09/08/2025
Something pretty cool that I found on the last placenta I encapsulated! Yolk Sac remnant 🥰
In the earliest weeks of pregnancy, the yolk sac acts as the embryo’s first source of nourishment until the placenta is ready to take over. From about the 5th to the 10th week, the yolk sac slowly grows as the baby develops. Eventually, the baby outgrows it, and parts of the yolk sac help form the gastrointestinal tract. The rest gradually disappears, usually becoming invisible on ultrasounds after about 14–20 weeks.
On rare occasions, though, the yolk sac doesn’t completely vanish. It can sometimes be found after birth as a tiny, seed-like structure, only 1–5 millimeters wide. Nestled between the two layers of the amniotic sac—the amnion and chorion—it might sit close to the placenta or a little farther away. It is like a small, delicate reminder of the pregnancy’s very first days.