21 Weeks Pregnant

Baby’s Development

Your baby is now about 25.5 centimeters long — around the size of a carrot — and weighs roughly 360 grams [1]. The digestive system is active: your baby swallows amniotic fluid, absorbs the water, excretes through the kidneys, and the intestines absorb sugars. The bone marrow is now producing blood cells, sharing the load with the liver and spleen. Eyebrows and eyelids are visible, and the lips are more defined. Lanugo still covers the body, and the skin is less translucent and taking on a pinker tone. Movement is lively — kicks, punches, rolls, and hiccups — and sleep-wake cycles are distinct. Your baby will even startle at loud noises [2].

Body Changes

Your uterus is about 1 to 2 centimeters above your navel, and a weight gain of 13 to 18 pounds by week 21 is typical. Your bump is clearly visible. You might see stretch marks, the linea nigra, or melasma, and your breasts may be up 1.5 to 2 cup sizes with possible colostrum leaks. Visible veins and varicose veins (on your legs or vulva) can appear, and your skin may be oilier or drier than usual [2].

Tips for Week 21

• Address restless legs if you have them — iron, folate, and magnesium may help. Try stretching before bed, a warm bath, or a massage, and avoid caffeine. Talk with your OB about what’s right for you.
• Begin researching perineal massage (optional) — five minutes daily from week 34 on can help reduce perineal tearing at birth. It’s too early to start now, but you can research the technique and pick up an oil (vitamin E, almond, or coconut).
• Keep up strength training — moderate weights with higher reps, focusing on your posture muscles (back, glutes, and core). It prevents back pain and prepares you for carrying a baby and car seat.
• Stay on top of hydration and fiber — aim for 80 to 100 ounces of water and 25 to 30 grams of fiber per day. It eases constipation, swelling, and UTIs.

Things To Do (Checklist)

• Address restless legs (if present): iron, magnesium, stretch
• Start light strength training 2x/week
• Track hydration + fiber intake
• Research perineal massage technique
• Schedule glucose screening (24-28 weeks)
• Cyst + exercise: confirm no restrictions on running/lifting

Frequently Asked Questions

Q: I have leg cramps at night. Help? A: They’re very common. Stretch your calves before bed (a wall push-up works well), try magnesium glycinate (with your provider’s okay), stay hydrated, and avoid pointing your toes. When a cramp hits, stretch immediately and dorsiflex your foot [1].

Q: Can I lift weights? A: Yes, moderate weight is fine. Modify by using lighter weights with more reps, avoiding the Valsalva maneuver (holding your breath), and skipping supine lifts after 20 weeks. Compound movements are OK — just listen to your body [2].

Q: Why am I getting varicose veins? A: It’s the combination of increased blood volume, hormone-driven relaxation, and your uterus pressing on your veins. Compression socks, elevating your legs, avoiding crossing your legs, and exercise all help, and they often resolve after birth [1].

Sources

1. ACOG — How Your Fetus Grows During Pregnancy
2. Mayo Clinic — 21 Weeks Pregnant
3. What to Expect When You’re Expecting — Heidi Murkoff (Chapters 13-14: Second Trimester)