At 20 weeks, your baby is roughly the size of a banana, measuring about 6.5 inches (16.5 cm) from crown to rump and weighing around 10 ounces (about 300 grams). This is the halfway point of pregnancy, and it’s a big week: your baby’s senses are coming online, you’re likely feeling movement for the first time, and you may be heading in for the detailed anatomy scan.
Size and Proportions at 20 Weeks
At this stage, your baby’s head is still large relative to the body but less dramatically so than in the first trimester. The average head circumference is about 17.5 cm (roughly 7 inches), and the thighbone measures around 3.2 cm. These proportions shift quickly over the coming weeks as the limbs and torso catch up to the head.
To put the weight in perspective, 10 ounces is a little more than a can of soda’s worth of weight. Your baby will roughly triple in length and increase tenfold in weight between now and delivery, so this halfway mark is really just the beginning of the most dramatic growth phase.
What’s Developing Right Now
Twenty weeks is when several systems hit important milestones at once. Your baby’s skin is developing a waxy, cheese-like coating called vernix caseosa, which acts as a barrier against the amniotic fluid. Without it, the skin would chap and harden from constant exposure. Fine, downy hair called lanugo is also spreading across the body, helping the vernix stick to the skin.
The digestive system is actively practicing. Your baby has been making swallowing motions since around week 11, but by weeks 18 to 20, these movements become more complex and include sucking. The swallowing is still uncoordinated at this point, with some fluid going back up, but this practice is essential preparation for feeding after birth.
Hearing begins to emerge around 20 weeks. Your baby can start picking up low-frequency sounds, though the amniotic fluid and surrounding tissue muffle most of what reaches them. Deep voices and the rhythm of your heartbeat are among the first things they hear. Higher-pitched sounds don’t come through as clearly until later in pregnancy.
Feeling Your Baby Move
Most women feel their baby move for the first time by 20 weeks, a milestone called quickening. The sensation is subtle enough that many people mistake it for gas or muscle twitches at first. Common descriptions include bubbles popping, light tapping, tiny flutters like a butterfly, or small rolling movements. If this is your first pregnancy, it may take until 22 to 24 weeks before you’re confident that what you’re feeling is actually the baby.
At 20 weeks, the top of your uterus sits right at your belly button, so movement tends to be felt low in the abdomen. You won’t notice kicks or rolls above the navel until the uterus grows higher in the weeks ahead. The movements are also inconsistent at this stage. Your baby is still small enough to change position frequently, and you’ll feel more activity on some days than others.
The 20-Week Anatomy Scan
This is typically the week you’ll have a detailed ultrasound, often called the anatomy scan or mid-pregnancy ultrasound. The sonographer takes a series of precise measurements to check that your baby is growing on track. These include the circumference of the head, the circumference of the abdomen (about 14.9 cm at this stage), the diameter of the skull (about 4.9 cm), and the length of the thighbone.
Beyond measurements, the scan examines the heart’s four chambers, the spine, the brain, kidneys, and the placenta’s position. Many parents also learn the sex of the baby during this appointment, since the anatomy is usually clear enough to see at this point. The scan typically takes 30 to 45 minutes, longer if the baby is in a position that makes certain views difficult.
Changes in Your Body
Your uterus has expanded to the level of your belly button by week 20, and your healthcare provider may start measuring fundal height at this visit. Fundal height is simply the distance in centimeters from the top of your pubic bone to the top of your uterus. After 20 weeks, that number in centimeters roughly matches your week of pregnancy, so at 20 weeks you’d expect a measurement close to 20 cm. It’s a quick, low-tech way to track whether the baby is growing as expected between ultrasounds.
You may also notice your center of gravity shifting as your belly grows, and round ligament pain (sharp or pulling sensations on the sides of your abdomen) is common as the uterus stretches. Weight gain by this point is typically 8 to 10 pounds for most pregnancies, though there’s a wide range of normal.