Quantitative and morphological assessment of early gestational sacs using three-dimensional ultrasonography.

OBJECTIVE: Our main objective was to determine the value of three-dimensional ultrasonography (3DUS) and Virtual Organ Computer-aided AnaLysis (VOCAL) in the evaluation of gestational sac volume and morphology during early pregnancy. METHODS: Twenty-eight normal early pregnancies were scanned approximately every 2 weeks using transabdominal (TAS) and transvaginal (TVS) sonography. The VOCAL technique was used to create computerized surface models to classify gestational sac shapes as discoid or ellipsoid. Serial sac volume changes were analyzed using repeated measures ANOVA. Bland-Altman plots determined examiner bias and limits of agreement (LOA) for sac volume measurements. Gestational sac volumes were compared between the two-dimensional (2D) ellipsoid and VOCAL techniques. Differences between volume measurements were tested using the two-tailed paired t-test with statistical significance at the P < 0.05 level. RESULTS: Each subject was examined at a mean +/- SD menstrual age of 7.9 +/- 0.6 weeks (Scan 1), 9.9 +/- 0.6 weeks (Scan 2), and 11.9 +/- 0.6 weeks (Scan 3). Sac volumes significantly increased over time from 22 +/- 11 mL at Scan 1, to 57 +/- 21 mL at Scan 2 and 116 +/- 35 mL at Scan 3 (P < 0.001). Predominant sac shapes were classified as ellipsoid (76.2%) or discoid (23.8%). Additional descriptors included: concave (60.7%), irregular (53.6%), or smooth (7.1%), with 19% of the overall group having more than one additional shape attribute. Clinically acceptable volume measurement bias and agreement were found for the following comparisons: (1) TAS versus TVS; (2) interobserver volume measurements; and (3) intraobserver volume measurements. The VOCAL technique yielded slightly greater sac volumes (64 +/- 45.4 mL) when compared to the 2D ellipsoid model (48.6 +/- 36.8 mL) (28.9 +/- 24.3% (95% limit of agreement range, - 18.7 to 76.5%), P < 0.001). CONCLUSIONS: Reproducible sac volume measurements can be obtained using VOCAL with either TAS or TVS. Early gestational sacs variably appear as discoid or ellipsoid structures with a concave indentation from the placenta. Sac volumes can be underestimated if an ellipsoid shape is assumed. Morphological and quantitative analysis of the gestational sac may provide baseline parameters for studying patients at risk for early pregnancy failure.

Individualized growth assessment of fetal soft tissue using fractional thigh volume.

OBJECTIVES: The main goals of this study were to introduce fractional thigh volume (TVol) as a new soft tissue parameter for fetal growth evaluation, define its relationship to menstrual age, and develop individualized fetal growth standards based on Rossavik growth models. METHODS: A prospective, longitudinal study of 22 fetuses was conducted with conventional biometry and TVol measurements by three-dimensional ultrasonography. Infant growth outcomes were determined from modified neonatal growth assessment scores. Rossavik functions (P = c(t)k+s(t)) were used to fit complete datasets to examine relationships between TVol and model coefficients. Second-trimester models were subsequently specified from the linear slopes of growth curves before 28.0 menstrual weeks with each fetus acting as its own control. Third-trimester trajectories and birth measurements were predicted for standard growth parameters and TVol. Observed and predicted measurements were compared using percent deviations and growth potential realization index values. Four additional infants, with serial prenatal scans and postnatal evidence of intrauterine growth restriction (IUGR), were also evaluated. RESULTS: All 22 fetuses had no evidence of growth abnormalities after delivery. Accelerated soft tissue deposition occurred in the fetal thigh by 28 menstrual weeks. A mean TVol start point of 9.0 +/- 1.4 menstrual weeks was consistent with embryological studies of thigh development. Rossavik functions fitted all TVol trajectories well (mean R2 = 0.998 +/- 0.002). By fixing the coefficient k at its mean value (2.976), the fit did not change and the variabilities of coefficients c and s were reduced. The mean percent deviation between observed and predicted third-trimester TVol measurements was -0.048 +/- 7.5%. Relatively early pathological deviations were observed for TVol in all four fetuses with IUGR; in these cases the abdominal circumference was abnormal in only one fetus and thigh circumference in none. CONCLUSIONS: Individualized growth assessment can be used to accurately predict TVol during the third trimester of pregnancy and at birth. Expected growth trajectories, from second-trimester data, do not rely on population-based standards because each fetus serves as its own control. This new parameter may allow earlier detection and improved monitoring of fetal soft tissue abnormalities such as IUGR.