit distributions of umbilical cord displacement, placental disk diameter, area, perimeter, and maximal radius calculated from the cord insertion point are of heavy-tailed type, similar in shape to log-normal distributions. This is consistent with a stochastic origin of deviations of placental shape from normal.

CONCLUSIONS

Deviations of placental shape descriptors from average have heavy-tailed distributions similar in shape to log-normal. This evidence points away from trophotropism, and towards a spontaneous stochastic evolution of the variants of placental surface shape features.

Is the placental disk really an ellipse?

The mean surface shape of placenta is round and common abnormalities of shape are associated with vascular abnormalities and reduced placental functional efficiency. A long-standing approach is to describe shapes as elliptic, and to quantify them by "length" and "breadth". We test this description in two cohorts: National Collaborative Perinatal Project and Pregnancy, Infection and Nutrition Study. We conclude that quantifying placental shape as elliptic is ambiguous and problematic. The "breadth" of the placenta should be interpreted as a combination of two different measurements: placental size and irregularity of the placental surface. It has no intrinsic functional significance.

Impact of fetal versus perinatal hypoxia on sex differences in childhood outcomes: developmental timing matters

PURPOSE

To examine how the timing of hypoxic exposure results in specific childhood outcomes and whether there is a differential effect by sex.

METHODS

A sample of 10,879 prospectively followed pregnancies was drawn from the Boston and Providence sites (New England, NE) of the National Collaborative Perinatal Project. Based on placental pathology, we developed and validated a measure of probable chronic placental hypoxia (CHP) and contrasted the effects of acute perinatal hypoxia on age 7 emotional, behavioral, and cognitive outcomes.

RESULTS

Perinatal hypoxia had a significant impact on multiple behavioral and cognitive outcomes in boys and girls by age 7, in contrast to probable CHP which had a differential effect on girls and boys such that there was decreased verbal IQ and increased inhibition in females alone.

CONCLUSIONS

Findings underscore the importance of considering the timing of obstetric complications and offspring sex in investigations of the impact of fetal and perinatal hypoxia on offspring's outcomes throughout the life course.

Modeling oxygen transport in human placental terminal villi

Oxygen transport from maternal blood to fetal blood is a primary function of the placenta. Quantifying the effectiveness of this exchange remains key in identifying healthy placentas because of the great variability in capillary number, caliber and position within the villus-even in placentas deemed clinically "normal". By considering villous membrane to capillary membrane transport, stationary oxygen diffusion can be numerically solved in terminal villi represented by digital photomicrographs. We aim to provide a method to determine whether and if so to what extent diffusional screening may operate in placental villi. Segmented digital photomicrographs of terminal villi from the Pregnancy, Infection and Nutrition study in North Carolina 2002 are used as a geometric basis for solving the stationary diffusion equation. Constant maternal villous oxygen concentration and perfect fetal capillary membrane absorption are assumed. System efficiency is defined as the ratio of oxygen flux into a villus and the sum of the capillary areas contained within. Diffusion screening is quantified by comparing numerical and theoretical maximum oxygen fluxes. A strong link between various measures of villous oxygen transport efficiency and the number of capillaries within a villus is established. The strength of diffusional screening is also related to the number of capillaries within a villus. Our measures of diffusional efficiency are shown to decrease as a function of the number of capillaries per villus. This low efficiency, high capillary number relationship supports our hypothesis that diffusional screening is present in this system. Oxygen transport per capillary is reduced when multiple capillaries compete for diffusing oxygen. A complete picture of oxygen fluxes, capillary and villus areas is obtainable and presents an opportunity for future work.

Placental morphologic features and chorionic surface vasculature at term are highly correlated with 3-dimensional sonographic measurements at 11 to 14 weeks

OBJECTIVES

The purpose of this study was to examine the potential for 3-dimensional sonographic measurement of the early placenta in predicting ultimate placental morphologic features at delivery.

METHODS

In this prospective cohort study, we collected 3-dimensional sonographic volume sets of placentas at 11 to 14 weeks and then collected the placentas after delivery. The sonographic data were manipulated to obtain various novel measurements of early gross placental morphologic features and the umbilical cord insertion location. The placental weight, chorionic plate area, cord location, and mean chorionic vascular density were obtained from the delivered postpartum placentas. Analyses were performed to identify potential early placental characteristics that were correlated with the ultimate placental morphologic features. The placental weight, cord marginality, and mean chorionic vascular density served as the outcome measures of interest.

RESULTS

Measurements of the early placental volume correlated with the delivered placental weight. An irregular early placental shape, as measured by sonography, was significantly inversely correlated with placental weight (P < .05). The placental morphologic index, a measure of a flatter placenta, was inversely correlated with both the placental weight and chorionic plate area, possibly indicating the importance of placental thickness even in the first trimester before villous arborization. In addition, early sonographic measures of the location of the umbilical cord insertion were significantly correlated with the ultimate marginality of the cord insertion as well as the mean chorionic vascular density (P < .05).

CONCLUSIONS

Many important ultimate placental morphologic features are likely predetermined early in pregnancy. Three-dimensional sonography may play an increasing role in the in utero evaluation of the early placenta.

Placental surface shape, function, and effects of maternal and fetal vascular pathology

GOAL

In clinical practice, variability of placental surface shape is common. We measure the average placental shape in a birth cohort and the effect deviations from the average have on placental functional efficiency. We test whether altered placental shape improves the specificity of histopathology diagnoses of maternal uteroplacental and fetoplacental vascular pathology for clinical outcomes.

MATERIALS AND METHODS

1225 Placentas from a prospective cohort had chorionic plate digital photographs with perimeters marked at 1-2 cm intervals. After exclusions of pre-term (n = 202) and velamentous cord insertion (n = 44), 979 (95.7%) placentas were analyzed. Median shape and mean perimeter were estimated. The relationship of fetal and placental weight was used as an index of placental efficiency termed "β". The principal placental histopathology diagnoses of maternal uteroplacental and fetoplacental vascular pathologies were coded by review of individual lesion scores. Acute fetal inflammation was scored as a "negative control" pathology not expected to affect shape. ANOVA with Bonferroni tests for subgroup comparisons were used.

RESULTS

The mean placental chorionic shape at term was round with a radius estimated at 9.1 cm. Increased variability of the placental shape was associated with lower placental functional efficiency. After stratifying on placental shape, the presence of either maternal uteroplacental or fetoplacental vascular pathology was significantly associated with lower placental efficiency only when shape was abnormal.

CONCLUSIONS

Quantifying abnormality of placental shape is a meaningful clinical tool. Abnormal shapes are associated with reduced placental efficiency. We hypothesize that such shapes reflect deformations of placental vascular architecture, and that an abnormal placental shape serves as a marker of maternal uteroplacental and/or fetoplacental vascular pathology of sufficiently long standing to impact placental (and by extension, potentially fetal) development.

Centrality of the umbilical cord insertion in a human placenta influences the placental efficiency

GOAL

We assess the effect on placental efficiency of the non-centrality of the umbilical cord insertion and on chorionic vascular distribution to determine if cord centrality measurably affects placental function as reflected in birth weight.

MATERIALS AND METHODS

1225 placentas collected from a prospective cohort had digital photographs of the chorionic plate. Of these, 1023 were term, 44 had velamentous cord insertion and 12 had missing clinical data, leaving N=967 (94.5%) cases for analysis. Mathematical tools included a dynamical stochastic growth model of placental vasculature, Fourier analysis of radial parameterization of placental perimeters, and relative chorionic vascular density (a measure of "gaps" in the vascular coverage) derived from manual tracings of the fetal chorionic surface images. Bivariate correlations used Pearson's or Spearman's rank correlation as appropriate, with p<0.05 considered significant.

RESULTS

The correlation of the standard deviation of the placental radius (a measure of non-roundness of the placenta) with cord displacement was negligible (r=0.01). Empirical simulations of the vascular growth model with cord displacement showed no deviation from a normal round-to-oval placental shape for cord displacement of 10-50% of placental radius. The correlation of the metabolic scaling exponent beta with cord displacement measured by Fourier analysis is 0.17 (p<0.001). Analysis of the chorionic vascular density in traced images shows a high correlation of the relative vascular distance with cord displacement: 0.59 in one set of 12 images, and 0.20 in the other set of 28 images.

CONCLUSION

Non-central cord insertion has little measurable correlation with placental shape in observed or simulated placentas. However, placentas with a displaced cord show a markedly reduced transport efficiency, reflected in a larger value of beta and hence in a smaller birth weight for a given placental weight. Placentas with a non-central cord insertion have a sparser chorionic vascular distribution, as measured by the relative vascular distance. Even if typically a placenta with a non-central insertion is of a normal round shape, its vasculature is less metabolically effective. These findings demonstrate another method by which altered placental structure may affect the fetal environment, influencing birth weight and potentially contributing to later health risks.

Non-linear and gender-specific relationships among placental growth measures and the fetoplacental weight ratio

GOALS

Fetal growth depends on placental growth; the fetoplacental weight ratio (FPR) is a common proxy for the balance between fetal and placental growth. Male and female infants are known to have differing vulnerabilities in fetal life, during parturition and in infancy. We hypothesized that these differences may be paralleled by differences in how birth weight (BW) and the fetoplacental weight ratio (FPR) are affected by changes in placental proportions.

MATERIALS AND METHODS

Placental proportion measures (disk shape, larger and smaller chorionic diameters, chorionic plate area calculated as the area of an ellipse with the 2 given diameters, disk thickness, cord eccentricity and cord length) were available for 24,601 participants in the Collaborative Perinatal Project delivered between >34 and <43 completed weeks. The variables were standardized and entered into multiple automated regression splines (MARS 2.0, Salford Systems, Vista CA) to identify nonlinearities in the relationships of placental growth measures to BW and FPR with results compared for male and female infants.

RESULTS

Changes in chorionic plate growth in female compared to male infants resulted in a greater change in BW and FPR. The positive effects of umbilical cord length on BW reversed at the mean umbilical cord length in females and at +0.08 SD in male infants.

CONCLUSIONS

Female infants' BW and FPR are each more responsive to changes in placental chorionic plate growth dimensions than males; this may account for greater female resilience (and greater male vulnerability) to gestational stressors. The effect of umbilical cord length on FPR may be due to longer cords carrying greater fetal vascular resistance. Again male fetuses show a higher "threshold" to the negative effects of longer cords on FPR.

Methodologic issues in the study of the relationship between histologic indicators of intraamniotic infection and clinical outcomes

GOAL

To determine the structure of the relationships of the histology scores for acute intraamniotic infection collected in the Collaborative Perinatal Project (CPP).

MATERIALS AND METHODS

44,427 subjects of the CPP had complete histology scores available for the 9 measures that related to acute intraamniotic infection (i.e., neutrophil infiltrates in umbilical cord, amnion of extraplacental membranes and chorionic plate, decidua, chorionic plate and fetal chorionic vessels). Confirmatory factor analysis was used to determine the relationships among the different markers of maternal inflammatory responses (in amnion, chorion and decidua) and fetal inflammatory responses (in umbilical cord and fetal chorionic vessels).

RESULTS

A single CFA model could not be developed across all CPP sites. A well-fit model was developed from the Boston site (N=10,803) and the factor loadings applied to the histology scores from the other CPP sites. The resultant scores for the latent variables (maternal and fetal inflammatory responses) were compared across sites. There was not only considerable variability in factor loadings, and the signs of factor loadings were also inconsistent across sites.

CONCLUSION

Histopathology scores of neutrophil infiltrates performed by different observers do not have the same interrelationships and, by extension, the latent variables they are supposed to reflect may not be equivalent. The lack of measurement invariance renders their use as indicators of the underlying processes of maternal and fetal inflammatory responses problematic in analysis with any clinical outcome.

Gross placental structure in a low-risk population of singleton, term, first-born infants

Suboptimal fetal growth has been associated with an increased risk of adult disease, which may be exacerbated by an increased placental weight-to-fetal weight ratio. Placental weight is a summary measure of placental growth and development throughout pregnancy. However, measures of placental structure, including the chorionic disk surface area and thickness and eccentricity of the umbilical cord insertion, have been shown to account for additional variance in birth weight beyond that explained by placental weight. Little is known of the variability of these placental parameters in low-risk populations; their association with maternal, pregnancy, and neonatal characteristics; and the agreement between manual and digital measures. This study used manual and digital image analysis techniques to examine gross placental anatomy in 513 low-risk, singleton, term, first-born infants. Parametric methods compared groups and examined relationships among variables. Maternal birth weight, prepregnancy weight, and body mass index were associated with increased placental and birth weight (all P < 0.005), but only maternal birth weight was associated with increased placental surface area (P < 0.0005) and thickness (P = 0.005). Smoking during pregnancy reduced birth weight and increased the eccentricity of umbilical cord insertion (P = 0.012 and 0.034, respectively). The variability in these placental parameters was consistently lower than that reported in the literature, and correlations between digital and manual measurements were reasonable (r = .87-.71). Detailed analyses of gross placental structure can provide biologically relevant information regarding placental growth and development and, potentially, their consequences.

Gross placental measures and childhood growth

OBJECTIVES

We hypothesised that the gross placental measures would be positively associated with childhood growth.

METHODS

We analysed data on 23,967 mother-infant pairs enrolled in the Collaborative Perinatal Project. In race-stratified regression models, the main outcomes were birthweight and z-score body-mass index (BMI) at ages 4 and 7.

RESULTS

Some placental measures were significantly associated with z-score BMI at age 7: in Blacks, placental weight (beta = 0.0004/g; 95%CI: 0.0001, 0.0008), chorionic plate area (beta = 0.0007; 95%CI: 0.0001, 0.0012) and largest diameter (beta = 0.013; 95%CI: 0.004, 0.026); and in Whites placental weight (beta = 0.0004/g; 95%CI: 0.0001, 0.0003) and largest diameter (Model 3: beta = 0.020; 95%CI: 0.007, 0.032). Tested as group, placental measures significantly predicted z-score BMI at age 7 (all p values < 0.005).

CONCLUSIONS

Placental structure independently predicts birthweight and childhood growth. Strategies to improve placental structure might favourably influence birthweight and childhood development.

Metabolic scaling law for fetus and placenta

The human fetal birth weight does not scale linearly with the weight of the placenta, but exhibits an allometric scaling consistent with Kleiber's Law for the basal metabolic rate. We discuss the possible causes of such scaling, and its clinical consequences. In particular, we show that the value of the scaling exponent is an indicator of a normal fetoplacental development.

Allometric metabolic scaling and fetal and placental weight

BACKGROUND

We tested the hypothesis that the fetal-placental relationship scales allometrically and identified modifying factors of that relationship.

MATERIALS AND METHODS

Among women delivering after 34 weeks but prior to 43 weeks' gestation, 24,601 participants in the Collaborative Perinatal Project (CPP) had complete data for placental gross proportion measures, specifically, placental weight (PW), disk shape, larger and smaller disk diameters and thickness, and umbilical cord length. The allometric metabolic equation was solved for alpha and beta by rewriting PW = alpha(BW)beta as ln(PW) = ln alpha + beta[ln(BW)]. alpha(iota) was then the dependent variable in regressions with p < 0.05 significant.

RESULTS

Mean beta was 0.78 + 0.02 (range 0.66, 0.89), which is consistent with the scaling exponent 0.75 predicted by Kleiber's Law. Gestational age, maternal age, maternal BMI, parity, smoking, socioeconomic status, infant sex, and changes in placental proportions each had independent and significant effects on alpha.

CONCLUSIONS

We find an allometric scaling relation between the placental weight and the birthweight in the CPP cohort with an exponent approximately equal to 0.75, as predicted by Kleiber's Law. This implies that: (1) placental weight is a justifiable proxy for fetal metabolic rate when other measures of fetal metabolic rate are not available; and (2) the allometric relationship between placental and birthweight is consistent with the hypothesis that the fetal-placental unit functions as a fractal supply limited system. Furthermore, our data suggest that the maternal and fetal variables we examined have at least part of their effects on the normal balance between placental weight and birth weight via effects on gross placental growth dimensions.

Risk factors for uteroplacental vascular compromise and inflammation

OBJECTIVE

The purpose of this study was to identify potentially modifiable risk factors of placental injury that reflect maternal uteroplacental vascular compromise (UPVC) and acute and chronic placental inflammation.

STUDY DESIGN

A prospective epidemiologic study was conducted. A total of 1270 placentas were characterized by gross and microscopic examination. Placental pathologic condition was coded for features of amniotic fluid infection syndrome (AFIS), chronic villitis, UPVC, and fetal vascular obstructive lesions. Odds ratios between UPVC, the acute and the chronic inflammatory lesions, and risk factors of interest were calculated.

RESULTS

After adjustment for confounders, we found that women with a history of preterm birth had 1.60 times the odds of chronic inflammation (95% CI, 1.10, 2.55). Women with a previous elective termination had 3.28 times the odds of acute inflammation (95% CI, 1.89, 5.70). The odds of chronic villitis increased with parity; the odds of AFIS decreased with parity.

CONCLUSION

We have identified several predictors of UPVC, AFIS, and chronic villitis. Further studies are needed to examine whether interventions to alter UPVC, AFIS, and chronic villitis will lead to improved pregnancy outcomes.

Modeling the variability of shapes of a human placenta

BACKGROUND

Placentas are generally round/oval in shape, but "irregular" shapes are common. In the Collaborative Perinatal Project data, irregular shapes were associated with lower birth weight for placental weight, suggesting variably shaped placentas have altered function.

METHODS

(I) Using a 3D one-parameter model of placental vascular growth based on Diffusion Limited Aggregation (an accepted model for generating highly branched fractals), models were run with a branching density growth parameter either fixed or perturbed at either 5-7% or 50% of model growth. (II) In a data set with detailed measures of 1207 placental perimeters, radial standard deviations of placental shapes were calculated from the umbilical cord insertion, and from the centroid of the shape (a biologically arbitrary point). These two were compared to the difference between the observed scaling exponent and the Kleiber scaling exponent (0.75), considered optimal for vascular fractal transport systems. Spearman's rank correlation considered p<0.05 significant.

RESULTS

(I) Unperturbed, random values of the growth parameter created round/oval fractal shapes. Perturbation at 5-7% of model growth created multilobate shapes, while perturbation at 50% of model growth created "star-shaped" fractals. (II) The radial standard deviation of the perimeter from the umbilical cord (but not from the centroid) was associated with differences from the Kleiber exponent (p=0.006).

CONCLUSIONS

A dynamical DLA model recapitulates multilobate and "star" placental shapes via changing fractal branching density. We suggest that (1) irregular placental outlines reflect deformation of the underlying placental fractal vascular network, (2) such irregularities in placental outline indicate sub-optimal branching structure of the vascular tree, and (3) this accounts for the lower birth weight observed in non-round/oval placentas in the Collaborative Perinatal Project.

Placental characteristics and birthweight

Standard gross placental measures capture dimensions relevant to specific placental functions. Our objective was to determine their accountability independent of placental weight for variance in birthweight, an important proxy for intrauterine 'adequacy' in fetal origins studies. The sample consisted of 24 152 singleton liveborn children of the Collaborative Perinatal Project delivered from 34 to 42 completed weeks gestation, with complete data for six placental measures (placental disc shape, umbilical cord length, distance from cord insertion to nearest margin, large diameter, small diameter, placental thickness) and placental weight. Associations between birthweight and placental measures were examined using multiple linear regression. Placental weight alone accounted for 36.6% of birthweight variation; the six other placental measures accounted for 28.1%. Combined, all placental measures accounted for 39.1% of birthweight variation. Seven maternal characteristics (age, height, weight, parity, socio-economic status, cigarette use, and race) were investigated to determine whether their known associations with birthweight were mediated by placental markers. Analysis suggested that the impact of all maternal characteristics except smoking was consistent with mediation by placental characteristics.

Placenta and fetal growth restriction

The placenta, as the vector for all maternal-fetal oxygen and nutrient exchange, is a principal influence on birthweight. Placental weight summarizes laterally expanding growth of the chorionic disc, and villous arborization yielding the nutrient exchange surface. These different growth dimensions alter fetoplacental weight ratio and ponderal index, and thus may modify placental functional efficiency. The placenta may show a range of histopathologies, some of which are also associated with fetal growth restriction. Different fetal intrinsic abilities to compensate for gross and histo-pathology may clarify the imperfect relationships between fetal growth and both intrauterine pathology, and the long-term health risks associated with poor fetal growth.

Placental growth patterns affect birth weight for given placental weight

BACKGROUND

An important contributor to fetal growth is growth of the placenta, the fetus' sole source of nutrients and oxygen. Here we use placental growth measures (larger and smaller disk diameters, reflecting the laterally expanding chorionic plate, and disk thickness) to test the hypothesis that placental growth patterns, while associated with placental weight and birth weight, measure placental functional efficiency, and will have independent effects on the feto-placental weight ratio (FPR).

METHODS

Placental measures were available from 23,313 participants in the Collaborative Perinatal Project delivered between 34 and 43 completed weeks. Continuous variables were analyzed by regression for associations with placental weight, birth weight, and FPR, to further explore effects of placental growth patterns on the FPR (lateral chorionic plate growth and chorionic disk thickness were grouped as low, normal, and high values). The relationships of the nine resultant combinations of placental growth categories to the FPR using birth weight adjusted for gestational age, infant gender, parity, and African American race were analyzed (ANOVA).

RESULTS

As chorionic disk area and thickness increased, birth weight and placental weight increased, and the FPR decreased (each p < .0001) after adjustment for gestational age, parity, race, and infant gender. Small, thin placental disks had an adjusted FPR of 8.46; the largest, thickest placentas had an adjusted FPR of 6.33. The nine categories of FPRs were significantly different, consistent with chorionic plate area and disk thickness combining to determine the FPR.

CONCLUSIONS

Patterns of placental growth, relating to different functional dimensions of the placenta, deliver a different birth weight for a given placental weight.