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3 Weeks
The baby is in a ball of cells called a blastocyst. The blastocyst has a full set of DNA from you and your partner in it. The blastocyst determines sex, eye color, and other traits. -
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First Trimester
The first trimester is week 3 to week 12. -
4 Weeks
The ball of cells has finally become an embryo. The embryo is about the size of a poppy seed. (https://docs.google.com/drawings/d/1pbo9UcLC8ojWPU5Ju5khiY-TJ9JjsCNfDApg2VUCJLo/edit?usp=sharing) Over the next six weeks, all of the baby's organs will start to develop, and some will start to function. -
5 Weeks
The baby's small heart begins to beat (at twice the rate of yours). The baby's body is only about the size of a sesame seed. -
6 Weeks
Facial features are beginning to formed like, the eyes and nose. Little buds appear where arms and legs will develop. -
8 Weeks
Arms and legs are starting to grow, and the baby now has little fingers, a nose and a upper lip. By this time the baby is starting to move quite a bit now, but the mother can't feel it. The bay is about 5/8 of an inch long and weighs four-hundredths of an ounce. -
9 Weeks
The baby's eyes have developed though the baby's eyelids. The baby's eyelids are blended shut for now. The baby is starting to look like a human. -
10 Weeks
The embryo has become a fetus. The baby's vital organs like the kidneys, intestines, brain, and liver are starting to function. Little fingernails and toenails are starting to form. -
11 Weeks
The baby is almost fully formed. The bones are beginning to harden, and her genitalia are developing externally. -
12 Weeks
You can hear your baby's heartbeat at a prenatal checkup. The baby's a little over 2 inches long and weighs about half an ounce. -
14 Weeks
The baby's kidneys are producing urine, and it releases it into the amniotic fluid. The baby can now make facial expressions and may have started thumb-sucking. -
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Second Trimester
The second trimester is week 14 to week 27. -
15 Weeks
The baby can see light that filters in from the outside of the womb, even though their eyelids are still shut. -
16 Weeks
The baby's sex may be detectable at your mid-pregnancy ultrasound, which typically happens between 16 and 20 weeks. -
19 Weeks
The baby can hear the mother's heartbeat and sounds that come from outside your body. The baby's skin is wrinkly and is covered by a protective, waxy coating. The baby is about 6 inches from head to bottom and weighs about 8 1/2 ounces. -
23 Weeks
The baby's sense of movement has developed, so they can feel the motion if you dance. The baby's sense of hearing continues to improve. You may sometimes be able to see him moving under the surface of your belly. -
24 Weeks
The baby's taste buds are developing. Their brain is growing very quickly, and their hair may be growing, too. The baby's almost a foot long and weighs just over a pound. -
27 Weeks
The baby's lungs are starting to develop but won't be fully functional for several more weeks. The baby is starting to "practice" for life on the outside by inhaling and exhaling amniotic fluid, sleeping and waking up at regular intervals, opening and closing his eyes, and sucking his fingers. -
28 Weeks
The baby has eyelashes, and their eyesight is improving. Billions of neurons are developing in their brain. The baby weighs about 2 1/4 pounds and is about 15 inches long. -
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Third Trimester
The third trimester is week 28 to week 41. -
32 Weeks
The baby has little fingernails and toenails. The baby is also starting to plump up in preparation for birth. The baby is almost 17 inches long and weighs about 3 3/4 pounds. -
34 Weeks
The baby's lungs and central nervous system are continuing to develop. Their skin has become soft and smooth, and is filling out and getting even rounder. The baby is almost 18 inches long and weighs about 4 3/4 pounds. -
39 Weeks
The baby is now considered full-term and is ready for life outside the womb. The average weight of a newborn is about 7 1/2 pounds, and the average length is about 20 inches.
