The use of fetal foot length to determine stillborn gestational age in Vietnam

ObjectiveTo assess the use of fetal foot length for predicting gestational age in stillborn fetuses in Vietnam and the ability of this measurement to differentiate early from late fetal deaths.MethodsIn a prospective case series, gestational age was determined from either certain first day of last menstrual period or early ultrasound scan. Foot length was measured, with a non-elastic tape measure, from the heel to the tip of the longest toe. Agreement of observed and predicted foot length for gestational age was tested, as well as the influence of fetal characteristics.ResultsAccurate gestational age and foot length were available for 52 of 107 participants. Strong agreement was demonstrated between observed and predicted values of foot length across gestations (95% confidence interval, –4.7 to 4.3 weeks). Accuracy of fetal foot length in predicting gestational age was affected by growth restriction but not fetal gender, maceration, or congenital anomalies. Fetal foot length of 55 mm or greater demonstrated a sensitivity and specificity of 88% in identifying late fetal deaths.ConclusionFoot length is a good differentiator of early and late fetal death, which is important for the global recording of the number of stillbirths.     

Comparison of the accuracy of gestational age estimation from fetal heart rate and crown-rump length

Objective: To compare the accuracy of gestational age (GA) estimation predicted by fetal heart rate (FHR) versus crown-rump length (CRL) measurements in early pregnancies.Methods: A total of 145 infertile women with singleton intrauterine pregnancies conceived through in vitro fertilization underwent vaginal ultrasonographic examination in early stage of pregnancy. We performed 197 FHR and 398 CRL measurements. The relationship between GA (counted with the day of oocyte retrieval used as day 14) and the FHR or CRL was explored with regression analysis by means of least squares. Polynomials up to the third order were analyzed, and the coefficient of determination (R²) was calculated.Results: Fetal cardiac activity could be detected as early as 38 days, gradually increased to 188 beats per minute at 62 days of gestation. Regression analysis with GA as dependent variable resulted in R² values of 0.906, 0.907, and 0.908 for the first, second, and third order polynomials, respectively. The standard deviations around the regression line were 2.90, 2.81, and 2.84 days, respectively. The second order polynomial to describe GA (days) estimated by FHR (beats per min): GA = 3.02E-41FHR² + 1.60E-11FHR + 2.22E+1. On the other hand, the CRL was measured at 38 days to 62 days of gestation. Regression analysis resulted in R² values of 0.827, 0.839, and 0.841, respectively. The deviations were 4.11, 3.83, and 3.89 days, respectively. The second order polynomial to describe GA estimated by CRL (mm): GA = −2.10E-21CRL² + 1.49E+01CRL + 3.86E+1. There was no difference between the R² values and no difference between the standard deviations around the regression lines.Conclusion: Our results indicate no statistically significant difference in the accuracy of GA estimation predicted by FHR versus CRL measurements. But better mathematical fits were obtained when the data of FHR were used for GA estimation. These findings suggest that the FHR measurement may be a new method for early ultrasound dating. This study mentions for the first time the possibility of “FHR dating” with functional data.     

Fetal foot length: relationship to menstrual age and fetal measurements in the second trimester

The purpose of this study was to describe the ultrasonic measurement of fetal foot length and to develop mathematical models to quantify the relationships between menstrual age and commonly measured fetal structures. We evaluated 120 patients with known last menstrual periods and normal pregnancies to develop a cross-sectional study population. All patients had ultrasonic measurement of the fetal foot length, biparietal diameter, head circumference, abdominal circumference, and femur length. Least-squares estimation of linear models was used to select the best mathematical models to describe the relationship between menstrual age and fetal foot length. A similar evaluation of the relationship between fetal foot length and the other measured parameters was performed. All models were best described by a linear equation. An R2 value of 0.94, with a standard error of the estimate of 0.204, was obtained for menstrual age versus fetal foot length. When the model for fetal foot length and menstrual age was compared with published anatomical data, close agreement was seen over the time interval studied. Our results suggest that the measurement of fetal foot length with ultrasound gives a reliable assessment of anatomical fetal or neonatal foot length and is highly correlated to the menstrual age of the fetus.     

Fetal foot length as a predictor of gestational age

Ultrasonographic measurement of fetal foot length is useful in the assessment of gestational age. Two hundred twenty-three postpartum and 224 ultrasonographic measurements were performed between 11 and 43 weeks' gestation; 207 postpartum and 160 ultrasonographic measurements met our requirements of secure dates and no physical anomaly or maternal disease. Mean foot length at each week of gestation compared favorably with Streeter's data, based on pathologic specimens, described in 1920. Comparison of curvilinear regression of foot length versus gestational age demonstrated a strong correlation with an R2 value of 0.981; 95% confidence intervals at each week compared favorably with both biparietal diameter and femur length data. Fetal foot length is a reliable parameter for use in the assessment of gestational age and is particularly useful when other parameters do not accurately predict gestational age, for example, hydrocephalus, anencephaly, short limb dysplasia.     

Improving the accuracy of fetal foot length to confirm gestational duration

OBJECTIVE: To establish normative fetal foot length ranges using last menstrual period (LMP) and ultrasound dating by biparietal diameter and to examine variations in these ranges by ethnicity. METHODS: A consecutive series of 1,099 eligible subjects receiving abortions had fetal foot lengths measured directly. Models of fetal foot length were developed by using assessment of gestational duration by LMP alone, ultrasonography alone, and "best estimate" (LMP confirmed by ultrasonography). RESULTS: The full sample model using ultrasound dating (n = 1,099) yielded the following equation: foot length = -30.3 + days of gestation x 0.458 (R(2) of 0.92). Regression by LMP-determined gestational duration by using the "best estimate" sample (n = 491) provided an almost identical equation (foot length = -29.8 + days of gestation x 0.45) and a similar R(2) value of 0.87, although the standard errors were larger. Gestational duration by ultrasonography alone produced a better model fit than duration by LMP alone. Regressions by ethnicity were not significantly different compared with the simple regression, regardless of method used to determine gestational duration. CONCLUSION: A reconsideration of fetal foot length measurements to confirm gestational duration is important. More accurate tables of these measurements allow for greater precision in correlating gestational duration and foot length. Fetal foot length tables using ultrasonographically confirmed gestational duration and current statistical standards should replace tables currently used. Biparietal diameter as a single measurement provides adequate estimation of gestational duration in the second trimester for pregnancy termination, proving more reliable than LMP dating. LEVEL OF EVIDENCE: II-2.     

Ultrasound estimation of fetal weight in small for gestational age pregnancies

Objective.?Approximately half of small for gestational age (SGA) cases are due to maternal or fetal pathology, and may result in significant neonatal morbidity and mortality. The estimated fetal weight (EFW) measurement is the cornerstone of ultrasonographic findings when diagnosing and managing SGA pregnancies. Our objective was to determine the ultrasound accuracy of EFW in SGA pregnancies.

Methods.?A retrospective chart review was performed of all pregnancies complicated by SGA from a single institution (Stanford University) over a 2-year-period (2004–2006). SGA was defined as EFW?≤?10%. 98 neonates whose last ultrasound for EFW occurred within 7 days of delivery were included in the study. The absolute differences between the EFW and birthweight (BW) were analyzed, and the absolute percent errors were calculated as (EFW???BW)/BW?× 100. The mean absolute differences and mean absolute percent errors were analyzed across all gestational ages (GA) and EFWs using one-way analysis of variance.

Results.?The mean absolute percent error for the entire cohort was 8.7% (±6.3%). There was no statistically significant difference in the mean absolute percent error across all GAs (<32 weeks, 32–36 weeks, >36 weeks), and EFWs (<1500?g, 1500–2000?g, >2000?g).

Conclusion.?Ultrasound measurement of EFW in SGA pregnancies is consistent across all GAs and EFW measurements.     

Accuracy of ultrasonic fetal weight estimation and detection of small for gestational age fetuses

One hundred and eight-six pregnant women were studied with ultrasound for clinical suspicion of poor fetal growth. Fetal weight was estimated using biparietal diameter and mean abdominal diameter with a special nomogram. The fetal femur length (FL) to abdominal circumference (AC) ratio was also calculated. The mean interval between the last ultrasound examination and delivery was 9 days (range, 0 to 14 days). Eighty-three women had their last ultrasonic examination 0 to 4 days (mean, 2 days) before delivery. In this group the arithmetic mean of weight estimation errors was -1 gm (SD, 159 gm). The signed mean percent error was +0.6% (SD, 6.6%). Neither systematic nor random errors were found between different growth percentile groups. When small for gestational age (SGA) was defined as birthweight below 2.5 percentile, the sensitivity, specificity, and positive predictive value of the weight estimations were 82%, 92%, and 84%, respectively, in 186 cases. Significant differences were found in FL to AC ratios between growth pattern groups but fetal weight estimation was found to be superior in the detection of SGA fetuses.     

Ultrasonographic assessment of gestational age with the distal femoral and proximal tibial ossification centers in the third trimester

A prospective sonographic evaluation of the distal femoral and proximal tibial epiphyseal ossification centers in 228 normal pregnant women was carried out from 28 to 40 weeks' gestation. The mean gestational age at which the distal femoral epiphysis and proximal tibial epiphysis were imaged was 34 and 38 weeks, respectively. The distal femoral epiphysis was not identifiable before 28 weeks but was observed in 72% of fetuses at 33 weeks and in 94% of fetuses at 34 weeks' gestation. The presence of a distal femoral epiphysis measuring 1 or 2 mm was associated with a gestational age of greater than 33 weeks in 87.0% of fetuses, whereas a distal femoral epiphysis measuring greater than or equal to 3 mm was associated with a gestational age greater than 37 weeks in 85% of fetuses. The proximal tibial epiphysis, which was absent before 34 weeks' gestation, was observed in 56% of fetuses at 36 weeks, in 80% of fetuses at 37 weeks, and in 100% of fetuses at 39 weeks of gestation. The presence of a proximal tibial epiphysis of 1 or 2 mm was associated with a gestational age of greater than 36 weeks in 88% of fetuses, whereas a proximal tibial epiphysis greater than or equal to 3 mm was associated with a gestational age of greater than 38 weeks in 94% of fetuses. The sonographic evaluation of distal femoral epiphysis/proximal tibial epiphysis can be used as independent markers for estimation of gestational age during the third trimester, a period in which standard fetal biometric estimates of gestational age are least accurate.     

The significance of fetal sacral length in the ultrasonographic assessment of gestational age

Objective  

The present study aims to establish a more sensitive nomogram of fetal sacral length measurements, as well as to specify the accuracy of fetal sacral length for the ultrasonographic assessment of gestational age.     

The accuracy of radiological estimates of gestational age using early fetal crown-rump length measurements by ultrasound as a basis for comparison.

Radiological estimates of gestational age in late pregnancy were compared with the gestational ages based on first trimester ultrasound crown-rump length measurements in a series of 125 patients. It was found that the 95 per cent confidence limits of a radiological estimate were +/- 3 1/2 weeks, that both distal femoral and upper tibial epiphyses were frequently present much earlier than 36 and 38 weeks respectively, and that in almost half of the growth-retarded babies in the series there was a bone-age discrepancy of three or more weeks. It is recommended that more liberal use is made of early ultrasound measurements for the assessment of gestational age.     

Sonographic study of the relationship between gestational diabetes mellitus and fetal activity

Objective: To evaluate the relationship between gestational diabetes mellitus (GDM) and fetal activity. Materials and methods: We prospectively studied 18 pregnant patients with GDM and 20 pregnant patients with normal glucose screening test. An ultrasound equipmentwas used to perform a 30?min transabdominal sonographic recording for each patient. Each ultrasound exam was recorded using a DVD recorder. Fetal activity was analyzed using duration and number of episodes of fetal breathing and body movements. The recordings were analyzed using a stopwatch in order to accurately evaluate each recording. The data was statistically analyzed using the parametric and non-parametric t-test. Results: The results of the study indicated that there was a significant correlation (p?=?0.007) between the duration of fetal breathing movement and GDM. Fetuses of mothers suffering from GDM had a significantly longer duration of fetal breathing movements compared with fetuses of non diabetic mothers. In addition, the total duration of fetal activity (time of fetal body movements plus fetal breathing movements) was significantly higher (p?=?0.005) in GDM compared with non GDM pregnancies. The difference in fetal body movements between GDM and normal pregnancies was not statistically significant. Conclusion: The results of this study support the hypothesis that GDM has a direct influence on fetal activity. The significance of this finding should be further evaluated.     

Fetal foot length--a new parameter for assessment of gestational age

Ultrasonographic measurement of fetal foot length, a new parameter, was correlated with the gestation age. One hundred and five ultrasonographic measurement of fetal foot length was performed between 13 and 42 weeks gestation. Comparison of linear regression of foot length versus gestational age demonstrated a strong correlation with an r2 value of 0.84 (P less than 0.001). Ninety-five percent confidence intervals at each week compared favorably with both biparietal diameter and femur length data. Mean foot lengths at each week of gestation compared favorably with data based on pathological specimens described in 1920 (Streeter GL: Weight, sitting height, head size, foot length and menstrual age of the human embryo. Contrib Embryol Carnegie Inst. 11: 143, 1920). Measurement of fetal foot length is of particular use when other parameters do not accurately predict gestational age, e.g. hydrocephalus, anencephaly, short limb dysplasia. It can also be used in conjunction with biparietal diameter and femur length in the management of patients with premature labor in order to patients with premature labor in order to accurately predict gestational age. Hence the present study demonstrates that the ultrasonographic measurement of foot length is a reliable indicator of gestational age.     

Conceptual age and ultrasound measurements of gestational sac and crown-rump length in in vitro fertilization pregnancies

The growth of the mean gestational sac diameter and the crown-rump length were evaluated from individual series and found to be linear in singletons, twins, and triplets from an in vitro fertilization program as well as in pregnancies with ovulation determined from serial ultrasound folliculograms. No difference in growth rate between the different groups was observed. The 95% confidence limits were 7.7 days before and 7.5 days after mean for the gestational sac diameter, and 5.2 days before and 5.6 days after mean for the crown-rump length. These limits, used together with new linear equations, create less anxiety and less unnecessary surgical intervention than current nonlinear standards when conceptual age is known and the gestational sac or the crown-rump length are too small to be measured.     

Accuracy of serum human chorionic gonadotropin concentrations and ultrasonic fetal measurements in determining gestational age

Prior to 60 days' gestation, the maternal serum concentration of human chorionic gonadotropin (hCG) can predict the estimated date of confinement, but later in pregnancy, hCG concentrations vary widely. The current study was performed to compare the accuracy of hCG measurements with other determinants of gestational age. Fifteen patients in whom gestational age was documented were monitored prospectively throughout pregnancy. One to two determinations of hCG (beta subunit) were obtained during the first 60 days. Then, ultrasonographic measurements of crown-rump length were obtained between 8 and 16 weeks' gestation and two measurements of biparietal diameter were performed between 18 and 32 weeks. These results were compared to actual dates of gestation. The mean (+/- SD) difference between gestational age predicted by single measurements of hCG and actual gestational age was 3.2 +/- 2.5 days (r = 0.94, p less than 0.0001), which compared favorably with estimates by crown-rump measurements (6.7 +/- 6.5 days) and measurements of biparietal diameter (6.3 +/- 5.3 days). These results demonstrate that hCG measurements during the first 60 days accurately predict gestational age and complement ultrasonic determinations of gestational age used later in pregnancy.     

The ultrasonic measurement of fetal crown-rump length as a method of assessing gestational age.

The fetal crown-rump length (CRL) was measured by means of pulsed ultrasound, and the normal values between 47 and 101 days from the onset of the last menstrual period were determined from cross-sectional data in 253 patients. For any given CRL, the range was found to be within three days of the menstrual age with a maximum variation for a given occasion of three days. Detailed statistical analysis showed that the acceleration in the rate of change in the CRL was a constant and that the intrapatient variability, where measured, was low. A close correlation between the measurement and the date of ovulation was demonstrated in a further 40 patients.     

Prediction of fetal outcome in small for gestational age fetuses: comparison of Doppler measurements obtained from different fetal vessels.

Blood flow velocity waveforms were recorded from different vascular districts including umbilical artery, descending aorta, renal artery, internal carotid artery and middle cerebral artery in a population of 120 small for gestational age fetuses free from structural and chromosomal abnormalities. The pulsatility index from each vessel as well as the ratios between the pulsatility indices from peripheral and cerebral vessels were calculated and related to perinatal outcome. The pulsatility index of middle cerebral artery resulted the most efficient measurement to predict the development of perinatal adverse outcome when each vessel was considered singularly, however, better results were achieved when the ratios between pulsatility indices were related to perinatal outcome; this is mot evident for the ratio between the pulsatility indices of umbilical artery and middle cerebral artery. Our results suggest the usefulness of this ratio in differentiating small for gestational age fetuses at risk of unfavorable outcome.     

Symphysis-fundus measurements for detection of small for gestational age pregnancies

BACKGROUND: In Sweden measurements of the symphysis-fundus (SF) distance are used to detect small for gestational age (SGA) pregnancies. The aim of this study was to evaluate the efficiency of Swedish ultrasound-based SF reference curves in detecting SGA pregnancies. METHODS: To assess the sensitivity for detection of SGA pregnancies we performed a case-control study. Through the Swedish Medical Birth Register we identified all singleton SGA infants born in Uppsala in 1993-1997 and randomly recruited non-SGA singleton infants as controls. We included 169 term and 73 preterm SGA cases and 296 controls, all born at term. The reference curves constructed by Steingrimsdottir (S curve) and Kieler (K curve) were evaluated. Gestational age at the first alarm in the preterm SGA group was recorded. RESULTS: In term pregnancies the S curve showed a sensitivity of 32% and specificity of 90% at a cut-off of -2 SDs. The corresponding values for the K curve were 51% and 83%, respectively. In preterm SGA pregnancies the sensitivity of the S curve was 49% and of the K curve 58%. The first alarm below 2 SDs was noted before 32 weeks in 37% with the S curve and 43% with the K curve for preterm SGA pregnancies. CONCLUSIONS: Both tested Swedish SF reference curves had low sensitivities for term SGA pregnancies. Sensitivity was higher for the preterm group and SF measurements seem to be better for detecting the most severe cases of SGA.