Ultrasonographic measurement of fetal femur length in growth disturbances

Normal Fetal Growth Assessment: A Review of Literature and Current Practice

A review of literature and current practice of normal fetal growth assessment is presented. Ultrasonographic dating of pregnancy in the first, second, and third trimester is reviewed. Individual biometric parameters are examined, and the proper use of the fetal growth profile is explained. Use of this information is discussed as it pertains to the single pregnancy.

Shortened fetal long bones: a possible in utero manifestation of placental function

Shortened fetal long bones (SFLB) are usually indicative of a skeletal dysplasia. Our aim in this observational retrospective study was to describe a new association between SFLB, small for gestational age (SGA) fetuses and placental abnormalities, and to suggest an aetiologic explanation. During the last decade we have evaluated nine cases in which SFLB (more than 2SD below the mean) was associated with SGA, abnormal maternal serum placental hormones and abnormal placental sonography. Six cases had significantly increased second trimester maternal serum beta hCG and four developed toxaemia of pregnancy or had chronic hypertension. On histology, mature placentas with vascular abnormalities, including chorangiosis, large infarcts and slightly increased syncytial knots were noted. The combination of SFLB, SGA fetuses and placental abnormalities (sonographic, as well as histological) suggested a possible common pathway in the aetiology of this association.

Fetal biometric parameters, twin type and birth weight difference. A longitudinal study

OBJECTIVE

To examine the relationship between twin type, divided by zygosity, chorionicity, and birth weight difference [more or less than 15% intertwin weight difference at delivery] on fetal biometric measurements, including biparietal diameter, transverse abdominal diameter, head and abdominal circumferences (AC) and head and abdominal areas, femur length (FL), transverse cerebellar diameter, cerebellar circumference and cerebellar area at 18, 23, 28 and 32 weeks of gestational age.

STUDY DESIGN

A prospective and longitudinal study was done on 75 twin pairs that did not present the twin-twin transfusion syndrome (150 fetuses) divided into birth weight difference group I (<15%) and group II (>/=15%). The twin pairs were divided into three groups: dizygotic, monochorionic, and dichorionic-monozygotic. In each group the differences in various ultrasound indices were evaluated in reference to discordant growth or concordant growth.

RESULTS

In our sample, there were no monozygotic twin pairs with dichorionic placentation with a birth weight difference of more than 15%. Significant associations of group and gestational age were found in dizygotic and monochorionic twins. Intrapair differences were significantly higher in group II (>/=15%) than in group I (<15%) for all fetal parameters studied except for AC, abdominal area and all cerebellar parameters. The value of these discrepancies increased according to gestational age except for FL. Significant interactions between group and zygosity type indicated that intrapair FL differences were more associated with group in monochorionic twins, whereas intrapair transverse cerebellar diameter differences were more associated with group in dizygotic twins.

CONCLUSION

Our data show that most fetal biometric parameters are associated with birth weight discordancy. Abdominal area could be a relevant marker for twins with obstetric complications. Note that this is the first research that has studied a twin sample divided by both twin type and birth weight group.

Intrapartum fetal subcutaneous tissue/femur length ratio: an ultrasonographic clue to fetal macrosomia

OBJECTIVE

Our purpose was to compare the accuracy of ultrasonographic intrapartum measurement of fetal abdominal circumference, estimated fetal weight, and fetal subcutaneous tissue/femur length ratio in predicting large-for-gestational-age fetuses.

STUDY DESIGN

A cross-sectional analysis of 173 normal patients delivered of normal, appropriate-for-gestational-age infants (group 1) was performed to determine the normal changes of standard fetal biometric parameters and subcutaneous tissue throughout pregnancy. Measurements of fetal subcutaneous tissue were made at the level of the femoral diaphysis. A second group of 101 well-dated patients had these measurements obtained within 24 hours of delivery (group 2). Large for gestational age was defined as a birth weight > 90th percentile for gestational age. The sensitivity and specificity for prediction of large for gestational age of an intrapartum measurement of an abdominal circumference > 90th percentile, estimated fetal weight > 90th percentile, and fetal subcutaneous tissue/femur length ratio > 2 deviations of the mean was calculated.

RESULTS

In group 1 the mean gestational age was 31.4 +/- 5.4 weeks (range 17 to 41 weeks). The femur length, abdominal circumference, and fetal subcutaneous tissue correlated well with gestational age (p < 0.0001). The fetal subcutaneous tissue/femur length ratio was stable throughout pregnancy, with a mean of 0.05 +/- 0.014 (range 0.02 to 0.09, R2 0.09). In group 2 mean gestational age was 38 +/- 2.5 weeks (range 30 to 42 weeks). Mean birth weight was 3280 +/- 740 gm (range 1513 to 4801 gm). Nineteen (19%) fetuses were large for gestational age. Significant differences were found between the appropriate- and large-for-gestational-age fetuses for birth weight, abdominal circumference, estimated fetal weight, and fetal subcutaneous tissue/femur length ratio (p < 0.0001). The sensitivity and specificity of the fetal abdominal circumference, estimated fetal weight, and fetal subcutaneous tissue/femur length ratio were 44% and 98%, 68% and 85%, and 82% and 96%, respectively.

CONCLUSION

The fetal subcutaneous tissue/femur length ratio is a gestational age-independent parameter that has a greater sensitivity than the fetal abdominal circumference or estimated fetal weight formula for the intrapartum identification of large-for-gestational-age fetuses.

Ultrasonographic measurement of cheek-to-cheek diameter in fetal growth disturbances

OBJECTIVE

Our purpose was to assess the value of the cheek-to-cheek diameter and the cheek-to-cheek diameter/biparietal diameter ratio in the ultrasonographic detection of abnormal fetal growth.

STUDY DESIGN

The cheek-to-cheek diameter and cheek-to-cheek diameter/biparietal diameter ratio were examined in 21 small-for-gestational-age (< 10th percentile for estimated weight) and 87 large-for-gestational-age (> 90th percentile) fetuses. Statistical analysis consisted of Student's t test comparison between means and analysis of covariance for comparison of regression lines slope between these 108 fetuses and previously published nomograms of appropriate-for-gestational-age fetuses.

RESULTS

The mean cheek-to-cheek diameters in small-for-gestational-age fetuses were significantly smaller than in appropriate-for-gestational-age fetuses (p < 0.0001). In large-for-gestational-age fetuses the mean cheek-to-cheek diameters were significantly larger (p < 0.005). Although large-for-gestational-age fetuses of diabetic mothers exhibited higher cheek-to-cheek diameter/biparietal diameter ratios than did appropriate-for-gestational-age fetuses (p < 0.0001), in fetuses of nondiabetic mothers this ratio was only minimally larger (p < 0.05).

CONCLUSION

The cheek-to-cheek diameter and cheek-to-cheek diameter/biparietal diameter ratio are innovative ultrasonographic parameters for detecting abnormal fetal growth. Furthermore, the cheek-to-cheek diameter/biparietal diameter ratio permits insight into the possible underlying pathophysiologic mechanisms of fetal macrosomia.

Fetal sacral length in the ultrasonographic assessment of gestational age

OBJECTIVE

Our purpose was to establish a nomogram of fetal sacral length throughout gestation and to assess its value in cases of abnormal fetal growth.

STUDY DESIGN

A prospective cross-sectional study of 506 singleton fetuses with normal growth between 15 and 41 weeks' gestation was performed. Regression analyses were performed on sacral length, gestational age, biparietal diameter, head circumference, and femur length. The sacral length in 80 singleton gestations with abnormal growth (40 > 90th percentile and 40 < 10th percentile for gestational age) were compared with the nomogram.

RESULTS

Linear relationships between gestational age and sacral length, biparietal diameter, head circumference, and femur length were demonstrated. Sacral length (centimeters) as a function of gestational age (weeks) was expressed by the regression equation: Sacral length = -0.108 + 0.102 Gestational age, with a Pearson correlation coefficient of R2 = 0.959. The sacral length of all 80 fetuses with abnormal growth demonstrated the same relationship to gestational age as did the 506 normal controls.

CONCLUSION

This study defines the normal limits of sacral length; demonstrates a high correlation between sacral length, gestational age, and other standard measurements of fetal growth; and indicates that sacral length can predict gestational age, irrespective of fetal nutritional status.