Week 21 of pregnancy
Updated 25 Oct 2026
Your baby this week
About the size of a carrot
Source: Vinmec – Bảng cân nặng và chiều dài thai nhi theo tiêu chuẩn của WHO
Your baby's development
Your baby is about 26.7 cm long and weighs about 350 grams, about the size of a carrot. At this stage your baby's eyes are still tightly closed but can tell light from dark. The eyelids and eyebrows are also clearer.
Until now your baby's liver and spleen were responsible for making red blood cells. Now the bone marrow is ready to take over making blood cells. It will also be the main blood-making organ later on.
Most of your baby's nutrition comes from the placenta through the umbilical cord. Your baby's digestive system is gradually maturing to prepare for life later on. The pancreas has started to release some essential enzymes. Your baby is starting to drink. A small amount of amniotic fluid is digested with these enzymes and becomes nutrition for your baby. Your baby's drink is amniotic fluid; your baby swallows a little every day. Your baby's sense of taste has developed enough to taste the amniotic fluid. Whatever you eat can affect the flavour of the amniotic fluid.
Your body
In week 21 of pregnancy your bump gets bigger by the day. Your body's centre of gravity changes, putting pressure on your back. Your legs become swollen and your joints become looser. Stretch marks continue to develop on your bottom, thighs, hips and breasts. This can get worse if you gain weight too quickly! If your own mum, your baby's grandmother, had stretch marks during pregnancy, you are very likely to get them too. No method for preventing stretch marks has been proven, but they will fade after birth. Don't worry too much about this.
A heightened sense of taste makes you want to eat more. Your gums bleed and become inflamed easily. Your nails and hair grow faster. Back pain continues. At this stage you may also have more trouble sleeping. Heartburn bothers you. You also need to pee more often as the growing uterus presses on your bladder.
Advice for you
Do light exercise and raise your legs when lying down. Limit diuretic foods at night, as they make you pee more and lead to poor sleep.
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Signs that need a doctor now
If you notice any of the signs below, please go to the nearest health facility to be checked by a doctor.
Vaginal bleeding in pregnancy
This sign needs to be checked by a doctor. Please go to the nearest health facility now. If the bleeding is heavy or comes with severe pain or faintness, call the emergency number 115.
Source: Bệnh viện Đa khoa Tâm Anh – Các dấu hiệu nguy hiểm trong thai kỳ
Convulsions (fits)
A convulsion in pregnancy is an emergency. Family members should call 115 at once, lay the mother on her side in a safe place and get her to the nearest hospital.
Source: Bệnh viện Đa khoa Tâm Anh – Các dấu hiệu nguy hiểm trong thai kỳ
Fever in pregnancy
A temperature above 38°C counts as a fever. Please go to a health facility so a doctor can find the cause and advise on safe ways to bring it down; do not take medicine on your own.
Source: Bệnh viện Đa khoa Tâm Anh – Các dấu hiệu nguy hiểm trong thai kỳ
Leaking fluid or waters breaking
Fluid leaking from the vagina may mean the waters are leaking or have broken and needs to be checked by a doctor. Please go to a health facility soon, lying with your head low while travelling.
Source: Bệnh viện Đa khoa Tâm Anh – Các dấu hiệu nguy hiểm trong thai kỳ
Severe headache, blurred vision, sudden swelling
Headache with blurred vision, or sudden swelling of the face, hands or eyelids, can be a sign of high blood pressure in pregnancy or pre-eclampsia. This sign needs to be checked by a doctor. Please go to the nearest health facility now.
Source: Bệnh viện Đa khoa Tâm Anh – Các dấu hiệu nguy hiểm trong thai kỳ
Reduced or no fetal movement
A clear drop in the baby's movements, or no movement, needs to be checked by a doctor. Please go to the nearest health facility now rather than waiting until tomorrow.
Source: Bệnh viện Đa khoa Tâm Anh – Các dấu hiệu nguy hiểm trong thai kỳ
Severe or worsening abdominal pain
Abdominal pain that keeps getting worse, does not ease, or is severe needs to be checked by a doctor. Please go to the nearest health facility now. If the pain is severe with sweating, faintness or bleeding, call 115.
Source: Bệnh viện Đa khoa Tâm Anh – Các dấu hiệu nguy hiểm trong thai kỳ
Sources
Content advised by our doctors.
- ACOG (accessed 22 Oct 2026)
- NHS (accessed 22 Oct 2026)
- Vinmec (accessed 22 Oct 2026)
- Source for fetal size: Vinmec – Bảng cân nặng và chiều dài thai nhi theo tiêu chuẩn của WHO
- Source for the signs that need a doctor: Bệnh viện Đa khoa Tâm Anh – Các dấu hiệu nguy hiểm trong thai kỳ
This article helps you understand and prepare. It does not replace a check-up. For an answer about your own situation, please ask the doctor who is caring for you.