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

Description

The fetus lies in a flexed, curled attitude within the amniotic cavity, enclosed by the translucent amniotic sac and surrounded by the vascular uterine wall. At approximately 21 weeks the head remains proportionally large relative to the trunk, the eyelids are fused and closed, and the auricle of the external ear is well modelled against the skull. The upper limbs are flexed at the elbows with the hands raised close to the face, while the lower limbs are drawn up with the knees flexed and the feet crossed near the midline, illustrating the space still available for free movement at this stage. Inferiorly and to the right, the discoid placenta is seen in section with chorionic vessels fanning across its fetal surface, and the coiled umbilical cord, carrying its paired arteries and single vein, passes from the placental insertion toward the fetal abdomen. The midpoint of the second trimester is when detailed anomaly screening is performed, and images of this stage support discussion of biometry such as biparietal diameter, head and abdominal circumference and femur length, along with assessment of amniotic fluid volume and placental site. Cord insertion, cord coiling and the appearance of the chorionic plate vessels are routinely evaluated at this gestation, as are fetal lie and limb posture. Around 21 weeks the fetus is approaching the threshold of viability, making this a critical reference point for counselling on preterm birth, growth restriction and invasive procedures such as amniocentesis. The rendering suits obstetric and midwifery teaching, embryology and developmental anatomy courses, antenatal class handouts and clinic posters explaining fetal growth week by week. It also serves publishers producing pregnancy atlases, ultrasound training material and patient-facing apps that track development across successive gestational weeks. Anatomical accuracy verified by SciePro's Medical Advisory Board.