Delivery outcomes in the subsequent pregnancy following the conservative management of placenta accreta spectrum disorder: a systematic review and meta-analysis

OBJECTIVE

Cesarean hysterectomy is generally presumed to decrease maternal morbidity and mortality secondary to placenta accreta spectrum disorder. Recently, uterine-sparing techniques have been introduced in conservative management of placenta accreta spectrum disorder to preserve fertility and potentially reduce surgical complications. However, despite patients often expressing the intention for future conception, few data are available regarding the subsequent pregnancy outcomes after conservative management of placenta accreta spectrum disorder. Thus, we aimed to perform a systematic review and meta-analysis to assess these outcomes.

DATA SOURCES

PubMed, Scopus, and Web of Science databases were searched from inception to September 2022.

STUDY ELIGIBILITY CRITERIA

We included all studies, with the exception of case studies, that reported the first subsequent pregnancy outcomes in individuals with a history of placenta accreta spectrum disorder who underwent any type of conservative management.

METHODS

The R programming language with the "meta" package was used. The random-effects model and inverse variance method were used to pool the proportion of pregnancy outcomes.

RESULTS

We identified 5 studies involving 1458 participants that were eligible for quantitative synthesis. The type of conservative management included placenta left in situ (n=1) and resection surgery (n=1), and was not reported in 3 studies. The rate of placenta accreta spectrum disorder recurrence in the subsequent pregnancy was 11.8% (95% confidence interval, 1.1-60.3; I2=86.4%), and 1.9% (95% confidence interval, 0.0-34.1; I2=82.4%) of participants underwent cesarean hysterectomy. Postpartum hemorrhage occurred in 10.3% (95% confidence interval, 0.3-81.4; I2=96.7%). A composite adverse maternal outcome was reported in 22.7% of participants (95% confidence interval, 0.0-99.4; I2=56.3%).

CONCLUSION

Favorable pregnancy outcome is possible following successful conservation of the uterus in a placenta accreta spectrum disorder pregnancy. Approximately 1 out of 4 subsequent pregnancies following conservative management of placenta accreta spectrum disorder had considerable adverse maternal outcomes. Given such high incidence of adverse outcomes and morbidity, patient and provider preparation is vital when managing this population.

Polystyrene micro- and nanoplastics cause placental dysfunction in mice†

Maternal exposure to microplastics and nanoplastics has been shown to result in fetal growth restriction in mice. In this study, we investigated the placental and fetal hemodynamic responses to plastics exposure in mice using high-frequency ultrasound. Healthy, pregnant CD-1 dams were given either 106 ng/L of 5 μm polystyrene microplastics or 106 ng/L of 50 nm polystyrene nanoplastics in drinking water throughout gestation and were compared with controls. Maternal exposure to both microplastics and nanoplastics resulted in evidence of placental dysfunction that was highly dependent on the particle size. The umbilical artery blood flow increased by 48% in the microplastic-exposed group and decreased by 25% in the nanoplastic-exposed group compared to controls (p < 0.05). The microplastic- and nanoplastic-exposed fetuses showed a significant decrease in the middle cerebral artery pulsatility index of 10% and 13%, respectively, compared to controls (p < 0.05), indicating vasodilation of the cerebral circulation, a fetal adaptation that is part of the brain sparing response to preserve oxygen delivery. Hemodynamic markers of placental dysfunction and fetal hypoxia were more pronounced in the group exposed to polystyrene nanoplastics, suggesting nanoplastic exposure during human pregnancy has the potential to disrupt fetal brain development, which in turn may cause suboptimal neurodevelopmental outcomes.

Maternal exposure to polyethylene micro- and nanoplastics impairs umbilical blood flow but not fetal growth in pregnant mice

While microplastics have been recently detected in human blood and the placenta, their impact on human health is not well understood. Using a mouse model of environmental exposure during pregnancy, our group has previously reported that exposure to polystyrene micro- and nanoplastics throughout gestation results in fetal growth restriction. While polystyrene is environmentally relevant, polyethylene is the most widely produced plastic and amongst the most commonly detected microplastic in drinking water and human blood. In this study, we investigated the effect of maternal exposure to polyethylene micro- and nanoplastics on fetal growth and placental function. Healthy, pregnant CD-1 dams were divided into three groups: 106 ng/L of 740-4990 nm polyethylene with surfactant in drinking water (n = 12), surfactant alone in drinking water (n = 12) or regular filtered drinking water (n = 11). At embryonic day 17.5, high-frequency ultrasound was used to investigate the placental and fetal hemodynamic responses following exposure. While maternal exposure to polyethylene did not impact fetal growth, there was a significant effect on placental function with a 43% increase in umbilical artery blood flow in the polyethylene group compared to controls (p < 0.01). These results suggest polyethylene has the potential to cause adverse pregnancy outcomes through abnormal placental function.

Feasibility of MRI assessment of maternal-fetal oxygen transport and consumption relative to maternal position in healthy late gestational pregnancies

Late gestational supine positioning reduces maternal cardiac output due to inferior vena caval (IVC) compression, despite increased collateral venous return. However, little is known about the impact of maternal position on oxygen (O2 ) delivery and consumption of the gravid uterus, fetus, placenta and lower limbs. We studied the effects of maternal positioning on these parameters in 20 healthy pregnant subjects at 36 ± 2 weeks using magnetic resonance imaging (MRI); a follow-up MRI was performed 6-months postpartum (n = 16/20). MRI techniques included phase-contrast and T1/T2 relaxometry for blood flow and oximetry imaging, respectively. O2 transport was measured in the following vessels (bilateral where appropriate): maternal abdominal descending aorta (DAoabdo ), IVC, ovarian, paraspinal veins (PSV), uterine artery (UtA) and external iliacs, and umbilical. Maternal cardiac output was measured by summing DAothoracic and superior vena cava flows. Supine mothers (n = 6) had lower cardiac output and O2 delivery in the DAoabdo , UtA and external iliac arteries, and higher PSV flow than those in either the left (n = 8) or right (n = 6) lateral positions during MRI. However, O2 consumption in the gravid uterus, fetus, placenta and lower limbs was unaffected by maternal positioning. The ratio of IVC/PSV flow decreased in supine mothers while ovarian venous flow and O2 saturation were unaltered, suggesting a major route of pelvic venous return unaffected by maternal position. Placental-fetal O2 transport and consumption were similar between left and right lateral maternal positions. In comparison to non-pregnant findings, DAoabdo and UtA O2 delivery and pelvic O2 consumption increased, while lower-limb consumption remained constant , despite reduced external iliac artery O2 delivery in late gestation. KEY POINTS: Though sleeping supine during the third trimester is associated with an increased risk of antepartum stillbirth, the underlying biological mechanisms are not fully understood. Maternal cardiac output and uteroplacental flow are reduced in supine mothers due to inferior vena caval compression from the weight of the gravid uterus. This MRI study provides a comprehensive circulatory assessment, demonstrating reduced maternal cardiac output and O2 delivery (uteroplacental, lower body) in supine compared to lateral positioning; however, O2 consumption (gravid uterus, fetus, placenta, lower limbs) was preserved. Unlike other mammalian species, the ovarian veins conduct substantial venous return from the human pregnant uterus that is unaffected by maternal positioning. Lumbar paraspinal venous flow increased in supine mothers. These observations may have important considerations during major pelvic surgery in pregnancy (i.e. placenta percreta). Future studies should address the importance of maternal positioning as a potential tool to deliver improved perinatal outcomes in pregnancies with compromised uteroplacental O2 delivery.

Maternal exposure to polystyrene nanoplastics alters fetal brain metabolism in mice

INTRODUCTION

Plastics used in everyday materials accumulate as waste in the environment and degrade over time. The impacts of the resulting particulate micro- and nanoplastics on human health remain largely unknown. In pregnant mice, we recently demonstrated that exposure to nanoplastics throughout gestation and during lactation resulted in changes in brain structure detected on MRI. One possible explanation for this abnormal postnatal brain development is altered fetal brain metabolism.

OBJECTIVES

To determine the effect of maternal exposure to nanoplastics on fetal brain metabolism.

METHODS

Healthy pregnant CD-1 mice were exposed to 50 nm polystyrene nanoplastics at a concentration of 106 ng/L through drinking water during gestation. Fetal brain samples were collected at embryonic day 17.5 (n = 18-21 per group per sex) and snap-frozen in liquid nitrogen. Magic angle spinning nuclear magnetic resonance was used to determine metabolite profiles and their relative concentrations in the fetal brain.

RESULTS

The relative concentrations of gamma-aminobutyric acid (GABA), creatine and glucose were found to decrease by 40%, 21% and 30% respectively following maternal nanoplastic exposure when compared to the controls (p < 0.05). The change in relative concentration of asparagine with nanoplastic exposure was dependent on fetal sex (p < 0.005).

CONCLUSION

Maternal exposure to polystyrene nanoplastics caused abnormal fetal brain metabolism in mice. The present study demonstrates the potential impacts of nanoplastic exposure during fetal development and motivates further studies to evaluate the risk to human pregnancies.

Inpatient vs outpatient management of pregnancies with vasa previa: A historical cohort study

INTRODUCTION

Vasa previa, a condition where unprotected fetal blood vessels lie in proximity to the internal cervical opening, is a potentially lethal obstetric complication. The precarious situation of these vessels increases the risk of fetal hemorrhage with spontaneous or artificial rupture of membranes, frequently causing fetal/neonatal demise or severe morbidity. As a result, in many centers, inpatient management forms the mainstay when vasa previa is diagnosed antenatally. This study aimed to determine whether a subpopulation of pregnancies diagnosed antenatally with vasa previa could be safely managed as outpatients.

MATERIAL AND METHODS

We reviewed all cases of vasa previa in singleton pregnancies, with no fetal anomalies, diagnosed at Mount Sinai Hospital, Toronto, from January 2008 to December 2017. Cases were categorized into three arms for analysis: outpatients (OP), asymptomatic hospitalized (ASH) and symptomatic hospitalized (SH). The SH arm included patients admitted with any antepartum bleeding or suspicious fetal non-stress test. Those that presented with symptomatic uterine activity/threatened preterm labor and delivered within 7 days of diagnosis were excluded from the study. Records were analyzed for details on hospitalization, antenatal corticosteroid administration, cervical length measurements, and fetal/neonatal mortality and morbidity.

RESULTS

Of the 84 antenatally-diagnosed cases of vasa previa, 47 fulfilled eligibility criteria. A total of 15 cases were managed as OP, 22 as ASH and 10 as SH. Unplanned cesareans were highest in the SH arm (40% vs. 0% ASH vs. 13.3% OP). Those in the SH arm delivered earliest (median 33.8 weeks, interquartile range (IQR) 33.2-34.3 weeks). Of the asymptomatic patients, those in the ASH arm delivered earlier than those in the OP arm (35.3 [34.6-36.2] weeks vs. 36.7 [35.6-37.2] weeks, p = 0.037). There were no cases of fetal/neonatal death, anemia or severe neonatal morbidity and no significant differences between groups based on cervical length or antenatal corticosteroid administration.

CONCLUSIONS

Our study suggests that asymptomatic women with an antenatal diagnosis of vasa previa, singleton pregnancies, and at low risk for preterm birth may safely managed as outpatients, as long as they are able to access hospital promptly in the event of antepartum bleeding or early labor.

Indications and Outcomes for Planned Cesarean Hysterectomy in Non-Placenta Accreta Spectrum Disorder Patients: A Systematic Review

OBJECTIVE

Planned hysterectomy at the time of cesarean delivery may be reasonable in cases other than placenta accreta spectrum disorders. Our objective was to synthesize the published literature on the indications and outcomes for planned cesarean hysterectomy.

DATA SOURCES

We performed a systematic review of published literature from the following databases from inception (1946) to June 2021: MEDLINE, PubMed, EMBASE, Cochrane CENTRAL, DARE, and clinicaltrials.gov.

STUDY SELECTION

We included all study designs where subjects underwent planned cesarean delivery with simultaneous hysterectomy. Emergency procedures and those performed for placenta accreta spectrum disorders were excluded.

DATA EXTRACTION AND SYNTHESIS

The primary outcome was surgical indication, though other surgical outcomes were evaluated when data permitted. Quantitative analysis was limited to studies published in 1990 or later. Risk of bias was assessed using an adaptation of the ROBINS-I tool.

CONCLUSION

The most common indication for planned cesarean hysterectomy was malignancy, with cervical cancer being the most frequent. Other indications included permanent contraception, uterine fibroids, menstrual disorders, and chronic pelvic pain. Common complications included bleeding, infection, and ileus. The surgical skill for cesarean hysterectomy continues to be relevant in contemporary obstetrical practice for reproductive malignancy and several benign indications. Although the data indicate relatively safe outcomes, these studies show significant publication bias and, therefore, further systematic study of this procedure is justified.

PROSPERO REGISTRATION NUMBER

CRD42021260545, registered June 16, 2021.

Rosiglitazone-Mediated Activation of PPARγ Restores HO1 Expression in the Human Preeclamptic Placenta

BACKGROUND

Preeclampsia is a hypertensive disorder of pregnancy characterized by chronic placental ischemia and suppression of proangiogenic proteins, causing oxidative stress, hypertension, and maternal systemic organ damage. The transcription factor, PPARγ (peroxisome proliferator-activated receptor-γ) promotes healthy trophoblast differentiation but is dysregulated in the preeclampsia placenta. Our study identifies the beneficial impact of Rosiglitazone-mediated PPARγ-activation in the stressed preeclampsia placenta.

METHODS

We used first trimester placentas, preeclamptic and preterm control placentas, and human trophoblast cell lines to study PPARγ activation.

RESULTS

Induction of PPARγ activates cell growth and antioxidative stress pathways, including the gene, heme oxygenase 1 (Hmox1). Protein expression of both PPARγ and HO1 (heme oxygenase 1) are reduced in preeclamptic placentas, but Rosiglitazone restores HO1 signaling in a PPARγ-dependent manner.

CONCLUSIONS

Restoring disrupted pathways by PPARγ in preeclampsia offers a potential therapeutic pathway to reverse placental damage, extending pregnancy duration, and reduce maternal sequelae. Future research should aim to understand the full scope of impaired PPARγ signaling in the human placenta and focus on compounds for safe use during pregnancy to prevent severe perinatal morbidity and mortality.

Placenta Accreta Spectrum Disorders: A National Survey

OBJECTIVES

Describe the current practice of Canadian obstetricians-gynaecologists in managing placenta accreta spectrum (PAS) disorders from suspicion of diagnosis to delivery planning and explore the impact of the latest national practice guidelines on this topic.

METHODS

We distributed a cross-sectional bilingual electronic survey to Canadian obstetricians-gynaecologists in March-April 2021. Demographic data and information on screening, diagnosis, and management were collected using a 39-item questionnaire. The survey was validated and pretested among a sample population. Descriptive statistics were used to present the results.

RESULTS

We received 142 responses. Almost 60% of respondents said they had read the latest Society of Obstetricians and Gynaecologists of Canada clinical practice guideline on PAS disorders, published in July 2019. Nearly 1 in 3 respondents changed their practice following this guideline. Respondents highlighted the importance of 4 key points: (1) limiting travel to thereby remain close to a regional care centre, (2) preoperative anemia optimization, (3) performance of cesarean-hysterectomy leaving the placenta in situ (83%), (4) access via midline laparotomy (65%). Most respondents recognized the importance of perioperative blood loss reduction strategies such as tranexamic acid and perioperative thromboprophylaxis via sequential compression devices and low-molecular-weight heparin until full mobilization.

CONCLUSIONS

This study demonstrates the impact of the Society of Obstetricians and Gynaecologists of Canada's PAS clinical practice guideline on management choices made by Canadian clinicians. Our study highlights the value of a multidisciplinary approach to reducing maternal morbidity in individuals facing surgery for a PAS disorder and the importance of regionalized care that is resourced to provide maternal-fetal medicine and surgical expertise, transfusion medicine, and critical care support.

Peripheral cord insertion is associated with adverse pregnancy outcome only when accompanied by clinically significant placental pathology

OBJECTIVE

To examine the relationship between umbilical cord insertion site, placental pathology and adverse pregnancy outcome in a cohort of normal and complicated pregnancies.

METHODS

Sonographic measurement of the cord insertion and detailed placental pathology were performed in 309 participants. Associations between cord insertion site, placental pathology and adverse pregnancy outcome (pre-eclampsia, preterm birth, small-for-gestational age) were examined.

RESULTS

A total of 93 (30%) participants were identified by pathological examination to have a peripheral cord insertion site. Only 41 of the 93 (44%) peripheral cords were detected by prenatal ultrasound. Peripherally inserted cords were associated significantly (P < 0.0001) with diagnostic placental pathology (most commonly with maternal vascular malperfusion (MVM)); of which 85% had an adverse pregnancy outcome. In cases of isolated peripheral cords, without placental pathology, the incidence of adverse outcome was not statistically different when compared to those with central cord insertion and no placental pathology (31% vs 18%; P = 0.3). A peripheral cord with an abnormal umbilical artery (UA) pulsatility index (PI) corresponded to an adverse outcome in 96% of cases compared to 29% when the UA-PI was normal.

CONCLUSIONS

This study demonstrates that peripheral cord insertion is often part of the spectrum of findings of MVM disease and is associated with adverse pregnancy outcome. However, adverse outcome was uncommon when there was an isolated peripheral cord insertion and no placental pathology. Therefore, additional sonographic and biochemical features of MVM should be sought when a peripheral cord is observed. © 2023 International Society of Ultrasound in Obstetrics and Gynecology.

Engaging pregnant individuals and healthcare professionals in an international mixed methods study to develop a core outcome set for studies on placenta accreta spectrum disorder (COPAS): a study protocol

INTRODUCTION

Placenta accreta spectrum (PAS) disorder is a life-threatening condition that may result in serious maternal complications, including mortality. The placenta which is pathologically adherent to the uterine wall, places individuals at high risk of major haemorrhage during the third stage of labour. Current research reports on PAS disorder outcomes have highly variable levels of information, which is therefore difficult for investigators to aggregate to inform practice. There is an urgent need to harmonise data collection in prospective studies to identify and implement best practices for management. One approach to standardise outcomes across any health area via the use of core outcome sets (COSs), which are consensus-derived standardised sets of outcomes that all studies for a particular condition should measure and report. This protocol outlines the steps for developing a COS for PAS disorder (COPAS).

METHODS AND ANALYSIS

This protocol outlines steps for the creation of COPAS. The first step, a systematic review, will identify all reported outcomes in the scientific literature. The second step will use qualitative one-on-one interviews to identify additional outcomes identified as important by patients and healthcare professionals that are not reported in the published literature. Outcomes from the first two steps will be combined to form an outcome inventory. This outcome inventory will inform the third step which is a Delphi survey that encourages agreement between patients and healthcare professionals on which outcomes are most important for inclusion in the COS. The fourth step, a consensus group meeting of representative participants, will finalise outcomes for inclusion in the PAS disorder COS.

ETHICS AND DISSEMINATION

This study has obtained Research Ethics Board approval from Sunnybrook Health Sciences Centre (#2338, #1488). We will aim to publish the study findings in an international peer-reviewed OBGYN journal.

REGISTRATION DETAILS

COMET Core Outcome Set Registration: https://www.comet-initiative.org/Studies/Details/1127.

PROSPERO REGISTRATION NUMBER

CRD42020173426.

Comparison of circulating maternal placenta growth factor levels and sonographic evaluation of patients with abnormal first trimester screening analytes

OBJECTIVE

To evaluate the role of mid-trimester placental growth factor (PlGF) in patients with abnormal circulating levels of first-trimester biomarkers.

METHODS

Retrospective cohort study including singleton pregnancies complicated by abnormal first-trimester biomarkers (2017-2020). Pregnancies complicated with chromosomal/structural anomalies were excluded. All patients had ultrasound imaging including uterine artery Doppler combined with measurement of maternal circulating PlGF. Sonographic findings, maternal and perinatal outcomes, and placental histopathology were compared between pregnancies with normal and low (<10th percentile for gestational age) PlGF levels. The diagnostic accuracy of PlGF for the prediction of specific placental-mediated complications was compared with the uterine artery Doppler assessment and additional sonographic findings.

RESULTS

Seventy-one pregnancies were assessed, of which 35 (49.3%) had low PlGF levels. Maternal sociodemographic characteristics, nulliparity, and aspirin consumption were comparable. In comparison with patients with normal PlGF levels, individuals with low PlGF levels had a higher rate of fetal growth restriction (EFW <3rd centile; 42.9% vs. 8.3%, p = 0.001), preterm-preeclampsia (22.9% vs. 0%, p = 0.002), preterm delivery <34 weeks (54.3% vs. 8.3%, p < 0.001) and maternal vascular malperfusion placental pathology (72.7% vs. 21.7%, p < 0.001) following delivery. Adjusting for uterine artery Doppler and fetal biometry status, mid-trimester low PlGF remained significantly associated with these placental-mediated complications. The predictive capacity of PlGF outperformed ultrasound imaging with only minimal diagnostic improvement when ultrasound information was combined with PlGF status.

CONCLUSION

In pregnancies with unexplained abnormal first-trimester biomarkers, mid-trimester PlGF outperformed a comprehensive ultrasound assessment in the identification of a subset of patients destined to develop placental dysfunction. This blood test may be an alternative initial approach in this context, especially where access to specialist care is more geographically challenging.

Maternal exposure to polystyrene microplastics alters placental metabolism in mice

INTRODUCTION

The rapid growth in the worldwide use of plastics has resulted in a vast accumulation of microplastics in the air, soil and water. The impact of these microplastics on pregnancy and fetal development remains largely unknown. In pregnant mice, we recently demonstrated that exposure to micro- and nanoplastics throughout gestation resulted in significant fetal growth restriction. One possible explanation for reduced fetal growth is abnormal placental metabolism.

OBJECTIVES

To evaluate the effect of maternal exposure to microplastics on placental metabolism.

METHODS

In the present study, CD-1 pregnant mice were exposed to 5 μm polystyrene microplastics in filtered drinking water at one of four concentrations (0 ng/L (controls), 10² ng/L, 10⁴ ng/L, 10⁶ ng/L) throughout gestation (n = 7-11/group). At embryonic day 17.5, placental tissue samples were collected (n = 28-44/group). Metabolite profiles were determined using ¹ H high-resolution magic angle spinning magnetic resonance spectroscopy.

RESULTS

The relative concentration of lysine (p = 0.003) and glucose (p < 0.0001) in the placenta were found to decrease with increasing microplastic concentrations, with a significant reduction at the highest exposure concentration. Multivariate analysis identified shifts in the metabolic profile with MP exposure and pathway analysis identified perturbations in the biotin metabolism, lysine degradation, and glycolysis/gluconeogenesis pathways.

CONCLUSION

Maternal exposure to microplastics resulted in significant alterations in placental metabolism. This study highlights the potential impact of microplastic exposure on pregnancy outcomes and that efforts should be made to minimize exposure to plastics, particularly during pregnancy.

Volumetric Fetal Flow Imaging With Magnetic Resonance Imaging

Fetal development relies on a complex circulatory network. Accurate assessment of flow distribution is important for understanding pathologies and potential therapies. In this paper, we demonstrate a method for volumetric imaging of fetal flow with magnetic resonance imaging (MRI). Fetal MRI faces challenges: small vascular structures, unpredictable motion, and inadequate traditional cardiac gating methods. Here, orthogonal multislice stacks are acquired with accelerated multidimensional radial phase contrast (PC) MRI. Slices are reconstructed into flow sensitive time-series images with motion correction and image-based cardiac gating. They are then combined into a dynamic volume using slice-to-volume reconstruction (SVR) while resolving interslice spatiotemporal coregistration. Compared to prior methods, this approach achieves higher spatiotemporal resolution ( 1×1×1 mm³, ~30 ms) with reduced scan time - important features for the quantification of flow through small fetal structures. Validation is demonstrated in adults by comparing SVR with 4D radial PCMRI (flow bias and limits of agreement: -1.1 ml/s and [-11.8 9.6] ml/s). Feasibility is demonstrated in late gestation fetuses by comparing SVR with 2D Cartesian PCMRI (flow bias and limits of agreement: -0.9 ml/min/kg and [-39.7 37.8] ml/min/kg). With SVR, we demonstrate complex flow pathways (such as parallel flow streams in the proximal inferior vena cava, preferential shunting of blood from the ductus venosus into the left atrium, and blood from the brain leaving the heart through the main pulmonary artery) for the first time in human fetal circulation. This method allows for comprehensive evaluation of the fetal circulation and enables future studies of fetal physiology.

Doppler Ultrasound of the Fetal Descending Aorta: An Objective Tool to Assess Placental Blood Flow Resistance in Pregnancies With Discordant Umbilical Arteries

OBJECTIVES

To determine the relationship between blood flow in the fetal descending aorta and discordant umbilical arteries (UAs).

METHODS

Pulsed wave Doppler of both UAs and the descending aorta was performed at 4-weekly intervals between 14 and 40 weeks of gestation in 209 pregnant women. In datasets with discordant UAs, a linear mixed effects model was used to determine the categorical relationship between the UA pulsatility index (PI) (high, low and average) and the descending aorta PI.

RESULTS

Of the 209 cases, 81 had a discordance of greater than 25% in UA PI during one of their visits. There were no differences in birth outcomes between the groups with concordant and discordant UA PIs. In the cases with discordant UA PIs, the descending aorta PI was most strongly associated with both the average UA PI (P = .008), and with the UA with the lower PI (P = .008).

CONCLUSIONS

The relationship between blood flow in the descending aorta and UAs is consistent with the law for combining resistances in parallel. Measurements of the descending aorta PI, particularly in a scenario with discordant UAs, may inform the stability of the feto-placental circulation where discordant UA PIs are found.

Phenotype‐Directed Management of Hypertension in Pregnancy

Hypertensive disorders of pregnancy are among the most serious conditions that pregnancy care providers face; however, little attention has been paid to the concept of tailoring clinical care to reduce associated adverse maternal and perinatal outcomes based on the underlying disease pathogenesis. This narrative review discusses the integration of phenotype‐based clinical strategies in the management of high‐risk pregnant patients that are currently not common clinical practice: real‐time placental growth factor testing at Mount Sinai Hospital, Toronto and noninvasive hemodynamic monitoring to guide antihypertensive therapy at the University of Washington Medical Center, Seattle. Future work should focus on promoting more widespread integration of these novel strategies into obstetric care to improve outcomes of pregnancies at high risk of adverse maternal‐fetal outcomes from these complications of pregnancy.

Clinical Opinion: The diagnosis and management of suspected fetal growth restriction: an evidence-based approach

This study reviewed the literature about the diagnosis, antepartum surveillance, and time of delivery of fetuses suspected to be small for gestational age or growth restricted. Several guidelines have been issued by major professional organizations, including the International Society of Ultrasound in Obstetrics and Gynecology and the Society for Maternal-Fetal Medicine. The differences in recommendations, in particular about Doppler velocimetry of the ductus venosus and middle cerebral artery, have created confusion among clinicians, and this review has intended to clarify and highlight the available evidence that is pertinent to clinical management. A fetus who is small for gestational age is frequently defined as one with an estimated fetal weight of <10th percentile. This condition has been considered syndromic and has been frequently attributed to fetal growth restriction, a constitutionally small fetus, congenital infections, chromosomal abnormalities, or genetic conditions. Small for gestational age is not synonymous with fetal growth restriction, which is defined by deceleration of fetal growth determined by a change in fetal growth velocity. An abnormal umbilical artery Doppler pulsatility index reflects an increased impedance to flow in the umbilical circulation and is considered to be an indicator of placental disease. The combined finding of an estimated fetal weight of <10th percentile and abnormal umbilical artery Doppler velocimetry has been widely accepted as indicative of fetal growth restriction. Clinical studies have shown that the gestational age at diagnosis can be used to subclassify suspected fetal growth restriction into early and late, depending on whether the condition is diagnosed before or after 32 weeks of gestation. The early type is associated with umbilical artery Doppler abnormalities, whereas the late type is often associated with a low pulsatility index in the middle cerebral artery. A large randomized clinical trial indicated that in the context of early suspected fetal growth restriction, the combination of computerized cardiotocography and fetal ductus venosus Doppler improves outcomes, such that 95% of surviving infants have a normal neurodevelopmental outcome at 2 years of age. A low middle cerebral artery pulsatility index is associated with an adverse perinatal outcome in late fetal growth restriction; however, there is no evidence supporting its use to determine the time of delivery. Nonetheless, an abnormality in middle cerebral artery Doppler could be valuable to increase the surveillance of the fetus at risk. We propose that fetal size, growth rate, uteroplacental Doppler indices, cardiotocography, and maternal conditions (ie, hypertension) according to gestational age are important factors in optimizing the outcome of suspected fetal growth restriction.

Circulating maternal placental growth factor responses to low-molecular-weight heparin in pregnant patients at risk of placental dysfunction

BACKGROUND

Patients at high risk of severe preeclampsia and fetal growth restriction have low circulating levels of placental growth factor and features of maternal vascular malperfusion placental pathology at delivery. Multimodal screening and commencement of aspirin prophylaxis at 11 to 13 weeks' gestation markedly reduces the risk of preterm delivery with preeclampsia. However, the additional role of low-molecular-weight heparin and mechanisms of action remain uncertain. Because low-molecular-weight heparin augments the production and release of placental growth factor in vitro by both placental villi and vascular endothelium, it may be effective to suppress the risk of severe preeclampsia in a niche group of high-risk patients with low circulating placental growth factor in the early second trimester.

OBJECTIVE

This study aimed to define a gestational age-specific reference range for placental growth factor and to test the hypothesis that prophylactic low-molecular-weight heparin administered in the early second trimester may restore deficient circulating placental growth factor levels and thereby prolong pregnancy.

STUDY DESIGN

Centile curves for circulating placental growth factor levels from 12 to 36 weeks' gestation were derived using quantile regression of combined data from a published cohort of 4207 unselected nulliparous patients in Cambridge, United Kingdom, at 4 sampling time points (12, 20, 28, and 36 weeks' gestation) and the White majority (n=531) of a healthy nulliparous cohort in Toronto, Canada, at 16 weeks' gestation using the same test platform. Within a specialty high-risk clinic in Toronto, a niche group of 7 patients with a circulating placental growth factor at the <10th centile in the early second trimester received daily prophylactic low-molecular-weight heparin (enoxaparin; 40 mg subcutaneously) and were followed up until delivery (group 1). Their baseline characteristics, delivery details, and placental pathologies were compared with 5 similar patients who did not receive low-molecular-weight heparin during the observation period (group 2) and further with 21 patients who delivered with severe preeclampsia (group 3) in the same institution.

RESULTS

A gestational age-specific reference range for placental growth factor levels at weekly intervals between 12 and 36 weeks was established for White women with singleton pregnancies. Within group 1, 5 of 7 patients demonstrated a sustained increase in circulating placental growth factor levels, whereas placental growth factor levels did not increase in group 2 or group 3 patients who did not receive low-molecular-weight heparin. Group 1 patients receiving low-molecular-weight heparin therapy exhibited a later gestation at delivery, relative to groups 2 and 3 (36 weeks [33-37] vs 23 weeks [22-26] and 28 weeks [27-31], respectively), and consequently had higher birthweights (1.93 kg [1.1-2.7] vs 0.32 kg [0.19-0.39] and 0.73 kg [0.52-1.03], respectively). The incidence of stillbirth was lowest in group 1 (14% [1 of 7]), relative to groups 2 and 3 (80% [4 of 5] and 29% [6 of 21], respectively). Maternal vascular malperfusion was the most common placental pathology found in association with abnormal uterine artery Doppler.

CONCLUSION

In patients at high risk of a serious adverse pregnancy outcome owing to placental disease, the addition of low-molecular-weight heparin to aspirin prophylaxis in the early second trimester may restore deficient circulating placental growth factor to mediate an improved perinatal outcome. These data support the implementation of a multicenter pilot randomized control trial where patients are recruited primarily based on the assessment of placental function in the early second trimester.

MRI characterization of hemodynamic patterns of human fetuses with cyanotic congenital heart disease

OBJECTIVES

To characterize, using magnetic resonance imaging (MRI), the distribution of blood flow and oxygen transport in human fetuses with subtypes of congenital heart disease (CHD) that present with neonatal cyanosis.

METHODS

Blood flow was measured in the major vessels of 152 late-gestation human fetuses with CHD and 40 gestational-age-matched normal fetuses, using cine phase-contrast MRI. Oxygen saturation (SaO₂ ) was measured in the major vessels of 57 fetuses with CHD and 40 controls.

RESULTS

Compared with controls, we found lower combined ventricular output in fetuses with single-ventricle physiology, with the lowest being observed in fetuses with severe forms of Ebstein's anomaly. Obstructive lesions of the left or right heart were associated with increased flow across the contralateral side. Pulmonary blood flow was reduced in fetuses with Ebstein's anomaly, while those with Ebstein's anomaly and tricuspid atresia had reduced umbilical flow. Flow in the superior vena cava was elevated in fetuses with transposition of the great arteries, normal in fetuses with hypoplastic left heart, tetralogy of Fallot or tricuspid atresia and reduced in fetuses with Ebstein's anomaly. Umbilical vein SaO₂ was reduced in fetuses with hypoplastic left heart or tetralogy of Fallot. Ascending aorta and superior vena cava SaO₂ were reduced in nearly all CHD subtypes.

CONCLUSIONS

Fetuses with cyanotic CHD exhibit profound changes in the distribution of blood flow and oxygen transport, which result in changes in cerebral, pulmonary and placental blood flow and oxygenation. These alterations of fetal circulatory physiology may influence the neonatal course and help account for abnormalities of prenatal growth and development that have been described in newborns with cyanotic CHD. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

The antithrombin binding regions of heparin mediate fetal growth and reduced placental damage in the RUPP model of preeclampsia†

Preeclampsia is a serious hypertensive disorder of pregnancy, which is only cured with delivery of the placenta, thereby commonly necessitating preterm birth of the fetus. Low-molecular-weight heparin (LMWH) has demonstrated potential to reduce the incidence of preeclampsia in high-risk pregnant women, although the underlying mechanism by which LMWH protects against preeclampsia is unknown. Given the complex structure and biologic actions of heparin, we tested the hypothesis that heparin can mediate preeclampsia prevention via nonanticoagulant pathways. We compared the effects of a nonanticoagulant, glycol-split LMWH (gsHep)—rendered nonanticoagulant through disruption of the antithrombin binding regions—with the LMWH dalteparin in the rat reduced uterine perfusion pressure (RUPP) surgical model of preeclampsia. Although RUPP animals exhibit significantly elevated blood pressure and reduced plasma levels of placental growth factor (PGF) compared to sham, neither dalteparin nor gsHep treatment significantly impacted these parameters. However, the observed positive correlation between PGF levels and number of viable fetuses in RUPP-induced animals suggests that reduced PGF levels were predominately due to placental loss. Daily subcutaneous injections of low-dose dalteparin but not gsHep significantly restored fetal growth that was impaired by RUPP surgery. Placentas from RUPP animals exhibited an abnormal labyrinth structure, characterized by expanded sinusoidal blood spaces, relative to sham-operated animals. Morphometric analysis demonstrated that dalteparin but not gsHep treatment normalized development of the labyrinth in RUPP-exposed conceptuses. These data suggest that the antithrombin-binding regions of LMWH are required to confer its protective effects on fetal growth and placental development.

Stillbirth Following Normal Ultrasound Findings and Maternal Placental Growth Factor Levels

BACKGROUND

Attempts to reduce the current rate of antepartum stillbirth in the late third trimester have largely focused on the accurate identification of fetal growth restriction. Universal ultrasound significantly increases detection, especially when combined with maternal angiogenic growth factors, but this screening strategy is not well suited to identify umbilical cord pathology. While this poses unique challenges to pregnancy care, the recurrence risk of cord obstruction is low in comparison with many intrinsic placental diseases.

CASE

A 30-year-old woman with normal uterine artery Doppler waveforms, fetal growth ultrasounds, and circulating placental growth factor experienced an unexpected third-trimester stillbirth. Placental pathology demonstrated fetal vascular malperfusion and cord hyper-coiling.

CONCLUSION

Despite normal placental function, the otherwise healthy fetus is at risk of antepartum stillbirth due to cord-related pathology.

Maternal and Fetal Hemodynamic Adaptations to Pregnancy and Clinical Outcomes in Maternal Cardiac Disease

BACKGROUND

Although insufficient maternal cardiac output (CO) has been implicated in poor outcomes in mothers with heart disease (HD), maternal-fetal interactions remain incompletely understood. We sought to quantify maternal-fetal hemodynamics using magnetic resonance imaging (MRI) and explore their relationships with adverse events.

METHODS

Pregnant women with moderate or severe HD (n=22; age 32±5 years) were compared with healthy controls (n=21; 34±3 years). An MRI was performed during the third trimester at peak output (maternal-fetal) and six-months postpartum with return of maternal hemodynamics to baseline (reference). Phase-contrast MRI was used for flow quantification and was combined with T1/T2 relaxometry for derivation of fetal oxygen delivery/consumption.

RESULTS

 Third trimester CO and cardiac index (CI) measurements were similar in HD and control groups (CO 7.2±1.5 versus 7.3±1.6 L/min, p=0.79; CI 4.0±0.7 versus 4.3±0.7 L/min/m², p=0.28). However, the magnitude of CO/CI increase (Δ, peak-pregnancy-reference) in the HD group exceeded controls (CO 46±24% versus 27±16%, p=0.007; CI 51±28% versus 28±17%, p=0.005). Fetal growth and oxygen delivery/consumption were similar between groups. Adverse cardiovascular outcomes (non-mutually exclusive) in 6 HD women included arrhythmia (n=4), heart failure (n=2) and hypertensive disorder of pregnancy (n=1); fetal prematurity was observed in 2 of these women. The odds of a maternal cardiovascular event were inversely associated with peak CI (OR 0.10 [95% confidence interval 0.001-0.86], p=0.04) and ΔCI (0.02 [0.001-0.71], p=0.03).

CONCLUSIONS

 Maternal-fetal hemodynamics can be well-characterized in pregnancy using MRI. Impaired adaptation to pregnancy in women with HD appears to be associated with development of adverse outcomes of pregnancy.

BRIEF SUMMARY

Maternal and placental-fetal vascular flows in women with heart disease (HD) were measured using magnetic resonance imaging. Adaptive peak pregnancy cardiac output and cardiac index (CI) were formidable in the majority of mothers. Placental-fetal hemodynamics were maintained and neonatal outcomes were favourable. Women with adverse cardiovascular events in pregnancy had insufficient augmentation of CI antenatally. Understanding hemodynamic responses of HD mothers in pregnancy may help physicians counsel women pre-conceptually and further optimize management antenatally.

Placental growth factor as a diagnostic tool for placental mediated fetal growth restriction

OBJECTIVE

Placental growth factor (PlGF) has shown promise in identification of placental fetal growth restriction (FGR). We aimed to investigate the association between PlGF and sonographic markers of placental dysfunction and assess its ability to diagnose FGR secondary to maternal vascular malperfusion (MVM).

STUDY DESIGN

A retrospective study of singleton pregnancies with small for gestational age (SGA) fetuses, who had PlGF testing at 16-36 weeks. Fetuses with major chromosomal and/or structural anomalies and pregnancies with missing outcomes were excluded. Sonographic characteristics, perinatal outcomes and placental histopathology were compared between pregnancies with normal and low PlGF (<10th percentile for gestational age). The diagnostic accuracy of PlGF for prediction of MVM was calculated.

RESULTS

130 fetuses met inclusion criteria. Compared to normal PlGF (n = 65), pregnancies with low PlGF (n = 65) were associated with an estimated fetal weight < 5th centile (73.8% (48) vs 53% (35), respectively, p = 0.01), abnormal uterine, umbilical and MCA Dopplers (p = 0.001 for all), fetal demise (18.8% (12) vs 0% respectively, p = 0.01) and preterm delivery (100% (65) vs 39% (59), respectively, p < 0.001) . Low PlGF had a 70.1% (58.6-80.0) sensitivity and a 79.6% (64.7-90.2) specificity for identifying MVM, with an AUC of 0.73 (0.63-0.84). Positive and negative predictive values were 85.7% (76.8-91.2) and 60.3% (51.2-68.9), respectively. PlGF outperformed other parameters of placental FGR (uterine, umbilical artery, middle cerebral artery and abdominal circumference < 5th centile), in isolation and when combined.

CONCLUSION

PlGF is a useful tool to aid in the diagnosis of placental FGR secondary to MVM.

Induction of the PPARγ (Peroxisome Proliferator-Activated Receptor γ)-GCM1 (Glial Cell Missing 1) Syncytialization Axis Reduces sFLT1 (Soluble fms-Like Tyrosine Kinase 1) in the Preeclamptic Placenta

[Figure: see text].

PlGF (Placental Growth Factor) Testing in Clinical Practice: Evidence From a Canadian Tertiary Maternity Referral Center

[Figure: see text].

An MRI approach to assess placental function in healthy humans and sheep

KEY POINTS

Human placental function is evaluated using non-invasive Doppler ultrasound of umbilical and uterine artery pulsatility indices as measures of resistance in placental vascular beds, while measurement of placental oxygen consumption ( V O 2 ) is only possible during Caesarean delivery. This study shows the feasibility of using magnetic resonance imaging (MRI) in utero to measure blood flow and oxygen content in uterine and umbilical vessels to calculate oxygen delivery to and V O 2 by the gravid uterus, uteroplacenta and fetus. Normal late gestational human uteroplacental V O 2 by MRI was ∼4 ml min^-1  kg^-1 fetal weight, which was similar to our MRI measurements in sheep and to those previously measured using invasive techniques. Our MRI approach can quantify uteroplacental V O 2 , which involves the quantification of maternal- and fetal-placental blood flows, fetal oxygen delivery and V O 2 , and the oxygen gradient between uterine- and umbilical-venous blood, providing a comprehensive assessment of placental function with clinical potential.

ABSTRACT

It has not been feasible to perform routine clinical measurement of human placental oxygen consumption ( V O 2 ) and in vitro studies do not reflect true metabolism in utero. Here we propose an MRI method to non-invasively quantify in utero placental and fetal oxygen delivery ( D O 2 ) and V O 2 in healthy humans and sheep. Women (n = 20) and Merino sheep (n = 10; 23 sets of measurements) with singleton pregnancies underwent an MRI in late gestation (36 ± 2 weeks and 128 ± 9 days, respectively; mean ± SD). Blood flow (phase-contrast) and oxygen content (T1 and T2 relaxometry) were measured in the major uterine- and umbilical-placental vessels, allowing calculation of uteroplacental and fetal D O 2 and V O 2 . Maternal D O 2 (ml min^-1  kg^-1 fetus) to the gravid uterus was similar in humans and sheep (human = 54 ± 15, sheep = 53 ± 21, P = 0.854), while fetal D O 2 (human = 25 ± 4, sheep = 22 ± 5, P = 0.049) was slightly lower in sheep. Uteroplacental and fetal V O 2 (ml min^-1  kg^-1 fetus; uteroplacental: human = 4.1 ± 1.5, sheep = 3.5 ± 1.9, P = 0.281; fetus: human = 6.8 ± 1.3, sheep = 7.2 ± 1.7, P = 0.426) were similar between species. Late gestational uteroplacental:fetal V O 2 ratio did not change with age (human, P = 0.256; sheep, P = 0.121). Human umbilical blood flow (ml min^-1  kg^-1 fetus) decreased with advancing age (P = 0.008), while fetal V O 2 was preserved through an increase in oxygen extraction (P = 0.046). By contrast, sheep fetal V O 2 was preserved through stable umbilical flow (ml min^-1  kg^-1 ; P = 0.443) and oxygen extraction (P = 0.582). MRI derived measurements of uteroplacental and fetal V O 2 between humans and sheep were similar and in keeping with prior data obtained using invasive techniques. Taken together, these data confirm the reliability of our approach, which offers a novel clinical 'placental function test'.

Sex differences in fetal Doppler parameters during gestation

BACKGROUND

Fetal sex is known to affect pregnancy outcomes. In current clinical practice, monitoring of fetal well-being is based on Doppler ultrasound measurements of major placental and fetal vessels. The objective of this study was to investigate the effect of fetal sex on Doppler parameters throughout gestation in healthy pregnancy.

METHODS

A prospective study was conducted in 240 pregnant women with ultrasound examinations at a 4-weekly interval between 12 and 38 weeks of gestation. Pulsed Doppler spectra were collected for the umbilical arteries (UAs), middle cerebral artery (MCA), descending abdominal aorta (DAo), and ductus venosus (DV). Linear mixed effects models were used to determine if the pulsatility indices (PIs) of these vessels depended on gestational age and fetal sex.

RESULTS

While there were no differences in the MCA PI and DV PIV over gestation between female and male fetuses, the trajectory of the UA and DAo PIs differed by fetal sex (p = 0.02 and p = 0.01, respectively).

CONCLUSIONS

Doppler ultrasound parameters were found to be dependent on fetal sex for some vessels and not for others in healthy pregnancies. Further investigations are needed to understand the physiological mechanisms for these sex differences and the relevance for disease processes in pregnancy.

Customized birth-weight centiles and placenta-related fetal growth restriction

OBJECTIVE

The value of using customized birth-weight centiles to improve the diagnostic accuracy for fetal growth restriction (FGR), in comparison with using population-based charts, remains a matter of debate. One potential explanation for the conflicting data is that most studies used measures of perinatal mortality and morbidity as proxies for placenta-mediated FGR, many of which are not specific and may be confounded by other factors such as prematurity. The aim of this study was to compare the diagnostic accuracy of small-for-gestational age (SGA) at birth, defined according to customized vs population-based charts, for associated abnormal placental pathology.

METHODS

This was a secondary analysis of data from a prospective cohort study on risk factors for placenta-mediated complications and abnormal placental pathology in low-risk nulliparous women. All placentae were sent for detailed histopathological examination by two perinatal pathologists. The primary exposure was SGA, defined as birth weight < 10^th centile for gestational age using either a customized (SGA_cust ) or a population-based (SGA_pop ) birth-weight reference. The outcomes of interest were one of three types of abnormal placental pathology associated with FGR: maternal vascular malperfusion (MVM), chronic villitis and fetal vascular malperfusion (FVM). Adjusted relative risks (aRR) with 95% CIs were estimated using modified Poisson regression analysis, with adjustment for smoking, body mass index and aspirin treatment.

RESULTS

A total of 857 nulliparous women met the study criteria. The proportions of infants identified as SGA based on the customized and population-based charts were 12.6% (108/857) and 11.4% (98/857), respectively. A diagnosis of SGA using either customized or population-based charts was associated with an increased risk of any placental pathology (aRR, 3.04 (95% CI, 2.29-4.04) and 1.60 (95% CI, 1.10-2.31), respectively) and MVM pathology (aRR, 12.33 (95% CI, 6.60-23.03) and 5.29 (95% CI, 2.87-9.76), respectively). SGA_cust , but not SGA_pop , was also associated with an increased risk for chronic villitis (aRR, 1.85 (95% CI, 1.07-3.18)) and FVM pathology (aRR, 2.48 (95% CI, 1.25-4.93)). SGA_cust had a higher detection rate for any placental pathology (30.3% vs 17.1%; P < 0.001), MVM pathology (63.2% vs 39.5%; P = 0.003) and chronic villitis (20.8% vs 8.3%; P = 0.007) than did SGA_pop , for a similar false-positive rate. This was mainly the result of a higher detection rate for abnormal pathology in the white and East-Asian subgroups and a lower false-positive rate for abnormal pathology in the South-Asian subgroup by SGA_cust than by SGA_pop . In addition, pregnancies in the SGA_cust group, but not those in the SGA_pop group, were more likely to be complicated by preterm birth and a low 5-min Apgar score than were the corresponding non-SGA group.

CONCLUSION

These findings suggest that customized birth-weight centiles may be superior to population-based birth-weight centiles in detecting FGR that is due to underlying placental disease. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

Second Trimester Placental Growth Factor Levels and Placental Histopathology in Low-Risk Nulliparous Pregnancies

OBJECTIVE

Placental growth factor (PlGF) levels are lower at delivery in pregnancies with preeclampsia or fetuses small for gestational age (SGA). These obstetrical complications are typically mediated by placental dysfunction, most commonly related to the specific placental phenotype termed placental maternal vascular malperfusion (MVM). The objective of this study was to determine the relationship between PlGF levels in the second trimester and the development of placental diseases that underlie adverse perinatal outcomes.

METHODS

We performed a secondary analysis of the prospective Placental Health Study in unselected healthy nulliparous women (n = 773). Maternal demographic data, Doppler ultrasound measurements, and plasma PlGF levels at 15 to 18 weeks gestation were analyzed for association with pregnancy outcomes and placental pathology following delivery.

RESULTS

Low PlGF levels in the second trimester (<10th percentile; <72 pg/mL) was associated with preterm delivery (<37 weeks; 26% vs. 6%, P < 0.001; unadjusted odds ratio (OR) 5.75, 95% CI 3.2-10.5), reduced mean birthweight (2998 vs. 3320 g, P < 0.001), SGA deliveries (25% vs. 11%, P = 0.001; OR 2.6, 95% CI 1.5-4.6), and preeclampsia (7% vs. 2%, P = 0.02; OR 4.3, 95% CI 1.5-12.8) relative to normal PlGF levels (≥10th percentile; ≥72 pg/mL). Low PlGF was associated with lower mean placental weight (447 vs. 471 g, P = 0.01), aberrant cord insertion (25% vs. 12%, P = 0.001) and a pathologic diagnosis of MVM (18% vs. 11%, P = 0.04; OR 1.9, 95% CI 1.01-3.55) but not with other placental pathologies.

CONCLUSION

MVM placental pathology and related adverse perinatal outcomes are associated with low PlGF in the early second trimester for healthy nulliparous women.

Sex differences in uterine artery Doppler during gestation in pregnancies complicated by placental dysfunction

BACKGROUND

There is growing evidence of sex differences in placental vascular development. The objective of this study was to investigate the effect of fetal sex on uterine artery pulsatility index (PI) throughout gestation in a cohort of normal and complicated pregnancies.

METHODS

A prospective longitudinal study was conducted in 240 pregnant women. Pulsed wave Doppler ultrasound of the proximal uterine arteries was performed at a 4-weekly interval between 14 and 40 weeks of gestation. The patients were classified retrospectively as normal or complicated (one or more of maternal preeclampsia, preterm birth, or small for gestational age). To assess if the change in uterine artery PI during gestation differed between normal and complicated pregnancies and between fetal sexes, the uterine artery PI was modeled using a linear function of gestational age and the rate of change was estimated from the slope.

RESULTS

While the uterine artery PI did not differ over gestation between females and males for normal pregnancies, the trajectory of this index differed by fetal sex for pregnancies complicated by either preeclampsia, preterm birth, or fetal growth restriction (p < 0.0001). The male fetuses in the complicated pregnancy group had an elevated slope compared to the other groups (p < 0.0001), suggesting a more progressive deterioration in uteroplacental perfusion over gestation.

CONCLUSIONS

The uterine artery PI is widely used to assess uteroplacental function in clinical settings. The observation that this metric changes more rapidly in complicated pregnancies where the fetus was male highlights the importance of sex when interpreting hemodynamic markers of placental maturation.

Diagnostic accuracy of fetal growth charts for placenta-related fetal growth restriction

INTRODUCTION

The choice of fetal growth chart to be used in antenatal screening for fetal growth restriction (FGR) has an important impact on the proportion of fetuses diagnosed as small for gestational age (SGA), and on the detection rate for FGR. We aimed to compare diagnostic accuracy of SGA diagnosed using four different common fetal growth charts [Hadlock, Intergrowth-21st (IG21), World Health Organization (WHO), and National Institute of Child Health and Human Development (NICHD)], for abnormal placental pathology.

METHODS

A secondary analysis of data from a prospective cohort study in low-risk nulliparous women. The exposure was SGA (birthweight <10th centile for gestational age) using each of the four charts. The outcomes were one of three types of abnormal placental pathology associated with fetal growth restriction: maternal vascular malperfusion (MVM), chronic villitis, and fetal vascular malperfusion.

RESULTS

A total of 742 nulliparous women met the study criteria. The proportion of SGA was closest to the expected rate of 10% using the Hadlock chart (12.7%). The detection rates (DR) and false positive rates (FPR) for MVM pathology were similar for the Hadlock (DR = 53.1%, FPR = 10.8%), WHO (DR = 59.4%, FPR = 14.2%), and NICHD (DR = 53.1%, FPR = 12.3%) charts, and each was superior when compared to the IG21 chart (DR = 34.4%, FPR = 3.8%, p < 0.001). The diagnosis of SGA was associated with increased risks of preeclampsia and preterm birth for all four charts.

DISCUSSION

The selection of fetal growth chart to be used in screening programs for FGR has important implications with regard to the false positive and detection rate for FGR.

Determination of fetal heart rate short-term variation from umbilical artery Doppler waveforms

OBJECTIVE

To evaluate the feasibility of using umbilical artery (UA) Doppler waveforms to measure fetal heart rate (FHR) short-term variation (STV) across gestation.

METHODS

This was a prospective longitudinal study, conducted at two study sites, of 195 pregnancies considered low risk. Pulsed-wave Doppler of the UAs was performed at 4-weekly intervals, between 14 and 40 weeks of gestation, using a standardized imaging protocol. Up to 12 consecutive UA Doppler waveforms were analyzed using offline processing software. FHR STV was calculated using average R-R intervals extracted from the waveforms and baseline corrected for FHR.

RESULTS

Baseline-corrected FHR STV increased significantly with gestational age (conditional R²  = 0.37; P < 0.0001) and was correlated inversely with FHR (conditional R²  = 0.54; P < 0.0001). The STV ranged (median (interquartile range)) from 3.5 (2.9-4.1) ms at 14-20 weeks' gestation to 6.3 (4.8-7.7) ms at 34-40 weeks' gestation. The change in heart rate STV did not differ between study sites or individual sonographers.

CONCLUSIONS

UA Doppler waveforms offer a robust and feasible method to derive STV of the FHR. It should be emphasized that the UA Doppler-derived STV is not interchangeable with measurements derived with computerized cardiotocography. Accordingly, further investigations are needed to validate associations with outcome, in order to determine the value of concurrent fetal cardiovascular and heart rate evaluations that are possible with the technique described here. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

Sex differences in modulation of fetoplacental vascular resistance in growth-restricted mouse fetuses following betamethasone administration: comparisons with human fetuses

BACKGROUND

Maternally administered corticosteroids are routinely used to accelerate fetal lung maturation in pregnancies at risk of early preterm delivery. Although, among the subgroup with growth restriction, a majority show a temporary improvement in umbilical artery Doppler waveforms that may be sustained up to 7 days, a minority will acutely decompensate in response to corticosteroids in association with deteriorating umbilical and fetal Doppler waveforms. The basis for such acute Doppler changes is presently unknown. Our group has developed a noninvasive ultrasound methodology to measure wave reflections in the umbilical artery and have established that wave reflection metrics are sensitive to structural changes in the placental vasculature and to acute changes in vascular tone. Using this approach, we demonstrated in healthy pregnant mice that fetoplacental vascular resistance decreased in betamethasone-treated mice compared with saline-treated controls.

OBJECTIVE

This study aimed to investigate the effects of betamethasone administration on the wave reflection metrics in a mouse model of fetal growth restriction and to compare these findings with equivalent measurements in human fetuses.

STUDY DESIGN

Pregnant CD-1 mice were housed from embryonic day 14.5 to embryonic day 17.5 in either a normoxic (21% O₂, n=24) or hypoxic environment (11% O₂, n=22), the latter being an established mouse model of fetal growth restriction. To investigate the effect of maternally administered betamethasone on the fetoplacental vasculature, ultrasound imaging was performed at baseline and 4 hours after treatment (either betamethasone or sterile saline). Umbilical artery wave reflection metrics were compared between the groups and for the effect of fetal sex. In addition, a cohort of 10 pregnant women with elevated umbilical artery pulsatility index and evidence of fetal growth restriction and 6 controls were imaged before and after corticosteroid administration.

RESULTS

In the mouse model, after betamethasone administration, the female fetuses from the hypoxia group showed a 15% increase in umbilical artery diameter, a 98% increase in umbilical artery blood flow, and a 27% decrease in umbilical artery reflection coefficient, whereas the males from the hypoxia group showed no substantial changes. In agreement with our mouse findings, umbilical artery reflections were found to be larger in human growth-restricted fetuses than controls in women at risk of preterm birth.

CONCLUSION

Our studies provide insight into the mechanism whereby the human growth-restricted fetus may exhibit a temporary favorable fetoplacental vascular response to maternally administered corticosteroids. Further investigations are needed to understand why the male growth-restricted fetus seems unable to mount this favorable vascular response.

Effect of maternal betamethasone administration on feto-placental vascular resistance in the mouse†

Antenatal corticosteroids are often administered to women at risk of preterm birth to accelerate fetal lung development; however, there is evidence that this treatment may adversely affect placental function in some fetuses. Our group has recently demonstrated that wave reflections in the umbilical artery (UA), measured using high-frequency ultrasound, are sensitive to placental vascular abnormalities. In the present study, we used this approach to investigate the effect of maternal administration of betamethasone, a clinically relevant corticosteroid, on the feto-placental vasculature of the mouse. Fetuses were assessed at embryonic day (E)15.5 and E17.5 in C57BL6/J mice. At both gestational ages, the UA diameter, UA blood flow, and the wave reflection coefficient were significantly elevated in the betamethasone-treated mice compared to vehicle-treated controls. These observations support the interpretation that placental vascular resistance dropped with betamethasone treatment to an extent that could not be explained by vasodilation of the UA alone. Consistent with clinical studies, the effect of betamethasone on UA end-diastolic velocity was heterogeneous. Our results suggest that UA wave reflections are more sensitive to acute changes in placental vascular resistance compared with the UA pulsatility index, and this technique may have clinical application to identify a favorable placental vascular response to fetal therapies such as antenatal corticosteroids, where the fetal heart rate is likely to vary.