Week 21 is settling into the rhythm of the second trimester. Your bump is unmistakably visible now, the uncomfortable early weeks are behind you, and your baby is entering a fascinating sensory phase. This week marks the beginning of real taste perception — your baby is sampling the flavors of your diet through the amniotic fluid. What you eat is literally shaping their early preferences.
Use our Due Date Calculator to track exactly where you are in your pregnancy.
Your Baby This Week
Size: Banana — about 26.7 cm (head to toe)
Weight: About 360 grams
Your baby has officially crossed the 350-gram mark and is growing fast. Here's what's developing this week:
- Taste buds are functional. Your baby swallows amniotic fluid regularly, and taste receptor cells are now active. Research published in journals affiliated with the ACOG shows that babies who are exposed to strong flavors in utero — garlic, carrots, vanilla — show preferences for those flavors after birth.
- Eyebrows and eyelids are fully formed. The eyes themselves are still sealed shut, but the structures around them are complete.
- Bone marrow takes over blood cell production. For most of early pregnancy, the liver and spleen were producing red blood cells. This week, the bone marrow begins taking over that role, which it will continue for life.
- Movements are becoming coordinated. Your baby is moving arms, legs, and head in increasingly purposeful patterns. Some of those movements are reflexive; others may already be responses to external stimuli like sound and touch.
- The placenta continues to grow. It's now a substantial organ, filtering waste, delivering oxygen and nutrients, and producing hormones that support the pregnancy.
The digestive system is getting real practice now. Swallowing amniotic fluid processes through the intestines, and meconium — the dark, tarry first stool — is continuing to build up.
Your Body This Week
By week 21, most people are firmly in the comfortable zone of the second trimester. That said, your body is still doing a lot.
- Round ligament pain. The ligaments that support the uterus are stretching to accommodate its growth. You may feel sharp, stabbing pains on one or both sides of your lower abdomen, especially when you stand up quickly, cough, or sneeze. This is normal and harmless, but catching.
- Increased appetite. Your caloric needs are higher now, and many people find genuine hunger returning after first-trimester nausea. The recommended extra intake is about 300-350 calories per day in the second trimester (Mayo Clinic).
- Varicose veins. Increased blood volume and pressure from the growing uterus can cause veins in the legs to become swollen and visible. Compression socks and regular walking can help.
- Backache. The center of gravity is shifting, and the lower back is under more strain. A supportive pregnancy pillow at night can make a real difference.
- Nasal congestion. Hormonal changes increase blood flow to mucous membranes, which can make you feel permanently stuffy. This is called "pregnancy rhinitis" and is common from mid-pregnancy onward.
- Skin changes. The linea nigra (a dark vertical line on the abdomen) may be more visible now. Stretch marks may begin appearing on the abdomen, breasts, and thighs.
Your uterus is now measurably above your navel. Your provider will check fundal height at each visit to confirm appropriate growth.
Tips for Week 21
1. Experiment with flavor. Since your baby is tasting your diet, this is a genuinely fun time to eat a varied, nutrient-rich range of foods. Spices, herbs, and different vegetables all pass flavor compounds into the amniotic fluid. You may be building their palate right now.
2. Start thinking about childbirth education. Classes fill up, and many hospitals recommend attending between 28 and 36 weeks. Research your options now — hospital-run courses, Lamaze, hypnobirthing, or online programs — so you can book in advance.
3. Invest in comfortable shoes. Foot swelling tends to worsen as pregnancy progresses. Supportive, wide-toe-box shoes now will save you discomfort later. Many people go up half a size during pregnancy and stay there permanently.
4. Eat enough iron. Iron needs increase significantly in the second trimester. Good sources include lean red meat, legumes, spinach, and fortified cereals. Pair iron-rich foods with vitamin C to improve absorption. According to WHO guidelines, iron supplementation is recommended throughout pregnancy in many regions.
5. Keep moving. Low-impact exercise — walking, swimming, prenatal yoga — reduces back pain, improves sleep, and supports cardiovascular health. The American College of Obstetricians and Gynecologists (ACOG) recommends at least 150 minutes of moderate-intensity activity per week for uncomplicated pregnancies.
When to Call Your Doctor
Most weeks pass without complications, but call your provider if you experience:
- Preterm labor signs: Regular contractions before 37 weeks, even if they don't hurt — pressure, cramping, or a low backache that comes and goes rhythmically
- Heavy bleeding or bright red spotting — light pinkish discharge can be normal after sex or a pelvic exam, but heavier bleeding warrants a call
- Severe abdominal pain that doesn't go away with rest or position changes
- Decreased fetal movement — you may not feel consistent movement yet at 21 weeks, but if you've been feeling regular kicks and notice a significant slowdown, mention it to your provider
- Signs of a UTI: burning with urination, cloudy urine, pelvic pressure — UTIs are more common in pregnancy and can cause complications if untreated
- Sudden or severe swelling in the face or hands, especially combined with headache or visual changes, which can be early signs of preeclampsia
Related Tools & Articles
- Due Date Calculator — Know exactly how many days until your estimated due date
- Pregnancy Week-by-Week Overview — the full 40-week timeline
- Fetal Development Guide — trimester-by-trimester development
- Hospital Bag Checklist — start planning ahead
- Milestone Tracker — track your baby's development