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

Description

At approximately 21 weeks of gestation the fetus lies in a flexed attitude within the translucent amniotic sac, suspended in amniotic fluid and surrounded by the vascular uterine wall. The head remains proportionally large relative to the trunk, with the developing auricle, closed eyelids and a hand raised toward the mouth; the lower limbs are drawn up so that the plantar surfaces and separated toes are visible. The umbilical cord emerges from the anterior abdominal wall at the umbilicus and spirals away in its characteristic helical course, its paired umbilical arteries and single umbilical vein distinguishable within the cord, running toward the placental disc seen at the lower right of the field. This stage sits at the heart of the second-trimester anomaly scan window, when biometry such as biparietal diameter, head and abdominal circumference and femur length is used to confirm gestational age and assess growth. The relationship of cord insertion, placental site and amniotic fluid volume shown here underpins assessment of placental position, cord coiling and oligohydramnios or polyhydramnios, and is the same anatomy navigated during amniocentesis. Fetal posture, hand-to-mouth movement and limb tone at this age are also relevant to discussions of fetal viability thresholds and neurobehavioural development. The image suits obstetrics and midwifery teaching sequences on trimester-by-trimester development, embryology and prenatal care lectures, and antenatal clinic material explaining what parents will see at the mid-pregnancy ultrasound. It works equally well as a publication or textbook figure on fetal growth, placental and umbilical anatomy, and in editorial or app content tracking week-by-week pregnancy milestones for a lay readership. Anatomical accuracy verified by SciePro's Medical Advisory Board.