20 weeks pregnant

Your baby at 20 weeks

Twenty weeks is the halfway mark of a pregnancy that is counted as 40 weeks from the first day of your last period. A lot of the basic building work is done, and the second half is mostly about growing and maturing.

ACOG's week-by-week guide groups weeks 17 to 20 together and lists what is in place by now. The part of the brain that controls movement is fully formed, and the digestive system is working. The ears, nose and lips can be recognized on an ultrasound screen, which is one reason the mid-pregnancy scan pictures look so much more like a baby than the early ones. A fine, soft hair called lanugo has started to cover the body.

The length on this page is measured from the crown of the head to the rump, because the legs are still folded up and hard to measure. From week 21 our size guide switches to crown-to-heel length, so the number on the next page jumps sharply. Your baby has not suddenly grown; the ruler has moved to the heels.

The weight shown above is an estimate, not a weighing. On a scan, the sonographer measures the head, abdomen and thigh bone, and a formula turns those into an estimated fetal weight. The WHO charts give the middle value and the spread for each week, so a baby who measures above or below the middle line is not automatically a concern. Your care team looks at the trend across scans and at your own history, not at one number.

Your body at 20 weeks

By now most people have a bump that others can see. Your uterus keeps expanding to make room, and by the birth it will be many times its usual size, so clothes that fit last month may not fit now.

Stretch marks often start to appear in the middle of pregnancy as the skin over your bump stretches. The NHS says they affect around 8 in 10 pregnant women and that itching is often the first sign. They are not harmful. The NHS notes limited evidence that oils or creams prevent them, and after the birth they usually fade to paler lines.

Many people also notice that they have more energy than in the first trimester. Tiredness tends to be worst in the first 12 weeks, so the middle weeks can feel like a breather before the third trimester. It is a good time to keep up regular movement: the NHS suggests aiming for 150 minutes of moderate activity a week, such as walking or swimming, at a pace where you can still talk but not sing.

Common symptoms around 20 weeks

• Back pain. In pregnancy your ligaments become softer and stretch to prepare for labor, which strains the joints of the lower back and pelvis. Wear flat shoes, sit with your back supported, split heavy shopping between two bags, and bend your knees rather than your back when you lift.
• Heartburn. Hormone changes and your growing baby pressing on your stomach both play a part. The NHS suggests small meals more often, sitting up straight while you eat, and not eating in the 3 hours before bed.
• First movements. Early movements can feel like fluttering, bubbles or a gentle swirl rather than kicks. If this is your first pregnancy you may not notice them until after 20 weeks.
• Itchy skin over the bump. As the skin stretches it can itch, and the NHS notes that itching is often the first sign of a stretch mark.

Tips for this week

• Get ready for the anatomy scan. Ask whether you need a full bladder, wear clothes that make your belly easy to reach, and check whether you can bring someone with you. Most hospitals do not allow children in the scan room.
• Decide whether you want to know the sex. Talk it over before the appointment, so you can tell the sonographer straight away.
• Write your questions down. The scan checks your baby's growth, organs, the amount of fluid and where the placenta sits. If your baby is lying in an awkward position, the NHS says you may be asked to walk around or come back for another appointment so every check can be done.
• Start learning your baby's pattern. The NHS and the RCOG say you do not need to count kicks to a set number. Once movements are regular, get to know when your baby is usually active; a change in that pattern is what matters. If your care provider asks you to keep a kick count, follow their advice.
• Avoid lying flat on your back for long. In later pregnancy the NHS advises against exercises that keep you flat on your back for more than a few minutes, because it can make you dizzy.

When to call your doctor or midwife

These are reasons to call now, not to wait for your next appointment. If you cannot reach your maternity unit or clinic, call your local emergency number.

• Call now if you have vaginal bleeding of any amount. Call your emergency number if the bleeding is heavy, or if it comes with severe belly pain, shoulder pain, or feeling faint or dizzy.
• Call now if fluid leaks or gushes from your vagina, if you have regular tightenings or cramps, pressure low in your pelvis, a dull backache that does not go away, or a change in your discharge. Before 37 weeks these can be signs of preterm labor.
• Call now if you have a severe headache that does not ease, blurred vision or flashing lights, pain just below your ribs, or sudden swelling of your face, hands or feet. Pre-eclampsia is most likely from 20 weeks onwards, and these symptoms need to be checked straight away.
• Call now if you have started feeling a regular pattern of movements and your baby moves less, stops moving, or the pattern changes. Contact your midwife or maternity unit straight away; do not wait until the next day.
• Call now if you are still being sick and nothing has stayed down for 24 hours, or your pee is very dark and scanty.
• Call now if you have back pain together with a fever, bleeding, or pain when you pee, or pain in your side under the ribs.