At 20 weeks, a baby is about the length of a banana, roughly 25 centimeters (10 inches) from head to heel, and weighs around 300 grams (10 ounces). This is the halfway point of pregnancy, and the baby has shifted from a curled-up shape to something that looks unmistakably human, with defined facial features, visible fingers and toes, and skin coated in a protective layer of fine hair and waxy film.
Overall Size and Proportions
Up until about 12 weeks, doctors measure a fetus from the top of the head to the rump because the legs are curled tightly against the body. By 20 weeks, the legs have stretched out enough that the measurement switches to crown-to-heel length. At this stage, the head is still large relative to the body, making up roughly a third of the baby’s total length, but the limbs and torso are catching up. The thighbone (femur) measures about 3.2 centimeters, and the head circumference averages around 17.5 centimeters.
Skin, Hair, and Protective Coatings
A 20-week baby’s skin is thin and somewhat translucent, with blood vessels visible beneath the surface. Two features give the baby a distinctive appearance at this stage: lanugo and vernix caseosa.
Lanugo is a soft, fine, feathery hair that covers most of the body. It serves several purposes. It helps regulate the baby’s temperature before enough body fat has built up to do the job. It also anchors vernix caseosa, a waxy, cheese-like white coating that protects the baby’s delicate skin from the amniotic fluid. Without these layers, the fluid would irritate and damage the skin over months of constant exposure. Lanugo does something else that’s less obvious: as the hair moves in the fluid, it sends vibrations to sensory receptors in the skin, which help stimulate growth.
Most of the lanugo will shed before birth, though some babies, especially those born early, still have patches of it when they arrive.
Facial Features
By 20 weeks, the baby’s face looks recognizably human. The ears have moved into their final position on the sides of the head, and the eyes, while still sealed shut behind fused eyelids, are in the correct forward-facing location. Eyebrows are beginning to form. The nose, lips, and chin are distinct enough to be visible on an ultrasound, and the upper lip has its characteristic shape. The eyelids won’t open for several more weeks, typically around weeks 26 to 28.
Movement You Can Feel
Twenty weeks is when most pregnant people first feel their baby move, a milestone called quickening. The baby has been moving for weeks already, but it’s only now large enough for those movements to register. People describe quickening in different ways: fluttering like a butterfly, tiny tapping or pulses, bubbles popping, light rolls, or small muscle spasms. These sensations are typically felt low in the belly, near the pubic bone.
At this point, the baby cycles between sleeping and waking on a regular schedule. It can be startled awake by loud noises or sudden movement from the mother.
Early Hearing and Sensory Development
Around 20 weeks, the baby can begin to hear sounds from outside the womb. The amniotic fluid and surrounding tissue muffle most noise, so what gets through is limited to low-frequency sounds: the rhythm of the mother’s heartbeat, the rumble of her voice, and deep external sounds. This early exposure plays a role in shaping the auditory system even before birth.
Reflexes and Early Behaviors
Between 18 and 24 weeks, the nerves controlling the face, tongue, and jaw are developing rapidly. On ultrasound, babies at this stage can be seen opening and closing their mouths and making suckling motions with their tongues. These are early rehearsals for feeding after birth. Consistent swallowing of amniotic fluid begins around 22 to 24 weeks, and this process helps regulate the volume and composition of the fluid while also preparing the baby’s digestive tract for life outside the womb.
Some parents catch their baby sucking a thumb on ultrasound around this time. It’s a reflex, not a conscious choice, but it’s one of the behaviors that makes this stage feel particularly real.
The 20-Week Anatomy Scan
This is the week most people have their detailed mid-pregnancy ultrasound, sometimes called the anatomy scan. The sonographer examines the baby’s bones, heart, brain, spinal cord, face, kidneys, and abdomen in detail. They also check the placenta and blood flow in the uterus.
The scan screens for a range of structural conditions, including heart abnormalities, spina bifida, cleft lip and palate, and certain chromosomal conditions like Edwards’ syndrome and Patau’s syndrome. For many parents, it’s also the first clear look at their baby’s face and the appointment where they can learn the sex if they choose to. Because the baby is now large enough for each organ system to be visible, this scan provides the most comprehensive picture of development that ultrasound can offer during pregnancy.
The baby may be cooperative and hold still, or it may be curled in a position that makes certain views difficult. If the sonographer can’t get all the images they need, you may be asked to come back for a follow-up scan.