Twin pregnancies, crown-rump length and birthweight discordancy: the influence of chorionicity / Gestações gemelares, comprimento craniocaudal e discordância de peso ao nascimento: a influência da corionicidade

Abstract Objective The purpose of the present study was to analyze the influence of chorionicity in the biometric parameters crown-rump length (CRL), birthweight (BW), crown-rump length discordancy (CRLD) and birthweight discordancy (BWD), determine the correlation between these latter two in cases of intertwin discordancy, and to analyze the influence of chronicity in the presence of these discordancies with clinical relevance (> 10% and > 15%, respectively). Methods The present study was a retrospective study based on the twin pregnancy database of the Centro Hospitalar S. João (2010-2015), including 486 fetuses among 66 monochorionic (MC) and 177 dichorionic gestations (DC). The inclusion criteria were multiple pregnancies with 2 fetuses and healthy twin gestations. The exclusion criteria were trichorionic gestations and pregnancies with inconclusive chorionicity, multiple pregnancy with ≥ 3 fetuses and pathological twin gestations. Results No statistically significant difference was found in BW (p = 0.09) and in its discordancy (p = 0.06) nor in CRL (p = 0.48) and its discordancy (p = 0.74) between MCs and DCs. Crown-rump length discordancy and birthweight discordancy were correlated by the regression line "BWD = 0.8864 x CRLD + 0.0743," with r2 = 0.1599. Crown-rump length discordancy > 10% was found in 7.58% of monochorionic and in 13.56% of dichorionic twins. Birthweight discordancy > 15% was detected in 16.67% of monochorionic and in 31.64% of dichorionic twins. Conclusion No statistically significant influence of chorionicity was identified in both birthweight and birthweight discordancy, as in crown-rump length and crown-rump length discordancy. Birthweight discordancy was correlated to crown-rump length discordancy in 20% of cases.

Resumo Objetivo O objetivo do presente estudo foi analisar a influência da corionicidade nos parâmetros biométricos comprimento craniocaudal, peso ao nascimento, discordância de comprimento craniocaudal e discordância de peso ao nascimento, determinar a correlação entre estes dois últimos caso haja discordância intergemelar e analisar a influência da corionicidade na presença destas discordâncias com relevância clínica (> 10% e > 15%, respectivamente). Métodos O presente estudo foi um estudo retrospectivo baseado na base de dados de gestações gemelares do Centro Hospitalar S. João (2010-2015), incluindo 486 fetos de 66 gestações monocoriônicas e 177 dicoriônicas. Os critérios de inclusão foram gestações múltiplas de 2 fetos e gestações gemelares saudáveis. Os critérios de exclusão foram gestações tricoriônicas ou de corionicidade inconclusiva, gestações múltiplas com ≥ 3 fetos e gestações gemelares patológicas. Resultados Não se encontrou diferença estatisticamente significativa no peso ao nascimento (p =0,09) e sua discordância (p = 0,06) nem no comprimento craniocaudal (p = 0,48) e sua discordância (p = 0,74) entre gestações monocoriônicas e dicoriônicas. Considerando todas as gestações, as discordâncias de comprimento craniocaudal e peso ao nascimento foram correlacionadas pela reta de regressão "discordância de peso ao nascimento = 0.8864 x discordância de comprimento craniocaudal + 0.0743," com r2 = 0,1599. A discordância de comprimento craniocaudal > 10% descobriu-se em 7.58% das gestações monocoriônicas e em 13.56% das dicoriônicas. A discordância de peso ao nascimento > 15% detectou-se em 16.67% das gestações monocoriônicas e em 31.64% das dicoriônicas. Conclusão Não se identificou influência estatisticamente significativa no peso ao nascimento e sua discordância, bem como no comprimento craniocaudal e sua discordância. A discordância de peso ao nascimento correlacionou-se com a discordância de comprimento craniocaudal em 20% dos casos.

Twin Pregnancies, Crown-rump Length and Birthweight Discordancy: The Influence of Chorionicity.

OBJECTIVE: The purpose of the present study was to analyze the influence of chorionicity in the biometric parameters crown-rump length (CRL), birthweight (BW), crown-rump length discordancy (CRLD) and birthweight discordancy (BWD), determine the correlation between these latter two in cases of intertwin discordancy, and to analyze the influence of chronicity in the presence of these discordancies with clinical relevance (> 10% and > 15%, respectively). METHODS: The present study was a retrospective study based on the twin pregnancy database of the Centro Hospitalar S. João (2010-2015), including 486 fetuses among 66 monochorionic (MC) and 177 dichorionic gestations (DC). The inclusion criteria were multiple pregnancies with 2 fetuses and healthy twin gestations. The exclusion criteria were trichorionic gestations and pregnancies with inconclusive chorionicity, multiple pregnancy with ≥ 3 fetuses and pathological twin gestations. RESULTS: No statistically significant difference was found in BW (p = 0.09) and in its discordancy (p = 0.06) nor in CRL (p = 0.48) and its discordancy (p = 0.74) between MCs and DCs. Crown-rump length discordancy and birthweight discordancy were correlated by the regression line "BWD = 0.8864 x CRLD + 0.0743," with r2 = 0.1599. Crown-rump length discordancy > 10% was found in 7.58% of monochorionic and in 13.56% of dichorionic twins. Birthweight discordancy > 15% was detected in 16.67% of monochorionic and in 31.64% of dichorionic twins. CONCLUSION: No statistically significant influence of chorionicity was identified in both birthweight and birthweight discordancy, as in crown-rump length and crown-rump length discordancy. Birthweight discordancy was correlated to crown-rump length discordancy in 20% of cases.

OBJETIVO: O objetivo do presente estudo foi analisar a influência da corionicidade nos parâmetros biométricos comprimento craniocaudal, peso ao nascimento, discordância de comprimento craniocaudal e discordância de peso ao nascimento, determinar a correlação entre estes dois últimos caso haja discordância intergemelar e analisar a influência da corionicidade na presença destas discordâncias com relevância clínica (> 10% e > 15%, respectivamente). MéTODOS: O presente estudo foi um estudo retrospectivo baseado na base de dados de gestações gemelares do Centro Hospitalar S. João (2010­2015), incluindo 486 fetos de 66 gestações monocoriônicas e 177 dicoriônicas. Os critérios de inclusão foram gestações múltiplas de 2 fetos e gestações gemelares saudáveis. Os critérios de exclusão foram gestações tricoriônicas ou de corionicidade inconclusiva, gestações múltiplas com ≥ 3 fetos e gestações gemelares patológicas. RESULTADOS: Não se encontrou diferença estatisticamente significativa no peso ao nascimento (p = 0,09) e sua discordância (p = 0,06) nem no comprimento craniocaudal (p = 0,48) e sua discordância (p = 0,74) entre gestações monocoriônicas e dicoriônicas. Considerando todas as gestações, as discordâncias de comprimento craniocaudal e peso ao nascimento foram correlacionadas pela reta de regressão "discordância de peso ao nascimento = 0.8864 x discordância de comprimento craniocaudal + 0.0743," com r2 = 0,1599. A discordância de comprimento craniocaudal > 10% descobriu-se em 7.58% das gestações monocoriônicas e em 13.56% das dicoriônicas. A discordância de peso ao nascimento > 15% detectou-se em 16.67% das gestações monocoriônicas e em 31.64% das dicoriônicas. CONCLUSãO: Não se identificou influência estatisticamente significativa no peso ao nascimento e sua discordância, bem como no comprimento craniocaudal e sua discordância. A discordância de peso ao nascimento correlacionou-se com a discordância de comprimento craniocaudal em 20% dos casos.

The effect of vaginal bleeding and non-spesific pelvic pain on pregnancy outcomes in subchorionic hematomas cases.

OBJECTIVES: To determine the clinical differences and factors affecting early pregnancy outcome in the first and early secondtrimester subchorionic hematoma cases. MATERIAL AND METHODS: This study involved with the retrospective analysis and evaluation of 81 cases diagnosed withsubchorionic hematoma. The patients were grouped according to the gestational periods, symptoms at the time of admission,ratio of surrounding hematoma to the gestational sac, and whether there was a pregnancy loss. The groups werecompared according to the clinical features and pregnancy outcomes. RESULTS: The ratio of surrounding hematoma to the gestational sac in the group with pregnancy loss was significantly higher(p = 0.002). When the cut-off value was 35.5%, it could determine the possibility of a complication in pregnancy with 70%sensitivity and 75% specificity. Nonspecific pelvic pain were significantly higher in the pregnancy loss group than in theother group. Logistic regression analysis was performed to determine the effect of these two parameters on the pregnancyoutcome. Although the presence of non-specific pelvic pain is more in the group with pregnancy loss; there was no effectof on pregnancy outcome (p = 0.141). The risk of pregnancy loss increased 4.5 fold if the ratio of ScH to gestational sacwas above 35% (p = 0.027). CONCLUSIONS: In the cases of subchorionic hematoma, we concluded that when the ratio of surrounding hematoma tothe gestational sac increased and when it was accompanied by nonspecific pelvic pain, the hospitalization period of thepatients increased and the ratio of pregnancy loss was higher.

Impairment of BKca channels in human placental chorionic plate arteries is potentially relevant to the development of preeclampsia.

Preeclampsia has known associations with insufficient placental perfusion. The large-conductance Ca2+-activated K+ (BKca) channels that have recently been found to play important roles in cellular growth and vasodilatation could potentially participate in the development of preeclampsia. However, the mechanisms by which downregulated BKca channels are involved in the development of preeclampsia remain unknown. In this study, we investigated the mechanism(s) underlying the impairment of vascular tone regulation by BKca channels in human placental chorionic plate arteries (CPAs) in preeclampsia. The levels of BKca channel α and ß1 subunits were compared using immunohistochemistry, western blotting, and RT-PCR in CPAs of normal and preeclamptic pregnant women. To explore the role of BKca channels in the regulation of proliferation and apoptosis in human placental CPA smooth muscle cells (SMCs), a specific BKca opener, NS1619, was used to investigate proliferative reduction and apoptotic induction in human placental chorionic plate arterie smooth muscle cells (CPASMCs) collected from normal pregnancies. The vasodilator effects of BKca channels and their response to SNP (an NO donor) in both groups were also evaluated by wire myography. We found that BKca channel ß1 subunits were less expressed in preeclamptic CPAs. After pretreatment with NS1619, cellular proliferation was significantly suppressed, and cellular apoptosis was dramatically promoted in cultured CPASMCs, demonstrating a relationship between increased Bax expression and decreased Bcl-2 expression in CPASMCs. Downregulated BKca is also associated with decreased vasodilatation and reduced susceptibility to NO donors. In conclusion, the decreased expression or activation of BKca channels may induce pathologic remodeling of human CPAs, weaken the vasodilation response, and decrease vascular sensitivity to vasoactive substances, thereby reducing fetal-placental blood flow and leading to the future development of preeclampsia.

Function and failure of the fetal membrane: Modelling the mechanics of the chorion and amnion.

The fetal membrane surrounds the fetus during pregnancy and is a thin tissue composed of two layers, the chorion and the amnion. While rupture of this membrane normally occurs at term, preterm rupture can result in increased risk of fetal mortality and morbidity, as well as danger of infection in the mother. Although structural changes have been observed in the membrane in such cases, the mechanical behaviour of the human fetal membrane in vivo remains poorly understood and is challenging to investigate experimentally. Therefore, the objective of this study was to develop simplified finite element models to investigate the mechanical behaviour and rupture of the fetal membrane, particularly its constituent layers, under various physiological conditions. It was found that modelling the chorion and amnion as a single layer predicts remarkably different behaviour compared with a more anatomically-accurate bilayer, significantly underestimating stress in the amnion and under-predicting the risk of membrane rupture. Additionally, reductions in chorion-amnion interface lubrication and chorion thickness (reported in cases of preterm rupture) both resulted in increased membrane stress. Interestingly, the inclusion of a weak zone in the fetal membrane that has been observed to develop overlying the cervix would likely cause it to fail at term, during labour. Finally, these findings support the theory that the amnion is the dominant structural component of the fetal membrane and is required to maintain its integrity. The results provide a novel insight into the mechanical effect of structural changes in the chorion and amnion, in cases of both normal and preterm rupture.

Effects of Intrauterine Environment on the Magnitude of Differences Within the Pairs of Monozygotic and Dizygotic Twins.

The aim of this study was to determine the effects of intrauterine environment on the magnitude of intrapair differences in six somatic traits of monozygotic (MZ) and dizygotic (DZ) twins (1,263 pairs; 424 MZ twins and 839 DZ twins). Differences in intrauterine environments of MZ twins enforced division of the research material into four groups: (1) MZ-MC-TTTS - MZ twins from monochorionic (MC) pregnancies with twin-to-twin transfusion syndrome (TTTS), (2) MZ-MC (without TTTS)-MZ twins from MC pregnancies without TTTS, (3) MZ-DC-MZ twins from dichorionic (DC) pregnancies, and (4) DZ-DZ twins. The intrapair differences in all analyzed somatic traits, especially body weight and circumference of the chest, were the largest in the case of MZ twins from MC pregnancies with TTTS. DZ twins were the group presenting with the second largest intrapair differences in the analyzed traits. At the end of pregnancy, that is, in lunar months 9 and 10, the magnitude of intrapair differences in all traits of twins from this group was significantly greater than in MZ twins from both MC and DC pregnancies. Irrespective of the analyzed period, the least evident, statistically insignificant intrapair differences in the studied traits were documented in the case of MZ twins from MC pregnancies without TTTS and twins from DC pregnancies. These findings imply that the differentiating effect of intrauterine environment is associated with the occurrence of TTTS, rather than with chorionicity, as postulated previously.

Perinatal outcome according to chorionicity in twins - a Polish multicenter study.

OBJECTIVES: The aim of the study was to analyze the perinatal outcome of twin gestations and estimate the influence of chorionicity on the outcome in a large cohort of twin pregnancies in Poland. MATERIAL AND METHODS: A retrospective analysis of 465 twin deliveries in 6 Polish centers in 2012 was conducted. Baseline characteristics, the course of pregnancy and labor, as well as the neonatal outcome were analyzed in the study group and according to chorionicity. RESULTS: A total of 356 twin pregnancies were dichorionic (DC group) (76.6%), and 109 were monochorionic (MC group) (23.4%). There were no differences in the occurrence of pregnancy complications according to chorionicity, except for IUGR of at least one fetus (MC 43.1% vs. DC 34.6%; p = 0.003). 66.5% of the women delivered preterm, significantly more in the MC group (78% vs. 62.9%; p = 0.004). Cesarean delivery was performed in 432 patients (92.9%). Mean neonatal birthweight was statistically lower in the MC group (2074 g vs. 2370 g; p < 0.001). Perinatal mortality of at least one twin was 4.3% (2.8% in the DC group vs. 9.2% in the MC group; p = 0.004). Neonatal complications, including NICU admission, respiratory disorders, and infections requiring antibiotic therapy, were significantly more often observed among the MC twins. CONCLUSIONS: The overall perinatal outcome in the presented subpopulation of Polish twins and its dependence on cho-rionicity is similar to the reports in the literature. Nevertheless, the rates of preterm and cesarean deliveries remain higher. It seems that proper counselling of pregnant women and education of obstetricians may result in reduction of these rates.

Ex Vivo Human Placental Perfusion Model for Analysis of Fetal Circulation in the Chorionic Plate.

OBJECTIVES: The purpose of this study was to develop an ex vivo placental perfusion model to assess changes in the umbilical artery systolic-to-diastolic (S/D) ratio due to progressive occlusion of the placental arterial system. METHODS: Ex vivo human placentas were connected to a computerized pulse duplicator mimicking pulsatile flow from the fetal heart. Doppler sonographic measurements were conducted on the umbilical and chorionic arteries of 25 mature placentas. Simulation of placental occlusion was performed by progressive ligature of the chorionic arteries, including one umbilical artery. The correlation between the umbilical artery S/D ratio and the severity of simulated placental occlusion was analyzed. RESULTS: The normal mean S/D ratio ± SD decreased gradually along the chorionic plate from 2.66 ± 0.47 at the cord insertion to 1.90 ± 0.59 in generation IV of the chorionic vessels. The Doppler index initially increased slowly with simulated placental occlusion. Only when all 4 generations were occluded was the umbilical artery S/D ratio elevated. Complete occlusion of one umbilical artery resulted in a 39% increase in the umbilical artery S/D ratio. CONCLUSIONS: This unique model combining Doppler sonography with perfusion of an ex vivo placenta can be used for a better understudying of pathologic placental blood flow circulation.

Impact of Monochorionicity and Twin to Twin Transfusion Syndrome on Prenatal Attachment, Post Traumatic Stress Disorder, Anxiety and Depressive Symptoms.

Monochronioric (MC) twin pregnancies are considered as high-risk pregnancies with potential complications requiring in-utero interventions. We aimed to assess prenatal attachment, anxiety, post-traumatic stress disorder (PTSD) and depressive symptoms in MC pregnancies complicated with Twin-To-Twin-transfusion syndrome (TTTS) in comparison to uncomplicated monochorionic (UMC) and dichorionic pregnancies (DC). Auto-questionnaires were filled out at diagnosis of TTTS and at successive milestones. Prenatal attachment, PTSD, anxiety and perinatal depression were evaluated respectively by the Prenatal Attachment Inventory (PAI) completed for each twin, the Post-traumatic Checklist Scale (PCLS), the State-Trait Anxiety Inventory (STAI) and the Edinburgh Perinatal Depression Scale (EPDS). There was no significant difference in the PAI scores between the two twins. In the DC and UMC groups, PAI scores increased throughout pregnancy, whilst it didn't for TTTS group. TTTS and DC had a similar prenatal attachment while MC mothers expressed a significantly higher attachment to their fetuses and expressed it earlier. At the announcement of TTTS, 72% of the patients present a score over the threshold at the EPDS Scale, with a higher score for TTTS than for DC (p = 0.005), and UMC (p = 0.007) at the same GA. 30% of mothers in TTTS group have PTSD during pregnancy. 50% of TTTS- patients present an anxiety score over the threshold (STAI-Scale), with a score significantly higher in TTTS than in UMC (p<0.001) or DC (p<0.001). The proportion of subject with a STAI-State over the threshold is also significantly higher in TTTS than in DC at 20 GW (p = 0.01) and at 26 GW (p<0.05). The STAI-state scores in UMC and DC increase progressively during pregnancy while they decrease significantly in TTTS. TTTS announcement constitutes a traumatic event during a pregnancy with an important risk of PTSD, high level of anxiety and an alteration of the prenatal attachment. These results should guide the psychological support provided to these patients.

Intertwin estimated fetal weight or crown rump length discordance and adverse perinatal outcome.

AIM: In the current review study, we present recent data regarding the importance of intertwin estimated fetal weight (EFW) and crown rump length (CRL) discordance for the prediction of adverse perinatal outcome both in monochorionic and in dichorionic diamniotic gestations. RESULTS: Twins with significant weight disparity are associated with higher rates of perinatal morbidity and mortality, regardless of gestational age at delivery. However, there is no agreement regarding as to the cut off value above which the perinatal outcome is unfavorably affected and the threshold range from 10 to 30%. On the other hand, CRL discrepancy has proved to be a weak predictor of adverse outcomes, such as fetal or neonatal death in fetuses without chromosomal and structural abnormalities. In clinical practice, decisions about obstetric surveillance of discordant twin gestations, frequency of fetal sonographic monitoring and time of delivery are usually based on amniotic fluid volume and Doppler assessments on a weekly basis. CONCLUSION: Significant EFW discordance leads to adverse perinatal outcome, although the cut-off value has not yet been estimated. CRL discrepancy is not correlated well with adverse perinatal outcome. However, increased monitoring of women with EFW and CRL discrepancy is suggested.

Risk of late-preterm stillbirth and neonatal morbidity for monochorionic and dichorionic twins.

OBJECTIVE: The purpose of this study was to determine the prospective risk of intrauterine fetal death (IUFD) at ≥34 weeks' gestation for monochorionic and dichorionic twins receiving intensive antenatal fetal surveillance. The secondary objective was to calculate the incidence of prematurity-related neonatal morbidity/mortality rates that have been stratified by gestational week and chorionicity. STUDY DESIGN: A retrospective cohort study of all twins at ≥34 weeks' gestation who were delivered at the Medical University of South Carolina (1987-2010) was performed. Twins were cared for in a longstanding Twin Clinic with standardized treatment and surveillance protocols and supervised by a consistent Maternal-Fetal Medicine specialist. Gestational age-specific fetal/neonatal mortality rates and composite neonatal morbidity rates were compared by chorionicity. A generalized linear mixed model was used to identify variables that were associated with increased composite neonatal morbidity. RESULTS: Among 768 twin gestations (601 dichorionic and 167 monochorionic), only 1 dichorionic IUFD occurred. The prospective risk of IUFD at ≥34 weeks' gestation was 0.17% for dichorionic twins and 0% for monochorionic twins. Composite neonatal morbidity decreased with each gestational week (P < .0001). Morbidity was increased by white race, gestational diabetes mellitus, and elective indication for delivery. The nadir of composite neonatal morbidity occurred at 36/0-36/6 weeks' gestation for monochorionic twins and 37/0-37/6 weeks' gestation for dichorionic twins. CONCLUSION: Our data do not support concern for an increased risk of stillbirth in uncomplicated intensively monitored monochorionic twins at ≥34 weeks' gestation. However, our data do show significantly increased rates of neonatal morbidity in late preterm monochorionic twins that cannot be justified by a corresponding reduction in the risk of stillbirth. We believe that our data support delivery of uncomplicated monochorionic twins at 37 weeks' gestation.

Perinatal death of triplet pregnancies by chorionicity.

OBJECTIVE: The purpose of this study was to evaluate the perinatal risk of death by chorionicity at >22 weeks of gestation of triplet pregnancies. STUDY DESIGN: In a retrospective cohort study, the perinatal data were collected from triplet pregnancies in Japanese perinatal care centers between 1999 and 2009. We included maternal characteristics and examined the following factors: prenatal interventions, pregnancy outcome, and neonatal outcome. The association between fetal or neonatal death of triplets and chorionicity was evaluated by logistic regression analysis. RESULTS: After the exclusion of 253 cases, the study group comprised 701 cases: 507 trichorionic triamniotic (TT) triplet pregnancies, 144 diamniotic triamniotic (DT) triplet pregnancies, and 50 monochorionic triamniotic (MT) triplet pregnancies. The mortality rate (fetal death at >22 weeks of gestation; neonatal death) in triplets was 2.6% and included 2.1% of TT triplet pregnancies, 3.2% of DT triplet pregnancies, and 5.3% of MT triplet pregnancies. No significant risk of death was identified in DT triplet pregnancies; however, MT triplet pregnancies had a 2.6-fold greater risk (adjusted odds ratio, 2.60; 95% confidence interval, 1.17-5.76; P = .019) compared with TT triplet pregnancies. Prophylactic cervical cerclage did not reduce the perinatal mortality rate at >22 weeks of gestation in triplets. CONCLUSION: The risk of death for MT triplet pregnancies is significantly higher than that of TT triplet pregnancies; however, the risk of death for DT triplet pregnancies is not.

[Massive subchorial thrombosis].

Massive subchorial thrombosis (MSCT) is a placental abnormality, the etiology and pathogenesis of which remain inadequately studied. MSCT is characterized by a clinical symptom complex comprising marked intrauterine growth retardation, oligohydramnios, and fetal distress due to placental circulatory problems. Perinatal outcomes are appreciably determined by the term of pregnancy, the degree of placental insufficiency, and neonatal status. Prolonged MSCT makes it possible to diagnose this pathology by echographic and magnetic resonance imaging studies and to attempt to treat placental dysfunction through tocolytic therapy and correction of oligohydramnios, to prolong pregnancy, and to have a viable newborn infant. The clinical and morphological diagnosis of MSCT calls for its differential diagnosis with other focal placental lesions, such as subamniotic, intraplacental, and retroplacental hematomas, cytotrophoblastic cyst, umbilical cord cysts, and chorangioma.

Monochorionic diamniotic twin pregnancies: natural history and risk stratification.

About 30% of monochorionic twin pregnancies are complicated by twin-to-twin transfusion syndrome (TTTS), isolated discordant growth, twin anemia-polycythemia sequence, congenital defects or intrauterine demise. About 15% will be eligible for invasive fetal therapy, either fetoscopic laser treatment for TTTS or fetoscopic or ultrasound-guided umbilical cord coagulation for a severe congenital defect in one twin or severe discordant growth with imminent demise of the growth-restricted twin. Ultrasound examination in the first and early second trimester can differentiate the monochorionic twins at high risk for adverse outcome from those likely to be uneventful, which may be useful for patient counselling and planning of care.

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.

Premature rupture of the fetal membranes: is the amnion the major determinant?

OBJECTIVE: The objective of the study was to evaluate the relative contributions of amnion and chorion to the strength of fetal membranes and to correlate these findings with gestational age. STUDY DESIGN: Fetal membranes from 78 pregnancies were tested for biaxial puncture force using a blunt, instrumented probe with a low-force load cell connected through a load cell conditioner to an oscilloscope. The average of 2 to 4 tests performed on independent regions of the membrane was recorded. Means and SDs were calculated through the gestational age ranges of less than 32, 32 to 36, or 37 weeks or longer. Linear regression analysis was performed across gestational age after grouping data by labor and mode of delivery. RESULTS: There were trends toward decreasing puncture force with gestational age for both chorioamnion and amnion for both vaginal deliveries and cesarean sections. The trends were significant by linear regression for labored deliveries but not unlabored cesarean sections for both chorioamnion and amnion alone. There was no trend in chorion puncture force with either gestational age or delivery mode and the mean puncture force values were, on average, half those for the amnion. CONCLUSION: The amnion is significantly stronger than the chorion when subjected to biaxial strength testing. The amnion but not the chorion is significantly affected by the chemical and mechanical changes during gestation and the labor process. These data will help direct future studies on the effects of clinical and molecular modulators of inflammation on membrane rupture thresholds with special emphasis on the biochemical and structural changes in the amnion.

The physiology of fetal membrane rupture: insight gained from the determination of physical properties.

Premature rupture of the fetal membranes is a major cause of preterm birth and its associated infant morbidity and mortality. Recently, it has become clear that rupture of the fetal membranes, term or preterm, is not merely the result of the stretch and shear forces of uterine contractions, but is, in significant part, the consequence of a programmed weakening process. Work in the rat model has demonstrated that collagen remodeling, with activation of matrix metalloproteinases (MMPs), and apoptosis increase markedly in the amnion at end-gestation, suggesting that these processes are involved in fetal membrane weakening. We have developed fetal membrane strength testing equipment and a systematic tissue sampling methodology that has allowed us to demonstrate that term, non-labored, fetal membranes have a zone of weakness overlying the cervix, which contains biochemical markers of both collagen remodeling and apoptosis. These findings provide strong support for the concept of programmed fetal membrane weakening prior to labor. Our model has also been used to establish the physical properties of individual fetal membrane components (amnion, chorion), determine the sequence of events during the fetal membrane rupture process, and demonstrate that treatment of fetal membranes with TNF or IL-1beta, in vitro, induces weakness and the identical biochemical markers of collagen remodeling and apoptosis seen in the physiological weak zone. The ability to simultaneously correlate macroscopic physical properties with histological and biochemical fetal membrane characteristics, presents a unique perspective on the physiology of fetal membrane rupture.

Mechanical failure of human fetal membrane tissues.

Mechanical integrity of the chorioamnion membrane, and the component chorion and amnion layers, was assessed with biaxial puncture testing. Fetal membranes were obtained from term placentas following labored natural delivery or scheduled cesarean section. Preterm specimens were obtained from deliveries prior to 37 weeks gestation. Dividing and peripheral membranes were obtained from multiple gestation pregnancies. Specimens were gripped between parallel plates with circular openings and loaded with an instrumented, hand-held blunt probe until rupture occurred. Peak force was recorded and rupture sites were examined. Defects in multi-layered membranes differed in both size and shape in the individual layers. Compared with chorion and whole chorioamnion, amnion was more mechanically sensitive to different obstetrical conditions. Amnion varied in response at different physical locations within the same patient. Membrane and component puncture force data were used to calculate biaxial failure strength. Membrane stresses arising from amniotic fluid pressure were computed as a function of gestational age, and compared to membrane strength to examine the criterion for membrane failure in vivo. Possible mechanical conditions for preterm membrane rupture were examined.

Fisiopatología de la rotura prematura de las membranas ovulares em embarazos de pretérmino / Physiopathology of the premature rupture of membranes in preterm pregnancies

Se revisa la información de la literatura respecto de la estructura de las membranas ovulares, describiendo la zona de morfología alterada extrema, los mecanismos fisiopatológicos involucrados en la rotura prematura de membranas (destacando el proceso de apoptosis), relacionados a infección, isquemia placentaria, distensión de membranas, hemorragia coriodecidual, tabaquismo, relaxina, prolactina, hormona paratiroídea.