Human Fetus at 21 Weeks in the Womb (Asian Skin)

Description

The fetus lies in a flexed attitude inside the translucent amniotic sac, suspended in amniotic fluid and surrounded by the vascular uterine wall. At about 21 weeks the head remains proportionally large relative to the trunk, with fused eyelids, a formed external ear, distinct nose and lips, and an open mouth. Both upper limbs are drawn toward the face with the fingers loosely clenched, while the lower limbs are folded at the hips and knees so the feet cross near the midline. The umbilical cord leaves the anterior abdominal wall and coils toward the disc-shaped placenta at the right of the field, where the paired umbilical arteries and the single umbilical vein can be traced across the chorionic surface into the branching fetal vessels. This stage sits within the window used for the mid-trimester anomaly scan, when biometry such as biparietal diameter, head and abdominal circumference and femur length is measured and structural survey of the heart, spine, limbs and abdominal wall is completed. Cord insertion site, placental position relative to the internal os, and amniotic fluid volume are assessed at the same visit, and the coiled three-vessel cord seen here is the reference appearance against which single umbilical artery is judged. Fetal movements and limb posture are also observed, since persistent abnormal positioning may point to neuromuscular or skeletal disorders. The rendering suits obstetric and midwifery teaching on second-trimester development, antenatal class materials, and clinic handouts explaining what parents will see at the twenty-week scan. It also serves embryology atlases, ultrasound training resources that pair sonographic planes with anatomical context, and editorial or publisher figures charting week-by-week gestational progress alongside the neighbouring images in this series. Anatomical accuracy verified by SciePro's Medical Advisory Board.