Gestation sac - USS in early pregnancy

  Gestation sac

• The gestation sac is the first pregnancy structure that can be detected - usually visualised at 31 days or 4+3 weeks from the LMP using trans-vaginal scanning and measures 2-3mm in diameter

• Detectable by trans-abdominal scanning at ~5+3 weeks gestation

• Typically centrally located within the fundus

• Grows by 1 mm per day in diameter at this stage and becomes elliptical in shape when diameter exceeds 10mm