PU First Trimester Ultrasound and Dating

Question 1

What is the earliest structure visualized on transvaginal ultrasound in a normal intrauterine pregnancy?

Accepted Answer

Gestational sac

Answer

The gestational sac is the earliest structure visible on transvaginal ultrasound, typically seen by 4.5 to 5 weeks of gestation as a small anechoic structure within the decidua.

Question 2

At what beta-hCG level should a gestational sac be visible on transvaginal ultrasound?

Accepted Answer

1,500–2,000 mIU/mL

Answer

A gestational sac should be visible on transvaginal ultrasound when serum beta-hCG reaches approximately 1,500 to 2,000 mIU/mL; failure to visualize raises concern for ectopic pregnancy.

Question 3

What is the normal location for a yolk sac in early pregnancy?

Accepted Answer

Within the gestational sac between the amnion and chorion

Answer

The yolk sac is located within the gestational sac in the chorionic space (between the amnion and chorion) and is the first structure seen inside the sac before the embryo.

Question 4

What is the double decidual sac sign (DDSS)?

Accepted Answer

Two concentric rings of decidua surrounding the gestational sac, confirming intrauterine location

Answer

The DDSS describes two concentric echogenic rings surrounding the gestational sac — the decidua capsularis and decidua parietalis — confirming intrauterine implantation.

Question 5

What crown-rump length (CRL) corresponds to the first detectable fetal cardiac activity?

Accepted Answer

2–4 mm (approximately 5.5–6 weeks)

Answer

Fetal cardiac activity is typically first detected on transvaginal ultrasound when the CRL reaches 2 to 4 mm, corresponding to approximately 5.5 to 6 weeks gestation.

PU - Pregnancy Ultrasound Certification Practice Test

PU - Pregnancy Ultrasound Certification Practice Test

PU First Trimester Ultrasound and Dating