Performance of third-trimester ultrasound for prediction of small-for-gestational-age neonates and evaluation of contingency screening policies

The role of the PLGF in the prediction of the outcome in pregnancies with a small for gestational age fetus

PURPOSE

To explore the value of measuring maternal serum PLGF in the prediction of the outcome of small for gestational age fetuses (SGA).

METHODS

Singleton pregnancies referred with suspicion of SGA in the third trimester were included if they had: no indication for nor signs of imminent delivery, fetal abdominal circumference (AC) at or below the 10th centile and/or estimated fetal weight (EFW) at or below the 10th centile and/or umbilical artery pulsatility index (Umb-PI) at or above the 90th centile for gestation. Women with pre-eclampsia at presentation were excluded. Maternal blood was drawn at the first (index) visit and analyzed retrospectively.

RESULTS

Fifty-one fetuses were examined. Multiple regression analysis showed that family history of microsomia, index EFW and PLGF were significant predictors of the birthweight centile; index femur length centile and PLGF were significant predictors of pre-eclampsia; PLGF and index systolic blood pressure were significant predictors of iatrogenic preterm delivery < 37 weeks, whereas PLGF and index EFW were significant predictors of birthweight ≤ 5th centile and admission to the neonatal intensive care unit. For all outcomes, the addition of maternal-fetal parameters did not improve the prediction compared to PLGF alone. Using a cutoff of 0.3 MoM for PLGF would identify 94.1% of the pregnancies with iatrogenic preterm delivery and/or intra-uterine death and all of the cases that developed pre-eclampsia, for a screen positive rate of 54.9%. Women with PLGF ≤ 0.3 MoM had a poor fetal/maternal outcome (iatrogenic preterm delivery, pre-eclampsia, intra-uterine death) in 61.5% of cases.

CONCLUSION

In pregnancies complicated by SGA, PLGF identifies a very high-risk group that may benefit from intense surveillance.

Personalized Model to Predict Small for Gestational Age at Delivery Using Fetal Biometrics, Maternal Characteristics, and Pregnancy Biomarkers: A Retrospective Cohort Study of Births Assisted at a Spanish Hospital

Small for gestational age (SGA) is defined as a newborn with a birth weight for gestational age < 10th percentile. Routine third-trimester ultrasound screening for fetal growth assessment has detection rates (DR) from 50 to 80%. For this reason, the addition of other markers is being studied, such as maternal characteristics, biochemical values, and biophysical models, in order to create personalized combinations that can increase the predictive capacity of the ultrasound. With this purpose, this retrospective cohort study of 12,912 cases aims to compare the potential value of third-trimester screening, based on estimated weight percentile (EPW), by universal ultrasound at 35−37 weeks of gestation, with a combined model integrating maternal characteristics and biochemical markers (PAPP-A and β-HCG) for the prediction of SGA newborns. We observed that DR improved from 58.9% with the EW alone to 63.5% with the predictive model. Moreover, the AUC for the multivariate model was 0.882 (0.873−0.891 95% C.I.), showing a statistically significant difference with EPW alone (AUC 0.864 (95% C.I.: 0.854−0.873)). Although the improvements were modest, contingent detection models appear to be more sensitive than third-trimester ultrasound alone at predicting SGA at delivery.

Prenatal prediction of very late onset small-for-gestational age newborns in low-risk pregnancies

OBJECTIVE

To find a multivariate model for predicting small-for-gestational age newborns at 36 weeks' gestation by using clinical, biochemical and ultrasound measurements.

MATERIALS AND METHODS

We evaluated 564 low-risk pregnant women and recorded maternal age, maternal body mass index, maternal mean blood pressure, soluble fms-like tyrosine kinase-1 (multiples of the median), placental growth factor (multiples of the median), soluble fms-like tyrosine kinase-1/placental growth factor ratio, estimated fetal weight centile and mean uterine artery pulsatility index at 36 weeks. Binary logistic regression was used. Statistical significance was set at 95% level (p < 0.05).

RESULTS

We found three multivariate models showing relatively small differences in predictive capability. Model 1 only included estimated fetal weight centiles (area under the curve [AUC] 0.86; R2 = 0.42; p < 0.0001), Model 2 estimated fetal weight centiles and placental growth factor (multiples of the median) (AUC 0.87; R2 = 0.44; p < 0.0001) and Model 3 estimated fetal weight centiles, placental growth factor (multiples of the median) and mean uterine artery pulsatility index (AUC 0.88; R2 = 0.45; p < 0.0001).

CONCLUSION

Small-for-gestational age at delivery may be predicted by using a multivariate formula. The inclusion of parameters other than estimated fetal weight centile at 36 weeks' gestation modestly improves the predictive capability of the model. Clinical decisions should consider whether or not these slight differences deserve a change in current strategies.

Third trimester ultrasound. A long-standing debate

Third trimester ultrasound has long been in obstetrics a topic of debate. This issue is framed in a historical debate on the effectiveness of routine obstetrical ultrasound and two opposing trends originated in America and Europe, respectively. Primary function of this ultrasound has been to detect fetal growth restriction, but no study has shown evidence of improving perinatal outcomes. Other secondary functions are detection of fetal abnormalities or evaluation of fetal presentation, and they have also shown no evidence. Despite the continuous appearance of works in this regard, health policies of both american and european trends have not been modified. Future seems to show a prolongation of the stalemate. Those health systems with a universal third trimester policy should propose an optimization of the test, in order to improve the benefits and obtain data for future studies that could resolve this longstanding debate.

Prevalence of abnormal umbilical arterial flow on Doppler ultrasound in low-risk and unselected pregnant women: a systematic review

Background

While Doppler ultrasound screening is beneficial for women with high-risk pregnancies, there is insufficient evidence on its benefits and harms in low- and unselected-risk pregnancies. This may be related to fewer events of abnormal Doppler flow, however the prevalence of absent or reversed end diastolic flow (AEDF or REDF) in such women is unknown. In this systematic review, we aimed to synthesise available data on the prevalence of AEDF or REDF.

Methods

We searched PubMed, Embase, CINAHL, CENTRAL and Global Index Medicus with no date, setting or language restrictions. All randomized or non-randomized studies reporting AEDF or REDF prevalence based on Doppler assessment of umbilical arterial flow > 20 weeks’ gestation were eligible. Two authors assessed eligibility and extracted data on primary (AEDF and REDF) and secondary (fetal, perinatal, and neonatal mortality, caesarean section) outcomes, with results presented descriptively.

Results

A total of 42 studies (18,282 women) were included. Thirty-six studies reported zero AEDF or REDF cases. However, 55 AEDF or REDF cases were identified from just six studies (prevalence 0.08% to 2.13%). Four of these studies were in unselected-risk women and five were conducted in high-income countries. There was limited evidence from low- and middle-income countries.

Conclusions

Evidence from largely observational studies in higher-income countries suggests that AEDF and REDF are rare among low- and unselected-risk pregnant women. There are insufficient data from lower-income countries and further research is required.

Diagnosing Small for Gestational Age during second trimester routine screening: Early sonographic clues

OBJECTIVE

Small for gestational age (SGA) is generally defined as birth weight being at or below the 10th percentile. Children with SGA have a higher risk for complications. There is a need for early predictors, as the accurate diagnosis rate is only 50%. In the current study, we aimed to evaluate diagnostic performance of ultrasound (US)/color Doppler ultrasound (CDUS) parameters (umbilical vein-UV, right portal vein-RPV diameter/flow rate, and portal sinus-PS diameter) examined at 20-22 gestational week as SGA diagnostic factors.

MATERIALS AND METHODS

93 pregnant included (32 SGA, 61 controls). All the US examinations were performed between 20 and 22 weeks of gestation. UV, RPV, and PS measurements were performed by using the same image acquired for abdominal circumference measurement. A fetus with as estimated fetal weight (EFW) below the 10th percentile was diagnosed as SGA and SGA at birth was defined as having a birth weight under the 10th percentile.

RESULTS

Pregnant women in the SGA group were significantly older (30 ± 4.8 vs. 26.6 ± 5.4 years, p < 0.01). Median UV diameter was significantly lower in SGA group (2.20 vs. 2.40 mm, p = 0.001). Median RPV diameter was significantly lower in SGA group (2 vs. 2.10 mm, p = 0.018). Median PS diameter was significantly lower in SGA group (2 vs. 20.10 mm, p = 0.008).

CONCLUSION

UV, RPV, and PS diameters can be earlier predictors for SGA diagnosis. Routinely evaluation of these parameters during second trimester screening can increase SGA diagnosis rates and serve for early diagnose.

Biochemical tests of placental function versus ultrasound assessment of fetal size for stillbirth and small-for-gestational-age infants

BACKGROUND

Stillbirth affects 2.6 million pregnancies worldwide each year. Whilst the majority of cases occur in low- and middle-income countries, stillbirth remains an important clinical issue for high-income countries (HICs) - with both the UK and the USA reporting rates above the mean for HICs. In HICs, the most frequently reported association with stillbirth is placental dysfunction. Placental dysfunction may be evident clinically as fetal growth restriction (FGR) and small-for-dates infants. It can be caused by placental abruption or hypertensive disorders of pregnancy and many other disorders and factorsPlacental abnormalities are noted in 11% to 65% of stillbirths. Identification of FGA is difficult in utero. Small-for-gestational age (SGA), as assessed after birth, is the most commonly used surrogate measure for this outcome. The degree of SGA is associated with the likelihood of FGR; 30% of infants with a birthweight < 10th centile are thought to be FGR, while 70% of infants with a birthweight < 3rd centile are thought to be FGR. Critically, SGA is the most significant antenatal risk factor for a stillborn infant. Correct identification of SGA infants is associated with a reduction in the perinatal mortality rate. However, currently used tests, such as measurement of symphysis-fundal height, have a low reported sensitivity and specificity for the identification of SGA infants.

OBJECTIVES

The primary objective was to assess and compare the diagnostic accuracy of ultrasound assessment of fetal growth by estimated fetal weight (EFW) and placental biomarkers alone and in any combination used after 24 weeks of pregnancy in the identification of placental dysfunction as evidenced by either stillbirth, or birth of a SGA infant. Secondary objectives were to investigate the effect of clinical and methodological factors on test performance.

SEARCH METHODS

We developed full search strategies with no language or date restrictions. The following sources were searched: MEDLINE, MEDLINE In Process and Embase via Ovid, Cochrane (Wiley) CENTRAL, Science Citation Index (Web of Science), CINAHL (EBSCO) with search strategies adapted for each database as required; ISRCTN Registry, UK Clinical Trials Gateway, WHO International Clinical Trials Portal and ClinicalTrials.gov for ongoing studies; specialist abstract and conference proceeding resources (British Library's ZETOC and Web of Science Conference Proceedings Citation Index). Search last conducted in Ocober 2016.

SELECTION CRITERIA

We included studies of pregnant women of any age with a gestation of at least 24 weeks if relevant outcomes of pregnancy (live birth/stillbirth; SGA infant) were assessed. Studies were included irrespective of whether pregnant women were deemed to be low or high risk for complications or were of mixed populations (low and high risk). Pregnancies complicated by fetal abnormalities and multi-fetal pregnancies were excluded as they have a higher risk of stillbirth from non-placental causes. With regard to biochemical tests, we included assays performed using any technique and at any threshold used to determine test positivity.

DATA COLLECTION AND ANALYSIS

We extracted the numbers of true positive, false positive, false negative, and true negative test results from each study. We assessed risk of bias and applicability using the QUADAS-2 tool. Meta-analyses were performed using the hierarchical summary ROC model to estimate and compare test accuracy.

MAIN RESULTS

We included 91 studies that evaluated seven tests - blood tests for human placental lactogen (hPL), oestriol, placental growth factor (PlGF) and uric acid, ultrasound EFW and placental grading and urinary oestriol - in a total of 175,426 pregnant women, in which 15,471 pregnancies ended in the birth of a small baby and 740 pregnancies which ended in stillbirth. The quality of included studies was variable with most domains at low risk of bias although 59% of studies were deemed to be of unclear risk of bias for the reference standard domain. Fifty-three per cent of studies were of high concern for applicability due to inclusion of only high- or low-risk women.Using all available data for SGA (86 studies; 159,490 pregnancies involving 15,471 SGA infants), there was evidence of a difference in accuracy (P < 0.0001) between the seven tests for detecting pregnancies that are SGA at birth. Ultrasound EFW was the most accurate test for detecting SGA at birth with a diagnostic odds ratio (DOR) of 21.3 (95% CI 13.1 to 34.6); hPL was the most accurate biochemical test with a DOR of 4.78 (95% CI 3.21 to 7.13). In a hypothetical cohort of 1000 pregnant women, at the median specificity of 0.88 and median prevalence of 19%, EFW, hPL, oestriol, urinary oestriol, uric acid, PlGF and placental grading will miss 50 (95% CI 32 to 68), 116 (97 to 133), 124 (108 to 137), 127 (95 to 152), 139 (118 to 154), 144 (118 to 161), and 144 (122 to 161) SGA infants, respectively. For the detection of pregnancies ending in stillbirth (21 studies; 100,687 pregnancies involving 740 stillbirths), in an indirect comparison of the four biochemical tests, PlGF was the most accurate test with a DOR of 49.2 (95% CI 12.7 to 191). In a hypothetical cohort of 1000 pregnant women, at the median specificity of 0.78 and median prevalence of 1.7%, PlGF, hPL, urinary oestriol and uric acid will miss 2 (95% CI 0 to 4), 4 (2 to 8), 6 (6 to 7) and 8 (3 to 13) stillbirths, respectively. No studies assessed the accuracy of ultrasound EFW for detection of pregnancy ending in stillbirth.

AUTHORS' CONCLUSIONS

Biochemical markers of placental dysfunction used alone have insufficient accuracy to identify pregnancies ending in SGA or stillbirth. Studies combining U and placental biomarkers are needed to determine whether this approach improves diagnostic accuracy over the use of ultrasound estimation of fetal size or biochemical markers of placental dysfunction used alone. Many of the studies included in this review were carried out between 1974 and 2016. Studies of placental substances were mostly carried out before 1991 and after 2013; earlier studies may not reflect developments in test technology.

Diagnostic performance of third-trimester ultrasound for the prediction of late-onset fetal growth restriction: a systematic review and meta-analysis

OBJECTIVE

The objective of the study was to establish the diagnostic performance of ultrasound screening for predicting late smallness for gestational age and/or fetal growth restriction.

DATA SOURCES

A systematic search was performed to identify relevant studies published since 2007 in English, Spanish, French, Italian, or German, using the databases PubMed, ISI Web of Science, and SCOPUS.

STUDY ELIGIBILITY CRITERIA

We used rrospective and retrospective cohort studies in low-risk or nonselected singleton pregnancies with screening ultrasound performed at ≥32 weeks of gestation.

STUDY APPRAISAL AND SYNTHESIS METHODS

The estimated fetal weight and fetal abdominal circumference were assessed as index tests for the prediction of birthweight <10th (i.e. smallness for gestational age), less than the fifth, and less than the third centile and fetal growth restriction (estimated fetal weight less than the third or estimated fetal weight <10th plus Doppler signs). Quality of the included studies was independently assessed by 2 reviewers, using the Quality Assessment of Diagnostic Accuracy Studies-2 tool. For the meta-analysis, hierarchical summary receiver-operating characteristic curves were constructed, and quantitative data synthesis was performed using random-effects models. The sensitivity of the abdominal circumference <10th centile and estimated fetal weight <10th centile for a fixed 10% false-positive rate was derived from the corresponding hierarchical summary receiver-operating characteristic curves. Heterogeneity between studies was visually assessed using Galbraith plots, and publication bias was assessed by funnel plots and quantified by Deeks' method.

RESULTS

A total of 21 studies were included. Observed pooled sensitivities of abdominal circumference and estimated fetal weight <10th centile for birthweight <10th centile were 35% (95% confidence interval, 20-52%) and 38% (95% confidence interval, 31-46%), respectively. Observed pooled specificities were 97% (95% confidence interval, 95-98%) and 95% (95% confidence interval, 93-97%), respectively. Modeled sensitivities of abdominal circumference and estimated fetal weight <10th centile for 10% false-positive rate were 78% (95% confidence interval, 61-95%) and 54% (95% confidence interval, 46-52%), respectively. The sensitivity of estimated fetal weight <10th centile was better when aimed to fetal growth restriction than to smallness for gestational age. Meta-regression analysis showed a significant increase in sensitivity when ultrasound evaluation was performed later in pregnancy (P = .001).

CONCLUSION

Third-trimester abdominal circumference and estimated fetal weight perform similar in predicting smallness for gestational age. However, for a fixed 10% false-positive rate extrapolated sensitivity is higher for abdominal circumference. There is evidence of better performance when the scan is performed near term and when fetal growth restriction is the targeted condition.

Prediction of small for gestational age neonates: screening by maternal factors, fetal biometry, and biomarkers at 35-37 weeks' gestation

BACKGROUND

Small for gestational age (SGA) neonates are at increased risk for perinatal mortality and morbidity; however, the risks can be substantially reduced if the condition is identified prenatally, because in such cases close monitoring and appropriate timing of delivery and prompt neonatal care can be undertaken. The traditional approach of identifying pregnancies with SGA fetuses is maternal abdominal palpation and serial measurements of symphysial-fundal height, but the detection rate of this approach is less than 30%. A higher performance of screening for SGA is achieved by sonographic fetal biometry during the third trimester; screening at 30-34 weeks' gestation identifies about 80% of SGA neonates delivering preterm but only 50% of those delivering at term, at a screen-positive rate of 10%. There is some evidence that routine ultrasound examination at 36 weeks' gestation is more effective than that at 32 weeks in predicting birth of SGA neonates.

OBJECTIVE

To investigate the potential value of maternal characteristics and medical history, sonographically estimated fetal weight (EFW) and biomarkers of impaired placentation at 35⁺⁰- 36⁺⁶ weeks' gestation in the prediction of delivery of SGA neonates.

MATERIALS AND METHODS

A dataset of 19,209 singleton pregnancies undergoing screening at 35⁺⁰-36⁺⁶ weeks' gestation was divided into a training set and a validation set. The training dataset was used to develop models from multivariable logistic regression analysis to determine whether the addition of uterine artery pulsatility index (UtA-PI), umbilical artery PI (UA-PI), fetal middle cerebral artery PI (MCA-PI), maternal serum placental growth factor (PlGF) and soluble fms-like tyrosine kinase-1 (sFLT) would improve the performance of maternal factors and EFW in the prediction of delivery of SGA neonates. The models were then tested in the validation dataset to assess performance of screening.

RESULTS

First, in the training dataset, in the SGA group, compared to those with birthweight in ≥10th percentile, the median multiple of the median (MoM) values of PlGF and MCA-PI were reduced, whereas UtA-PI, UA-PI, and sFLT were increased. Second, multivariable regression analysis demonstrated that in the prediction of SGA in <10th percentile there were significant contributions from maternal factors, EFW Z-score, UtA-PI MoM, MCA-PI MoM, and PlGF MoM. Third, in the validation dataset, prediction of 90% of SGA neonates delivering within 2 weeks of assessment was achieved by a screen-positive rate of 67% (95% confidence interval [CI], 64-70%) in screening by maternal factors, 23% (95% CI, 20-26%) by maternal factors, and EFW and 21% (95% CI, 19-24%) by the addition of biomarkers. Fourth, prediction of 90% of SGA neonates delivering at any stage after assessment was achieved by a screen-positive rate of 66% (95% CI, 65-67%) in screening by maternal factors, 32% (95% CI, 31-33%) by maternal factors and EFW and 30% (95% CI, 29-31%) by the addition of biomarkers.

CONCLUSION

The addition of biomarkers of impaired placentation only marginally improves the predictive performance for delivery of SGA neonates achieved by maternal factors and fetal biometry at 35⁺⁰-36⁺⁶ weeks' gestation.

Prediction of SGA at Birth by Using the Right Portal Vein Diameter Measurement at the 30-35-Week Scan

OBJECTIVE

This study sought to test the hypothesis that the measurement of the right portal vein (RPV) diameter on the transverse abdominal view at the 32-week ultrasound scan is small in fetuses with growth retardation and to validate the use of this measurement as a tool for detecting small for gestational age (SGA) at birth.

METHODS

This was a retrospective cohort study at a single centre. The study population comprised 326 consecutive pregnancies, including 29 SGA at delivery and 297 unaffected cases. Stored images of the transverse view of the abdomen, obtained at the routine third trimester scan, were used to assess the diameters of the umbilical vein, the portal sinus, and the RPV.

RESULTS

The portal sinus and RPV diameter were smaller compared with the reference group (P = 0.021 and P < 0.001, respectively). Using a 10th percentile cut-off, the detection rate for SGA at birth was 38% for the RPV diameter versus 45% for the estimated fetal weight. The false-positive rates were 9% versus 8%, respectively. Multiple regression analysis revealed that RPV below the 10th percentile remained an independent four-fold risk factor for SGA (odds ratio [OR] 5.05; 95% confidence interval [CI] 1.94-13.14). Further analysis revealed a higher prevalence of induction of labour for non-reassuring fetal well-being (P = 0.005), fetal acidemia (P = 0.028), and admission to a neonatal intensive care unit (NICU, P = 0.029) in the RPV ≤10th percentile group.

CONCLUSION

RPV below the 10th percentile could be a reliable third trimester ultrasound marker of a subnormal fetal environment. This study proposed a new and accessible approach for prediction of SGA.

Placental volume at 11 to 14 gestational weeks in pregnancies complicated with fetal growth restriction and preeclampsia

OBJECTIVE

The study aims to evaluate the predictive value of first trimester placental volume in pregnancies destined to develop fetal growth restriction (FGR) and preeclampsia (PE).

METHODS

Prospective observational study including placentas from 34 FGR, 12 PE, 15 GH (gestational hypertension) pregnancies, and 265 controls. Placental volume (PV) was obtained using VOCAL technique, and a z score was calculated (z-PV). The association of PV with other first trimester variables and maternal characteristics was assessed with Spearman's correlation.

RESULTS

PV increased exponentially with crown-rump length (CRL) and was unrelated to maternal factors (weight, age, parity, and smoking status) as well as first trimester uterine artery Doppler, free β-hCG, nuchal translucency, or fetal heart rate. However, PV was positively associated with maternal height, CRL, PAPP-A, and birth weight. z-PV was a strong predictor for FGR with abnormal fetal Dopplers (AUC = 0.9472, P < 0.001). z-PV provided moderate prediction of FGR with normal fetal Dopplers (AUC = 0.8396, P < 0.001), PE (AUC = 0.8312, P < 0.001), and GH (AUC = 0.7640, P < 0.001). The addition of maternal weight, PAPP-A, β-hCG, and uterine artery Doppler improved our models.

CONCLUSION

At 11 to 14 weeks, PV is an independent predictor of pregnancy complications related to placental insufficiency, and the predictive ability is greater for FGR pregnancies with abnormal fetal Dopplers.

Selective versus universal third trimester ultrasound: Time for a rethink? An audit of current practices at a metropolitan Sydney hospital

INTRODUCTION

Routine third-trimester ultrasound (T3US) is not recommended in evidence-based clinical guidelines despite occurring frequently. This study investigated the incidence, indication for, results and follow-up needs of T3US performed at a Sydney metropolitan teaching hospital.

METHODS

Audit of T3US amongst singleton pregnancies at St George Hospital, Sydney: retrospective review October-December 2012, prospective cohort with clinician survey February-April 2013. Data included are as follows: maternal demographics, aneuploidy screening results, T3US ordering patterns, results, follow-up management and pregnancy outcomes. Comparison of demographic characteristics and pregnancy outcomes was performed for women undergoing T3US vs. no T3US.

RESULTS

One thousand and thirty-five women (623 retrospective, 412 prospective) were included, of whom 560 (54%) received at least one T3US. Characteristics of retrospective and prospective cohorts were similar, so combined data are presented. Most initial T3USs were for valid indications (463 of 560; 83%), most frequently low-lying placenta at morphology (19%), reduced fundal height (10%) and to follow-up fetal concerns at morphology ultrasound (9%). One hundred and sixty-two out of 560 (29%) of initial T3US were not normal, predominantly related to accelerated or reduced fetal growth. Detection of SGA babies was significantly higher in the T3US group (32% SGA babies detected vs. 0% if no T3US, P < 0.001). However, overall detection rates remained low, with 5.2% and 3.0% of babies who had a T3US unexpectedly <10th and <3rd centile birthweight, respectively.

DISCUSSION/CONCLUSION

The majority of women received at least one, usually indicated, T3US in routine practice at our metropolitan Sydney hospital. This may impact obstetric care, resource allocation and patient well-being. Detection of small for gestational age fetuses was poor.

Placental exosomes profile in maternal and fetal circulation in intrauterine growth restriction - Liquid biopsies to monitoring fetal growth

INTRODUCTION

Placenta-derived exosomes may represent an additional pathway by which the placenta communicates with the maternal system to induce maternal vascular adaptations to pregnancy and it may be affected during Fetal growth restriction (FGR). The objective of this study was to quantify the concentration of total and placenta-derived exosomes in maternal and fetal circulation in small fetuses classified as FGR or small for gestational age (SGA).

METHODS

Prospective cohort study in singleton term gestations including 10 normally grown fetuses and 20 small fetuses, sub-classified into SGA and FGR accordingly to birth weight (BW) percentile and fetoplacental Doppler. Exosomes were isolated from maternal and fetal plasma and characterized by morphology, enrichment of exosomal proteins, and size distribution by electron microscopy, western blot, and nanoparticle tracking analysis, respectively. Total and specific placenta-derived exosomes were determined using quantum dots coupled with CD63^+ve and placental-type alkaline phosphatase (PLAP)^+ve antibodies, respectively.

RESULTS

Maternal concentrations of CD63^+ve and PLAP^+ve exosomes were similar between the groups (all p > 0.05). However, there was a significant positive correlation between the ratio of placental-derived to total exosomes (PLAP^+ve ratio) and BW percentile, [rho = 0.77 (95% CI: 0.57 to 0.89); p = 0.0001]. The contribution of placental exosomes to the total exosome concentration in maternal and fetal circulation showed a significant decrease among cases, with lower PLAP^+ve ratios in FGR compared to controls and SGA cases.

DISCUSSION

Quantification of placental exosomes in maternal plasma reflects fetal growth and it may be a useful indicator of placental function.

Prediction of fetal growth restriction using estimated fetal weight vs a combined screening model in the third trimester

OBJECTIVES

To compare the performance of third-trimester screening, based on estimated fetal weight centile (EFWc) vs a combined model including maternal baseline characteristics, fetoplacental ultrasound and maternal biochemical markers, for the prediction of small-for-gestational-age (SGA) neonates and late-onset fetal growth restriction (FGR).

METHODS

This was a nested case-control study within a prospective cohort of 1590 singleton gestations undergoing third-trimester (32 + 0 to 36 + 6 weeks' gestation) evaluation. Maternal baseline characteristics, mean arterial pressure, fetoplacental ultrasound and circulating biochemical markers (placental growth factor (PlGF), lipocalin-2, unconjugated estriol and inhibin A) were assessed in all women who subsequently delivered a SGA neonate (n = 175), defined as birth weight < 10^th centile according to customized standards, and in a control group (n = 875). Among SGA cases, those with birth weight < 3^rd centile and/or abnormal uterine artery pulsatility index (UtA-PI) and/or abnormal cerebroplacental ratio (CPR) were classified as FGR. Logistic regression predictive models were developed for SGA and FGR, and their performance was compared with that obtained using EFWc alone.

RESULTS

In SGA cases, EFWc, CPR Z-score and maternal serum concentrations of unconjugated estriol and PlGF were significantly lower, while mean UtA-PI Z-score and lipocalin-2 and inhibin A concentrations were significantly higher, compared with controls. Using EFWc alone, 52% (area under receiver-operating characteristics curve (AUC), 0.82 (95% CI, 0.77-0.85)) of SGA and 64% (AUC, 0.86 (95% CI, 0.81-0.91)) of FGR cases were predicted at a 10% false-positive rate. A combined screening model including a-priori risk (maternal characteristics), EFWc, UtA-PI, PlGF and estriol (with lipocalin-2 for SGA) achieved a detection rate of 61% (AUC, 0.86 (95% CI, 0.83-0.89)) for SGA cases and 77% (AUC, 0.92 (95% CI, 0.88-0.95)) for FGR. The combined model for the prediction of SGA and FGR performed significantly better than did using EFWc alone (P < 0.001 and P = 0.002, respectively).

CONCLUSIONS

A multivariable integrative model of maternal characteristics, fetoplacental ultrasound and maternal biochemical markers modestly improved the detection of SGA and FGR cases at 32-36 weeks' gestation when compared with screening based on EFWc alone. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Small-for-gestational-age babies of low-risk term pregnancies: does antenatal detection matter?

OBJECTIVES

To compare delivery route and admission rate to neonatal intensive care unit between small- and appropriate-for-gestational-age babies among low-risk term pregnancies.

METHODS

A retrospective study was conducted using the database of deliveries in 2014 at a tertiary hospital. Babies delivered at ≥37 weeks with birthweight <10th centile were considered small-for-gestational-age (SGA) and >90th centile were considered large-for-gestational-age. Fetal weight estimation at 30-33 weeks ultrasound <10th centile was considered antenatal detection of SGA.

RESULTS

Among 1429 low-risk term pregnancies, 11% (151/1429) had SGA babies and 5% (75/1429) had large-for-gestational-age. SGA babies were associated with higher rate of cesarean sections for nonreassuring fetal status (18/151 versus 8/1202, p < .001) and higher rate of admissions to neonatal intensive care unit (16/151 versus 18/1202, p < .001) compared to appropriate-for-gestational-age. Within SGA group, antepartum detected fetuses were associated with lower rate of operative deliveries for nonreassuring fetal status than undetected group (3/31 versus 39/120, p = .01) Conclusions: In our series, women with SGA term babies were associated with more adverse obstetric and neonatal outcome than appropriate-for-gestational age, especially among those undetected prenatally.

An integrated approach to fetal growth restriction

Fetal growth restriction (FGR) is among the most common complications of pregnancy. FGR is associated with placental insufficiency and poor perinatal outcomes. Clinical management is challenging because of variability in clinical presentation. Fetal smallness (estimated fetal weight <10th centile for gestational age) remains the best clinical surrogate for FGR. However, it is commonly accepted that not all forms of fetal smallness represent true FGR. In a significant subset of small fetuses, there is no evidence of placental involvement, perinatal outcomes are nearly normal, and they are clinically referred to as "only" small for gestational age (SGA). Doppler may improve the clinical management of FGR; however, the need to use several parameters sometimes results in a number of combinations that may render interpretation challenging when translating into clinical decisions. We propose that the management of FGR can be simplified using a sequential approach based on three steps: (1) identification of the "small fetus," (2) differentiation between FGR and SGA, and (3) timing of delivery according to a protocol based on stages of fetal deterioration.

Patterns of Fetal Growth Based on Ultrasound Measurement and its Relationship with Small for Gestational Age at Birth in Rural Vietnam

BACKGROUND

Small for gestational age (SGA) is a global health problem. Identifying the timing of fetal growth faltering is critical for developing preventive interventions. We aim to describe patterns of fetal growth and to predict SGA at birth using fetal ultrasound measurements.

METHODS

We studied 1412 pregnant women enrolled in a randomised-controlled trial evaluating maternal micronutrient supplementation in Thai Nguyen province, Vietnam. Ultrasound examinations included biparietal diameter (BPD), head circumference (HC) and abdominal circumference (AC), and femur length (FL). Measures were assessed using the new international fetal growth standards (INTERGROWTH-21st Project). Generalised linear mixed logit regression models were used to examine the association between ultrasound measures and SGA at birth.

RESULTS

Overall fetal growth restriction began in early pregnancy and continued through delivery, but the timing of growth faltering varied by measure: it began by 20 weeks for HC, BPD and AC, earlier as compared to FL growth that started >30 weeks. SGA infants had significantly lower mean fetal growth parameters as early as 14 weeks. Ultrasound measures below the 10th percentile were associated with a two to four times higher risk of SGA at birth compared to fetuses greater than the 50th percentile, with the largest odds ratios for AC (OR 3.9, 95% confidence interval (CI) 2.7, 5.7).

CONCLUSIONS

Fetal growth faltering by ultrasound begins in early gestation among rural Vietnamese populations; these patterns clearly identified those to be born SGA. Efforts to prevent fetal growth faltering must begin early in pregnancy and perhaps even before pregnancy.

Associations of maternal personal exposure to air pollution on fetal weight and fetoplacental Doppler: A prospective cohort study

We determined the influence of maternal air pollution exposure during each trimester of pregnancy on fetal and birth weight and fetoplacental hemodynamics. In total, 366 women with singleton pregnancies were prospectively followed in the city of São Paulo, Brazil. Nitrogen dioxide (NO2) and ozone (O3) were measured during each trimester using passive personal samplers. We evaluated fetal weight and Doppler velocimetry data from the umbilical, middle cerebral, and uterine arteries in the 3rd trimester, and birth weight. Multivariate analysis was performed, controlling for known determinants of fetal weight. Exposure to higher levels of O3 during the 2nd trimester was associated with higher umbilical artery pulsatility indices (PIs) [p=0.013; beta=0.017: standard error (SE)=0.007]. Exposure to higher levels of O3 during the 3rd trimester was associated with lower umbilical artery PIs (p=0.011; beta=-0.021; SE=0.008). Our results suggest that in the environment of São Paulo, O3 may affects placental vascular resistance.

Contingent versus routine third-trimester screening for late fetal growth restriction

OBJECTIVE

To evaluate the use of third-trimester ultrasound screening for late fetal growth restriction (FGR) on a contingent basis, according to risk accrued in the second trimester, in an unselected population.

METHODS

Maternal characteristics, fetal biometry and second-trimester uterine artery (UtA) Doppler were included in logistic regression analysis to estimate risk for late FGR (birth weight < 3(rd) percentile, or 3(rd) -10(th) percentile plus abnormal cerebroplacental ratio or UtA Doppler, with delivery ≥ 34 weeks). Based on the second-trimester risk, strategies for performing contingent third-trimester ultrasound examinations in 10%, 25% or 50% of the cohort were tested against a strategy of routine ultrasound scanning in the entire population at 32 + 0 to 33 + 6 weeks.

RESULTS

Models were constructed based on 1393 patients and validated in 1303 patients, including 73 (5.2%) and 82 late FGR (6.3%) cases, respectively. At the second-trimester scan, the a-posteriori second-trimester risk (a-posteriori first-trimester risk (baseline a-priori risk and mean arterial blood pressure) combined with second-trimester abdominal circumference and UtA Doppler) yielded an area under the receiver-operating characteristics curve (AUC) of 0.81 (95% CI, 0.74-0.87) (detection rate (DR), 43.1% for a 10% false-positive rate (FPR)). The combination of a-posteriori second-trimester risk plus third-trimester estimated fetal weight (full model) yielded an AUC of 0.92 (95% CI, 0.88-0.96) (DR, 74% for a 10% FPR). Subjecting 10%, 25% or 50% of the study population to third-trimester ultrasound, based on a-posteriori second-trimester risk, gave AUCs of 0.81 (95% CI, 0.75-0.88), 0.84 (95% CI, 0.78-0.91) and 0.89 (95% CI, 0.84-0.94), respectively. Only the 50% contingent model proved statistically equivalent to performing routine third-trimester ultrasound scans (AUC, 0.92 (95% CI, 0.88-0.96), P = 0.11).

CONCLUSION

A strategy of selecting 50% of the study population to undergo third-trimester ultrasound examination, based on accrued risk in the second trimester, proved equivalent to routine third-trimester ultrasound scanning in predicting late FGR.

Angiogenic Factors and Doppler Evaluation in Normally Growing Fetuses at Routine Third-Trimester Scan: Prediction of Subsequent Low Birth Weight

Objective: To evaluate in normally growing fetuses at routine 32-36 weeks scan the performance of maternal angiogenic factors, Doppler and ultrasound indices in predicting smallness for gestational age (SGA) at birth. Methods: A cohort of 1,000 singleton pregnancies with normal estimated fetal weight (EFW, ≥10th centile) at 32-36 weeks scan was included. At inclusion, Doppler indices (mean uterine artery pulsatility index [mUtA-PI], cerebroplacental ratio and normalized umbilical vein blood flow by EFW (ml/min/kg) were evaluated, and blood samples were collected and frozen. Nested in this cohort, maternal circulating placental growth factor (PlGF) and soluble fms-like tyrosine kinase-1 (sFlt-1) were assayed by enzyme-linked immunosorbent assay in all cases with a birth weight <10th centile by customized standards and in an equivalent number of controls (birth weight ≥10th centile). Results: 160 cases were included (80 SGA and 80 controls). EFW (2,128 vs. 2,279 g, p < 0.001), mUtA-PI z-values (-0.25 vs. -0.65, p = 0.034) and sFlt-1/PlGF ratio (11.10 vs. 6.74, p < 0.005) were lower in SGA. The combination of sFlt-1/PlGF ratio and EFW resulted in a 66.3% detection rate for subsequent SGA, with 20% of false-positives. Fetal Doppler indices were not predictive of SGA. Conclusions: In normally growing fetuses, maternal angiogenic factors add to ultrasound parameters in predicting subsequent SGA at birth. This supports further research to investigate composite scores in order to improve the definition and identification of fetal growth restriction.

Ultrasound screening for fetal growth restriction at 36 vs 32 weeks' gestation: a randomized trial (ROUTE)

OBJECTIVE

To compare the utility of routine third-trimester ultrasound examination at 36 weeks' gestation with that at 32 weeks in detecting fetal growth restriction (FGR).

METHODS

This was an open-label parallel randomized trial (ROUTE study) conducted at a single general hospital serving a geographically well-defined catchment area in Barcelona, Spain, between May 2011 and April 2014. Women with no adverse medical or obstetric history and a singleton pregnancy without fetal abnormalities at routine second-trimester scan were assigned randomly to undergo a scan at 32 weeks' gestation (n = 1272) or at 36 weeks' gestation (n = 1314). Primary outcome measures were detection rates of FGR (customized birth weight < 10(th) centile) and severe FGR (customized birth weight < 3(rd) centile).

RESULTS

There were no significant differences in perinatal outcome between those who underwent a scan at 32 weeks' gestation and those who underwent a scan at 36 weeks' gestation. Severe FGR at birth was associated significantly with emergency Cesarean delivery for fetal distress (odds ratio (OR), 3.4 (95% CI, 1.8-6.7)), neonatal admission (OR, 2.23 (95% CI, 1.23-4.05)), hypoglycemia (OR, 9.5 (95% CI, 1.8-49.8)) and hyperbilirubinemia (OR, 9.0 (95% CI, 4.6-17.6)). Despite similar false-positive rates (FPRs) (6.4% vs 8.2%), FGR detection rates were superior at 36 vs 32 weeks' gestation (sensitivity, 38.8% vs 22.5%; P = 0.006), with positive and negative likelihood ratios of 6.1 vs 2.7 and 0.65 vs 0.84, respectively. In cases of severe FGR, FPRs for both scans were also similar (8.5% vs 8.7%), but detection rates were superior at 36 vs 32 weeks' gestation (61.4% vs 32.5%; P = 0.008). Positive and negative likelihood ratios were 7.2 vs 3.7 and 0.4 vs 0.74, respectively.

CONCLUSION

In low-risk pregnancies, routine ultrasound examination at 36 weeks' gestation was more effective than that at 32 weeks' gestation in detecting FGR and related adverse perinatal and neonatal outcomes.

Prediction of small-for-gestational-age neonates: screening by uterine artery Doppler and mean arterial pressure at 19-24 weeks

OBJECTIVE

To investigate the potential value of uterine artery (UtA) pulsatility index (PI) and mean arterial pressure (MAP) at 19-24 weeks' gestation, in combination with maternal characteristics and medical history and fetal biometry in the prediction of delivery of small-for-gestational-age (SGA) neonates in the absence of pre-eclampsia (PE) and to examine the potential value of such assessment in deciding whether the third-trimester scan should be performed at 32 and/or 36 weeks' gestation.

METHODS

This was a screening study in 63 975 singleton pregnancies, including 3702 (5.8%) that delivered SGA neonates with birth weight < 5(th) percentile (SGA < 5(th) ) in the absence of PE. Multivariable logistic regression analysis was used to determine if screening by a combination of maternal factors, fetal head circumference (HC), abdominal circumference (AC), femur length (FL), UtA-PI and MAP had significant contribution in predicting SGA neonates. A model was developed to select gestational age for the third-trimester assessment, at 32 and/or 36 weeks, based on the results of screening at 19-24 weeks.

RESULTS

The detection rates (DRs) of combined screening by maternal factors, fetal biometry and UtA-PI at 19-24 weeks were 90%, 68% and 44% for SGA < 5(th) delivering < 32, 32-36 and ≥ 37 weeks' gestation, respectively, at a false-positive rate (FPR) of 10%. The performance of screening was not improved by the addition of MAP. The DR of SGA < 5(th) delivering at 32-36 weeks improved from 68% to 90% with screening at 32 rather than at 19-24 weeks. Similarly, the DR of SGA < 5(th) delivering ≥ 37 weeks improved from 44% with screening at 19-24 weeks to 59% and 76% when screening at 32 and 36 weeks, respectively. In a hypothetical model, it was estimated that if the desired objective of prenatal screening is to predict about 80% of the cases of SGA < 5(th) , it would be necessary to select 17% of the population at the 19-24-week assessment to be reassessed at 32 weeks and 38% to be reassessed at 36 weeks; 62% would not require a third-trimester scan.

CONCLUSION

Prenatal prediction of a high proportion of SGA neonates necessitates the undertaking of screening in the third trimester of pregnancy in addition to assessment in the second trimester, and the timing of such screening, at 32 and/or 36 weeks, should be contingent on the results of the assessment at 19-24 weeks.

Prediction of small-for-gestational-age neonates: screening by maternal serum biochemical markers at 19-24 weeks

OBJECTIVE

To investigate the value of maternal serum concentrations of placental growth factor (PlGF), soluble fms-like tyrosine kinase-1 (sFlt-1), pregnancy-associated plasma protein-A (PAPP-A), free β-human chorionic gonadotropin (β-hCG) and α-fetoprotein (AFP) at 19-24 weeks' gestation, in combination with maternal factors and fetal biometry, in the prediction of delivery of small-for-gestational-age (SGA) neonates, in the absence of pre-eclampsia (PE) and examine the potential value of such assessment in deciding whether the third-trimester scan should be performed at 32 and/or 36 weeks' gestation.

METHODS

This was a screening study in 9715 singleton pregnancies, including 481 (5.0%) that delivered SGA neonates with birth weight < 5(th) percentile (SGA < 5(th) ), in the absence of PE. Multivariable logistic regression analysis was used to determine if screening by a combination of maternal factors, Z-scores of fetal head circumference, abdominal circumference and femur length, and log10 multiples of the median (MoM) values of PlGF, sFlt-1, PAPP-A, free β-hCG or AFP had a significant contribution to the prediction of SGA neonates. A model was developed in selecting the gestational age for third-trimester assessment, at 32 and/or 36 weeks, based on the results of screening at 19-24 weeks.

RESULTS

Compared to the normal group, the mean log10 MoM value of PlGF was lower, AFP was higher and sFlt-1, PAPP-A and free β-hCG were not significantly different in the SGA < 5(th) group that delivered < 37 weeks. The detection rate (DR) of combined screening by maternal factors, fetal biometry and serum PlGF and AFP at 19-24 weeks was 100%, 76% and 38% for SGA < 5(th) delivering < 32, 32-36 and ≥ 37 weeks' gestation, respectively, at a false-positive rate (FPR) of 10%. In a hypothetical model, it was estimated that, if the desired objective of prenatal screening is to predict about 80% of the cases of SGA < 5(th) , it would be necessary to select 11% of the population at the 19-24-week assessment to be reassessed at 32 weeks and 46% to be reassessed at 36 weeks; 54% would not require a third-trimester scan.

CONCLUSION

Prenatal prediction of a high proportion of SGA neonates necessitates the undertaking of screening in the third trimester of pregnancy, in addition to assessment in the second trimester, and the timing of such screening, at 32 and/or 36 weeks, should be contingent on the results of the assessment at 19-24 weeks.

Prediction of small-for-gestational-age neonates: screening by fetal biometry at 19-24 weeks

OBJECTIVE

To investigate the value of fetal biometry at 19-24 weeks' gestation in the prediction of delivery of small-for-gestational-age (SGA) neonates, in the absence of pre-eclampsia (PE), and examine the potential value of such assessment in deciding whether the third-trimester scan should be at 32 and/or 36 weeks' gestation.

METHODS

This was a screening study in 88,187 singleton pregnancies, including 5003 (5.7%) that delivered SGA neonates with birth weight < 5(th) percentile (SGA < 5(th)). Multivariable logistic regression analysis was used to determine if screening by a combination of maternal characteristics and medical history and Z-scores of fetal head circumference (HC), abdominal circumference (AC) and femur length (FL) had significant contribution in predicting SGA neonates. A model was developed for selecting the gestational age for third-trimester assessment, at 32 and/or 36 weeks, based on the results of screening at 19-24 weeks.

RESULTS

Combined screening by maternal factors and fetal biometry at 19-24 weeks, predicted 76%, 58% and 44% of SGA < 5(th) delivering < 32, 32-36 and ≥ 37 weeks' gestation, respectively, at a false-positive rate (FPR) of 10%. The detection rate (DR) of SGA < 5(th) delivering at 32-36 weeks improved from 58% to 82% with screening at 32 weeks rather than at 19-24 weeks. Similarly, the DR of SGA < 5(th) delivering ≥ 37 weeks improved from 44% with screening at 19-24 weeks to 61% and 76% with screening at 32 and 36 weeks, respectively. In a hypothetical model, it was estimated that if the desired objective of prenatal screening is to predict about 80% of the cases of SGA < 5(th), it would be necessary to select 28% of the population at the 19-24-week assessment to be reassessed at 32 weeks and 41% to be reassessed at 36 weeks; in 59% of pregnancies there would be no need for a third-trimester scan.

CONCLUSION

Prenatal prediction of a high proportion of SGA neonates necessitates the undertaking of screening in the third trimester of pregnancy, in addition to assessment in the second trimester, and the timing of such screening, either at 32 and/or 36 weeks, should be contingent on the results of the assessment at 19-24 weeks.

Diagnostic accuracy of placental growth factor and ultrasound parameters to predict the small-for-gestational-age infant in women presenting with reduced symphysis-fundus height

OBJECTIVES

To assess the diagnostic accuracy of placental growth factor (PlGF) and ultrasound parameters to predict delivery of a small-for-gestational-age (SGA) infant in women presenting with reduced symphysis-fundus height (SFH).

METHODS

This was a multicenter prospective observational study recruiting 601 women with a singleton pregnancy and reduced SFH between 24 and 37 weeks' gestation across 11 sites in the UK and Canada. Plasma PlGF concentration < 5(th) centile, estimated fetal weight (EFW) < 10(th) centile, umbilical artery Doppler pulsatility index > 95(th) centile and oligohydramnios (amniotic fluid index < 5 cm) were compared as predictors for a SGA infant < 3(rd) customized birth-weight centile and adverse perinatal outcome. Test performance statistics were calculated for all parameters in isolation and in combination.

RESULTS

Of the 601 women recruited, 592 were analyzed. For predicting delivery of SGA < 3(rd) centile (n = 78), EFW < 10(th) centile had 58% sensitivity (95% CI, 46-69%) and 93% negative predictive value (NPV) (95% CI, 90-95%), PlGF had 37% sensitivity (95% CI, 27-49%) and 90% NPV (95% CI, 87-93%); in combination, PlGF and EFW < 10(th) centile had 69% sensitivity (95% CI, 55-81%) and 93% NPV (95% CI, 89-96%). The equivalent receiver-operating characteristics (ROC) curve areas were 0.79 (95% CI, 0.74-0.84) for EFW < 10(th) centile, 0.70 (95% CI, 0.63-0.77) for low PlGF and 0.82 (95% CI, 0.77-0.86) in combination.

CONCLUSIONS

For women presenting with reduced SFH, ultrasound parameters had modest test performance for predicting delivery of SGA < 3(rd) centile. PlGF performed no better than EFW < 10(th) centile in determining delivery of a SGA infant.

Impact on obstetric outcome of third-trimester screening for small-for-gestational-age fetuses

OBJECTIVES

To evaluate the performance of screening for small-for-gestational-age (SGA) fetuses by ultrasound biometry at 30-35 weeks' gestation, and to determine the impact of screening on obstetric and neonatal outcomes.

METHODS

For this prospective cohort study, pregnant women were recruited from two French university maternity centers between 2003 and 2006. Performance measures of third-trimester biometry for the prediction of SGA, defined as estimated fetal weight < 10(th) centile, were analyzed. Obstetric outcomes and neonatal health status were compared, first, between SGA neonates diagnosed correctly at ultrasound examination (true positive (TP); n = 45) and SGA neonates that went undiagnosed (false negative (FN); n = 110) and, second, between non-SGA neonates identified as normal at ultrasound examination (true negative (TN); n = 1641) and non-SGA neonates diagnosed incorrectly as SGA (false positive (FP); n = 101).

RESULTS

In the prediction of SGA, third-trimester ultrasound had a sensitivity of 29.0% (95% CI, 22.5-36.6%) and specificity of 94.2% (95% CI, 93.0-95.2%). Positive and negative predictive values were 30.8% (95% CI, 23.9-38.7%) and 93.7% (95% CI, 92.5-94.8%), respectively. One hundred and ten SGA neonates went undiagnosed at ultrasound. Compared to the TN neonates considered as of normal weight at ultrasound, planned preterm delivery (before 37 weeks) and elective Cesarean section for a fetal growth indication were 2.4 (P = 0.01) and 2.85 (P = 0.003) times more likely to occur, respectively, in the FP group of non-SGA neonates, diagnosed incorrectly as SGA during the antenatal period. There was no statistically significant difference in 5-min Apgar score < 7, cord blood pH at birth < 7.15 and need for neonatal resuscitation between the two subgroups (TN vs FP and TP vs FN).

CONCLUSIONS

The performance of third-trimester ultrasound screening for SGA seems poor, as it misses the diagnosis of a large number of SGA neonates. The consequences of routine screening for SGA in a low-risk population may lead to unnecessary planned preterm deliveries and elective Cesarean sections in FP pregnancies, without improved neonatal outcome in the FN pregnancies.

Unconditional and conditional standards for fetal abdominal circumference and estimated fetal weight in an ethnic Chinese population: a birth cohort study

BACKGROUND

Diagnosis of intrauterine fetal growth restriction and prediction of small-for-gestation age are often based on fetal abdominal circumference or estimated fetal weight (EFW). The present study aims to create unconditional (cross-sectional) and conditional (longitudinal) standards of fetal abdominal circumference and EFW for use in an ethnic Chinese population.

METHODS

In the Growing Up in Singapore Towards healthy Outcome (GUSTO) birth cohort study in Singapore, fetal biometric measurements were obtained at enrolment to antenatal care (11-12 weeks) and up to three more time points during pregnancy. Singleton pregnancies with a healthy profile defined by maternal, pregnancy and fetal characteristics and birth outcomes were selected for this analysis. The Hadlock algorithm was used to calculate EFW. Mixed effects model was used to establish unconditional and conditional standards in z-scores and percentiles for both genders pooled and for each gender separately.

RESULTS

A total of 313 women were included, of whom 294 had 3 and 19 had 2 ultrasound scans other than the gestational age dating scan. Fetal abdominal circumference showed a roughly linear trajectory from 18 to 36 weeks of gestation, while EFW showed an accelerating trajectory. Gender differences were more pronounced in the 10(th) percentile than the 50(th) or 90(th) percentiles. As compared to other published charts, this population showed growth trajectories that started low but caught up at later gestations.

CONCLUSIONS

Unconditional and conditional standards for monitoring fetal size and fetal growth in terms of abdominal circumference and EFW are available for this ethnic-Chinese population. Electronic spreadsheets are provided for their implementation.

Prediction of small-for-gestational-age neonates: screening by fetal biometry at 30-34 weeks

OBJECTIVE

To investigate the value of fetal biometry at 30-34 weeks' gestation in the prediction of delivery of small-for-gestational-age (SGA) neonates, in the absence of pre-eclampsia (PE).

METHODS

This was a screening study in 30 849 singleton pregnancies at 30-34 weeks' gestation, comprising 1727 that delivered SGA neonates with a birth weight < 5(th) percentile and 29 122 cases unaffected by SGA, PE or gestational hypertension. Multivariable logistic regression analysis was used to determine if screening by a combination of maternal factors and Z-scores of fetal head circumference (HC), abdominal circumference (AC) and femur length (FL) or estimated fetal weight (EFW) had a significant contribution to the prediction of SGA neonates.

RESULTS

Combined screening by maternal characteristics and obstetric history, with Z-scores of EFW at 30-34 weeks, predicted 79%, 87% and 92% of the SGA neonates that delivered < 5 weeks following assessment, with a birth weight < 10(th) , < 5(th) and < 3(rd) percentiles, respectively, at a 10% false-positive rate. The respective detection rates for the prediction of SGA neonates delivering ≥ 5 weeks from the time of assessment were 53%, 58% and 61%. The performance of screening by a combination of Z-scores of fetal HC, AC and FL was similar to that achieved by the EFW Z-score alone.

CONCLUSION

Combined testing by maternal characteristics and fetal biometry at 30-34 weeks could identify a high proportion of pregnancies that will deliver SGA neonates.

Prediction of small-for-gestational-age neonates: screening by fetal biometry at 35-37 weeks

OBJECTIVE

To investigate the value of fetal biometry at 35-37 weeks' gestation in the prediction of delivery of small-for-gestational-age (SGA) neonates, in the absence of pre-eclampsia (PE).

METHODS

This was a screening study in singleton pregnancies at 35-37 weeks' gestation, comprising 278 that delivered SGA neonates with a birth weight < 5th percentile and 5237 cases unaffected by SGA, PE or gestational hypertension. Multivariable logistic regression analysis was used to determine if screening by a combination of maternal factors and Z-scores of fetal head circumference (HC), abdominal circumference (AC) and femur length (FL) or estimated fetal weight (EFW) had a significant contribution to the prediction of SGA neonates.

RESULTS

Multivariable logistic regression analysis demonstrated that the likelihood of delivering a SGA neonate with a birth weight < 5th percentile decreased with maternal weight and height, and in parous women the risk increased with a longer interpregnancy interval. The risk was higher in women of Afro-Caribbean and South Asian racial origins, in cigarette smokers, nulliparous women and in those with history of SGA, with or without prior PE. Combined screening by maternal characteristics and history with EFW Z-scores at 35-37 weeks predicted 89% of SGA neonates with birth weight < 5th percentile delivering < 2 weeks following assessment, at a 10% false-positive rate (FPR). The respective detection rate for the prediction of SGA neonates delivering ≥ 37 weeks' gestation was 70%. The performance of screening by a combination of Z-scores of fetal HC, AC and FL was similar to that achieved by the EFW Z-score.

CONCLUSION

Combined testing by maternal characteristics and fetal biometry at 35-37 weeks could identify, at a 10% FPR, about 90% of pregnancies that subsequently deliver SGA neonates within 2 weeks of assessment and 70% of those that deliver ≥ 37 weeks.

Comparison of secondhand smoke exposure measures during pregnancy in the development of a clinical prediction model for small-for-gestational-age among non-smoking Chinese pregnant women

OBJECTIVE

To compare predictive values of small-for-gestational-age (SGA) by different measures for secondhand smoke (SHS) exposure during pregnancy and to develop and validate a prediction model for SGA using SHS exposure along with sociodemographic and pregnancy factors.

METHODS

We compared the predictability of different measures of SHS exposure during pregnancy for SGA among 545 Chinese pregnant women, and then used the optimal SHS measure along with other clinically available factors to develop and validate a prediction model for SGA. We fit logistic regression models to predict SGA by single measures of SHS exposure (self-report, serum cotinine and CYP2A6*4) and different combinations (self-report+cotinine, cotinine+CYP2A6*4, self-report+CYP2A6*4 and self-report+cotinine+CYP2A6*4).

RESULTS

We found that self-reported SHS exposure alone predicted SGA (area under the receiver operating characteristic curve or area under the receiver operating curve (AUROC), 0.578) better than the other two single measures (cotinine, 0.547; CYP2A6*4, 0.529) or as accurately as combined SHS measures (0.545-0.584). The final prediction model that contained self-reported SHS exposure, prepregnancy body mass index, gestational weight gain velocity during the second and third trimesters, gestational diabetes, gestational hypertension and the third-trimester biparietal diameter Z-score could predict SGA fairly accurately (AUROC, 0.698).

CONCLUSIONS

Self-reported SHS exposure at peribirth performs better in predicting SGA than a single measure of serum cotinine at the same time, although repeated biochemical cotinine assessments throughout pregnancy may be optimal. Our simple prediction model is fairly accurate and can be potentially used in routine prenatal care.

Reproducibility study of fetal 3-D volumetry in the first trimester: effect of fetal size and rotational angle of VOCAL software

Intra- and inter-observer reproducibility of fetal volume measurement by 3-D ultrasound scan (using VOCAL [Virtual Organ Computer-Aided Analysis] software) in 27 fetuses at 7 to 13 wk was studied. For intra-observer variability, the mean difference (MD) and 95% limits of agreement (95% LOA) at 12°, 18° and 30° were MD(12) = 0.097, 95% LOA(12) = -0.87 to +1.06; MD(18) = 0.07, 95% LOA(18) = -1.31 to +1.45; and MD(30) = -0.07, 95% LOA(30) = -1.55 to +1.41. The standard deviation of the differences (SD(DIF)) increased with crown-rump length at 12° (p = 0.0016), 18° (p = 0.0011) and 30° (p = 0.02). For inter-observer variability, MD(12) = 0.15, 95% LOA(12) = -1.65 to +1.95; MD(18) = 0.042, 95% LOA(18) = -1.79 to +1.87; and MD(30) = 0.19, 95% LOA(30) = -1.24 to +1.62. SDDIF increased with crown-rump length at 18° (p = 0.0084) and 30° (p = 0.0073). The accuracy of fetal volume measurement was not influenced by rotational angle or fetal size. Precision deteriorated for wider rotational angles and larger fetuses.

First-trimester screening for early and late small-for-gestational-age neonates using maternal serum biochemistry, blood pressure and uterine artery Doppler

OBJECTIVE

To assess the effectiveness of first-trimester screening for early and late small-for-gestational-age (SGA) neonates using maternal serum biochemistry, blood pressure and uterine artery Doppler.

METHODS

This was a prospective study of 4970 women with a singleton pregnancy who underwent routine first-trimester screening between 2009 and 2011. A logistic regression-based predictive model for SGA, defined as birth weight < 10(th) percentile, divided into early- or late-onset based on gestational age at delivery before or after 34 weeks' gestation, was constructed. The model included maternal baseline characteristics: serum levels of pregnancy-associated plasma protein-A and free β-human chorionic gonadotropin at 8-12 weeks and blood pressure and uterine artery Doppler at 11 + 0 to 13 + 6 weeks.

RESULTS

The prevalence of early and late SGA was 0.6% and 7.9%, respectively. Association with pre-eclampsia was 67% and 8%, respectively. At a false-positive rate of 15%, the detection rate for early SGA was 73%; however it differed substantially for cases with and without pre-eclampsia (90% vs 40%). For late SGA, at false-positive rates of 15 and 50%, detection rates were 32% and 70%, respectively, and did not substantially differ between cases with and without pre-eclampsia.

CONCLUSIONS

First-trimester screening predicts early SGA mainly because of its strong association with pre-eclampsia. Although prediction of late SGA was poorer, at a high false-positive rate it might be considered as part of a first-trimester strategy to select women requiring ultrasound assessment in the third trimester.

Third-trimester abnormal uterine artery Doppler findings are associated with adverse pregnancy outcomes

OBJECTIVES

To evaluate the association between third-trimester abnormal uterine artery Doppler findings and pregnancy outcomes.

METHODS

A prospective study was designed, including 198 consecutive singleton pregnancies between 27 and 41 weeks' gestation. In the study population, 144 had normal uterine artery Doppler waveforms, 37 had unilateral pathologic waveforms, and 17 had bilateral pathologic waveforms. Eighty patients had intrauterine growth restriction (IUGR), preeclampsia toxemia, or both, and 118 had no complications and served as a control group. The uterine artery Doppler waveform was considered abnormal when a notch or pulsatility index above the 90th percentile was noted.

RESULTS

In patients with bilateral pathologic uterine artery Doppler waveforms, the rates of cesarean delivery, small-for-gestational-age (SGA) neonates, preterm delivery, and low Apgar scores were increased compared to patients with normal or pathologic unilateral waveforms (P = .009; P > .001; P = .007; P > .001, respectively). The incidence rates for SGA neonates, cesarean delivery, and preterm delivery were significantly higher among patients without IUGR or preeclampsia toxemia when associated with pathologic bilateral waveforms in comparison to normal waveforms (P = .01 for all). A bilateral pathologic waveform was found to be an independent risk factor for cesarean delivery and SGA neonates. The incidence rates for SGA neonates and preterm delivery were significantly higher among patients with IUGR and/or preeclampsia toxemia when associated with bilateral abnormalities in comparison to normal waveforms (P = .01 for both).

CONCLUSIONS

Third-trimester abnormal uterine artery Doppler findings are associated with worse perinatal outcomes among patients both with and without pregnancy complications.

Association of third-trimester abdominal circumference with provider-initiated preterm delivery

OBJECTIVE

Evaluate the association of a small third-trimester abdominal circumference (AC < 10th percentile) in the setting of a normal estimated fetal weight (EFW ≥ 10th percentile) with gestational age at delivery, indication for delivery and neonatal outcomes.

METHODS

Retrospective cohort study at an academic hospital of women with singleton pregnancy seen for ultrasound from 28+0-33+6 weeks of gestation during 2009-2011. Outcomes were compared between two groups: normal AC (AC and EFW ≥ 10th percentile) and small AC (AC < 10th percentile and EFW ≥ 10th percentile).

RESULTS

Among 592 pregnancies, fetuses in the small AC group (n = 55) experienced a higher incidence of overall preterm delivery (RR: 2.2, 95% CI: 1.3-3.7) and provider-initiated preterm delivery (RR: 3.7, CI: 1.8-7.5) compared to those in the normal AC group (n = 537). Neonates in the small AC group had a lower median birth weight whether delivered at term (p < 0.001) or preterm (p = 0.04), but were not more likely to experience intensive care unit admission or respiratory distress syndrome (all p ≥ 0.35).

CONCLUSIONS

Small AC, even in the setting of an EFW ≥ 10th percentile, was associated with a higher incidence of overall and provider-initiated preterm delivery despite similar neonatal outcomes. Further investigation is warranted to determine whether these preterm deliveries could be prevented.

Specific formulas improve the estimation of fetal weight by ultrasound scan

OBJECTIVE

To develop and evaluate local, sex specific, small for gestational age (SGA) specific, large for gestational age (LGA) specific and combined (biometry, sex and Doppler indices) formulas for ultrasound estimated fetal weight (EFW).

METHOD

Low-risk singleton pregnancies that delivered within 7 days from ultrasound examination were assessed. A formula-generating group (1407 pregnancies) and a validation group (469 pregnancies) were created. Fractional regression analysis was used to develop the formulas. Systematic error, random error, fraction within the 10% of actual birth weight and Bland-Altman analysis were used.

RESULTS

The local formula and the Hadlock formula with local co-efficients performed better than the Hadlock formula. The SGA-specific formula, the LGA-specific formula and the combined formula had the lower systematic error (MSE: +0.0022291, -0.4226888, +0.8386222, respectively) and the narrower 95% LOA (-292.8 to +292.23, -485.6 to +461.5, -425.7 to +450.46, respectively). The SGA- and the LGA-specific formulas had higher fraction within the 10% of actual birth weight (81.5% and 84%, respectively).

CONCLUSIONS

Local formulas improve the EFW calculation. The combined formula can further optimize the accuracy and precision. Application of specific formulas for the small and the large fetus had the most pronounced effect in improving fetal weight estimation.

Doppler study of the fetal vertebral artery in small for gestational age fetuses with intrauterine growth restriction

OBJECTIVES

The purposes of this study were to evaluate the Doppler resistive index of the fetal vertebral artery in small for gestational age (SGA) fetuses and to examine the ability of the vertebral artery resistive index in the diagnosis of intrauterine growth restriction (IUGR).

METHODS

A total of 437 Doppler examinations of the vertebral and umbilical artery resistive indices were performed in 437 fetuses between 26 and 41 weeks' gestation. According to birth weight, fetuses were classified into 5 groups: 1, above the 10th percentile; 2, between the 10th and 5th percentiles; 3, between the 5th and 3rd percentiles; 4, below the 3rd percentile; and 5, below the 3rd percentile with an umbilical artery resistive index above the 95th percentile. Subsequently, vertebral artery resistive index values were converted into multiples of the median, and box and whisker charts were generated to evaluate differences. Finally, receiver operating characteristic curves were calculated to assess the accuracy of the vertebral artery resistive index for predicting IUGR and a low Apgar score.

RESULTS

Compared to normally grown fetuses, vertebral artery resistive index values were lower in fetuses with birth weight below the 3rd percentile, and this difference was greater in fetuses with birth weight below the 3rd percentile and Doppler anomalies of the umbilical artery. The receiver operating characteristic analysis showed that the vertebral artery resistive index diagnosed SGA fetuses and low Apgar scores poorly. However, it performed better in cases of severe IUGR with high umbilical artery resistive index values.

CONCLUSIONS

Preliminary data show that the vertebral artery resistive index diminishes in growth-restricted SGA fetuses. Doppler examination of the vertebral artery seems to identify a group of fetuses with brain sparing and severe IUGR.