Can a yolk sac be seen by transvaginal scan before 5 weeks?
By the 4th week, the yolk sac is fully functioning, but very small. It cannot be seen on transvaginal ultrasound until week 5. In early pregnancy, the gestational sac, yolk sac and fetal pole grow at nearly the same predictable rate for all pregnancies. Of course, there are factors which might not allow the yolk sac to be seen until a few days later. For example, we would see the yolk sac (or gestational sac or fetal pole) in a very thin woman earlier than we would see it in an obese woman. If the ultrasound beam must travel through more tissue to reach the area of interest, it would be harder to see. “Between days 7-10 from fertilization implantation usually occurs. Implantation should occur within the uterus if it does not this is considered an ectopic pregnancy.
