Fetal biparietal diameter: a critical re-evaluation of the relation to menstrual age by means of real-time ultrasound

The relationship between fetal biparietal diameter (BPD) and menstrual age was determined by cross-sectional analysis of 533 fetuses (12 to 40 weeks) examined with a linear array real-time (dynamic image) scanner using specifically defined methodology. Mathematical modeling of the data demonstrated that the optimal fit was the linear cubic function (r2 = 99 per cent); predicted BPD values calculated from the function were most comparable with composite data from cross-sectional studies performed with static scanners after 1974 (average difference, 0.22 mm) and least comparable with composite data from cross-sectional studies performed with static scanners before 1974 (average difference, 2.0 mm). The variability associated with predicting menstrual age from the BPD increased progressively throughout gestation; the maximal variability was noted between 36 and 42 weeks (+/- 3.6 weeks). Comparison with our longitudinal study of BPD growth indicates that the cross-sectional data represent a valid estimate of the true longitudinal BPD growth curve of the population.     

Prediction of Lung Maturity in Fetuses with Growth Restriction through Quantitative Ultrasound Analysis

The present study aimed to evaluate the performance of QuantusFLM software, which performs quantitative analysis of lung tissue texture through ultrasound images, in predicting lung maturity in fetal growth restriction (FGR). We included patients with singleton gestations between 34 and 38 6/7 wk and divided them into two groups: FGR and control (appropriate for gestational age [AGA]). The images were captured by ultrasound according to a specific protocol up to 48 h before delivery and analyzed with QuantusFLM software. The main clinical outcome evaluated was lung maturity (i.e., the absence of neonatal respiratory morbidity). We included 111 patients; one was excluded because of low image quality, leaving 55 patients in each group. The FGR group had a lower birth weight (2207 g vs. 2891 g, p < 0.001) and a longer stay in the neonatal intensive care unit (NICU) (10 d vs. 5 d, p = 0.043). QuantusFLM software was able to predict lung maturity in FGR with accuracy, sensitivity, specificity and positive and negative predictive values of 94.5%, 96.2%, 50%, 98.1% and 33.3%, respectively. QuantusFLM had good accuracy in predicting lung maturity in FGR with reliability in identifying pulmonary maturity.     

Relationship between Grade III placentas and biparietal diameter determinations

Grade III placentas were found in 133 (12 per cent) of 1,082 pregnant women evaluated ultrasonographically after 20 weeks of gestation. Associated biparietal diameter measurements ranged from 7.2 to 10 cm. In 11 women with no complications known to accelerate fetal lung maturity or to induce premature placental maturation, grade III placentas were observed between 30 and 33 weeks of gestation. Gestational ages determined according to the growth adjusted sonographic age method of Sabbagha were accurate within one to three days. Considering the risk of hyaline membrane disease at those gestational ages, a grade III placenta cannot be equated with fetal lung maturity. Criteria other than placental grading should be used to assess the pulmonary status of the fetus.     

Comparison of methods for determining crown-rump measurement by real-time ultrasound

Determination of gestational age without an accurate last menstrual period is difficult. In the later stages of pregnancy, the correlation between fetal biparietal diameter (BPD), as determined by ultrasound, and gestational age is compromised by normal biologic variation in fetal growth rates. The fetal crown-rump measurement (CRM) by gray-scale sonography has been described but has not been evaluated using real-time ultrasound. Currently available tables for determining gestational age from the fetal CRM were evaluated using a linear array real-time ultrasound system. A normal obstetric population with known menstrual histories, delivery dates, and Dubowitz scores at delivery was used for evaluation. On the basis of this study, Robinson's data listed as “regression analysis values” are suggested for application to real-time ultrasound. Alternatively, the equation generated from data on the above 86 patients could be used and further evaluated. The fetal CRM appears to be a valid and accurate assessment of gestational age.     

The use of ultrasonic fetal head circumference for predicting expected date of confinement

An ultrasonic fetal head circumference curve was developed from a group of 1278 ultrasound examinations in 710 normal obstetrical patients. These data were then used to compare the accuracy of head circumference (HC) to last menstrual period (LMP) and biparietal diameter (BPD) for the prediction of an accurate expected date of confinement (EDC) and, thereby calculate gestational age. The mean error of the signed differences (+/- standard deviation) for HC was -0.8 +/- 11.1 days, which was statistically different from the mean error of -6.1 +/- 10.6 days for BPD and -2.8 +/- 17.8 days for LMP. HC may have an advantage over BPD in situations where head shape (cephalic index) is significantly altered.     

Early sonographic evaluation for fetal growth delay and congenital malformations in pregnancies complicated by insulin-requiring diabetes. National Institute of Child Health and Human Development Diabetes in Early Pregnancy Study.

OBJECTIVE--It has been reported that early fetal growth retardation may be a useful marker for congenital malformations in diabetic pregnancies. To test this hypothesis, diabetic and nondiabetic women were sonographically evaluated during the first trimester. RESEARCH DESIGN AND METHODS--Fetal crown-rump lengths were measured sonographically at least once during the first 15 wk of pregnancy in 329 nondiabetic and 312 diabetic women. Of these, 289 nondiabetic and 269 diabetic women had sonograms before 10 wk of gestation and 283 nondiabetic and 269 diabetic women had sonograms between 10 and 15 wk of gestation. Early fetal growth delay was defined as a sonographic gestational age of greater than or equal to 6 days less than menstrual gestational age. RESULTS--The mean crown-rump lengths at 8 wk were 17.9 +/- 4.6 mm in the diabetic and 18.7 +/- 4.9 mm in the nondiabetic groups (P = 0.13). At 12 wk, the mean fetal crown-rump length was 58.5 +/- 8.8 mm for diabetic subjects and 60.6 +/- 8.7 mm for nondiabetic subjects (P = 0.04). Between 5 and 9 wk, 28 of 289 (9.7%) fetuses of nondiabetic subjects, 34 of 259 (13.1%) normal fetuses of diabetic subjects, and 2 of 10 (20%) malformed fetuses of diabetic subjects demonstrated growth delay (P = 0.31, normal vs. malformed diabetic). Between 10 and 15 wk of gestation, 28 of 283 (9.9%) fetuses of nondiabetic subjects, 32 of 256 (12.5%) normal fetuses of diabetic subjects, and 4 of 13 (30.8%) malformed fetuses of diabetic subjects demonstrated growth delay (P = 0.06, normal vs. malformed diabetic). Early fetal growth delay did not predict a reduced birth weight at term. CONCLUSIONS--Among insulin-dependent diabetic subjects who were moderately well controlled at conception, statistically significant but mild early fetal growth delay was present but did not appear to be useful clinically in predicting congenital malformations. Recommendations that growth delay demonstrated on early ultrasound be used as a predictor of congenital malformation require careful reexamination.     

Femur length and trisomy 21: impact of gestational age on screening efficiency.

OBJECTIVE: This study assesses two methods used to define relatively short femur in screening for trisomy 21 and examines changes in performance of screening with gestational age. DESIGN: Retrospective analysis of data on menstrual age, femur length (FL) and biparietal diameter (BPD) in 49 trisomy 21 pregnancies and 6069 normal controls. Reference ranges were derived for BPD/FL versus menstrual age and for FL versus BPD. Two methods of defining short femur (BPD/FL and observed-to-expected FL ratio) were examined for false-positive rates and detection rates for trisomy 21 at different gestational ages. RESULTS: In the control group the BPD/FL ratio and its standard deviation decreased with menstrual age. Trisomy 21 was associated with a significantly higher BPD/FL ratio (P < 0.001) and the deviation increased significantly with menstrual age (P < 0.05). Eleven percent of 28 fetuses examined at 15-17 weeks had a BPD/FL above the 95th centile compared with 24% of 21 fetuses examined at 18-20 weeks (P = 0.40). The median observed-to-expected FL ratio in the control group was 1.0 throughout the gestational age range but the standard deviation decreased significantly with menstrual age (P < 0.01). Trisomy 21 was associated with a significantly reduced observed-to-expected FL ratio (P < 0.001) and the deviation increased significantly with menstrual age (P < 0.05). A fixed cut-off of 0.91 for observed-to-expected FL ratio provided a false-positive rate of 12% at 15-17 weeks compared with 6% at 18-20 weeks of gestation (P < 0.001) with detection rates of 29 and 38%, respectively (P = 0.73). CONCLUSION: Irrespective of the definition used to define the condition, relatively short femur is a poor marker for trisomy 21 particularly when the assessment takes place before 18 weeks of gestation.     

Longitudinal studies of femur growth in normal fetuses

As an indicator of fetal limb growth, change in the femur diaphysis length (FDL) between 15 and 38 weeks, menstrual age, has been evaluated in a longitudinal study of 20 normal fetuses, as determined by prenatal biparietal diameter, head circumference, and abdominal circumference growth patterns as well as postnatal pediatric assessment. Individual FDL growth curves were uniformly parabolic and followed very similar trajectories. The projected start points [mean: 9.7 (+/- 1.5 SD) weeks] for these curves were in complete agreement with embryologic data, and the curves themselves were well characterized by the Rossavik model [R2 99.5 (+/- 0.5 SD)%]. No differences between males and females were detected, and good agreement was obtained between the average longitudinal growth curve and the cross-sectional growth curve derived from a previously studied data set. Individual growth curve standards, determined from Rossavik models based on data obtained before 26.1 weeks, menstrual age, were within 7% of actual measurements in 94% of the 97 time points studied after 26 weeks. These results indicate that the Rossavik model and its associated individual growth curve standards can be used to evaluate the growth of the femur and thus provide an improved means for detecting skeletal dysplasias and fetal growth retardation.     

Fetal growth: a comparison of growth curves with mathematical modeling

This study compared the use of fetal growth curves with the Rossavik mathematical model in predicting third trimester fetal growth in 27 Hispanic patients. The parameters tested were BPD, HC, AC, and FL. The growth curve method of predicting third trimester fetal growth was significantly more accurate than the mathematical model for three of the four fetal parameters tested: BPD, HC, and FL. We conclude that the mathematical model method offered no advantage over the more commonly used growth curve method for predicting third trimester fetal growth. In addition, growth curves do not require complex calculations and are conceptually simpler and easier to use.     

未足月胎膜早破390例期待疗法时间及终止妊娠时机分析

目的探讨未足月胎膜早破期待疗法时间及终止妊娠时机的选择,以降低围生儿死亡率。方法回顾性分析390例未足月胎膜早破患者的临床资料,其中孕周28-33辐周138例,孕周34-36柏周252例。对无临床感染征象或其他产科并发症者,采用保守治疗延长孕周;对于胎肺已成熟或有宫内感染、胎儿窘迫等终止妊娠指征者终止妊娠。结果孕周28-33“周新生儿窒息、感染、颅内出血、围生儿死亡、新生儿呼吸窘迫综合征发生率明显高于孕周34-36“周（均P〈0.05）。结论胎膜早破期待疗法时间及终止妊娠时机根据孕周及母婴情况而定。     

Second-trimester biparietal diameter/nasal bone length ratio is an independent predictor of trisomy 21.

OBJECTIVE: The purpose of this study was to evaluate the association between the second-trimester fetal biparietal diameter/nasal bone length (BPD/NBL) ratio and trisomy 21. METHODS: Thirty-one cases of trisomy 21 for which complete ultrasound images included the nasal bone were identified from the University of Washington prenatal diagnosis database and matched to 136 euploid fetuses based on maternal age, indication for referral, and gestational age. RESULTS: The mean NBL was shorter (mean +/- SD, 2.3+/-1.7 mm versus 3.9+/-1.2 mm; P<.001) and the BPD/NBL ratio was greater (17.7 [range, 6.2-114] versus 11.7 [range, 5.8-80]; P<.001) in the fetuses with trisomy 21. The risk of trisomy 21 increased 2.4-fold (95% confidence interval [CI], 1.7-3.4) with every 1-mm decrease in NBL and increased 1.08-fold (95% CI, 1.03-1.12) with each unit increase in the BPD/NBL ratio (P<.001). A multiple logistic regression model was constructed and included the BPD/NBL ratio, maternal indications (age>or=35 years, positive serum screening results, or both, yielding a risk of <1 per 270 for trisomy 21), and sonographic markers as covariates. The BPD/NBL ratio was found to be an independent predictor of trisomy 21 (odds ratio, 1.08; 95% CI, 1.03-1.11). An analysis of receiver operating characteristic curves revealed an improvement after the BPD/NBL ratio was added to a model containing the current second-trimester screening based on maternal age, serum screening, and sonographic markers (receiver operating characteristic curve area, mean +/-SE, 0.89+/-0.03 for the model with the BPD/NBL ratio versus 0.76+/- 0.06 without the BPD/NBL ratio; P=.009). CONCLUSIONS: The second-trimester BPD/NBL ratio was a significant and independent predictor of trisomy 21. An assessment of the BPD/NBL ratio may improve the diagnosis of trisomy 21 when used with current prenatal screening practices.     

Biparietal diameter and menstrual age in the black population attending Edendale Hospital

The relationship between fetal biparietal diameter measured by echography and menstrual age for blacks was studied. Predicted values and their confidence limits are presented in tables and graphs. The biparietal diameter was significantly smaller from 28 weeks than American and European studies, demonstrating that a composite graph was not applicable to the Zulus. The echographic results were checked at term by external cephalometry. Occipitofrontal circumference and birth weights for newborns were found similar to other studies. The smaller BPD in late pregnancy could be explained by the head's shape. The new charts are valuable in assessing fetal growth in African blacks.     

Intima-Media Thickness Measurements in the Fetus and Mother During Pregnancy: A Feasibility Study

Fetal intima-media thickness (IMT) has been suggested as a marker of pre-clinical atherosclerosis, and maternal IMT could be altered through dynamic circumstances related to pregnancy. We investigated the feasibility of measurement of IMT at four pre-defined fetal and four pre-defined maternal arterial locations to determine vascular changes that could be associated with impaired vascular function. IMT was measured from the first to third trimester (12–34 wk), in 38 low-risk pregnancies. We imaged a 10-mm region of interest using a Mindray (Shenzhen, China) high-resolution ultrasound machine with automated IMT measurement software. Fetal abdominal aorta IMT was measurable during the second trimester in 71% and during the third trimester in 100% of the case, and umbilical artery IMT was measurable in 50% and 82% of cases during the second and third trimesters, respectively. Fetal IMT measurements were not possible during the first trimester. It was not often feasible to measure the IMT of the fetal common carotid artery, fetal renal artery and maternal iliac artery (maximal 20% of cases). Maternal common carotid artery, abdominal aorta and uterine artery IMTs were measurable throughout pregnancy. There was a significant relation between gestational age and IMT in the umbilical artery (p = 0.03) and a significant relation between body mass index and IMT in the maternal common carotid artery (p = 0.01). IMT measurements are feasible in some maternal and fetal vessels of interest. Further studies are underway to obtain more insight into vascular development during normal and pathologic pregnancies.     

Simultaneous assessment of fetal lung maturity and sebaceous gland function by gas chromatography

Lipid profiles were analysed by gas chromatography of underivatised extracts from pellets and supernatant fractions of amniotic fluid (AFP and AFS). Peaks, identified as diglycerides resulting from on column decomposition of phosphoglycerides at high temperature, were obvious in gas chromatograms of AFS. The C₃₂ diglyceride, mainly derived from dipalmityl lecithin, was not a prominent peak in AFS from pregnancies from which babies subsequently developed respiratory distress syndrome. There was evidence of a moderate increase of squalene in AFS and AFP for 10 pregnancies of 36–38 weeks gestation resulting in the birth of small for gestational age babies. The increase was not obvious for 21 out of 22 control pregnancies delivering appropriate for gestational age babies. This demonstrated that we had an assessment of two fetal functions in one chromatographic run, the ratio of C₃₂/C₃₄ diglycerides providing a measure of lung maturity and squalene providing an index of proximity to term or of the presence of intrauterine growth retardation.     

Four-chamber view of the fetal heart: demonstration related to menstrual age.

The four-chamber view of the fetal heart is the most widely used screening examination for the detection of structural cardiac abnormalities during routine fetal ultrasonography. A prospective study of 520 consecutive routine fetal sonograms taken between 13 and 39 weeks of gestational age was performed to determine the frequency of obtaining a satisfactory four-chamber view, focusing on fetuses of less than 19 weeks' menstrual age. Menstrual age was a significant variable in procuring a satisfactory four-chamber view. Visualization of a normal four-chamber view on film progressively increased from five out of 15 (33%) at 14 weeks of menstrual age to 35 out of 38 (92%) at 19 weeks of menstrual age; real-time evaluation improved visualization to six out of 15 (40%) at 14 weeks of menstrual age and to 36 out of 38 (95%) at 19 weeks of menstrual age. Visualization in all fetuses scanned before 19 weeks' menstrual age improved from 62 (on film only) to 75% (real-time and film). Abnormalities on the four-chamber view were demonstrated before 19 weeks of menstrual age in four cases. Although not all serious cardiac defects can be detected, the four-chamber view remains a reliable screening examination of the fetal heart even early in gestation.     

The evaluation of fetal lung maturity by amniotic fluid analysis.

The frequent necessity for termination of pregnancy before the spontaneous onset of labor requires that we be able to accurately predict fetal lung maturity. We have used amniotic fluid studies for evaluation of fetal lung maturity and have found that (1) a "fat" cell concentration of 30% or more, or (2) a creatinine concentration of 2.0 mg/100 ml or more, or (3) a lecithin:spingomyelin (L:S) ratio of 2.0 or greater all correlated well with fetal maturity. Since each of these studies is open to a variety of possible errors, the use of several different ones adds reliability to the estimation of fetal lung maturity.     

Influence of the interval between time points on individual fetal growth curve standards derived from Rossavik models and two ultrasound scans before 26 weeks, menstrual age

We studied the influence of the interval between the two scans used before 26 weeks' menstrual age to generate individual fetal growth curve standards utilizing the Rossavik growth model: P = c(t) kappa + s(t) (model specification functions previously reported). Intervals of 3 weeks to 12 weeks were suitable for predicting the growth of the abdominal and head circumferences and femur diaphysis length in individual fetuses. However, large systematic and random errors were found with intervals less than 5 weeks for three-dimensional parameters such as the head and abdominal cubes and estimated fetal weight. In addition, the data suggest that the systematic errors for these latter parameters may increase with intervals of 10 weeks or more. Overall, optimal individual fetal growth curve standards were best generated from two scans before 26 weeks' menstrual age separated by 5 weeks to 9 weeks.     

Estimated fetal weight in the detection of the small-for-menstrual-age fetus

The purpose of this study was to assess the value of calculated fetal weight in the detection of the small-for-menstrual-age fetus. An ultrasound screening scan was performed on 1624 singleton pregnancies at 30 weeks to 36 weeks, menstrual age. Head, abdomen, and femur diaphysis measurements were recorded and used to estimate fetal weight. These and other more widely used parameters were used to predict birth weight below the 10th percentile for menstrual age. Estimated fetal weight at 34 weeks achieved sensitivity of 100% and specificity of 70%, the best result for any parameter. Specificity is improved using growth measurements.     

Estimation of gestational age during the first trimester by real-time measurement of fetal crown-rump length and biparietal diameter

A series of 237 patients in the first trimester of pregnancy were examined to derive normal growth curves for fetal crown-rump length (CRL) and biparietal diameter (BPD) using sector scanner real-time ultrasound equipment. Conventional B-scan CRL measurements were obtained from 50 of these patients: In 41 (82%), the values fell within a range ± 5 mm of those of real-time. Another group of 97 patients between 7 and 13 wk of gestation was then examined in a blind trial to confirm the accuracy of real-time measurements in estimating gestational age. An estimate was made in 95% of cases to within 4.6 days with CRL and to within 5 days with BPD. A similar comparison was made with both of these dimensions using a comparative nomogram, giving a prediction within 3.9 days in 957percnt; of cases. This method is now used routinely.     

The Ontogenesis of Human Fetal Hormones: I. GROWTH HORMONE AND INSULIN

The content and concentration of immunoreactive growth hormone (GH) were measured in 117 human fetal pituitary glands from 68 days of gestation to term and in the pituitary glands of 20 children 1 month to 9 yr of age. Physicochemical and immunochemical properties of GH of fetal pituitary glands and GH from adult pituitary glands were indistinguishable by disc gel electrophoresis, immunoelectrophoresis, starch gel electrophoresis, and radioimmunoassay techniques. In the fetal pituitary gland, the GH content rose from mean levels of 0.44+/-0.2 mug at 10-14 wk of gestation, to 9.21+/-2.31 mug at 15-19 wk, to 59.38+/-11.08 mug at 20-24 wk, to 225.93+/-40.49 mug at 25-29 wk, to 577.67+/-90 mug at 30-34 wk, and to 675.17+/-112.33 mug at 35-40 wk. There was a significant positive correlation between growth hormone content of the pituitary and gestational age, crown-rump length, and the weight of the pituitary gland.The content and concentration (micrograms/milligram) of human growth hormone (HGH) in the fetal pituitary showed significant increments (P < 0.001) for each 4 wk period of gestation until 35 wk. Further increases in the HGH content were noted in pituitaries of children aged 1-9 yr (range of 832 to 11.211 mug).Immunoreactive GH was detected in fetal serum at a concentration of 14.5 ng/ml as early as 70 days gestation, the youngest fetus assayed. At 10-14 wk, the mean concentration of serum growth hormone was 65.2+/-7.6 ng/ml; at 15-19 wk 114.9+/-12.5 ng/ml; at 20-24 wk 119.3+/-19.8 ng/ml; at 25-29 wk 72.0+/-11.5 ng/ml; and 33.5+/-4.2 ng/ml at term. A significant negative correlation of serum growth hormone with advancing gestational age after 20-24 wk was observed (P < 0.001). In 17 fetuses paired serum and pituitary samples were assayed; no significant correlation between the concentration of serum GH and the pituitary content or concentration of GH was demonstrable.The serum concentration of chorionic somatomammotropin (HCS) in the fetus was unrelated to gestational age. Insulin (1-30 muU/ml) was detected in 42 of 46 fetal sera assayed.These data suggest that the appearance and development of the secretory capacity for GH by the human fetal pituitary gland coincides with developmental changes in the portal system and hypothalamus. Maturation of inhibitory central nervous system control mechanisms for secretion of GH may not occur until infancy.