Administration of antenatal corticosteroid is associated with reduced fetal growth velocity: a longitudinal study

Unified standard for fetal growth velocity: the Eunice Kennedy Shriver National Institute of Child Health and Human Development Fetal Growth Studies

Previous studies have demonstrated that fetuses with an estimated fetal weight (EFW) less than the 10th percentile with concomitant abdominal circumference (AC) growth velocity < 10th percentile are at increased risk for adverse perinatal outcomes. This was a retrospective case series of 104 fetuses who had a prior study in which the EFW was > 10th percentile and were identified with a subsequent EFW < 10th percentile with concomitant AC growth velocity between two examinations of < 10th percentile. The AC, head circumference (HC), and femur length (FL) growth velocity was computed as follows: [(AC, HC, FLEFW < 10th - AC, HC, FLEFW Previous Examination)/(weeks gestationEFW < 10th - weeks gestationEFW Previous Examination)]. Growth velocity 10th and 90th percentile reference values for the AC, HC, and FL, were derived from equations published from Intergrowth-21st Project of longitudinal fetal growth protocol. Once abnormal growth was identified (EFW plus AC growth velocity < 10th percentile), the patients were asked to begin a course of complete maternal rest for 2 weeks, lying in the left lateral recumbent position. Following 2 weeks of maternal rest, the EFW percentile and the growth velocity of the AC, HC, and FL were reassessed as follows: Period 1: pre-diagnosis of an EFW > 10th percentile versus EFW < 10th percentile; Period II: diagnosis of an EFW < 10th percentile versus 2 weeks following maternal rest. The velocity values were plotted on graphs and z-scores were computed. A p-value of < 0.05 was considered significant. For Period I, 100% (N = 104) had an EFW and AC growth velocity < 10th percentile, 29% (30/104) a HC growth velocity < 10th percentile. Fifty-four percent (56/104) a FL growth velocity < 10th percentile. Period II, which evaluated growth after 2 weeks of maternal rest, demonstrated the following significant findings (p < 0.05): (1) increased EFW > 10th percentile (0% vs. 81%, 84/104); (2) increased AC growth velocity > 10th percentile (0% vs. 94%, 98/104); (3) increased HC growth velocity > 10th percentile (71%, 74/104 vs. 81%, 84/104), and FL growth velocity > 10th percentile (46%, 48/104 vs. 83%, 86/104). Following maternal rest in fetuses with an EFW < 10th percentile and an AC growth velocity < 10th percentile, there was a significant increase in the EFW percentile as well as the AC, HC, and FL growth velocities.

Objective:Pregnant women with HIV (PWHIV) are at increased risk of delivering babies that are small for gestational age (SGA). We aimed to determine the foetal growth trajectories of PWHIV, compared to HIV-negative women.Design:Prospective pregnancy cohort study in Soweto, South Africa, in 2013–2016.Methods:Serial ultrasound measurements (every 5 ± 1 weeks) of foetal head circumference, biparietal diameter (BPD), abdominal circumference and femur length were obtained from less than 14 weeks’ gestation to term. Multivariable linear mixed effects models were used to estimate differences in mean foetal growth measures [head circumference, BPD, abdominal circumference and femur length, and estimated foetal weight (EFW)] and mean foetal growth velocity increments (head circumference, BPD, abdominal circumference, and femur length) according to maternal HIV status. Z-scores and centiles were calculated according to the INTERGROWTH-21st standards for foetal growth. Multivariable mixed effects logistic regression was used to examine the association of maternal HIV infection with in-utero SGA (EFW <10th centile) and very SGA (VSGA, EFW <3rd centile).Results:Ultrasound measurements of 228 PWHIV and 384 HIV-negative pregnant women, with a median of five antenatal ultrasound scans per women, were analysed. There were no significant differences in mean foetal growth measures of head circumference [−0.37 mm, 95% confidence interval (CI) −1.46 to 0.72], BPD (0.07 mm, 95% CI −0.45 to 0.30), abdominal circumference (0.15 mm, 95% CI −1.47 to 1.17), femur length (0.04 mm, 95% CI −0.27 to 0.34) and EFW (1 g, 95% CI 0.98–1.02), and growth velocity increments for head circumference (−0.07 mm/week, 95% CI −0.24 to 0.10), BPD (−0.01 mm/week, 95% CI −0.06 to 0.04), abdominal circumference (0.19 mm/week, 95% CI −0.06 to 0.44) and femur length (0.00 mm/week, 95% CI −0.04 to 0.04) between foetuses of PWHIV and HIV-negative women. The prevalence of SGA ranged between 14.2% and 26.4% for PWHIV and between 18.5% and 24.1% for HIV-negative pregnant women during different gestation windows. There was no significant association between maternal HIV infection and in-utero SGA [adjusted odds ratio (aOR) 0.90, 95% CI 0.54–1.52] or VSGA (aOR 1.16, 95% CI 0.55–1.54). A sensitivity analysis restricted to PWHIV who received efavirenz-based antiretroviral therapy (ART) yielded results consistent with the overall analysis.Conclusion:Maternal HIV infection treated with ART does not appear to be associated with altered foetal growth, foetal growth velocity, or in-utero SGA, compared to HIV-negative women. Our findings support current international clinical guidelines recommending ART for PWHIV to improve maternal health and reduce vertical HIV transmission.

Pregnancies complicated by late-onset fetal growth restriction (FGR) are at increased risk of short- and long-term morbidities. Despite this, identification of cases at higher risk of adverse perinatal outcome, at the time of FGR diagnosis, is challenging. The aims of this study were to elucidate the strength of association between fetoplacental Doppler indices at the time of diagnosis of late-onset FGR and adverse perinatal outcome, and to determine their predictive accuracy. This was a prospective study of consecutive singleton pregnancies complicated by late-onset FGR. Late-onset FGR was defined as estimated fetal weight (EFW) or abdominal circumference (AC) < 3rd centile, or EFW or AC < 10th centile and umbilical artery (UA) pulsatility index (PI) > 95th centile or cerebroplacental ratio (CPR) < 5th centile, diagnosed after 32 weeks. EFW, uterine artery PI, UA-PI, fetal middle cerebral artery (MCA) PI, CPR and umbilical vein blood flow normalized for fetal abdominal circumference (UVBF/AC) were recorded at the time of the diagnosis of FGR. Doppler variables were expressed as Z-scores for gestational age. Composite adverse perinatal outcome was defined as the occurrence of at least one of emergency Cesarean section for fetal distress, 5-min Apgar score < 7, umbilical artery pH < 7.10 and neonatal admission to the special care unit. Logistic regression analysis was used to elucidate the strength of association between different ultrasound parameters and composite adverse perinatal outcome, and receiver-operating-characteristics (ROC)-curve analysis was used to determine their predictive accuracy. In total, 243 consecutive singleton pregnancies complicated by late-onset FGR were included. Composite adverse perinatal outcome occurred in 32.5% (95% CI, 26.7-38.8%) of cases. In pregnancies with composite adverse perinatal outcome, compared with those without, mean uterine artery PI Z-score (2.23 ± 1.34 vs 1.88 ± 0.89, P = 0.02) was higher, while Z-scores of UVBF/AC (-1.93 ± 0.88 vs -0.89 ± 0.94, P ≤ 0.0001), MCA-PI (-1.56 ± 0.93 vs -1.22 ± 0.84, P = 0.004) and CPR (-1.89 ± 1.12 vs -1.44 ± 1.02, P = 0.002) were lower. On multivariable logistic regression analysis, Z-scores of mean uterine artery PI (P = 0.04), CPR (P = 0.002) and UVBF/AC (P = 0.001) were associated independently with composite adverse perinatal outcome. UVBF/AC Z-score had an area under the ROC curve (AUC) of 0.723 (95% CI, 0.64-0.80) for composite adverse perinatal outcome, demonstrating better accuracy than that of mean uterine artery PI Z-score (AUC, 0.593; 95% CI, 0.50-0.69) and CPR Z-score (AUC, 0.615; 95% CI, 0.52-0.71). A multiparametric prediction model including Z-scores of MCA-PI, uterine artery PI and UVBF/AC had an AUC of 0.745 (95% CI, 0.66-0.83) for the prediction of composite adverse perinatal outcome. While CPR and uterine artery PI assessed at the time of diagnosis are associated independently with composite adverse perinatal outcome in pregnancies complicated by late-onset FGR, their diagnostic performance for composite adverse perinatal outcome is low. UVBF/AC showed better accuracy for prediction of composite adverse perinatal outcome, although its usefulness in clinical practice as a standalone predictor of adverse pregnancy outcome requires further research. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Guideline No. 442: Fetal Growth Restriction: Screening, Diagnosis, and Management in Singleton Pregnancies

Fetal growth velocity: the NICHD fetal growth studies

Former investigations have shown that the accuracy of fetal weight estimation is significantly higher if several ultrasonic fetal parameters are measured, because the total body mass depends on the size of fetal head, abdominal circumference and femur length. The aim of this investigation was to establish the best regression model, that is a number of combinations of fetal parameters providing the most accurate fetal weight estimation in utero in our population. This prospective study was carried out at the Gynecology and Obstetrics Clinic of the Clinical Center Novi Sad. It included 270 pregnant women with singleton pregnancies within 72 hours of delivery who underwent ultrasound measurements of the biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC) and femur length (FL). In regard to fetal weight estimation formulas, the deviation was lowest using regression models that simultaneously analyzed four fetal parameters (0. 55%) with SD +/- 7.61%. In these models the estimates of fetal weights were within +/- 5% of actual birth weight in 48.89%, and within +/- 10% of actual birth weight in 81.48%. Good results were also obtained using AC, FL measurements (0.92% +/- 8.20) as well as using AC, HC, FL measurements (-1.45% +/- 7.81). In our sample the combination of AC and FL model gave better results in fetal weight estimation (0.92 +/- 8.20%) than the one using BPD and AC (2.97 +/- 8.83%). Furthermore, the model using parameters AC, HC and FL showed a lower error in accuracy (-1.45 +/- 7.81%) than the model using BPD, AC and FL (2.51 +/- 7.82%). This investigation has confirmed that the accuracy of fetal weight estimation increases with the number of measured ultrasonic fetal parameters. In our population the greatest accuracy was obtained using BPD, HC, AC and FL model. In cases when fast estimation of fetal weight is needed, AC, HC, FL model may be appropriate, but if fetal head circumference cannot be measured (amnion rupture and/or fetal head already in the pelvis) the AC, FL model should be used.

To determine whether decreased fetal growth velocity precedes antepartum fetal death and to evaluate whether fetal growth velocity is a better predictor of antepartum fetal death compared to a single fetal biometric measurement at the last available ultrasound scan prior to diagnosis of demise. This was a retrospective, longitudinal study of 4285 singleton pregnancies in African-American women who underwent at least two fetal ultrasound examinations between 14 and 32 weeks of gestation and delivered a liveborn neonate (controls; n = 4262) or experienced antepartum fetal death (cases; n = 23). Fetal death was defined as death diagnosed at ≥ 20 weeks of gestation and confirmed by ultrasound examination. Exclusion criteria included congenital anomaly, birth at < 20 weeks of gestation, multiple gestation and intrapartum fetal death. The ultrasound examination performed at the time of fetal demise was not included in the analysis. Percentiles for estimated fetal weight (EFW) and individual biometric parameters were determined according to the Hadlock and Perinatology Research Branch/Eunice Kennedy Shriver National Institute of Child Health and Human Development (PRB/NICHD) fetal growth standards. Fetal growth velocity was defined as the slope of the regression line of the measurement percentiles as a function of gestational age based on two or more measurements in each pregnancy. Cases had significantly lower growth velocities of EFW (P < 0.001) and of fetal head circumference, biparietal diameter, abdominal circumference and femur length (all P < 0.05) compared to controls, according to the PRB/NICHD and Hadlock growth standards. Fetuses with EFW growth velocity < 10th percentile of the controls had a 9.4-fold and an 11.2-fold increased risk of antepartum death, based on the Hadlock and customized PRB/NICHD standards, respectively. At a 10% false-positive rate, the sensitivity of EFW growth velocity for predicting antepartum fetal death was 56.5%, compared to 26.1% for a single EFW percentile evaluation at the last available ultrasound examination, according to the customized PRB/NICHD standard. Given that 74% of antepartum fetal death cases were not diagnosed as small-for-gestational age (EFW < 10th percentile) at the last ultrasound examination when the fetuses were alive, alternative approaches are needed to improve detection of fetuses at risk of fetal death. Longitudinal sonographic evaluation to determine growth velocity doubles the sensitivity for prediction of antepartum fetal death compared to a single EFW measurement at the last available ultrasound examination, yet the performance is still suboptimal. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

Objective The use of growth velocities derived from fetal biometrics have been suggested to improve prediction of large for gestational age (LGA). Our objective was to determine if ultrasonographic growth velocities (GV) for abdominal circumference (AC) and estimated fetal weight (EFW) improve the prediction of LGA infants when compared to Hadlock EFW. Methods This was a secondary analysis of data from a prospective study of women referred for growth ultrasounds during the 3rd trimester. Growth velocities (GV) for AC (AC − GV) and EFW (EFW − GV) were derived from the difference in Z-scores between measurements at the time of anatomy survey (18–24 week) and third trimester ultrasound (26–36 weeks). Change in AC − GV and EFW − GV >90th %ile alone or in combination with Hadlock EFW >90th%ile were compared for prediction of a LGA neonate. The primary outcome was the sensitivity and specificity of the (1) Hadlock EFW >90%ile, (2) AC − GV, (3) EFW − GV, (4) Hadlock EFW + AC − GV, and (5) Hadlock EFW + EFW − GV for the prediction of neonatal LGA. Test characteristics and area under the ROC curve (AUC) were determined. The association between the ultrasound predicted growth and adverse neonatal outcome was assessed using logistic regression. Results Of 630 women meeting inclusion criteria, 85 (13.5%) had LGA neonates. Hadlock EFW showed a better NPV (98.0%) and sensitivity (71.1%) when compared to AC − GV (NPV 87.5%, sensitivity 17.7%) and EFW − GV (NPV 88.0%, sensitivity 22.6%). Combining Hadlock EFW and AC-GV or EFW − GV did little to improve the test characteristics for the prediction of LGA (AUC 0.65 and 0.64, respectively). All five measurements were unable to predict a composite of adverse neonatal outcome or need for maternal cesarean delivery. Adjustment of the growth velocities for gestational age at anatomy scan or 3rd trimester growth scan did not change these results. Conclusion AC and EFW growth velocities do not appear to improve the prediction of LGA infants when compared to using the third trimester Hadlock EFW.

Objective Growth velocities derived from fetal biometrics have been proposed to improve prediction of small for gestational age (SGA) neonates. We sought to determine if ultrasound growth velocities for abdominal circumference (AC) and estimated fetal weight (EFW) improve the prediction of SGA infants when compared to using EFW alone. Study design This is a secondary analysis from a prospective study of women referred for growth ultrasounds during the third trimester. Growth velocities for AC and EFW were derived from the difference in Z-scores between measurements at the anatomy survey (18–22 weeks gestation) and later growth ultrasound (26–36 weeks gestation). Change in AC and EFW growth velocities <10th percentile were compared with prenatally suspected SGA from Hadlock EFW <10th percentile for prediction of SGA neonates. The primary outcome was defined as the sensitivity and specificity of the growth velocities and Hadlock EFW in predicting SGA neonates. Logistic regression modeling was used to determine if the growth velocities improved prediction of neonatal SGA. Area under the ROC curves (AUC) were determined and compared. Results Of 612 singleton pregnancies meeting inclusion criteria, 68 (11.1%) resulted in SGA neonates. Hadlock EFW <10th percentile had higher sensitivity and specificity when compared to AC growth velocity and EFW growth velocity. Only AC growth velocity and Hadlock EFW had significant odds ratios for association with neonatal SGA. The AUC were 0.54, 0.53, and 0.61 using AC growth velocity, EFW growth velocity, and Hadlock EFW, respectively. The AUC did not significantly improve when the growth velocities were combined with Hadlock EFW (0.63). Adjustment of Z-scores for gestational age at anatomy scan or third trimester growth scan did not significantly change these results (AUC = 0.69). Conclusion EFW determined by Hadlock formula has the highest predictive value in detecting SGA neonates when compared to both AC and EFW growth velocities.

ObjectiveTo investigate whether fetuses with accelerated third trimester growth velocity are at increased risk of shoulder dystocia, even when they are not large-for-gestational-age (LGA; estimated fetal weight (EFW) >95th centile).MethodsFetal growth velocity and birth outcome data were prospectively collected from 347 nulliparous women. Each had blinded ultrasound biometry performed at 28 and 36 weeks’ gestation. Change in EFW and abdominal circumference (AC) centiles between 28–36 weeks were calculated, standardised over exactly eight weeks. We examined the odds of shoulder dystocia with increasing EFW and AC growth velocities among women with 36-week EFW ≤95th centile (non-LGA), who went on to have a vaginal birth. We then examined the relative risk (RR) of shoulder dystocia in cases of accelerated EFW and AC growth velocities (>30 centiles gained). Finally, we compared the predictive performances of accelerated fetal growth velocities to 36-week EFW >95th centile for shoulder dystocia among the cohort planned for vaginal birth.ResultsOf the 226 participants who had EFW ≤95th centile at 36-week ultrasound and birthed vaginally, six (2.7%) had shoulder dystocia. For each one centile increase in EFW between 28–36 weeks, the odds of shoulder dystocia increased by 8% (odds ratio (OR [95% Confidence Interval (CI)]) = 1.08 [1.04–1.12], p<0.001). For each one centile increase in AC between 28–36 weeks, the odds of shoulder dystocia increased by 9% (OR[95%CI] = 1.09 [1.05–1.12], p<0.001). When compared to the rest of the cohort with normal growth velocity, accelerated EFW and AC velocities were associated with increased relative risks of shoulder dystocia (RR[95%CI] = 7.3 [1.9–20.6], p = 0.03 and 4.8 [1.7–9.4], p = 0.02 respectively). Accelerated EFW or AC velocities predicted shoulder dystocia with higher sensitivity and positive predictive value than 36-week EFW >95th centile.ConclusionsAccelerated fetal growth velocities between 28–36 weeks’ gestation are associated with increased risk of shoulder dystocia, and may predict shoulder dystocia risk better than the commonly used threshold of 36-week EFW >95th centile.

To investigate whether fetuses with accelerated third trimester growth velocity are at increased risk of shoulder dystocia, even when they are not large-for-gestational-age (LGA; estimated fetal weight (EFW) >95th centile). Fetal growth velocity and birth outcome data were prospectively collected from 347 nulliparous women. Each had blinded ultrasound biometry performed at 28 and 36 weeks' gestation. Change in EFW and abdominal circumference (AC) centiles between 28-36 weeks were calculated, standardised over exactly eight weeks. We examined the odds of shoulder dystocia with increasing EFW and AC growth velocities among women with 36-week EFW ≤95th centile (non-LGA), who went on to have a vaginal birth. We then examined the relative risk (RR) of shoulder dystocia in cases of accelerated EFW and AC growth velocities (>30 centiles gained). Finally, we compared the predictive performances of accelerated fetal growth velocities to 36-week EFW >95th centile for shoulder dystocia among the cohort planned for vaginal birth. Of the 226 participants who had EFW ≤95th centile at 36-week ultrasound and birthed vaginally, six (2.7%) had shoulder dystocia. For each one centile increase in EFW between 28-36 weeks, the odds of shoulder dystocia increased by 8% (odds ratio (OR [95% Confidence Interval (CI)]) = 1.08 [1.04-1.12], p<0.001). For each one centile increase in AC between 28-36 weeks, the odds of shoulder dystocia increased by 9% (OR[95%CI] = 1.09 [1.05-1.12], p<0.001). When compared to the rest of the cohort with normal growth velocity, accelerated EFW and AC velocities were associated with increased relative risks of shoulder dystocia (RR[95%CI] = 7.3 [1.9-20.6], p = 0.03 and 4.8 [1.7-9.4], p = 0.02 respectively). Accelerated EFW or AC velocities predicted shoulder dystocia with higher sensitivity and positive predictive value than 36-week EFW >95th centile. Accelerated fetal growth velocities between 28-36 weeks' gestation are associated with increased risk of shoulder dystocia, and may predict shoulder dystocia risk better than the commonly used threshold of 36-week EFW >95th centile.

BackgroundFetal growth velocity standards have yet to be established for the Chinese population. This study aimed to establish such standards suitable for the Chinese population.MethodsWe performed a multicenter, population–based longitudinal cohort study including 9075 low–risk singleton pregnant women. Data were collected from the clinical records of 24 hospitals in 18 provinces of China. Demographic characteristics, reproductive history, fetal ultrasound measurements, and perinatal outcome data were collected. The fetal ultrasound measurements included biparietal diameter (BPD), abdominal circumference (AC), head circumference (HC), and femur diaphysis length (FDL). We used linear mixed models with cubic splines to model the trajectory of four ultrasound parameters and estimate fetal weight. Fetal growth velocity was determined by calculating the first derivative of fetal size curves. We also used logistic regression to estimate the association between fetal growth velocities in the bottom 10th percentile and adverse perinatal outcomes.ResultsFetal growth velocity was not consistent over time or among individuals. The estimated fetal weight (EFW) steadily increased beginning at 12 gestational weeks and peaked at 35 gestational weeks. The maximum velocity was 211.71 g/week, and there was a steady decrease in velocity from 35 to 40 gestational weeks. The four ultrasound measurements increased in the early second trimester; BPD and HC peaked at 13 gestational weeks, AC at 14 gestational weeks, and FDL at 15 gestational weeks. BPD and HC also increased from 19 to 24 and 19 to 21 gestational weeks, respectively. EFW velocity in the bottom 10th percentile indicated higher risks of neonatal complications (odds ratio [OR] = 2.23, 95% confidence interval [CI]: 1.79–2.78) and preterm birth < 37 weeks (OR = 3.68, 95% CI: 2.64–5.14). Sensitivity analyses showed that EFW velocity in the bottom 10th percentile was significantly associated with more adverse pregnancy outcomes for appropriate–for–gestational age neonates.ConclusionsWe established fetal growth velocity curves for the Chinese population based on real–world clinical data. Our findings demonstrated that Chinese fetal growth patterns are somewhat different from those of other populations. Fetal growth velocity could provide more information to understand the risk of adverse perinatal outcomes, especially for appropriate–for–gestational age neonates.

To assess the additive value of fetal growth velocity between 32 and 36 weeks' gestation to the performance of ultrasonographic estimated fetal weight (EFW) at 35 + 0 to 36 + 6 weeks' gestation for prediction of delivery of a small-for-gestational-age (SGA) neonate and adverse perinatal outcome. This was a prospective study of 14 497 singleton pregnancies undergoing routine ultrasound examination at 30 + 0 to 34 + 6 and at 35 + 0 to 36 + 6 weeks' gestation. Multivariable logistic regression analysis was used to determine whether addition of growth velocity, defined as the difference in EFW Z-score or abdominal circumference (AC) Z-score between the early and late third-trimester scans divided by the time interval between the scans, improved the performance of EFW Z-score at 35 + 0 to 36 + 6 weeks in the prediction of, first, delivery of a SGA neonate with birth weight < 10th and < 3rd percentiles within 2 weeks and at any stage after assessment and, second, a composite of adverse perinatal outcome, defined as stillbirth, neonatal death or admission to the neonatal unit for ≥ 48 h. Multivariable logistic regression analysis demonstrated that significant contributors to the prediction of a SGA neonate were EFW Z-score at 35 + 0 to 36 + 6 weeks' gestation, fetal growth velocity, by either AC Z-score or EFW Z-score, and maternal risk factors. The area under the receiver-operating characteristics curve (AUC) and detection rate (DR), at a 10% screen-positive rate, for prediction of a SGA neonate < 10th percentile born within 2 weeks after assessment achieved by EFW Z-score at 35 + 0 to 36 + 6 weeks (AUC, 0.938 (95% CI, 0.928-0.947); DR, 80.7% (95% CI, 77.6-83.9%)) were not significantly improved by addition of EFW growth velocity and maternal risk factors (AUC, 0.941 (95% CI, 0.932-0.950); P = 0.061; DR, 82.5% (95% CI, 79.4-85.3%)). Similar results were obtained when growth velocity was defined by AC rather than EFW. Similarly, there was no significant improvement in the AUC and DR, at a 10% screen-positive rate, for prediction of a SGA neonate < 10th percentile born at any stage after assessment or a SGA neonate < 3rd percentile born within 2 weeks or at any stage after assessment, achieved by EFW Z-score at 35 + 0 to 36 + 6 weeks by addition of maternal factors and either EFW growth velocity or AC growth velocity. Multivariable logistic regression analysis demonstrated that the only significant contributor to adverse perinatal outcome was maternal risk factors. Multivariable logistic regression analysis in the group with EFW < 10th percentile demonstrated that significant contribution to prediction of delivery of a neonate with birth weight < 10th and < 3rd percentiles and adverse perinatal outcome was provided by EFW Z-score at 35 + 0 to 36 + 6 weeks, but not by AC growth velocity < 1st decile. The predictive performance of EFW at 35 + 0 to 36 + 6 weeks' gestation for delivery of a SGA neonate and adverse perinatal outcome is not improved by addition of estimated growth velocity between 32 and 36 weeks' gestation. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

We aimed to create specific growth velocity reference charts for monochorionic (MC) twin pregnancies and provide additional information for assessing fetal growth in MC twins. This retrospective study collected data from uncomplicated MC twins with serial ultrasound parameters. The four ultrasound parameters, including biparietal diameter, femur length, head circumference, and abdominal circumference, were used to calculate the estimated fetal weight (EFW). Multilevel linear regression models were applied to fit growth velocity charts for each biometric parameter and EFW. Analysis of variance was used to examine differences in birthweight by whether EFW velocity and EFW values were <10th or ≥10th percentiles. The final analysis encompassed a total of 5956 ultrasound examinations conducted on 487 MC twins. The growth velocity of four biparietal diameters exhibited a gradual decrease in a nearly linear fashion progressing from 18 to 37 gestational weeks. The EFW velocity increased steadily from 18 to 36 gestational weeks, reaching a peak of 178.2 g/week, and then the velocity gradually decreased until delivery. At 32 weeks for illustration, the lightest birth weight was observed when both EFW and EFW velocity were <10th percentile (1899 g). The study also found that birth weight was higher when EFW velocity was ≥10th percentile compared with <10th percentile, regardless of EFW being below or above the 10th percentile (2263 and 1906 g, respectively; P < 0.001). We developed specific growth velocity reference charts for MC twins, which could provide a valuable reference point for a more precise evaluation of fetal growth in MC twins. Preliminary findings indicate that the inclusion of fetal growth velocity in monitoring fetal growth provides additional information beyond EFW alone.