Embryo volume estimated by three-dimensional ultrasonography at seven to ten weeks of pregnancy

PURPOSE: to evaluate the embryo's volume (EV) between the seventh and the tenth gestational oreek, through tridimensional ultrasonography. METHODS: a transversal study wvith 63 normal pregnant women between the seventh and the tenth gestational week. The ultrasonographical exams have been performed with a volumetric abdominal transducer. Virtual Organ Computer-aided Analysis (VOCAL) has been used to calculate EV, :with a rotation angle of 1 2 and a delimitation of 1.5 sequential slides. The average, median, standard deviation and maximum and minimum values have been calculated for the EV in all the gestational ages. A dispersion graphic has been drawn to assess the correlation between EV and the craniogluteal length (Ca), the adjustment being done by the determination coefficient (R-2). To determine EV's reference intervals as a function of the CGL, the following formula was used: percentile=EV+K versus SD, with K=1.96. RESULTS: CGL has varied from 9.0 to 39.7 mm, with an average of 23.9 mm ( 7.9 mm), while EV has varied from 0.1 to 7.6 cm', with an average of 2.7 cm(3) ( 3.2 cm3). EV was highly correlated to CGL, the best cdiustiment being obtained \.vith auddre.,7tic regression (EV=0.2-0.055 versus Ca +0.005 versus OSP; R-2=0.8>. The average EV has varied from 0.1 (-0.3 to 0.5 cm(3)) to 6.7 cm(3) (3.8 to 9.7 cm') vvithin the interval of 9 to 40 mm of CGL. EV has increased 67 times in this interval,-vvhile CGL, only 4.4 times. CONCLUSIONS: EV is a more sensitive parameter than CGL to evaluate embryo growth between the seventh and the tenth vveek of gestation.