Biochemical, 2D and 3D Ultrasonographic Predictors of Pregnancy Outcome in Women With Threatened Abortion: A Prospective Cohort Study

First ultrasound scans: between 6 and 11 weeks of gestation that included the following:

• Crow- rump length (CRL) measurement using 2D ultrasound. Proper measurement of the CRL was done according to obtaining a true, unflexed, longitudinal section of the embryo or fetus, with the end-points of the crown (the top of the head) and rump (the end of the trunk) clearly defined, and then placing the calipers correctly on these defined end-points.
• Yolk sac diameter (largest outer to outer measure).
• Mean gestational sac diameter (arithmetic mean of 3 diameters).
• Embryonic heart rate. the heart rate was determined from M-mode tracings using electronic calipers .The sweep speed was set at 4 s and the calculation of the heart rate was made by measuring the time interval of two cardiac cycles, using clearly identified points in the M-mode tracing
• For volume calculation, 3D ultrasound rotational VOCAL method was used. YSV measurement (axial, sagittal and coronal). The sagittal plane was chosen as the reference plane and 'scanned' to obtain the longest axis of the yolk sac. Then a magnification of image was used and the yolk sac moved to the center of the plane. The VOCAL switch was then activated using a 30° rotation angle and the manual setting. Calipers were positioned on the superior and inferior extremities of the structure and after obtaining six sequential planes, the equipment automatically displayed the yolk sac as a 3D image with its volume in cm3.

Follow up scans was done one to two weeks later according the patient condition then at the end of 1st trimester where the previously mentioned parameters were measured.