18 weeks pregnant: symptoms and baby development
They may be listening to you.
Second trimesterMonth 55 min read
By Solesia, from public clinical guidanceUpdated
A bubble, a flutter, the faintest tap, and then nothing for an hour. If it is your first pregnancy you may not be sure, and that uncertainty is itself the sign: the first movements are easy to mistake for something else, and this is the week they often begin. Your baby is wriggling enough to be felt now, and their ears have settled into their final place, so the voice they hear best is yours. For you, the week is about blood pressure, which is at its lowest point of the whole pregnancy, so stand up slowly and sit down if the room swims. Eat something small and often; it helps more than it sounds.
How big is your baby at 18 weeks
About the size of a bell pepper
5.6 in long·8 oz
Baby development at 18 weeks
At 18 weeks your baby measures about 5.6 inches from crown to rump and weighs around 8 ounces, roughly a bell pepper. Half a pound is a milestone of sorts: they have doubled their weight in about three weeks, and the pace does not slow down from here.
The ears have moved from the neck to the sides of the head and are standing out from it, and the nerves that carry sound are wiring up. Hearing, feeling, swallowing and sucking are all coming online this week, and a sudden loud noise can wake them. Your voice, your heartbeat and the churn of your stomach are their soundtrack.
They move a lot: stretching, turning, kicking, moving arms and legs. Myelin, the coating that lets nerves fire faster, is starting to wrap the nerves, so movements are getting quicker and better aimed. If your baby is a girl, the uterus and fallopian tubes are formed; if a boy, the genitals are visible on ultrasound. Either way, the scan can often tell you now.
Your body at 18 weeks
Your blood pressure is at its lowest about now. Progesterone relaxes the walls of the blood vessels, so blood pools in your legs when you stand, and a fast move from lying to standing can leave you lightheaded. This is expected. Get up in stages, sit on the edge of the bed for a moment, and keep a snack and water within reach. It climbs back to normal over the third trimester.
The first movements often arrive between now and 22 weeks, and they are subtle: a bubbling, a flutter, a soft roll, usually when you are lying still. If this is your first pregnancy and you feel nothing yet, that is expected too. A placenta on the front wall of the uterus can cushion the kicks for a few more weeks.
A dark line may be appearing from your belly button downward, the linea nigra. Pregnancy hormones stir up the pigment in your skin, and the line, like the darker patches on the face and the darker nipples, fades after birth. Your breasts are growing again, especially in a first pregnancy, and a bra that fits is worth the trip. Clumsiness is expected as the bump changes how you balance.
Common pregnancy symptoms at 18 weeks
- Dizziness when you stand. Blood pressure is at its lowest and blood pools in your legs. Rise in stages, eat and drink regularly.
- Clumsiness. A bump that shifts your balance and looser joints. Slow down on stairs and wet floors.
- Growing breasts. Milk glands are developing. A properly fitted bra, cotton and soft, without underwire if it digs.
- Dark line on your belly. Hormones raising pigment in the skin. It fades in the months after birth.
- Leg cramps. Often at night, usually the calf. Straighten the leg and pull your toes up toward your shin.
- Constipation. A slower gut and pressure from the uterus. Fiber, water and a daily walk.
- Stuffy nose. Swollen nasal lining from extra blood. Saline spray, and a humidifier by the bed.
When to call your provider at 18 weeks
Two things are worth a same-day call at any point in pregnancy: bleeding that is more than spotting, and pain that is severe or does not ease. From the second trimester, add fluid leaking and any change in your baby’s usual pattern of movement. You do not need to be sure something is wrong to call; that is what the number is for.
What to do at 18 weeks
- Anatomy ultrasound. From this week to 22 weeks, a detailed scan checks the brain, heart, spine, kidneys, limbs and the placenta, and measures growth. It takes 30 to 45 minutes. Ask beforehand whether they can hold back the sex if you do not want to know.
- Quad screen, if you chose it. It can still be drawn until 22 weeks, but 16 to 18 gives the clearest result, so this week is the time if it is on your list.
- Standing up slowly. With blood pressure at its lowest, this is the week to make a habit of sitting first, then standing, and of not skipping meals.
- Movement diary, without the pressure. If you feel something that might be a flutter, note when. There is nothing to count yet; you are just learning what your baby feels like.
Common questions at 18 weeks
What does the 18-week anatomy scan check?
Every major part of your baby: the brain, face, spine, heart and its four chambers, stomach, kidneys, bladder, arms, legs, hands and feet. It measures the head, belly and thigh bone to check growth, looks at where the placenta sits and how much fluid there is, and can usually tell the sex. It is the longest ultrasound of the pregnancy.
Should I feel my baby move at 18 weeks?
Maybe. Between 18 and 22 weeks is the usual window for a first flutter in a first pregnancy, so feeling nothing yet is expected. It comes as a bubble, a flutter or a soft turn, mainly when you are lying still. People in later pregnancies often feel it a few weeks earlier because they know what to feel for.
Why am I dizzy when I stand up?
Your blood pressure reaches its lowest point of the pregnancy around now. Progesterone relaxes the blood vessels, blood pools in your legs, and a quick move to standing leaves the brain briefly short. Stand up in stages, eat regularly and drink enough. If you actually faint, or the dizziness comes with a racing heart, tell your provider.
What is the dark line down my belly?
The linea nigra, a line of pigment from the belly button to the pubic bone, sometimes above it too. The line was always there, faint and pale; hormones darken it. It is expected, it is harmless, and it fades in the months after birth, faster if you keep the sun off it.
Written from public clinical guidance, including NHS: Week 18, ACOG: How your baby grows, ACOG: Changes in your body, NHS: Your baby’s movements and ACOG: Skin conditions during pregnancy. This page is general information, not medical advice, and does not replace your provider.