Ultrasound biometry of Arabian fetuses.

OBJECTIVE: To establish fetal ultrasound biometry charts for Arabian fetuses between 14 and 40 weeks of gestation. METHOD: Cross-sectional fetal ultrasound data of normal singleton pregnancies, which had been performed over a period of 7 years, were retrieved. Only pregnant Arab women with certain last menstrual period dates and/or early ultrasound examinations were included. Each fetus contributed to only one set of data. Normal ranges for biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur length (FL) were established. The mean and 5th and 95th percentiles at 18th, 28th, and 36 weeks of gestation were compared with similar ranges of published data from pregnancies of American and Anglo-Saxon population. RESULTS: Fetal ultrasound biometry has been established for our local population. Comparing our data with Western population emphasizes the presence of significant variation in fetal morphometric measurements, particularly in the later weeks of gestation and at the extremes of the range of fetal size. CONCLUSION: The clinical significance of this variation differs according to the primary objective of ultrasound fetal measurements. For estimation of fetal age, usually by head and femur measurements in early gestation, ethnic variation seems to have limited significance. Whereas for estimation of fetal growth and/or weight in the third trimester, based on abdominal circumference, the use of given points, e.g., 10th or 5th percentile derived from other population charts, has the potential of either over- or underdiagnosis of IUGR fetuses. The adoption of locally developed charts is recommended.     

Screening for the Small Fetus: A Study of the Relative Efficacies of Ultrasound Biometry and Symphysiofundal Height

Summary: In this study 3 different methods of screening for birth-weight <10th percentile in pregnancy were evaluated both indivually and in combination; 1,135 women with singleton pregnancies were studied. Measurements of symphysiofundal height by tape measure, and amniotic fluid index and fetal abdominal circumference by ultrasound imaging, were made at 18, 24, 28, 34 and 38 weeks. At none of these gestational ages did amniotic fluid index perform well as a screening test for birth-weight <10th percentile. Combining the tests, using symphysiofundal height to select a group at high risk who then had a fetal abdominal circumference measurement, reduced the false positive rate but significantly decreased the percentage of infants diagnosed. The results of this study confirm that the most appropriate antenatal diagnostic test for birth-weight < 10th percentile is ultrasound measurement of fetal abdominal circumference. Selecting pregnancies at risk by clinical measurement of symphysiofundal height will provide a lower false positive rate than a policy of performing ultrasound on all pregnancies during the third trimester, but will also reduce the sensitivity.     

Differences in amniotic fluid patterns and fetal biometric parameters in third trimester pregnancies with and without diabetes.

OBJECTIVE: The amniotic fluid index (AFI) has been increasingly used in the assessment of fetal well-being. We conducted the study to evaluate and compare the amniotic fluid index in third trimester normal and diabetic human pregnancy and to assess the correlation between the AFI and the fetal biometric parameters. METHODS: Real-time ultrasound was performed to evaluate the AFI (four-quadrant technique), and to measure the biparietal diameter, head circumference, abdominal circumference, and femur length in 225 normal and 120 diabetic pregnant women from 27 to 42 weeks of gestation. Each patient was studied only once. RESULTS: AFI in normal pregnancies was less than that in diabetic pregnancies throughout the gestational ages studied (27-42 weeks). In normal pregnancy, the mean AFI was 14.0 cm at 27 weeks and decreased to 11.4 cm at 42 weeks (r = 0.25, p = 0.0005), whereas in diabetic pregnancies, the values remained stable throughout the gestational ages studied. There exist significant differences in AFI, estimated fetal weight, estimated fetal weight %, abdominal circumference, abdominal circumference %, and head circumference to abdominal circumference ratio between the two groups. In both normal and diabetic pregnancies, there is a positive correlation between the AFI and the percentile of abdominal circumference (p < 0.0001), and between the AFI and the percentile of estimated fetal weight (p < 0.0001). CONCLUSION: This study provides gestational age-specific values of the AFI in normal and diabetic pregnancies. Diabetic pregnancy has greater AFI values than normal pregnancy between 27 and 42 weeks. The AFI correlates to the percentile of the estimated fetal weight and the abdominal circumference in both groups, suggesting that there may be a relationship between increased AFI and large for gestational age fetus independent of diabetes.     

Screening for detection of intra-uterine growth retardation by means of ultrasound

In a two-stage ultrasound screening program the gestational age was assessed by measurement of the fetal crown-rump length in early pregnancy. At an adjusted gestational age between 32 and 35 completed weeks the biparietal diameter, the abdominal circumference, the abdominal area and the ratio between fetal head area and abdominal area were estimated by means of ultrasound measurement. 'Acute' fetal weight was estimated by calculations from biparietal diameter and abdominal diameters. Percentile curves were constructed for these parameters and cut-off limits were tested for the predictability of intra-uterine growth retardation of the fetus. The abdominal circumference and area estimations were equally good for the detection of intra-uterine growth retardation. The biparietal diameter alone is of limited value for the detection of intra-uterine growth retardation but the combination with abdominal diameters in 'acute' fetal weight estimation can well be used. The ratio between the skull and abdominal areas seems to be of little use for the detection of intra-uterine growth retardation of two reasons: difficulty in measurement and low sensitivity. We consider that the assessment of gestational age in early pregnancy is a necessity both for the identification of suspected IUGR by means of ultrasound and the diagnosis of IUGR by measurement of fetal weight at birth. It is concluded that if the gestational age has been assessed by crown-rump length measurement in early pregnancy, a single estimation of the fetal abdominal circumference between 32 and 35 completed gestational weeks and a cut-off limit at the 15th percentile offers a detection rate of about 90% of the growth retarded infants.     

Fetal growth charts for Aboriginal fetuses

The study aimed to determine whether fetal growth parameters in Aboriginal pregnancies are such that separate fetal growth charts are necessary for their appropriate care. We designed a prospective study of a cohort of Aboriginal women presenting for antenatal care before 20 weeks gestation (ultrasound proven) and a reference cohort of Caucasian women. Four remote North Queensland communities served by the Far North Regional Obstetric and Gynaecological Service (FROGS) and the antenatal clinic at Cairns Base Hospital took part in the survey One hundred and four Aboriginal and 101 Caucasian women with no known medical factors affecting fetal growth or gestation were recruited, and 96 Aboriginal and 96 Caucasian women completed the study Measurements took the form of longitudinal percentile charts of fetal biparietal diameter, abdominal circumference and femur length. Ultrasound measurements of fetal biparietal diameter, abdominal circumference and femur length were obtained 3 to 5 times during Aboriginal and Caucasian pregnancies, where the gestation was established by ultrasound before 20 weeks gestation, and no known medical conditions which affect fetal growth were present in the mother. There were no statistical or clinically important differences in biparietal diameter, femur length and abdominal circumference of Aboriginal and Caucasian fetuses. We concluded that there is no reason to use separate fetal growth charts when examining Aboriginal fetal growth.     

Choroid plexus cysts do not affect fetal neurodevelopment.

OBJECTIVE: To determine whether an isolated finding of a choroid plexus cyst (CPC) during routine ultrasound is associated with altered fetal growth or development. STUDY DESIGN: Prospective, case-control study comparing 35 CPC cases to 67 controls. Neurobehavioral development assessment included 50 min long serial recordings of heart rate, motor activity and their interrelation at 24, 28, 32 and 36 weeks gestation. Growth measurement was based on three ultrasound evaluations of femur length, biparietal diameter, head circumference and abdominal circumference at initial exam, 28 and 36 weeks. RESULTS: Longitudinal analyses revealed no differences in fetal heart rate, variability or accelerations; the number or duration of fetal movements or total motor activity; nor fetal movement-fetal heart rate coupling. CPC cases had slightly smaller head and abdominal circumferences at 28 weeks, but these differences had disappeared by 36 weeks. CPC detection was more common when routine exams were conducted earlier (18.8 versus 19.5 weeks; P<0.01). CONCLUSION: Despite the presumption that CPCs with normal karyotypes are benign variants, little empirical support exists. These results indicate that CPCs detected by prenatal ultrasound do not pose or reveal a threat to fetal development.     

Diabetic macrosomia: accuracy of third trimester ultrasound

Sonar biparietal diameter, head circumference, and abdominal circumference percentile values obtained late in the third trimester were compared with birth weight percentile (relative to dates) in 147 diabetic mothers and 40 control fetuses of nondiabetics. Estimates of fetal weight by the method of Shepard et al were also calculated from these sonar data and compared with birth weight percentile. Abdominal circumference values greater than the 90th percentile correctly predicted macrosomia (defined as birth weight greater than 90th percentile) in 78% of cases. Biparietal diameter and head circumference percentiles were significantly less predictive of macrosomia. When analyzed in a similar manner, estimated fetal weights greater than the 90th percentile correctly predicted macrosomia at birth in 74% of cases. However, when both the abdominal circumference and the estimated fetal weight exceeded the 90th percentile, macrosomia was correctly diagnosed in 88.8% of pregnant women with diabetes mellitus.     

Prediction of the Extremes of Birth Weight From a Single Ultrasound Examination at 34 Weeks of Gestation

Summary: One hundred and forty patients were subjected to ultrasound examination at about 34 weeks of gestation. Using the product of the biparietal diameter measurement and either the fetal abdominal circumference or abdominal area measurement, it was possible to predict three-quarters of both large for dates infants (false positive rate, 21.3%) and small for dates infants (false positive rate, 15.7%). Using the presence of a head and/or abdomen measurement above the 90th percentile for gestation, it was possible to predict 62.5% of large for dates infants (false positive rate, 15.7%). Using the presence of any measurement below the 10th percentile, it was possible to predict 81.3% of small for dates infants (false positive rates, 21.3%).     

Differences in amniotic fluid patterns and fetal biometric parameters in third trimester pregnancies with and without diabetes

Objective.?The amniotic fluid index (AFI) has been increasingly used in the assessment of fetal well-being. We conducted the study to evaluate and compare the amniotic fluid index in third trimester normal and diabetic human pregnancy and to assess the correlation between the AFI and the fetal biometric parameters.

Methods.?Real-time ultrasound was performed to evaluate the AFI (four-quadrant technique), and to measure the biparietal diameter, head circumference, abdominal circumference, and femur length in 225 normal and 120 diabetic pregnant women from 27 to 42 weeks of gestation. Each patient was studied only once.

Results.?AFI in normal pregnancies was less than that in diabetic pregnancies throughout the gestational ages studied (27–42 weeks). In normal pregnancy, the mean AFI was 14.0 cm at 27 weeks and decreased to 11.4 cm at 42 weeks (r = 0.25, p = 0.0005), whereas in diabetic pregnancies, the values remained stable throughout the gestational ages studied. There exist significant differences in AFI, estimated fetal weight, estimated fetal weight %, abdominal circumference, abdominal circumference %, and head circumference to abdominal circumference ratio between the two groups. In both normal and diabetic pregnancies, there is a positive correlation between the AFI and the percentile of abdominal circumference (p < 0.0001), and between the AFI and the percentile of estimated fetal weight (p < 0.0001).

Conclusion.?This study provides gestational age-specific values of the AFI in normal and diabetic pregnancies. Diabetic pregnancy has greater AFI values than normal pregnancy between 27 and 42 weeks. The AFI correlates to the percentile of the estimated fetal weight and the abdominal circumference in both groups, suggesting that there may be a relationship between increased AFI and large for gestational age fetus independent of diabetes.     

Maternal obesity not maternal glucose values correlates best with high rates of fetal macrosomia in pregnancies complicated by gestational diabetes

AIM: The current therapeutic strategies to reduce macrosomia rates in gestational diabetes (GDM) have focused on the normalizing of maternal glucose levels. The aim of our study was 1.) to compare maternal glycemic values with the presence of fetal macrosomia at different gestational ages (GA) and with LGA at birth in a cohort of women with glucose intolerance and standard diabetic therapy. METHODS: 306 women with GDM and 97 with impaired glucose tolerance underwent ultrasound examinations at entry and, after initiation of therapy, monthly in addition to standard diabetic therapy. Measurements from the entry diagnostic oGTT, glucose profile and HbA1c and from subsequent glucose profiles obtained within 3 days of the ultrasound at 5 categories of GA age (20-23, 24-27 etc) were retrospectively compared between pregnancies with and without fetal macrosomia, defined as an abdominal circumference (AC) > or = 90th percentile. Maternal prepregnancy BMI was adjusted for and BMI > or = 30 kg/m2 was defined as obesity. RESULTS: At entry, neither the hourly oGTT values, HbA1c, nor the entry glucose profile differed significantly between pregnancies with and without fetal macrosomia. In a total of 919 pairs of ultrasound/glucose profiles there was no significant difference in glucose levels at every GA category neither in lean nor in obese woman except for the fasting glucose of 32-35 GA. The fetal macrosomia rate in each GA category and the rate of LGA were significantly higher in obese women: e.g. 14.5 vs 28% at diagnosis, 15.7 vs 26.7% at 32-35 weeks, 15.5 vs 25.0% at birth (p < 0.05 for each comparison). CONCLUSION: The association of maternal glucose values and fetal macrosomia was limited to the fasting glucose values between 32-35 weeks while maternal obesity appeared to be a strong risk factor for macrosomia throughout pregnancies with GDM. In obese women the high fetal macrosomia rate did not appear be normalized by therapy based on maternal euglycemia.     

Histologic chorioamnionitis is associated with fetal growth restriction in term and preterm infants

OBJECTIVE: Our aim was to evaluate associations between chorioamnionitis and fetal growth restriction in infants enrolled in the Collaborative Perinatal Project. STUDY DESIGN: A total of 2579 nonanomalous, singleton infants delivered at 28 to 44 weeks' gestation with chorioamnionitis were matched 1:3 for ethnicity, gestational age, parity, and maternal cigarette use (all of which were correlated with both chorioamnionitis and markers of fetal growth restriction) with 7732 control infants. Moderate or marked leukocytic infiltrates of the placenta defined chorioamnionitis. Birth weight, length, head circumference, weight/length ratio, ponderal index, and birth weight/head circumference ratio in the lowest 5th percentile were markers of fetal growth restriction. Placental weight and the birth weight/placental weight ratio were also evaluated. RESULTS: Compared with data on matched control infants, histologic chorioamnionitis was associated with all markers of fetal growth restriction and with low birth weight/placental weight ratios (odds ratios, 1.3-1.7). The strongest associations were found at 28 to 32 weeks' gestation (odds ratios, 2.2-11). Attributable risks for several markers of fetal growth restriction exceeded 50% in infants born at <33 weeks' gestation. CONCLUSION: Histologic chorioamnionitis is associated with multiple markers of fetal growth restriction, with stronger associations noted in prematurity.     

Sonographic evaluation of fetal abdominal growth: predictor of the large-for-gestational-age infant in pregnancies complicated by diabetes mellitus

Serial ultrasound examinations were performed during the third trimester in 79 pregnant women with diabetes to establish the onset of accelerated fetal growth. At least three ultrasound examinations were performed, with a minimum scan interval of 2 weeks. Growth curves constructed for femur length and head circumference were similar for fetuses appropriate for gestational age (n = 48) and fetuses large for gestational age (n = 31). The mean changes in femur length and head circumference (expressed as centimeters per week during the early and late third trimesters) did not differ statistically between these two groups. Abdominal circumference growth was clearly accelerated at 32 weeks' gestation in the large for gestational age group (mean +/- SD, 1.36 +/- 0.16 cm/wk) compared with the appropriate for gestational age group (0.901 +/- 0.21 cm/wk, p less than 0.001). With use of a receiver operator characteristic curve, a change in abdominal circumference of 1.2 cm/wk over the period of 32 to 39 weeks' gestation was determined to be an optimal cutoff for detecting excessive fetal growth (sensitivity 84%, specificity 85%). A change in abdominal circumference 1.2 cm/wk was present in 4/4 large-for-gestational age fetuses (less than 4000 gm), in 17/21 (81%) of fetuses with birth weights 4000 to 4499 gm, and in 5/6 (83%) whose weight exceeded 4500 gm. It appears that improved detection of the fetus large for gestational age in diabetic pregnancies may be accomplished by the use of serial ultrasonography during the third trimester.     

Ontogeny of gastric emptying patterns in the human fetus.

OBJECTIVE: Fetal swallowing and gastric emptying contribute importantly to amniotic fluid (AF) homeostasis and fetal gastrointestinal development. We speculated that fetal gastric emptying must be functional early in gestation to prevent rapid increases in AF. We sought to determine the human fetal ontogenic pattern of gastric emptying. STUDY DESIGN: Gastric emptying of eighty normal fetuses at 12-39 weeks was studied. Real-time ultrasound of the fetal stomach was continuously recorded for 1 hour. The gastric area ratio (GAR) was defined as the gastric area divided by the abdominal transverse area. The delta GAR was defined as the change between the maximum and the minimum gastric area ratiox100 (expressed as percent). A change of the fetal gastric area more than the 10th percentile of the delta GAR at 36-39 weeks was used to define gastric emptying. RESULTS: The 10th, 50th and 90th percentile of delta GAR at 36-39 weeks' was 5.2, 6.5 and 8.7%, respectively. Fetal gastric emptying was detected as early as 12 5/7 weeks of gestation. The proportion of fetuses demonstrating gastric emptying (>10th percentile delta GAR) increased with gestational age: 4/33 (12.1%) 12-23 weeks, 3/9 (33.3%) at 24-27 weeks, 8/11 (72.7%) at 28-31 weeks, 12/14 (85.7%) at 32-35 weeks, and 11/13 (84.6%) at 36-39 weeks. CONCLUSIONS: Fetal gastric emptying occurs by the beginning of the second trimester, contributing to AF regulation. The increased frequency of gastric emptying in late gestation is likely secondary to increased swallowing, altered fetal behavioral state or endogenous production of gastrointestinal motility factors.     

Improving customized fetal biometry by longitudinal modelling

Objective: To develop customized biometric charts to better define abnormal fetal growth.

Methods: A total of 1056 singleton fetuses from the Raine Study underwent serial ultrasound biometry (abdominal circumference [AC], head circumference, and femur length) at 18, 24, 28, 34, and 38 weeks’ gestation. Customized biometry trajectories were developed adjusting for epidemiological influences upon fetal biometry using covariates available at 18 weeks gestation. Prediction accuracy (areas under the receiver operating characteristic curve [AUC] and 95% confidence interval [95%CI]) was evaluated by repeated random sub-sampling cross-validation methodology.

Results: The model for derived estimated fetal weight (EFW) performed well for EFW less than 10th predicted percentile (AUC?=?0.695, 95%CI, 0.692–0.699) and EFW greater than 90th predicted percentile (AUC?=?0.705, 95%CI, 0.702–0.708). Fetal AC was also well predicted for growth restriction (AUC?=?0.789, 95%CI, 0.784–0.794) and macrosomia (AUC?=?0.796, 95%CI, 0.793–0.799). Population-derived, sex-specific charts misclassified 7.9% of small fetuses and 10.7% of large fetuses as normal. Conversely, 9.2% of those classified as abnormally grown by population-derived charts were considered normal by customized charts, potentially leading to complications of unnecessary intervention.

Conclusions: Customized fetal biometric charts may offer improved ability for clinicians to detect deviations from optimal fetal growth and influence pregnancy management.     

Reference charts and equations of Korean fetal biometry

OBJECTIVE: To construct new reference charts and equations for fetal biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC) and femur diaphysis length (FDL) from Korean fetuses at 12-40 weeks. METHOD: Prospective cross-sectional data obtained in one center for 5 years from a population of pregnant women undergoing ultrasound examination between the 12th and 40th week of gestation. Exclusion criteria comprised all maternal and fetal conditions possibly affecting fetal biometry. No fetuses were excluded on the basis of abnormal biometry. For each measurement, regression models were fitted to estimate both the mean and the standard deviation at each menstrual age. RESULTS: Biometric measurements were obtained for 10 455 fetuses. New charts and reference equations are reported for BPD, HC, AC and FDL. Reference equations are cubic models. CONCLUSION: We present new Korean reference charts and equations for fetal biometry. They can be easily used in obstetric ultrasound studies for the Korean population.     

Fetal anterior abdominal wall thickness between gestational diabetes and normal pregnant women

ObjectivesTo compare fetal anterior abdominal wall thickness (AAWT) between women with and without GDM during third trimester and to determine accuracy of AAWT to predict large for gestational age (LGA) infants.Materials and methodsA total of 250 pregnant women, including 125 women with GDM and 125 women without GDM, were enrolled. Tansabdominal ultrasonographic examinations were performed at 28–30, 32–34 and 36–38 weeks. In addition to standard fetal biometries, AAWT was measured. Patient characteristics and ultrasonographic measurements were compared between groups. Sensitivity and specificity of AAWT for identifying LGA were evaluated.ResultsWhile standard fetal biometries were comparable, mean fetal AAWT in GDM women were significantly higher than those without GDM at 28–30 weeks (2.8 ± 0.8 vs. 2.6 ± 0.6, p = 0.006) and 32–34 weeks (4.0 ± 0.9 vs. 3.5 ± 0.8, p = 0.042). LGA infants had significantly higher fetal AAWT at each time point only in GDM women. Using cut off values of AAWT of ≥2.0, 3.0, and 4.0 mm at 28–30, 32–34, and 36–38 weeks, sensitivity for LGA diagnosis in GDM women were 94.4%, 93.9%, and 89.3%, respectively. The use of abdominal circumference (AC) at >90th percentile showed lower sensitivity but higher specificity, regardless of GDM status. Combination of both measurements increased sensitivity to approximately 90% or higher in every time point, especially among GDM women.ConclusionSignificant increase in fetal AAWT was observed in GDM women at 28–30 and 32–34 weeks. Fetal AAWT significantly increased among LGA infants and had higher sensitivity than AC in identifying LGA during third trimester. In GDM women at 28–30 weeks, AAWT ≥2.0 mm and AC >90th percentile had 97.2% sensitivity for LGA diagnosis.     

Low Dose Aspirin for the Treatment of Fetal Growth Restriction: A Randomized Controlled Trial

Summary: The purpose of this study was to investigate the hypothesis that maternal administration of lOOmg aspirin each day will improve birth-weight and other measures of neonatal size when given as a treatment to pregnancies complicated by fetal growth restriction and umbilical-placental insufficiency. A randomized, double-blind, placebo controlled study design was employed; 51 pregnant women were enrolled. The entry criteria were a fetal abdominal circumference <10th per centile together with an umbilical artery Doppler systolic/diastolic ratio >95th per centile between 28 and 36 weeks'gestation. Compliance was assessed by serial measurement of maternal serum thromboxane B2 levels. The mean gestational age at enrolment was 32 weeks and at delivery was 36 weeks. There were no differences between the 2 groups in gestational age at birth; birth-weight or birth-weight ratio; circumferences of the head, chest or abdomen; skin fold thicknesses; or neonatal morbidity. Low dose aspirin therapy did not alter Doppler systolic/diastolic ratios. After 14 days therapy, mean thromboxane B2 levels fell more than 80% from baseline values; 10.5% of women did not demonstrate biochemical confirmation of aspirin ingestion, despite verbal confirmation of compliance. We conclude that low dose aspirin therapy is not of benefit in the treatment of pregnancies complicated by fetal growth restriction and umbilical-placental insufficiency between 28 and 36 weeks' gestation.     

Ultrasound evaluation of pregnancies at risk for homozygous alpha-thalassaemia-1

Twenty-six pregnant Chinese women who were at risk of giving birth to a fetus affected with homozygous alpha-thalassaemia-1 were examined serially by ultrasound. Six of these 26 pregnancies were affected. In one third of the affected pregnancies progressive fetal ascites appeared before 24 weeks gestation and these pregnancies were terminated. In the remaining two thirds abnormal estimated fetal weight-placental volume (EFW-PV) ratio and fetal growth retardation as evidenced by a falling biparietal diameter (BPD), femur length (FL) but a normal abdominal circumference (AC) was apparent by 28 weeks gestation. Increased transverse cardiac (TC) diameter was another consistent finding but appeared late. All these features appeared before the onset of fetal ascites. A normal EFW-PV ratio and fetal growth until 28 weeks gestation was a reassuring sign of normality. Abnormal EFW-PV ratio was the earliest sign to appear in affected pregnancies and a normal ratio until 28 weeks gestation had a 100 per cent predictive value.     

Neck Circumference Measurements in Second Trimester Fetuses with Down's Syndrome

Ultrasound examinations were performed on 132 normal fetuses between 12 and 25 weeks of gestation to measure the fetal neck circumference (NC), biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur length (FL). The relationships between the fetal neck circumference and gestational age, as well as between the fetal neck circumference and fetal biometric parameters (BPD, HC, AC, FL) were linear. Nomograms between the fetal neck circumference and all other parameters were established including the 5th, 50th, and 95th percentile lines. Only one of nine fetuses with Down's syndrome was found to have abnormally increased fetal neck circumference (above the 95th percentile), whereas the remaining eight cases were equally distributed above and below the 50th percentile of these nomograms. The positive predictive value of an abnormally increased fetal neck circumference was 1.6% in our tested population, where the prevalence of Down's syndrome was 1 in 132. Our observations suggest that the use of fetal neck circumference in second trimester fetuses does not add in the prenatal diagnosis of Down's syndrome.     

Sonographically estimated fetal weight percentile as a predictor of preterm delivery

OBJECTIVE: To evaluate the association between relative growth restriction and preterm birth. STUDY METHODS: Pregnant women referred for sonographic fetal weight assessments between 24 and 34 weeks of gestation were studied for gestational age at delivery. If a patient underwent more than one study, only the last one was considered. Patients with delivery induced iatrogenically or with abnormal growth patterns due to known pathology, such as maternal diabetes or fetal congenital anomaly, were excluded. A gestational age of 37 weeks or less was considered preterm and a gestational age of more than 37 weeks at delivery was considered term. Fetal weight estimation was obtained by Hadlock's formula based on biparietal diameter, femur length, and head and abdominal circumferences. The estimated fetal weight percentile was computed according to William's tables. Mean gestational age and incidence of preterm delivery for each fetal weight percentile between 1 and 100, at increments of 10, were calculated. The mean estimated fetal weight percentile, biparietal diameter, femur length, head circumferences and abdominal circumferences of preterm and term patients were compared. RESULTS: Among the 419 patients who met the inclusion criteria, duration of gestation was significantly shorter in fetuses with low estimated fetal weight percentile. The risk of preterm birth was 49% in fetuses of less than the 40th birth-weight percentile compared with a risk of 20% in fetuses of more than the 40th birth-weight percentile, representing a relative risk of 2.3. Individual fetal measurements indicate a head-sparing effect in the preterm group. CONCLUSION: Sonographically estimated fetal weight percentile measured between 24 and 34 weeks' gestation may be used as an additional and individually pertinent predictor of preterm birth.