At five months of pregnancy (roughly 20 to 24 weeks), a fetus is about 25 to 30 centimeters long from head to heel, or roughly the length of a banana, and weighs between 300 and 600 grams (about 10 to 21 ounces). Growth is rapid during this stretch. A fetus can nearly double its weight over the course of this single month.
Size Week by Week
Because “five months” doesn’t map neatly onto pregnancy weeks, it helps to look at the range. At 20 weeks, the fetus measures around 25 centimeters (10 inches) and weighs roughly 300 grams. By 24 weeks, length reaches about 30 centimeters (12 inches) and weight climbs to around 600 grams, or just over a pound. That’s a significant jump in a short window, driven largely by the fetus building fat stores and muscle tissue.
During the mid-pregnancy ultrasound (typically done around week 20), your care provider takes a set of specific measurements. Average values at 20 weeks include a head diameter of about 4.9 centimeters, a head circumference of 17.5 centimeters, an abdominal circumference of 14.9 centimeters, and a thighbone length of 3.2 centimeters. These numbers help confirm gestational age and flag any growth concerns early.
What the Fetus Looks Like at Five Months
By this stage, the fetus has a distinctly human appearance. Facial features are well defined, with eyebrows, eyelids, and tiny fingernails in place. The entire body is covered in a fine, downy hair called lanugo. This soft fuzz serves a purpose: it helps anchor a greasy, cheese-like coating on the skin known as vernix. That coating protects the fetus’s delicate skin from constant exposure to amniotic fluid, preventing it from chapping or hardening. Both the lanugo and vernix will mostly shed before birth.
Key Organ Development
Size is only part of the picture. Inside, the organs are hitting important milestones. Around week 20, the brain region responsible for the five senses (sight, hearing, smell, taste, and touch) begins active development. This is when the fetus starts responding more noticeably to sound and light. By week 24, the lungs have formed their basic structure, though they are not yet mature enough to function outside the uterus. The lungs will continue developing surfactant, a substance needed for breathing air, well into the third trimester.
Feeling the Baby Move
Five months is when most pregnant people first feel their baby move, a sensation called quickening. It typically happens between 16 and 20 weeks, though the timing varies. If this is your first pregnancy, you’re more likely to notice it closer to 20 weeks. People who have been pregnant before often recognize the feeling a few weeks earlier, simply because they know what to look for.
Quickening doesn’t feel like a kick at this stage. Women commonly describe it as fluttering like a butterfly, tiny bubbles popping, light tapping, or small muscle spasms. The sensation is usually felt low in the belly, near the pubic bone. Over the coming weeks, those subtle flutters will grow into unmistakable rolls and kicks as the fetus gets bigger and stronger.
How Size Varies
The measurements above are averages. Individual fetal size at five months depends on genetics, the parents’ body size, nutrition, placental function, and whether you’re carrying multiples. Twins and triplets tend to be smaller at each milestone. A fetus measuring a bit above or below average on an ultrasound is not automatically a concern. Your provider looks at the overall growth trend across multiple appointments rather than any single measurement. Consistent growth along a curve matters more than hitting an exact number at any one visit.