The Relationship of the Fetal Crown-Rump Length to the Yolk Sac Diameter in Normal Pregnancy

A wanted pregnancy is typically viewed as a time filled with excitement, but the uncertainty about its outcome can be quite worrisome to the patient. Parental concern often begins from the first trimester. Currently, significant data exist regarding normal and abnormal ultrasonographic measurements of the gestational sac (GS), yolk sac (YS), crown-rump length (CRL) in early gestations [1,2]. These parameters have been studied for the dual purpose of establishing standardized parameters for each gestational age and predicting early pregnancy failure [3-5]. The yolk sac is the primary source of nutrition, metabolic, immunologic, excretory, and hematopoietic functions prior to placental development, and the CRL is known to accurately correlate with gestational age during the first trimester of pregnancy [6-10]