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Gestational Sac

What Is Fetal

Gestational Sac?

A gestational sac is a fluid-filled structure that encloses a developing embryo in the very early stages of pregnancy. It is the first visual evidence of pregnancy before the embryo is even visible.

It can be identified via transvaginal ultrasound at approximately 4.5-5 weeks gestation when it is approximately a 2-3mm rounded collection of fluid. A gestational sac may indicate whether or not a typical pregnancy is developing by providing information on:

  • If an early pregnancy is developing properly.
  • If the location of the pregnancy is in the uterus or it is an ectopic pregnancy, which is a medical emergency.
  • The number of fetuses that are developing.
  • An estimate of the gestational age, or how far along the pregnancy is.

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Gestational Sac

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