At five months pregnant, your baby is roughly the length of a banana and weighs about 11 ounces (320 grams). The fifth month spans approximately weeks 17 through 20 of pregnancy, and your baby nearly doubles in weight during this stretch alone.
Week-by-Week Size
Your baby grows quickly during the fifth month. Here’s what to expect each week, measured from the top of the head to the bottom of the rump (not including the legs):
- Week 17: About the size of a turnip.
- Week 18: About the size of a bell pepper, measuring around 5.5 inches (140 mm) long and weighing 7 ounces (200 grams).
- Week 19: About the size of a pomegranate.
- Week 20: About the length of a banana, measuring roughly 6.3 inches (160 mm) and weighing 11 ounces (320 grams).
Those measurements use the “crown-to-rump” standard, meaning they don’t count the legs. If you measured your baby fully stretched out at 20 weeks, the total length would be closer to 10 inches. The fruit comparisons aren’t exact, but they give you a useful mental picture of what’s happening inside your uterus right now.
Why Your Baby Feels Bigger Than the Numbers Suggest
Even though your baby weighs less than a pound, your uterus has expanded dramatically by month five. It now sits at or near your belly button, and the combination of amniotic fluid, a growing placenta, and increased blood volume makes your bump noticeably larger than the baby alone would account for. Many people start needing maternity clothes around this time, and your center of gravity begins to shift.
Feeling Your Baby Move
Month five is when many parents feel their baby move for the first time, a sensation called “quickening.” If this is your first pregnancy, you’ll typically notice it around 20 weeks. If you’ve been pregnant before, you may pick up on it as early as 16 weeks because you know what to look for.
Quickening doesn’t feel like a kick at this stage. People describe it as fluttering like a butterfly, tiny bubbles popping, light tapping, or small muscle spasms. The movements are subtle enough that you might mistake them for gas at first. Over the coming weeks, those flutters will turn into unmistakable rolls and jabs as your baby gets bigger and stronger.
What’s Developing at This Stage
Size is only part of the picture. During the fifth month, your baby is building the systems that will support life outside the womb. The ears are developed enough to begin picking up sound, which means your baby can start hearing your voice and heartbeat. A waxy, white coating called vernix forms over the skin to protect it from constant exposure to amniotic fluid. Fine hair called lanugo covers the body and helps the vernix stick.
Your baby is also practicing movement constantly, flexing arms and legs, turning, and even sucking their thumb. These movements help muscles and joints develop properly. By week 20, your baby’s arms, legs, fingers, and toes are fully formed, and the bones are hardening from soft cartilage into actual bone tissue.
The 20-Week Anatomy Scan
Around the end of month five, you’ll likely have your mid-pregnancy ultrasound, sometimes called the anatomy scan. This is the most detailed ultrasound of the entire pregnancy, and it’s not just about size. The technician checks dozens of specific structures to make sure your baby is developing normally.
Four standard measurements are taken: the width and circumference of the head, the circumference of the abdomen, and the length of the thigh bone. Together, these give a reliable estimate of your baby’s growth and help confirm your due date.
Beyond measurements, the scan examines the brain in multiple views, the facial structures (eyes, nose, mouth), the heart’s chambers and major vessels, the spine from top to bottom, the kidneys and bladder, the diaphragm, lung fields, and the umbilical cord insertion point. Each of the twelve long bones in the arms and legs is individually checked, along with the hands and feet. The placenta’s position and health are also evaluated.
If you want to know your baby’s sex, this is typically when it can be determined. The scan takes 30 to 45 minutes, and you’ll usually see your baby moving on screen in real time. If the technician can’t get a clear view of a particular structure because of the baby’s position, you may be asked to walk around and come back, or schedule a brief follow-up.
How Size Varies Between Babies
The numbers above are averages. Healthy babies at 20 weeks can vary by an ounce or more in either direction, and length differences of half an inch are perfectly normal. Genetics play a large role: taller parents tend to have longer babies, and birth weight patterns often run in families. Your own nutrition, hydration, and overall health also influence growth, but at this stage, most of the variation is simply normal human diversity. The anatomy scan is partly designed to flag babies whose measurements fall significantly outside the expected range, so your care team can monitor more closely if needed.