When Can the Embryo Be Seen?

The embryo, or embryonic bud, appears as a structure attached to the yolk sac. It is typically visible via a transvaginal ultrasound starting at the sixth week of pregnancy, in both natural pregnancies and assisted reproduction treatments. However, it is important to bear in mind that its visibility depends on gestational age and the development of the gestational sac.

How Does the Embryo Develop During the First Weeks?

• Week 5–6: The gestational sac – the first anatomical structure indicating the presence of an intrauterine pregnancy –  begins to be visible, although visualizing the embryo is still difficult.
• Week 6–7: The embryo becomes visible through a transvaginal ultrasound, and the heartbeat can be detected.
• From week 8 onwards: The embryo becomes increasingly visible, and the first body features, such as limb development, begin to appear.

What Factors Influence Embryo Visibility?

1. Accuracy of Gestational Age: Gestational age is calculated based on the date of the last menstrual period (LMP). This method is designed for women with regular 28-day cycles, and since a normal menstrual cycle can range from 21 to 35 days, this calculation may not be accurate for many women.
2. Ultrasound Equipment Quality: High-resolution ultrasound machines facilitate early detection of embryonic structures.
3. Ultrasound Route: Transvaginal ultrasound allows the embryo to be seen earlier than abdominal ultrasound.

What to Do If the Embryo is Not Visible at the First Ultrasound? 

If the ultrasound is performed between weeks 5 and 6 of pregnancy and a gestational sac is observed, it is recommended to wait one week and to repeat the ultrasound. The absence of embryo visualization may be due to an error in gestational age.

If by week 7 the embryo and heartbeat are still not visible, the medical team may request additional tests or repeat the ultrasound to determine whether the pregnancy is developing correctly.