At five months of pregnancy (roughly 20 weeks), a fetus is about 10 inches long from head to heel and weighs around 10 ounces, or just over half a pound. That’s comparable in length to a banana. While still small enough to fit in the palm of your hand, the fetus has grown dramatically from the tiny embryo of the first trimester and is now developed enough that its proportions are starting to look recognizably human.
Size Measurements at 20 Weeks
The 10-inch, head-to-heel measurement is an average. Earlier in pregnancy, doctors measure only from the top of the head to the bottom of the torso (called crown-rump length), because the legs are curled tightly. By 20 weeks, the legs have stretched out enough that a full head-to-heel measurement becomes standard.
During the mid-pregnancy ultrasound, which typically happens right around the five-month mark, the technician takes several specific measurements to check that growth is on track. At 20 weeks, these averages give you a sense of how small individual body parts still are:
- Head circumference: about 17.5 cm (roughly 7 inches around)
- Abdomen circumference: about 14.9 cm (just under 6 inches around)
- Head width: about 4.9 cm (just under 2 inches across)
- Thighbone length: about 3.2 cm (a little over an inch)
These numbers can vary from one baby to the next. Your provider compares them against growth charts to make sure everything is developing proportionally.
What the Fetus Looks Like at This Stage
By five months, the body is covered in a fine, downy hair called lanugo, which develops between 16 and 20 weeks. This soft hair serves a surprisingly practical purpose: it holds a waxy, cream-colored coating (vernix) against the skin. Without that coating, the amniotic fluid surrounding the baby could irritate its delicate skin. Lanugo also helps regulate the baby’s temperature until enough body fat builds up later in the third trimester to take over that job. The hair even plays a role in growth itself, sending tiny vibrations to sensory receptors in the skin that stimulate further development.
Eyebrows and eyelids are formed by now, and the facial features are more defined. The limbs are well-proportioned relative to the body, and fingernails and toenails are developing.
What the Fetus Can Do at Five Months
A 20-week fetus has settled into a cycle of sleeping and waking, much like a newborn. It can be startled awake by loud noises or your movements. The ears are functional enough at this stage that the fetus responds to sound, and it regularly swallows amniotic fluid, which helps the digestive system practice for life outside the womb.
This is also the stage when most pregnant people start to feel the baby move, a milestone called quickening. If this is your first pregnancy, you may not notice movement until right around 20 weeks or even a bit later, up to 24 weeks. People who have been pregnant before often pick up on it earlier, around 16 weeks, because they recognize the sensation.
The movements at this stage are subtle. Most people describe them as flutters, tiny bubbles popping, light tapping, or small muscle twitches. You’ll typically feel them low in your belly, near your pubic bone. It’s normal for movement to come and go at this point. Some days you may feel several episodes of activity, and other days you may not notice much at all. Consistent, strong kicks come later in pregnancy as the baby grows bigger and stronger.
How Your Body Reflects the Baby’s Size
At 20 weeks, the top of your uterus reaches your belly button. This is a useful landmark because, from this point forward, the distance from your pubic bone to the top of the uterus (measured in centimeters) roughly matches your week of pregnancy. So at 20 weeks, that measurement is about 20 centimeters. At 25 weeks, it will be about 25 centimeters, and so on. Your provider may check this at each prenatal visit as a quick way to confirm the baby is growing as expected.
For many people, this is right around the time pregnancy becomes visibly obvious. The uterus has expanded well beyond the pelvis, and the belly is rounding out. The baby still has plenty of room to tumble and shift positions, which is why those early movements feel so unpredictable in their location and timing.
How Size Changes Through Month Five
Month five spans roughly weeks 18 through 22, and growth during this window is rapid. At the start of the month, the fetus is closer to 8 inches long and about 7 ounces. By the end, it can reach 11 inches and nearly a pound. That’s a roughly 40% increase in weight over just four weeks. Much of this growth comes from the baby filling out, as fat begins to accumulate under the skin and muscle tissue develops further.
This rapid growth is one reason the mid-pregnancy ultrasound is scheduled during this window. The baby is large enough for detailed anatomical evaluation but still small enough relative to the uterus that the technician can get clear images of the heart, brain, spine, kidneys, and other organs. It’s the most comprehensive ultrasound most pregnancies will have.