Watch our video guide to Week 21 of your pregnancy journey:
What's Happening in Week 21?
Your baby is now about 27cm long (head to toe) and weighs approximately 360g — roughly the size of a large carrot. You've officially passed the halfway point of pregnancy.
This is an exciting week for development:
- Movements are stronger and more coordinated: your baby can now kick, punch, roll, and somersault. You may even see your belly move from the outside during a particularly vigorous session
- Taste buds are active: your baby swallows amniotic fluid regularly, and research shows the fluid's flavour changes based on what you eat. Studies suggest babies develop early taste preferences in the womb
- Bone marrow is producing blood cells: previously this was done by the liver and spleen, but the bone marrow is now taking over this crucial role
- Digestive system is practising: the intestines are absorbing small amounts of sugar from swallowed amniotic fluid — early training for digesting food after birth
- Skin: still thin and translucent, but a waxy coating called vernix caseosa is forming to protect it from the amniotic fluid
Your baby is now covered in fine, downy hair called lanugo, which helps the vernix stick to the skin. Both will mostly shed before birth.
Your Body This Week
The second trimester "golden period" continues for most women, though the growing bump brings some new experiences:
- Stronger baby movements: most first-time mothers are feeling definite kicks and movements by now. Partners may be able to feel them from the outside by placing a hand on your belly
- Growing bump: your uterus now reaches roughly to your navel. You may find it harder to bend over or tie your shoes
- Backache: the shift in your centre of gravity as your bump grows can strain your lower back. Good posture and supportive shoes help
- Braxton Hicks contractions: you may start to notice occasional painless tightening of your uterus. These "practice contractions" are normal and different from labour contractions
- Skin changes: some women develop a "pregnancy glow" due to increased blood flow, while others experience breakouts or pigmentation changes
- Varicose veins: increased blood volume and pressure from the uterus can cause veins in the legs to become swollen
The Anatomy Scan
If you haven't already had your detailed anatomy scan (also known as the 20-week scan or anomaly scan), it's likely happening very soon. This is one of the most comprehensive assessments of your pregnancy, typically performed between 20 and 24 weeks.
The scan examines:
- Your baby's brain, face, and spine
- The heart — checking all four chambers and major blood vessels
- The stomach, kidneys, and bladder
- Arms, legs, hands, and feet (counting fingers and toes)
- Placenta position and cord attachment
- Amniotic fluid levels
- Cervix length
At Ultrasound Ireland, this scan also gives you the opportunity to find out your baby's sex, or to confirm what you may have been told at an earlier gender scan.
Nutrition and Movement
As your baby's bones continue to strengthen and their brain develops rapidly, your nutritional needs increase:
- Calcium: the HSE recommends 3 servings of dairy daily. Your baby's skeleton is demanding significant calcium
- Iron: blood volume is now significantly higher. If you experience signs that could indicate iron deficiency (extreme tiredness, breathlessness, pale skin), mention them to your GP or midwife
- Protein: aim for 2 servings of lean meat, fish, eggs, or plant-based protein daily
- Varied diet: eating a wide range of foods exposes your baby to different flavours through the amniotic fluid — research suggests this may lead to less fussy eating in childhood
Staying active remains important. Swimming is particularly beneficial as the water supports your bump, and walking is accessible exercise that can be done throughout pregnancy.
Common Questions
"How many kicks should I feel?" At 21 weeks, there's no set number to count yet. What matters is getting to know your baby's pattern. Some babies are more active in the morning, others at night. Established kick-counting guidance (monitoring 10 movements in a set period) typically starts from 28 weeks.
"What if the anatomy scan finds something?" The vast majority of anatomy scans show a healthy, normally developing baby. If anything unusual is identified, you'll be offered further specialist assessment. Finding variations early gives you and your medical team time to plan the best care.
"Is it safe to sleep on my back?" From the second trimester onwards, the NHS and HSE recommend sleeping on your side (particularly the left side). This improves blood flow to your baby. A pregnancy pillow between your knees can make side-sleeping more comfortable.
This article is for general information purposes only and is not intended as medical advice. Every pregnancy is different. Always consult your GP, midwife, or healthcare provider for guidance specific to your circumstances.
See your baby in incredible detail with a 3D/4D Baby Scan at Ultrasound Ireland — best between 26-32 weeks for the clearest images.