Hello I appreciate your query. The gestational sac(GS) is the earliest sonographic finding in pregnancy. It will be difficult to see if the mother has a retroverted uterus or fibroids. In case of ectopic pregnancy, the GS is not seen inside the uterus. The GS is identifiable until approximately 4 1/2 weeks only with a transvaginal scan. The yolk sac appears during the 5th week. It is the second structure to appear after the GS. It should be round with an anechoic centre. Failure to identify (with transvaginal ultrasound) a yolk sac when the gestational sac has grown to 12 mm is also usually indicative of a failed pregnancy. A mass of fetal cells, separate from the yolk sac, first becomes apparent on transvaginal ultrasound just after the 6th week of gestation. This is called the fetal pole. These parameters are seen on transvaginal ultrasound only. Since you probably had an abdominal ultrasound, these details might not be seen easily in early pregnancy. Please go for a TVS and then consult a gynecologist for further details. Absence of yolk sac/ fetal pole beyond gestational sac size 12 mm is usually indicative of a failed pregnancy, as I mentioned earlier. All the best and do post your TVS reports for further clarification.