Fetal clavicle length throughout gestation: a nomogram.

OBJECTIVE: To create a nomogram of fetal clavicle length (CL) throughout gestation. METHODS: Cross-sectional study of patients between 14 and 42 weeks' gestation. Inclusion criteria consisted of well-established dates (consistent with early ultrasound), singleton, non-anomalous fetuses, and intact amniotic membranes. Sonographic measurements included biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), femur length (FL), humerus length (HL) and sonographically estimated fetal weight (SEFW). For every case, the average of three separate measurements of the CL was used. The 5th, 50th and 95th centiles were obtained by least squares regression. Pearson's correlation coefficient and associated P-values for the relationships between CL and other biometric measurements were calculated. The data were compared to a nomogram of the CL generated in 1985 from the measurement of 85 fetuses. RESULTS: A total of 623 consecutive patients were studied. In all but three cases, CL was successfully measured. Mean maternal age was 27.7 +/- 6.2 years, median gravidity 3 (range, 1-14) and median parity 1 (range, 0-9). Mean CL (mm) = -75.30 + 32.70*ln(GA) and SD = -0.41 + 0.08328*GA, where ln represents the natural logarithm and GA the gestational age in weeks. Fetal CL correlated significantly and strongly with BPD, HC, AC, HL, FL and the logarithm of SEFW, with Pearson correlation values of 0.973, 0.977, 0.976, 0.979, 0.977 and 0.979, respectively (all P < 0.001). Measurements according to comparable 1985 data were consistently substantially below the present data (smaller CL for any given GA except below 17 weeks' gestation). CONCLUSIONS: We propose a new nomogram of CL, which differs significantly from the previously published nomogram. We suggest that the present data reflect the use of high-resolution ultrasound technology and propose that these data, based on a large number of fetuses, replace the previous nomogram. We also suggest that the '1 mm = 1 week' rule of thumb should no longer be used, since it can be erroneous by as much as 6 weeks.     

Revisiting first-trimester fetal biometry.

INTRODUCTION: Although advances in ultrasound have facilitated the diagnosis of fetal abnormalities in the first trimester, fetal biometry at this stage of pregnancy remains underused in prenatal diagnosis. We hypothesized that charts which directly correlate measurements to crown-rump length (CRL) could be more accurate than those based on gestational age (GA) derived from CRL measurement. The aim of this study was to construct CRL-based biometric charts. METHODS: Measurements of biparietal diameter (BPD), head circumference (HC) and abdominal circumference (AC) were prospectively collected from 939 normal singleton fetuses. Charts and predictive equations were constructed from data obtained from pregnancies in which the CRL was between 45 and 84 mm and for which the outcome was normal. RESULTS: Measurements of BPD, HC and AC from 880 fetuses who met the criteria were correlated with CRL and used to construct charts and predictive equations. The standard error of estimates using CRL was significantly lower than that using GA in all cases. DISCUSSION: First-trimester growth charts and predictive equations based on CRL instead of GA are more accurate. They might have a role in quality control of first-trimester ultrasound examination and may help in the diagnosis of fetal conditions that involve early growth abnormalities.     

Predicted and actual fetal weight throughout the last trimester.

The aim of our study was to obtain, in normal pregnancies, references values of predicted and actual fetal weight for both male and female fetuses and for fetuses born to nulliparous and multiparous women between weeks 28 and 41 of gestation. Predicted fetal weight curves represented calculations of weight in the third trimester based on weight data obtained during the second trimester. These curves were obtained from 134 ultrasonograms obtained between weeks 20 and 27. Actual fetal weight curves represented the values calculated from third trimester measurements and were based on 374 ultrasonograms obtained between weeks 28 and 41. For predicted fetal weight minor differences were found between male and female fetuses and between fetuses born to nulliparous and multiparous women. For actual weights, differences increased progressively for gender and parity during the last trimester. Predicted weights progressed at a steeper rate, and this effect was stressed in cases of female fetuses and fetuses born to nulliparous women. If predicted weights reflect normal growth, differences between fetal gender or maternal parity might be due to environmental influences. Therefore, it might not be justified to construct separate weight charts differentiated by sex or parity.     

Evaluation of Fetal Spine Biometry Between 11 and 14 Weeks of Gestation

This study was designed to establish a fetal spine nomogram for age 11 through 14 weeks of gestation and to document relations among fetal spine length, distance and angle. These parameters were prospectively measured during the first trimester of singleton pregnancies, along with nuchal translucency, over a 3-year period. A total of 430 fetuses were included in the study. The regression equations among fetal spine parameters and gestational age were as follows: Spine length (mm) = 1.116 × gestational age (days) − 59.169; spine distance (mm) = 1.079 × gestational age (days) − 59.038; head–spine angle = 0.740 × gestational age (days) + 4.735; spine length:spine distance ratio = −0.002 × gestational age (days) + 1.234. Prenatal age-specific reference intervals for fetal spine biometry between 11 and 14 weeks of gestation may assist in evaluation of fetuses investigated for genetic abnormalities that can be expressed by deviation in spine length, distance, or angle. (E-mail: pjcheng@cgmh.org.tw)     

Prenatal detection of fetal aneuploidy by sonographic ear length.

OBJECTIVE: To determine the usefulness of a fetal ear length nomogram in the prenatal detection of fetal aneuploidy and to determine whether ear smallness in cases of aneuploidy is a primary or secondary event. METHODS: Ear lengths of 447 singleton fetuses (October 1996 to October 1997)were prospectively evaluated between 14 and 41 weeks to establish a nomogram created by modeling the mean and SD separately. Records of aneuploid fetuses were retrospectively reviewed, and their ear lengths were plotted against the nomogram to determine detection rates, with ear length in or below the 10th and 50th percentiles for a given gestational age and biparietal diameter used as abnormal cutoffs. RESULTS: The nomogram for fetal ear length measurements provided sufficient data to derive the 10th, 50th, and 90th percentiles on the basis of gestational age and biparietal diameter. The ear length of euploid fetuses was significantly correlated with gestational age (R2 = 0.96; P < .001) and biparietal diameter (R2 = 0.95; P < .001). From 96 aneuploid fetuses identified, 63 had ear lengths in or below the 10th percentile for gestational age (sensitivity, 66%). When using ear length against biparietal diameter, the sensitivities for all aneuploid fetuses for cutoffs at or below the 10th and 50th percentiles were 43% (40 of 93) and 83% (77 of 93), respectively. CONCLUSIONS: Most aneuploid fetuses have sonographically small ears (< or = 10th percentile for gestational age). This smallness is not entirely related to overall small fetal size, but in almost half the cases, the fetal ear length is disproportionately smaller than the biparietal diameter.     

Fetal scapular length in the ultrasonographic assessment of gestational age.

A prospective cross-sectional study of 515 singleton fetuses of ages between 15 and 42 weeks' gestation was performed. At gestational ages greater than 26 weeks, only fetuses with a sonographic estimated fetal weight between the 10th and 90th percentiles for growth were included. Scapular length (cm) as a function of gestational age (weeks) was expressed by the regression equation: SL = 0.3289 + 0.9553 (GA) with a Pearson correlation coefficient of R2 = 0.942. This study defines the normal limits of scapular length, demonstrates a high correlation between scapular length, gestational age, and other standard measurements of fetal growth, and indicates that scapular length can predict gestational age in fetuses with normal growth.     

Duplex Doppler sonography of the umbilical arteries: predictive value in IUGR and correlation with birth weight

Forty-three women with either clinically high-risk singleton pregnancies or a predicted fetal weight less than the 10th percentile were studied in their third trimester by duplex Doppler sonography of the free umbilical artery to assess the associations between umbilical arterial flow resistance and intrauterine growth retardation (IUGR) and birth weight. Test criteria included: the greatest (GRI), mean (MRI), and least (LRI) resistive index. The criterion with the strongest association with IUGR (p = 0.001) was the parameter of the LRI predicting IUGR). Linear regression analysis showed a nonsignificant correlation between RI and percentile birth weight, with r2 = 0.05 and p = 0.131. While significant associations can be shown between RI and IUGR, the clinical use of the results of this test should reflect the imprecise nature of these correlations.     

Sonographic detection of undescended testes in the third trimester.

OBJECTIVE: To assess the sonographic detection rate of fetal undescended testes among a low-risk population during the third trimester. METHODS: A sonographic evaluation, which included biometric studies and a detailed examination of the fetal genitalia, was performed prospectively on 332 male fetuses of singleton pregnancies between 34 and 40 weeks' gestation. A qualified neonatologist examined the presence of the testes within the scrotum within 3 days after birth. RESULTS: The scrotum was visible in 294 (89%) of the 332 fetuses who were examined. It was visible in all fetuses evaluated between 34 and 36 weeks' gestation. Nine cases of undescended testes were detected (3%). Of these, the diagnosis of 1 case, examined at 34 weeks' gestation, was revealed after birth to be false-positive. There were no false-negative results. CONCLUSIONS: Sonographic examination during the late third trimester of pregnancy appears to allow accurate diagnosis of undescended testes prenatally. This early identification will alert the neonatologist of the possibility of cryptorchidism and will permit early postnatal identification and treatment.     

Foot length in fetuses with abnormal growth.

Sonographic fetal foot length is highly predictive of gestational age. In order to assess the reliability of this parameter in predicting gestational age in cases of abnormal fetal growth, we examined fetal foot length in small- and large-for-gestational-age fetuses. A nomogram of foot length versus gestational age between 15 and 37 weeks was constructed using cross-sectional data obtained from 5372 singleton fetuses. Fetal foot lengths for small-for-gestational-age fetuses (estimated fetal weight below the 10th percentile) and large-for-gestational-age fetuses (above the >90th percentile) fetuses were plotted against the foot length nomogram in order to determine the number of small-for-gestational-age fetuses and large-for-gestational-age fetuses with foot lengths below the 10th and above the 90th percentiles, respectively. Of the 586 small-for-gestational-age fetuses, 355 (60.6%) had foot lengths below the 10th percentile on the nomogram. When foot lengths from large-for-gestational-age fetuses were plotted on the foot length nomogram, 29.4% (219 of 744) had measurements above the 90th percentile. Fetal foot length can be influenced by growth restriction as well as states of accelerated fetal growth. Our findings imply that there are limitations to the use of fetal foot length for gestational age assessment, particularly in fetuses with growth abnormalities.     

Abnormal maternal cardiac function and morphology in pregnancies complicated by intrauterine fetal growth restriction.

OBJECTIVE: To explore maternal cardiac function through an echocardiographic evaluation, in a group of nulliparous patients with intrauterine fetal growth restriction during the third trimester of pregnancy. METHODS: Twenty-one consecutive nulliparous pregnant women who had fetuses with intrauterine growth restriction (IUGR) and abnormal umbilical artery Doppler pulsatility index (PI) underwent maternal echocardiographic examination during the third trimester of gestation. The data were then compared with those obtained from 21 normal nulliparous women who had fetuses with an estimated fetal weight > 10th percentile and a normal umbilical artery Doppler PI who were considered as the control group. RESULTS: Heart rate was slightly lower in the IUGR group, whereas blood pressure and total vascular resistance were higher compared with the control subjects. End-diastolic volume, stroke volume and cardiac output were lower in the IUGR patients compared with normal patients. The IUGR group had smaller left atrial maximal dimensions and greater left atrial minimal areas compared with the control subjects. Left atrial function was depressed in the IUGR group. A smaller left ventricular mass was present in the IUGR patients compared with the control subjects. Isovolumetric relaxation time (IVRT) was prolonged in the IUGR patients compared with the controls. CONCLUSIONS: The absence of a 'correct' maternal cardiovascular compensatory response to abnormal trophoblastic invasion, might be one of the factors that slowly determine the conditions of reduced placental perfusion and eventually of the development of fetal growth restriction.