Your Baby's Development At about 5.1 inches (13 cm) from crown to rump and weighing 4.9 ounces (140 grams), your baby is still very tiny. The placenta, which nourishes the fetus with nutrients and oxygen and removes wastes, is growing to accommodate your baby. It now contains thousands of blood vessels that bring nutrients and oxygen from your body to your baby's developing body. Your Body You may notice that your breasts have changed considerably since your pregnancy began. Hormones are preparing your breasts for milk production — more blood is flowing to the breasts, and the glands that produce milk are growing in preparation for breastfeeding. This can increase your breast size (many women increase one to two cup sizes) and make veins become visible. Buy supportive bras in a few different sizes to manage your breast growth during pregnancy. PREGNANCY CALENDAR: A week-by-week guide Previous Next 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 Trimester 1 Trimester 2 Trimester 3 Back to Articles Related Articles Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor. © 1995-2021 KidsHealth®. All rights reserved. Images provided by The Nemours Foundation, iStock, Getty Images, Veer, Shutterstock, and Clipart.com.