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Copyright of Ultrasound in Obstetrics & Gynecology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Introduction: Longitudinal studies of maternal hemodynamics in twin pregnancy are scarce and preload reserve in twin pregnancies has not been studied. Thus, we aimed to investigate serial changes in maternal systemic hemodynamics from the first to third trimester, and cardiovascular response to passive leg raising to evaluate preload reserve using impedance cardiography in a cohort of uncomplicated twin pregnancies.Material and Methods: This was a prospective longitudinal study of 50 twin pregnancies. Maternal hemodynamics was assessed at baseline and 120 seconds after passive leg raising using impedance cardiography, at five time points during gestation. Women were excluded from the analysis if there were pregnancy complications or fewer than three of five planned assessments were available.Results: Data from 37 uncomplicated twin pregnancies were available for analysis. Mean arterial pressure slightly decreased until 17 weeks' gestation, then increased. Systemic vascular resistance was constant in the first half of pregnancy before rising steadily thereafter, whereas the cardiac output increased from the first trimester, peaked by the end of the second trimester and then decreased in the third trimester. The change in stroke volume and cardiac output following passive leg raising during pregnancy ranged from -2.2% to 1.6% and from -3.7% to 3.2%, respectively. Although passive leg raising caused no significant changes in systemic vascular resistance, cardiac output or heart rate, mean arterial pressure decreased in the first and second trimesters.Conclusions: In uncomplicated twin pregnancies, maternal cardiovascular adaptation is evident from the first trimester. Twin pregnancies show a reduced preload reserve in the second half of gestation. [ABSTRACT FROM AUTHOR]

Objectives: The primary aim of this systematic review was to explore the strength of association between birth-weight (BW) discordance and perinatal mortality in twin pregnancy. The secondary aim was to ascertain the contribution of gestational age and growth restriction in predicting mortality in growth-discordant twins.Methods: MEDLINE, EMBASE, CINAHL and ClinicalTrials.gov databases were searched. Only studies reporting on the risk of mortality in twin pregnancies affected compared with those not affected by BW discordance were included. The primary outcomes explored were incidence of intrauterine death (IUD), neonatal death (NND) and perinatal death. Outcome was assessed separately for monochorionic (MC) and dichorionic (DC) twin pregnancies. Analyses were stratified according to BW discordance cut-off (≥ 15%, ≥ 20%, ≥ 25% and ≥ 30%) and selected gestational characteristics, including incidence of IUD or NND before and after 34 weeks' gestation, presence of at least one small-for-gestational age (SGA) fetus in the twin pair and both twins being appropriate-for-gestational age. Risk of mortality in the larger vs smaller twin was also assessed. Meta-analyses using individual data random-effects logistic regression and meta-analyses of proportion were used to analyze the data.Results: Twenty-two studies (10 877 twin pregnancies) were included in the analysis. In DC pregnancies, a higher risk of IUD, but not of NND, was observed in twins with BW discordance ≥ 15% (odds ratio (OR) 9.8, 95% CI, 3.9-29.4), ≥ 20% (OR 7.0, 95% CI, 4.15-11.8), ≥ 25% (OR 17.4, 95% CI, 8.3-36.7) and ≥ 30% (OR 22.9, 95% CI, 10.2-51.6) compared with those without weight discordance. For each cut-off of BW discordance explored in DC pregnancies, the smaller twin was at higher risk of mortality compared with the larger one. In MC twin pregnancies, excluding cases affected by twin-twin transfusion syndrome, twins with BW discordance ≥ 20% (OR 2.8, 95% CI, 1.3-5.8) or ≥ 25% (OR 3.2, 95% CI, 1.5-6.7) were at higher risk of IUD, compared with controls. MC pregnancies with ≥ 25% weight discordance were also at increased risk of NND (OR 4.66, 95% CI, 1.8-12.4) compared with those with concordant weight. The risk of IUD was higher when considering discordant pregnancies involving at least one SGA fetus. The overall risk of mortality in MC pregnancies was similar between the smaller and larger twin, except in those with BW discordance ≥ 20%.Conclusion: DC and MC twin pregnancies discordant for fetal growth are at higher risk of IUD but not of NND compared with pregnancies with concordant BW. The risk of IUD in BW-discordant DC and MC twins is higher when at least one fetus is SGA. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd. [ABSTRACT FROM AUTHOR]

Purpose: Accurate assessment of cardiac function is important during pregnancy. Echocardiography and impedance cardiography (ICG) are commonly used noninvasive methods to measure stroke volume (SV) and cardiac output (CO). The difference in stroke volume (ΔSV) or cardiac output (ΔCO) measured at baseline and after passive leg raising (PLR) is a measure of preload reserve that predicts volume responsiveness. However, the agreement between these two methods in measuring preload reserve during pregnancy is unclear. The aim of our study was to investigate the correlation and the agreement between Doppler echocardiography and ICG in assessing preload reserve in pregnant women.Methods: In this prospective observational cross-sectional study, preload reserve was assessed by measuring the SV and CO during baseline and 90 s after PLR simultaneously by Doppler echocardiography and ICG in healthy pregnant women during the second and third trimesters. Bland-Altman analysis was used to determine the agreement between the two methods. Bias was calculated as the mean difference between two methods and precision as 1.96 SD of the difference.Results: A total of 53 pregnant women were included. We found a statistically significant correlation between ΔSV (R = 0.56, p < 0.0001) and ΔCO (R = 0.39, p = 0.004) measured by ICG and Doppler echocardiography. The mean bias for ΔSV was 2.52 ml, with a precision of 18.19 ml. The mean bias for ΔCO was 0.21 l/min, with a precision of 1.51 l/min.Conclusion: There was a good agreement and a statistically significant correlation between ICG and Doppler echocardiography for measuring preload reserve. [ABSTRACT FROM AUTHOR]

Recent studies are beginning to focus on the external validity of well conducted internally valid research. This review gives an overview of external validity, the dimensions involved and suggestions for when future intervention trials are designed, using examples from perinatal research. Finally, we remind the perinatal researcher that it is their duty to provide extensive details beyond those needed to establish internal validity. The latter would help clinicians to determine whether the intervention is applicable to their population. [ABSTRACT FROM AUTHOR]

Copyright of Ultrasound in Obstetrics & Gynecology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Introduction: Our objective was to elucidate the overall diagnostic accuracy of ultrasound in detecting the severity of abnormally invasive placentation (AIP).Material and Methods: Medline, Embase, CINAHL and The Cochrane databases were searched. The ultrasound signs explored were: loss of hypoechoic (clear) zone in the placental-uterine interface, placental lacunae, bladder wall interruption, myometrial thinning, focal exophitic mass, placental lacunar flow, subplacental vascularity, and uterovesical hypervascularity.Results: Twenty studies (3209 pregnancies) were included. Ultrasound had an overall good diagnostic accuracy in identifying the depth of placental invasion with sensitivities of 90.6%, 93.0%, 89.5%, and 81.2% for placenta accreta, increta, accreta/increta, and percreta, respectively; the corresponding specificities were 97.1%, 98.4%, 94.7%, and 98.9%. Placental lacunae had sensitivities of 74.8%, 88.6%, and 76.3% for the detection of placenta accreta, increta, and percreta, respectively. Sensitivity and specificity of loss of the clear zone in identifying placenta accreta were 74.9% and 92.0%, whereas the corresponding figures for placenta increta and percreta were 91.6% and 76.9%, and 88.1% and 71.1%. Lacunar flow had sensitivities of 81.2%, 84.3%, and 45.2% for the detection of placenta accreta, increta, and percreta respectively; the corresponding figures for specificity were 84.0%, 79.7%, and 75.3%. Sensitivity of uterovesical hypervascularity was low for the detection of placenta accreta (12.3%) but high for placenta increta (94.4%) and percreta (86.2%); the corresponding figures for specificity were 90.8%, 88.0% and 88.2%, respectively.Conclusions: Ultrasound has an overall good diagnostic accuracy in recognizing the depth and the topography of placental invasion. [ABSTRACT FROM AUTHOR]

New Findings What is the central question of this study? The fetal aortic isthmus has an important physiological role, allowing communication between the left and right ventricular outputs, which are arranged in parallel. Can the aortic isthmus provide unrestrictive communication between the left and right ventricular circulations during occlusion of the ascending aorta?, What is the main finding and its importance? During occlusion of the ascending aorta, fetal carotid artery perfusion pressure fell significantly, showing that the aortic isthmus failed to redirect blood flow and pressure from the ductus arteriosus to the aortic arch. This suggests that the aortic isthmus cannot provide unrestrictive communication between left and right ventricular circulations., The fetal aortic isthmus (AoI) allows communication between left (LV) and right ventricular (RV) outputs and represents an arterial watershed between the brachiocephalic (brain) and subdiaphragmatic (placenta) circulations. To understand the capability of the AoI to maintain the balance between the upper and lower body circulations, we performed a complete occlusion of the fetal ascending aorta in nine chronically instrumented sheep at near term gestation. We hypothesized that the occlusion would significantly decrease LV output and concomitantly increase RV output in order to maintain adequate systemic cardiac output and perfusion pressure to the fetal brain circulation through retrograde filling of the AoI. Fetal cardiac function and haemodynamics were assessed by pulsed and tissue Doppler at baseline, 15 and 60 min after occlusion of the ascending aorta and 15 min after occlusion was released. Carotid artery and jugular vein pressures were monitored. Occlusion of the ascending aorta increased ( P < 0.002) RV output from [mean (SD)] 684 (369) to 907 (414) ml min−1 and decreased ( P < 0.0001) LV output from 440 (136) to 40 (16) ml min−1. Combined cardiac output decreased ( P < 0.02) from 1125 (494) to 946 (417) ml min−1. During occlusion, carotid artery mean pressure decreased from 32 (7) to 12 (7) mmHg ( P < 0.0001). Systemic venous pressure was unaffected. Left ventricular systolic and diastolic function deteriorated during occlusion. Right ventricular systolic function improved, while diastolic dysfunction developed. Fetal carotid artery perfusion pressure decreased significantly during occlusion of the ascending aorta, demonstrating that AoI failed to redirect blood flow and pressure from the ductus arteriosus to the aortic arch. Our finding suggests that at near term gestation the aortic AoI cannot provide unrestrictive communication between LV and RV circulations. [ABSTRACT FROM AUTHOR]

Objectives To investigate gestational age-specific serial changes in umbilical vein (UV) volume blood flow during the second half of normal pregnancy and establish sex-specific reference ranges. Methods This work was a prospective longitudinal study of singleton low-risk pregnancies. The UV diameter and maximum blood flow velocity were serially measured by sonography at the intra-abdominal portion of the UV over 19 to 41 weeks. Umbilical vein volume blood flow was calculated and normalized for estimated fetal weight. Results One hundred seventy-nine women and their fetuses (87 male and 92 female) were included in the final analysis, and a total of 746 observations were used to construct sex-specific reference intervals. We found no statistically significant sex-specific differences in the UV parameters examined. However, the temporal development patterns of normalized UV volume blood flow appeared to differ between male and female fetuses during the second half of pregnancy, with crossovers at 24 and 32 weeks' gestation. Conclusions Umbilical vein volume blood flow is similar among male and female fetuses in quantitative terms, but the pattern of gestational age-dependent temporal changes may be different, which may have important physiologic implications with regard to in utero development and maturation of the fetoplacental unit. [ABSTRACT FROM AUTHOR]

Introduction: Gestational weight gain varies widely among different populations, and an inappropriate gestational weight gain is associated with adverse pregnancy outcomes. We aimed to investigate week-specific serial changes in gestational weight gain in an urban Chinese population to derive clusters of gestational weight gain patterns and explore the impact of gestational weight gain patterns on birthweight.Material and Methods: This was an observational cohort study of 6130 women delivered at a university hospital in Shanghai, China. Pre-pregnancy bodyweight, height, week-specific and total gestational weight gain, pregnancy outcome and birthweight were extracted using electronic medical records. The association between gestational weight gain and gestational age was tested using linear regression, and week-specific reference percentiles for gestational weight gain were calculated. Hierarchical clustering was used to derive gestational weight gain clusters. Mean birthweight among the clusters was compared using Dunnet's test.Results: We found a significant linear association between gestational weight gain and gestational age (r = 0.56; p < 0.00001). Seven distinct clusters of gestational weight gain pattern were identified. The birthweight significantly correlated with gestational weight gain (r = 0.28; p < 0.00001). Compared with the cluster that had normal gestational weight gain throughout the pregnancy, the mean birthweight among the clusters that had abnormal gestational weight gain (inadequate or excessive) in the third trimester was significantly different (p < 0.001), but those who achieved normal gestational weight gain (between 5 and 95 percentile) in the third-trimester had similar mean birthweight.Conclusion: Women with abnormal gestational weight gain before the third-trimester still had a fair chance of delivering a normal birthweight baby if their gestational weight gain was normal in the third-trimester, suggesting that interventions started even late in pregnancy may have a positive effect on fetal growth. [ABSTRACT FROM AUTHOR]

Introduction: The pulsatility indices of the umbilical and uterine arteries are used as the surrogate measures of utero-placental perfusion. Combining the two might simplify the evaluation of total placental vascular impedance, possibly improve prediction of adverse outcomes, and help identify pregnancies with suspected fetal growth restriction that need more intense surveillance.Material and Methods: Umbilical and uterine blood flow velocities were recorded using pulsed-wave Doppler in a longitudinal study of 53 low-risk pregnancies (248 observations) during 20-40 weeks of gestation. Pulsatility indices was calculated for each of these vessels. A new placental pulsatility index was constructed as: (umbilical artery pulsatility index + mean of the left and right uterine artery pulsatility indices)/2, and mean +2 SD defined as abnormal. Gestational age-specific reference percentiles were calculated for the second half of pregnancy and related to values obtained from 340 pregnancies with suspected intra-uterine growth restriction to test its ability to predict adverse pregnancy outcome.Results: The placental pulsatility index was closely associated with gestational age and decreased with advancing gestation in normal pregnancy. The placental pulsatility index had a higher sensitivity and comparable specificity in predicting adverse outcome in pregnancies suspected of intra-uterine fetal growth restriction when compared with conventional umbilical and uterine artery pulsatility indices.Conclusions: The new placental pulsatility index, reflecting placental vascular impedance on both the fetal and maternal side of placenta, improves prediction of adverse outcome in pregnancies suspected of intra-uterine fetal growth restriction. [ABSTRACT FROM AUTHOR]