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

BackgroundNovel 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.Methods916 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.ResultsVariables 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).ConclusionsMeasures of CS and CV account for variation in placental efficiency defined by beta, independent of GA. Macroscopic placenta measurements can identify suboptimal placental development.     

Umbilical cord length in singleton gestations: A Finnish population-based retrospective register study

Introduction

Many complications of pregnancy and delivery are associated with umbilical cord length. It is important to examine the variation in length, in order to identify normal and abnormal conditions. Moreover, the factors influencing cord growth and development are not precisely known.

Objective

The main objectives were to provide updated reference charts for umbilical cord length in singleton pregnancies and to evaluate potential factors affecting cord length.

Methods

Birth register data of 47,284 singleton pregnant women delivering in Kuopio University Hospital, Finland was collected prospectively. Gender-specific centile charts for cord length from 22 to 44 gestational weeks were obtained using generalized additive models for location, scale, and shape (GAMLSS). Gestational, fetal, and maternal factors were studied for their potential influence on cord length with single variable analysis and stepwise multiple linear regression analysis.

Results

Cord length increased according to gestational age, while the growth decelerated post-term. Birth weight, placental weight, pregravid maternal body mass index, parity, and maternal age correlated to cord length. Gestational diabetes and previous miscarriages were associated with longer cords, while female gender and placental abruption were associated with shorter cords.

Discussion and conclusions

Girls had shorter cords throughout gestation although there was substantial variation in length in both genders. Cord length associated significantly with birth weight, placental weight, and gestational age. Significantly shorter cords were found in women with placental abruption. This important finding requires further investigation.     

Standards for measuring umbilical cord length

Umbilical cord length was measured in 9620 male and 9068 female infants and related to gestational age in order to construct a growth chart for umbilical cords. In addition to providing a standard for the US white population, these growth charts illustrate that umbilical cord length is widely divergent at the same gestational age, males have longer cords than females (P less than 0.0001), and umbilical cord growth continues throughout the third trimester.     

Maternal serum leptin concentrations do not correlate with cord blood leptin concentrations in normal pregnancy

OBJECTIVE: To determine whether there is a difference in maternal leptin concentration and cord blood concentration, consistent with the hypothesis of a noncommunicating, two-compartement model of fetoplacental leptin regulation. METHODS: Blood samples were collected from 139 women, identified as having an uncomplicated pregnancy, from an antecubital vein at delivery. Cord blood samples were taken from the umbilical vein. Leptin was measured by radioimmunoassay, and its relationship to fetal and maternal anthropometrics was assessed by Spearman correlation. Differences in maternal and cord blood leptin levels between male and female infants were tested with the Mann-Whitney Utest. Maternal and cord blood leptin were compared by the Wilcoxon signed rank test. The outcome measures were maternal and cord blood leptin at delivery, fetal birth weight, length, weight/length ratio, and ponderal index, maternal prepregnancy body mass index, pregnancy weight gain, relative weight gain, and body mass index at delivery. RESULTS: No correlations were found between maternal and cord blood leptin concentrations. Fetal leptin level correlated with birth weight (rho = 0.665; P <.0001), length (rho = 0.490; P <.0001), ponderal index (rho = 0.260; P =.002), and weight/length ratio (rho = 0.625; P <.0001). Median leptin concentrations were higher in female (9.3 ng/mL, range 1.5-34.4 ng/mL) than in male (8.2 ng/mL, range 1.6-38.3 ng/mL) neonates, but this difference was statistically not significant. Logistic regression analysis showed a significant influence on umbilical venous leptin concentration for birth weight (P <.0001) but not for gender. Maternal leptin concentrations were significantly higher than cord leptin concentrations (P <.0005 for the male and female neonates and the entire group). CONCLUSION: There was no correlation between maternal and cord leptin, which supports the hypothesis of a noncommunicating, two-compartment model of fetoplacental leptin regulation.     

Fetal umbilical cord oxygen values and birth to placental weight ratio in relation to size at birth

OBJECTIVE: Our purpose was to examine regulatory linkages between fetal oxygenation and fetal and placental growth. We determined umbilical cord PO (2) and oxygen saturation, fractional oxygen extraction, and birth to placental weight ratio values in relation to size at birth for a large tertiary hospital population delivering at term. STUDY DESIGN: The computerized perinatal database of St Joseph's Health Care London, London, Ontario, was used to obtain the umbilical cord gases, pH, birth weight, placental weight, and other selected information for all term, singleton, liveborn infants between January 1990 and December 1999 (N = 27,043). Oxygen saturation values were calculated from the umbilical cord PO(2) and pH data with a previously derived empirical equation; fractional oxygen extraction values were calculated from the umbilical cord oxygen saturation data. Size at birth was divided into the following 5 birth weight categories using neonatal growth standards: fetal growth restriction, <3%; borderline fetal growth restriction, >or=3% and <10%; appropriate for gestational age, >or=10% and 90% and 97%. RESULTS: Infants in the borderline fetal growth restriction and fetal growth restriction groups had umbilical vein and artery PO(2) and oxygen saturation values that were stepwise lower than respective values for infants in the appropriate for gestational age group. Conversely, infants in the borderline large for gestational age and large for gestational age groups had umbilical vein PO(2) and oxygen saturation values that were stepwise higher than respective appropriate for gestational age group values; infants in these groups showed no change in arterial PO (2) and oxygen saturation values. Therefore infants in the borderline fetal growth restriction and fetal growth restriction groups had fractional oxygen extraction values that were stepwise higher than the appropriate for gestational age group value, whereas values for infants in the borderline large for gestational age and large for gestational age groups remained unchanged. Birth weight was disproportional to placental weight for infants in the borderline fetal growth restriction and fetal growth restriction groups when compared with that of the infants in the appropriate for gestational age group, with the birth to placental weight ratio values stepwise decreased. Conversely, birth weight was proportional to placental weight for infants in the borderline large for gestational age and large for gestational age groups with the birth to placental weight ratio values thus unchanged when compared with that of the infants in the appropriate for gestational age group. CONCLUSION: We conclude that fetal oxygenation is related to size at birth across the entire range of birth weights as studied at term from macrosomic to growth-restricted infants; this conclusion supports oxygen as a primary determinant of fetal growth. However, there are differences in the linkage between fetal oxygenation and metabolic rate or growth for these cohort groups that may relate to underlying etiologic processes.     

Allometric Metabolic Scaling and Fetal and Placental Weight

BackgroundWe tested the hypothesis that the fetal–placental relationship scales allometrically and identified modifying factors of that relationship.Materials and methodsAmong 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 α and β by rewriting PW = α(BW)β as ln(PW) = ln α + β[ln(BW)]. α_ι was then the dependent variable in regressions with p < 0.05 significant.ResultsMean β 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 α.ConclusionsWe 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.     

Centrality of the Umbilical Cord Insertion in a Human Placenta Influences the Placental Efficiency

GoalWe 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 methods1225 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.ResultsThe 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 β 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.ConclusionNon-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 β 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.     

Human chorionic gonadotropin in cord blood and peripheral maternal blood in singleton and twin pregnancies at delivery

The influence of fetal sex on human chorionic gonadotropin (hCG) in cord and peripheral maternal blood was studied at delivery in 57 twin and 66 singleton uncomplicated pregnancies. In twin pregnancies the hCG levels were about twice as high in female-female and in female-male vis-à-vis male-male combinations in both maternal and cord blood. In singleton pregnancies the hCG levels were significantly higher in maternal and in cord blood in cases of female vis-à-vis male infants. The ratio of maternal hCG/placental weight was also highest in the twin pregnancies when one or both infants were female. This suggests a "female effect", possibly genetically based.     

In vitro umbilical cord wrapping and torsion: possible cause of umbilical blood flow occlusion

Abstract

Objective: Intrapartum fetal heart rate decelerations and bradycardia are often attributed to umbilical cord occlusion without knowing the anatomic basis of that occlusion. We hypothesized that umbilical cord twisting while looped around fetal parts could occlude blood flow.

Methods: Using an in vitro preparation, human umbilical cord veins were perfused at one end with water at approximately 40?cm H₂O. The cords were looped around pipes that approximated the diameter of fetal body or limb parts, after which the perfused segment of cord was twisted until water flow stopped. The number of rotations needed to stop perfusion was recorded for each length of twisted cord (4, 6 and 8?cm) and for each pipe diameter.

Results: There were 21 completed studies. All cords demonstrated that a decreasing number of twists were needed to stop venous flow as the segment twisted became shorter (from 8 to 4?cm). For each segment length, the number of twists required to stop flow decreased as the pipe diameter narrowed.

Conclusion: This model demonstrates that a wrapped umbilical cord, particularly with a short segment between the placental insertion and the fetal body part, may be predisposed to cord occlusion in response to fetal rotation.     

Abnormal fetal heart rate patterns and placental inflammation

Can acute inflammation in the placental membranes, amniotic fluid, or both, predispose to the development of abnormal fetal heart rate patterns? One hundred cases in which bradycardia was noted were compared with 48 cases in which abnormal fetal heart rate patterns did not occur. Case and control subjects were matched to provide an equivalent risk of developing ascending infection in the two groups. Fetoplacental weight ratio and the presence of other placental diseases were also considered. The presence of acute inflammation in the umbilical cord (p = 0.03), amnion (p = 0.01), and choriodecidua (p = 0.03), and higher grades of inflammation in chorionic plate (p = 0.03) were linked to the presence of abnormal fetal heart rate patterns. No other placental factors were associated with increased risk of fetal bradycardia. The association of abnormal fetal heart rate patterns with acute inflammation suggests that intra-amniotic inflammation is important in the genesis of fetal bradycardias. The inflamed amniotic fluid could alter fetal metabolism via effects on the pulmonary or gastrointestinal systems or effects on umbilical and chorionic vessels.     

Fused umbilical arteries near placental cord insertion

OBJECTIVE: This study was undertaken to study the frequency and cause of fused umbilical arteries (FUAs). STUDY DESIGN: Umbilical cord on the placental side was carefully examined for FUAs by continuous interval sections. RESULTS: The frequency was 3.1% or 22 in 702 infants with the frequency in female infants of 4.1% being significantly higher than that in male infants of 2.0%. The mean distance of fused points was 2.3 +/- 1.6 cm from placental cord insertion. Five of 22 cases showed both arterial fusion and division in the same umbilical cord. Marginal and velamentous insertions were significantly associated with FUAs. Gestational age, birth weight, and placental weight of 22 cases were within normal range. CONCLUSION: Single umbilical artery should be confirmed by 2 or 3 sections of umbilical cord because of the high frequency of FUA on the placental side.     

Impact of early- and late-onset preeclampsia on features of placental and newborn vascular health

IntroductionOffspring exposed to preeclampsia (PE) show an increased risk of cardiovascular disease in adulthood. We hypothesize that this is mediated by a disturbed vascular development of the placenta, umbilical cord and fetus. Therefore, we investigated associations between early-onset PE (EOPE), late-onset PE (LOPE) and features of placental and newborn vascular health.MethodsWe performed a nested case-control study in The Rotterdam Periconceptional Cohort, including 30 PE pregnancies (15 EOPE, 15 LOPE) and 218 control pregnancies (164 uncomplicated controls, 54 complicated controls including 28 fetal growth restriction, 26 preterm birth) and assessed macroscopic and histomorphometric outcomes of the placenta and umbilical cord.ResultsA significant association was observed between PE and a smaller umbilical vein area and wall thickness, independent of gestational age and birth weight. In EOPE we observed significant associations with a lower weight, length and width of the placenta, length of the umbilical cord, and thickness and wall area of the umbilical vein and artery. These associations attenuated after gestational age and birth weight adjustment. In LOPE a significant association with a larger placental width and smaller umbilical vein wall thickness was shown, independent of gestational age and birth weight.DiscussionOur study suggests that PE is associated with a smaller umbilical cord vein area and wall thickness, independent of gestational age and birth weight, which may serve as a proxy of disturbed cardiovascular development in the newborn. Follow-up studies are needed to ultimately predict and lower the risk of cardiovascular disease in offspring exposed to PE.     

Association between funisitis and elevated interleukin-6 in cord blood

OJBECTIVE: To determine whether elevated plasma interleukin-6 (IL-6) in umbilical venous cord blood at delivery is associated with funisitis and whether IL-6 can be used to screen for funisitis in preterm neonates. METHODS: At the time of delivery, umbilical venous cord blood samples were collected from 92 infants for whom placental pathology results were also available. Interleukin-6 concentrations in the umbilical venous cord blood plasma were measured by immunoassay. Histologic examinations of the placenta and umbilical cord were done to determine the presence or absence of funisitis and chorioamnionitis. For a power of 90% with an alpha of.05, 12 subjects were required in each group. RESULTS: We found a significant association between the presence of histologic funisitis and elevated umbilical venous cord blood plasma IL-6 concentrations (defined as 10 pg/mL or greater). Of 15 infants whose umbilical cords showed funisitis, 93% (14 of 15) had elevated umbilical venous cord blood plasma IL-6 concentrations. Of 77 infants without funisitis, 32% (25 of 77) had elevated IL-6 concentrations in their cords (P <.001, two-sided Fisher exact test). The negative predictive value of IL-6 as a screening test for funisitis was 98%. CONCLUSION: In preterm neonates, screening for funisitis by using the immunoassay for IL-6 appears to be valid. In the near future, elevated umbilical venous cord blood IL-6 concentrations at delivery could be clinically useful to identify children who might benefit from early treatment for systemic fetal inflammatory syndrome.     

Predisposing factors in the formation of true knots of the umbilical cord--analysis of morphometric and perinatal data

Fifty-four umbilical cords with a true knot were analysed and compared to 108 normal cords. True knots were found in 1.22% of births. They occurred at a significantly higher rate in longer cords (P less than 0.00001), in male fetuses (P less than 0.05) and in multiparous women (P less than 0.003). Signs of fetal distress were observed more frequently in female fetuses, especially in those with longer cords. A true knot seems to disrupt the significant correlation (P less than 0.007) between cord length and birth weight that we observed in controls. The present study reviews the literature on the subject and suggests a possible mechanism for true knot formation.     

Umbilical cord knots

BACKGROUND: Umbilical cord knots may represent a hazard to the fetus, particularly as regards intrauterine death and fetal distress or asphyxia in labor. The object of this study was to analyze the impact of associated umbilical cord encirclements and cord length on fetal outcome and fetal weight deviation. METHODS: Among 22,012 births occurring in Akershus Central Hospital, there were 216 instances of umbilical cord knots. Fetal outcome, fetal weight deviation, associated umbilical cord encirclements and cord length were assessed. RESULTS: Neonates with a knotted cord are more often large-for-gestational age compared to other babies, and have longer umbilical cords. There is a 10 times higher chance of intrauterine fetal death with a knotted cord, but if this does not occur then there is no increased risk of obstetrical intervention and Apgar scores are the same as in other babies and other fetuses. CONCLUSION: There is an association between umbilical cord knots and umbilical cord encirclements. Knotting of the cord is not by itself lethal. Pregnancies with knotted cords have characteristics different from those with ordinary umbilical cord encirclements.     

Differential expression of human placental PAPP-A2 over gestation and in preeclampsia

IntroductionPregnancy Associated Plasma Protein A2 (PAPP-A2) is a pregnancy related insulin-like growth factor binding protein-5 (IGFBP-5) protease, known to be elevated in preeclampsia. As the insulin-like growth factors are important in human implantation and placentation, we sought to determine the expression pattern of PAPP-A2 over human gestation in normal and preeclamptic pregnancies to evaluate its role in placental development and the pathogenesis of preeclampsia.MethodsPlacental basal plate and chorionic villi samples, maternal and fetal cord blood sera were obtained from preeclamptic and control pregnancies. Formalin-fixed tissue sections from across gestation were stained for cytokeratin-7, HLA-G, and PAPP-A2. PAPP-A2 immunoblot analysis was also performed on protein lysates and sera.ResultsPAPP-A2 expression is predominately expressed by differentiated trophoblasts and fetal endothelium. Chorionic villi show strong expression in the first trimester, followed by a progressive decrease in the second trimester, which returns in the third trimester. PAPP-A2 expression is not impacted by labor. PAPP-A2 is increased in the basal plate, chorionic villi and maternal sera in preeclampsia compared to controls, but is not detectable in cord blood.DiscussionPAPP-A2 is differentially expressed in different trophoblast populations and shows strong down regulation in the mid second trimester in chorionic villous samples. Both maternal sera and placental tissue from pregnancies complicated by preeclampsia show increased levels of PAPP-A2. PAPP-A2 levels are not altered by labor. Additionally, PAPP-A2 cannot be detected in cord blood demonstrating that the alterations in maternal and placental PAPP-A2 are not recapitulated in the fetal circulation.     

Implications of differences in coiling indices at different segments of the umbilical cord

The purpose of this study was to find out if the coiling density is similar in all segments of term singleton umbilical cords. We compared the coiling index (coils/cm) at three different segments of 159 cords. There was no statistical difference between the coiling indices of the placental and middle segment, but significantly increased coiling was found at the fetal end compared with the placental and middle segments. Coiling indices were not significantly correlated with gestational age, cord length or birth weight. We diagnosed concordant hypo- and hypercoiling when the placental and fetal segments had the same density classification, and discordant hypo- and hypercoiling when these segments had different density classifications. Concordant hypocoiling and hypercoiling were found in 4.4 and 6.3% of the cords examined, respectively (total of 10.7%), concordant normal coiling in 95 (59.7%) and discordant density classifications in 29.6%. We concluded that the coiling index should be established in two distinct segments and that the spatial configuration of the coils, which protects the blood flow in the umbilical cord, might not be measured by coil density only.     

Exploring sexual dimorphism in placental circulation at 22–24 weeks of gestation: A cross-sectional observational study

IntroductionPlacental blood flow is closely associated with fetal growth and wellbeing. Recent studies suggest that there are differences in blood flow between male and female fetuses. We hypothesized that sexual dimorphism exists in fetal and placental blood flow at 22–24 weeks of gestation.MethodsThis was a prospective cross-sectional study of 520 healthy pregnant women. Blood flow velocities of the middle cerebral artery (MCA), umbilical artery (UA), umbilical vein (UV) and the uterine arteries (UtA) were measured using Doppler ultrasonography. UV and UtA diameters were measured using two-dimensional ultrasonography and power Doppler angiography. Volume blood flows (Q) of the UV and UtA were calculated. Maternal haemodynamics was assessed with impedance cardiography. UtA resistance (R_uta) was computed as MAP/Q_uta.ResultsUA PI was significantly (p = 0.008) higher in female fetuses (1.19 ± 0.15) compared with male fetuses (1.15 ± 0.14). MCA PI, cerebro-placental ratio (MCA PI/UA PI), Q_uv, UtA PI, Q_uta and R_uta were not significantly different between groups. At delivery, the mean birth weight and placental weight of female infants (3504 g and 610 g) were significantly (p = 0.0005 and p = 0.039) lower than that of the male infants (3642 g and 634 g).DiscussionWe have demonstrated sexual dimorphism in UA PI, a surrogate for placental vascular resistance, at 22–24 weeks of gestation. Therefore, it would be useful to know when this difference emerges and whether it translates into blood flow differences that may impact upon the fetal growth trajectory.     

Intrauterine growth restriction is associated with structural alterations in human umbilical cord and decreased nitric oxide-induced relaxation of umbilical vein

IntroductionIntrauterine growth restriction (IUGR) affects ∼8% of all pregnancies and is associated with major perinatal mortality and morbidity, and with an increased risk to develop cardiovascular diseases in adulthood. Despite identification of several risk factors, the mechanisms implicated in the development of IUGR remain poorly understood. In case of placental insufficiency, reduced delivery of oxygen and/or nutrients to the fetus could be associated with alterations in the umbilical circulation, contributing further to the impairment of maternal–fetal exchanges. We compared the structural and functional properties of umbilical cords from growth-restricted and appropriate for gestational age (AGA) term newborns, with particular attention to the umbilical vein (UV).MethodsHuman umbilical cords were collected at delivery. Morphological changes were investigated by histomorphometry, and UV's reactivity by pharmacological studies.ResultsGrowth-restricted newborns displayed significantly lower growth parameters, placental weight and umbilical cord diameter than AGA controls. Total cross-section and smooth muscle areas were significantly smaller in UV of growth-restricted neonates than in controls. Maximal vasoconstriction achieved in isolated UV was lower in growth-restricted boys than in controls, whereas nitric oxide-induced relaxation was significantly reduced in UV of growth-restricted girls compared to controls.ConclusionIUGR is associated with structural alterations of the UV in both genders, and with a decreased nitric oxide-induced relaxation in UV of newborn girls, whereas boys display impaired vasoconstriction. Further investigations will allow to better understand the regulation of umbilical circulation in growth-restricted neonates, which could contribute to devise potential novel therapeutic strategies to prevent or limit the development of IUGR.     

Fetal weight/placental weight ratio and perinatal outcome

The relationship of placental size to perinatal outcome was investigated in a population of low-risk infants. A trimmed and drained placenta was weighed for each of 417 low-risk infants, and for 108 infants whose intrapartum course was complicated only by compression of the umbilical cord. Tracings from intrapartum electronic fetal heart rate monitoring were analyzed by an investigator who was unaware of the fetal weight/placental weight ratio. The incidence of perinatal problems was increased in those infants whose fetal weight/placental weight ratio was greater than 11: intrapartum fetal distress, 20% (p = 0.0046); meconium-stained amniotic fluid, 28.9% (p = 0.0017); Apgar score less than 7, 11.1% (p = 0.04); and hyperbilirubinemia, 24.4% (p = 0.0008). On the basis of these data, the conclusion drawn was that there is a population of presumably low-risk infants who are at increased risk because they have outgrown their placentas.