Longitudinal assessment of spiral artery and intravillous arteriole blood flow and adverse pregnancy outcome

OBJECTIVE

Superb microvascular imaging (SMI) has been shown to improve visualization of small vessels by suppressing global motions while preserving low-flow components, such as the microvessels in the placenta. We sought to determine if SMI-aided visualization of flow velocity waveforms in the spiral arteries (SA) and intravillous fetal arterioles (IVA) could predict fetal growth restriction (FGR), gestational hypertension (GH) and/or pre-eclampsia (PE).

METHODS

This was a prospective longitudinal study of singleton pregnancies without fetal anomaly, receiving prenatal care in one of two medical centers over a 5-year period. Using SMI-aided color Doppler, SA and IVA flow velocity was measured at three timepoints: 11 + 0 to 14 + 0, 18 + 0 to 22 + 6 and 28 + 0 to 34 + 6 weeks of gestation. SA and IVA flow velocity waveforms were reported as resistance indices (RI). RI values were analyzed using multilevel modeling; individual regression curves were estimated and combined to obtain the reference intervals for SA-RI and IVA-RI in uncomplicated pregnancies. The primary clinical outcome was FGR and secondary outcomes were PE and GH. FGR was defined as estimated fetal weight < 10^th percentile. Student's t-test was used to compare deviation from expected RI between normal and complicated pregnancies.

RESULTS

Among 540 pregnancies included in the analysis, 18 (3.3%) had FGR, 31 (5.7%) PE and 61 (11.3%) GH. In uncomplicated pregnancies, the SA-RI decreased progressively with advancing gestation, whereas the IVA-RI increased with gestational age. In the third trimester, the mean SA-RI and IVA-RI values were significantly higher in the FGR group compared with pregnancies that did not develop FGR, while the mean SA-RI was significantly higher in PE compared with non-PE pregnancies. There was no significant difference in mean SA-RI or IVA-RI between pregnancies with vs those without GH at any gestational age. When all three adverse outcomes were combined, SA-RI was significantly higher in pregnancies with these outcomes when compared to uncomplicated pregnancies in the third trimester (mean ± SD, 0.29 ± 0.12 vs 0.26 ± 0.12; P = 0.02). In screening for FGR using SA-RI, the areas under the receiver-operating-characteristics curves (AUC) were 0.68, 0.73 and 0.73 in the first, second and third trimesters, respectively. The respective AUCs for IVA-RI were 0.72, 0.72 and 0.73 for each trimester.

CONCLUSIONS

SA-RI and IVA-RI, measured using SMI technology, were significantly higher in pregnancies at risk for FGR in late gestation. Larger studies are needed to determine if SA and IVA flow are reliable predictors of adverse pregnancy outcome. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Outcome-based comparison of SMFM and ISUOG definitions of fetal growth restriction

OBJECTIVE

The recent international guidelines by the Society for Maternal-Fetal Medicine (SMFM) and the International Society of Ultrasound in Obstetrics and Gynecology (ISUOG) differ in their definitions of fetal growth restriction (FGR). Our aim was to compare the performance of the two definitions in predicting neonatal small-for-gestational age (SGA) and composite adverse neonatal outcome (ANO).

METHODS

This was a secondary analysis of data from a prospective study of women referred for fetal growth ultrasound examination between 26 + 0 and 36 + 6 weeks' gestation. The SMFM and ISUOG guidelines were used to define pregnancies with FGR. The SMFM definition of FGR is estimated fetal weight (EFW) or abdominal circumference (AC) < 10^th percentile. The ISUOG-FGR definition follows the Delphi consensus criteria and includes either EFW or AC < 3^rd percentile or EFW or AC < 10^th percentile combined with abnormal Doppler findings or a decrease in growth centiles. The primary outcome was the prediction of neonatal SGA, defined as birth weight < 10^th percentile, and a composite of ANO, which was defined as one or more of: Grade-III or -IV intraventricular hemorrhage, respiratory distress syndrome, neonatal death, cord blood pH < 7.1, seizures and admission to the neonatal intensive care unit. Test characteristics (sensitivity, specificity, positive predictive value (PPV), negative predictive value and positive (LR+) and negative likelihood ratios) and area under the receiver-operating-characteristics curve were determined. The association between FGR detected by each definition and selected adverse outcomes was assessed using logistic regression analysis.

RESULTS

Of the 1054 pregnancies that met the inclusion criteria, 137 (13.0%) and 55 (5.2%) were defined as having FGR by the SMFM and ISUOG definitions, respectively. Composite ANO and SGA neonate each occurred in 139 (13.2%) pregnancies. For the prediction of neonatal SGA, the SMFM-FGR definition had a higher sensitivity (54.7%) than did the ISUOG definition (28.8%). The ISUOG-FGR definition had higher specificity (98.4% vs 93.3%), LR+ (18.0 vs 8.2) and PPV (72.7% vs 55.5%) than did the SMFM definition for the prediction of a SGA neonate. The SMFM- and ISUOG-FGR definitions had similarly poor performance in predicting composite ANO, with sensitivities of 15.1% and 10.1%, respectively.

CONCLUSIONS

The SMFM definition of FGR is associated with a higher detection rate for SGA neonates but at the cost of some reduction in specificity. The ISUOG-FGR definition has a higher specificity, LR+ and PPV for the prediction of neonatal SGA. Both definitions of FGR performed poorly in predicting a composite ANO. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Validation of Delphi procedure consensus criteria for defining fetal growth restriction

OBJECTIVE

Recently, a Delphi procedure was used to establish new criteria for defining fetal growth restriction (FGR). These criteria require clinical validation. We sought to validate the Delphi consensus criteria by comparing their performance with that of our current definition (estimated fetal weight (EFW) < 10^th percentile) in predicting adverse neonatal outcome (ANO).

METHODS

This was a secondary analysis of data from a prospective cohort study of women referred for fetal growth assessment between 26 and 36 weeks' gestation. The current standard definition of FGR used in our clinical practice is EFW < 10^th percentile using Hadlock's fetal growth standard. The Delphi consensus criteria for FGR include either a very small fetus (abdominal circumference (AC) or EFW < 3^rd percentile) or a small fetus (AC or EFW < 10^th percentile) with additional abnormal Doppler findings or a decrease in AC or EFW by two quartiles or more. The primary outcome was the prediction of a composite of ANO including one or more of: admission to the neonatal intensive care unit, cord pH < 7.1, 5-min Apgar score < 7, respiratory distress syndrome, intraventricular hemorrhage, neonatal seizures or neonatal death. The discriminatory capacities of the two definitions of FGR for composite ANO and delivery of a small-for-gestational-age (SGA) neonate, defined as birth weight < 10^th percentile, were compared using area under the receiver-operating-characteristics curve (AUC). The sensitivity, specificity and predictive values of the methods were also compared.

RESULTS

Of 1055 pregnancies included in the study, composite ANO occurred in 139 (13.2%). There were only two cases of early FGR (before 32 weeks); therefore, the study focused on late FGR. Our current FGR diagnostic criterion of EFW < 10^th percentile was not associated significantly with composite ANO (relative risk (RR), 1.1 (95% CI, 0.6-1.8)), while the Delphi FGR criteria were (RR, 2.0 (95% CI, 1.2-3.3)). Our current definition of FGR showed higher discriminatory ability in the prediction of a SGA neonate (AUC, 0.69 (95% CI, 0.65-0.73)) than did the Delphi definition (AUC, 0.64 (95% CI, 0.60-0.67)) (P = 0.001). The AUCs of both definitions were poor for the prediction of composite ANO, despite slightly improved performance using the Delphi consensus definition of FGR (AUC, 0.53 (95% CI, 0.50-0.55)) compared with that of our current definition (AUC, 0.50 (95% CI, 0.48-0.53)) (P = 0.02).

CONCLUSION

The newly postulated criteria for defining FGR based on a Delphi procedure detects fewer cases of neonatal SGA than does our current definition of EFW < 10^th percentile, but is associated with a slight improvement in predicting ANO. Copyright © 2020 ISUOG. Published by John Wiley & Sons Ltd.

Risk factors for Cesarean delivery in pregnancy with small-for-gestational-age fetus undergoing induction of labor

OBJECTIVES

To identify risk factors for Cesarean delivery and non-reassuring fetal heart tracing (NRFHT) in pregnancies with a small-for-gestational-age (SGA) fetus undergoing induction of labor and to design and validate a prediction model, combining antenatal and intrapartum variables known at the time of labor induction, to identify pregnancies at increased risk of Cesarean delivery.

METHODS

This was a retrospective cohort study of non-anomalous, singleton gestations with a SGA fetus that underwent induction of labor, delivered in a single tertiary referral center between January 2011 and December 2016. SGA was defined as estimated fetal weight (EFW) < 10^th percentile. The primary outcome was to identify risk factors associated with Cesarean delivery. The secondary outcome was to identify risk factors associated with NRFHT. Univariate and multivariate analyses were used to determine which clinical characteristics, available at the time of admission, had the strongest association with Cesarean delivery and NRFHT during labor induction. The predictive value of the final models was assessed by the area under the receiver-operating-characteristics curve (AUC). Sensitivity and specificity of the models were also assessed. Internal validation of the models was performed using 10 000 bootstrap replicates of the original cohort. The adequacy of the models was evaluated using the Hosmer-Lemeshow goodness-of-fit test.

RESULTS

A total of 594 pregnancies were included. Cesarean delivery was performed in 243 (40.9%) pregnancies. Significant risk factors associated with Cesarean delivery, and included in the final model, were maternal age, gestational age at delivery and initial method of labor induction. The bootstrap estimate of the AUC of the final prediction model for Cesarean delivery was 0.82 (95% CI, 0.78-0.86). The model had sensitivity of 64.2%, specificity of 86.9%, positive likelihood ratio (LR) of 4.9 and negative LR of 0.41. The model had good fit (P = 0.617). NRFHT complicated 117 (19.7%) pregnancies. Significant risk factors for NRFHT included EFW < 5^th percentile, abnormal umbilical artery Doppler studies (pulsatility index > 95^th percentile or absent/reversed end-diastolic flow) and gestational age at delivery. The final prediction model for NRFHT had an AUC of 0.69 (95% CI, 0.63-0.75) and specificity of 97.0%.

CONCLUSION

We identified several significant risk factors for Cesarean delivery and NRFHT among SGA pregnancies undergoing induction of labor. Clinicians may use these risk factors to guide patient counseling and to help anticipate the potential need for operative delivery. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Early prediction and aspirin for prevention of pre-eclampsia (EPAPP) study: a randomized controlled trial

OBJECTIVE

To estimate the effect of early administration of aspirin on the prevention of pre-eclampsia in high-risk women.

METHODS

This was planned as a randomized, double-blind, placebo-controlled trial of aspirin for women with risk factors for pre-eclampsia. Participants were randomized to start either aspirin (81 mg/day) or placebo at 11 + 0 to 13 + 6 weeks of gestation. The primary outcome was pre-eclampsia and secondary outcomes included gestational hypertension and small-for-gestational age at birth.

RESULTS

The trial suffered from slow recruitment, leading to a protocol change to broaden the inclusion criteria (from a minimum score of multiple risk factors to at least one risk factor for pre-eclampsia). The trial was then terminated prematurely due to continuing slow recruitment and a lack of equipoise given a change in national guidelines to administer aspirin to high-risk women. From the 53 women who were randomized, 30 were included in the final analysis. There was no evidence that the primary outcome of pre-eclampsia was prevented by low-dose aspirin (relative risk (RR) 0.88, 95% CI 0.21-3.66). Gestational hypertension was seen in two women, both in the aspirin group. There was no evidence that the occurrence of small-for-gestational age was reduced by aspirin (RR 0.88, 95% CI 0.06-12.72).

CONCLUSIONS

Although this study was underpowered to show effectiveness of aspirin compared to placebo due to the premature termination and difficulties encountered, it highlights practical issues to inform future studies.

First-trimester serum soluble fms-like tyrosine kinase-1, free vascular endothelial growth factor, placental growth factor and uterine artery Doppler in preeclampsia

OBJECTIVE

To compare the first-trimester serum concentrations of soluble fms-like tyrosine kinase-1 (sFlt-1), free vascular endothelial growth factor (free-VEGF), placental growth factor (PlGF), and uterine artery pulsatility index (PI) in women who later developed preeclampsia (PE).

STUDY DESIGN

Prospectively collected maternal serum samples were evaluated for sFlt-1, free VEGF, and PlGF levels in 63 cases who later developed PE compared with 252 unaffected controls. Serum levels of these angiogenic factors were measured using Quantikine immunoassays. Both univariate and multivariate analyses were used to evaluate the association between angiogenic factors and PE. The relationship between the angiogenic factors and mean maternal uterine artery PI was also evaluated.

RESULT

Maternal serum sFlt-1 levels were not significantly different between the cases and controls. Mean free-VEGF levels were significantly higher in women destined to develop PE compared with the controls (P=0.04), and mean PlGF levels were significantly lower in women who later developed PE (P=0.01). There was no significant correlation between maternal mean uterine artery PI and angiogenic factors evaluated. Receiver-operating characteristic curves revealed that none of the factors were clinically useful for prediction in the first trimester of PE.

CONCLUSION

Despite some significant differences in the first-trimester serum levels of angiogenic factors, our models suggest that these factors are not clinically useful for prediction in women who later developed PE.

Prediction of intrauterine fetal death in small-for-gestational-age fetuses: impact of including ultrasound biometry in customized models

OBJECTIVE

Customized growth charts derived from maternal demographic characteristics alone have been shown to improve the prediction of pregnancy complications compared to population growth curves. We sought to estimate the impact of adding ultrasound biometric parameters to the customized chart for the prediction of intrauterine fetal death (IUFD).

METHODS

A retrospective cohort study was undertaken using an ultrasound database including singleton pregnancies followed between 16 and 20 weeks' gestation. After exclusion of preterm births, congenital anomalies, multifetal pregnancies and stillbirths (excluded only from derivation samples), we identified 59 016 births, divided into derivation (34 832) and validation (24 184) samples. Coefficients for significant physiological and pathological variables affecting fetal growth were derived using backward stepwise multiple regression (Cust-chart). The same process was repeated including second-trimester biometric parameters: biparietal diameter, head circumference, femur length and abdominal circumference in the regression models (Cust-plus-USS-chart). The association between small-for-gestational age < 10(th) centile (SGA) pregnancies, defined using the two customized charts or our population-based growth chart (Pop-chart) and IUFD, were compared. Statistical analyses including OR, 95% CI and screening accuracy using each chart were performed.

RESULTS

The derived coefficients for fetal growth are comparable to those of previously published series. Of 24 184 pregnancies in the validation sample, IUFD was seen in 169 (0.7%). The pregnancies identified as SGA were: 2482 (10.26%), 2499 (10.33%) and 2634 (10.89%) using the Cust-chart, Cust-plus-USS-chart and Pop-chart, respectively. The OR (95% CI) for the association between SGA defined by the three charts and IUFD was: 7.0 (4.5-11), 6.5 (4.2-10.2) and 2.4 (1.6-3.6) according to the Cust-chart, Cust-plus-USS-chart and Pop-chart, respectively. Screening efficiency for IUFD using both customized charts was similar, with both demonstrating a higher sensitivity compared with the Pop-chart.

CONCLUSIONS

Customized charts are more efficient in identifying pregnancies at risk for IUFD compared with population-based charts. However, adding second-trimester ultrasound biometric parameters to the customized model does not improve the prediction of IUFD compared with using maternal characteristics only.

First-trimester placental protein 13, PAPP-A, uterine artery Doppler and maternal characteristics in the prediction of pre-eclampsia

OBJECTIVE

To test the hypothesis that a combination of PP13, PAPP-A and first-trimester uterine artery Doppler would improve the prediction of pre-eclampsia.

METHODS

This is a prospective cohort study of pregnant women followed from the first-trimester to delivery. PP13 and PAPP-A were determined by immunoassay of maternal serum at 11-14 weeks', when uterine artery Doppler measurements were assessed. Cases identified with any form of pre-eclampsia were compared with a control group without pre-eclampsia. The sensitivity of each marker or their combinations in predicting pre-eclampsia for different fixed false positive rates was calculated from the ROC curves.

RESULTS

Forty two women were diagnosed with pre-eclampsia and 410 women with pregnancies not complicated by pre-eclampsia were used as controls. For a fixed false positive rate (FPR) of 20%, PP13, PAPP-A and mean uterine artery pulsatility index identified 49%, 58% and 62% respectively, of women who developed any form of pre-eclampsia. PP13 was best in predicting early onset pre-eclampsia with a sensitivity of 79% at a 20% FPR. Combinations of the three first-trimester assessments did not improve the prediction of pre-eclampsia in later pregnancy.

CONCLUSION

First-trimester PP13, PAPP-A and uterine artery PI are reasonable, individual predictors of women at risk to develop pre-eclampsia. Combinations of these assessments do not further improve the prediction of pre-eclampsia.

Placental volume and vascular flow assessed by 3D power Doppler and adverse pregnancy outcomes

OBJECTIVE

To estimate the utility of first-trimester 3D-placental volume and vascular flow indices in the prediction of adverse pregnancy outcomes.

METHODS

A prospective cohort study including women with singleton pregnancies seen between 11 and 14 weeks as part of a screening program for aneuploidy. Placental volume and vascularization indices were obtained using 3D power Doppler imaging and the VOCAL technique. Placental volume (PV), Vascularization Index (VI), Flow Index (FI) and Vascularization Flow Index (VFI) were calculated. The adverse pregnancy outcomes investigated include preeclampsia (PE), gestational hypertension (GH) and small for gestational age (SGA). The predictive ability of each variable was evaluated using receiver-operating characteristic (ROC) curves.

RESULTS

Of 388 women included, PE was seen in 30 (7.7%), GH in 37 (9.0%) and SGA in 31 (8.0%). Placental volume was not significantly different between the pregnancies with adverse outcomes and those without. The mean values of the VI and VFI were significantly lower in the pregnancies that developed PE but not in GH or SGA. The area under the ROC curve for the prediction of PE was 0.71, 0.69 and 0.70 for VI, FI and VFI, respectively.

CONCLUSION

The study confirms lower 3D power Doppler vascular flow indices in pregnancies that develop PE. The discriminatory ability of using these indices alone for predicting PE appears modest.

First-trimester serum analytes, biophysical tests and the association with pathological morphometry in the placenta of pregnancies with preeclampsia and fetal growth restriction

OBJECTIVE

We test the hypothesis that first-trimester serum analytes, 4-D power Doppler placental vascular indices and uterine artery Doppler (UAD) predicts abnormal placental morphometry in pregnancies with preeclampsia (PE) and fetal growth restriction (FGR).

STUDY DESIGN

Maternal serum analytes (PAPP-A, hCG, ADAM12s, and PP13), bilateral UADs, and placental vascular indices were measured at 11-14 weeks in a nested-case control study within a prospective cohort of women followed from the first-trimester to delivery. Vascularization index (VI), flow index (FI), and vascularization flow index (VFI) were obtained from 4-D power Doppler histograms. Serum analytes were measured using immunofluorometric assays and values converted to multiples of the median (MoM) for gestational age. Morphometric analysis was performed on placentas from pregnancies complicated by PE (n = 13), gestational hypertension (HBP, n = 7) and FGR (defined as fetal weight <10th percentile with abnormal umbilical artery Doppler: n = 7); and 20 uncomplicated pregnancies. Two pregnancies had both FGR and PE. Each placenta was weighed and random samples taken, and fixed in formalin within 1 h of delivery. Hematoxylin & Eosin stained slides were analyzed by design-based stereology to quantify linear dimensions, surface areas and volumes of placental components. Paired t-test and ANOVA with adjustments for multiple comparisons were used.

RESULTS

The surface areas of terminal and intermediate villi as well as the volume of terminal villi were significantly smaller in placentas from pregnancies complicated by FGR and PE. Compared with the control group the mean PAPP-A (MoM) was lower in the pregnancies with abnormal placenta morphometry (1.1 ± 0.5 versus 0.7 ± 0.5, P = 0.03). The morphometric indices were lower in those pregnancies with low PAPP-A and IUGR compared with preeclampsia.

CONCLUSION

First-trimester PAPP-A levels are associated with abnormal placental morphometry at delivery in pregnancies with PE and IUGR. These findings may explain the association between adverse pregnancy outcomes and first-trimester PAPP-A.