Your due date will be calculated from the first day of your last menstrual period. Conception occurs about two weeks from this day, and that's when you're truly considered pregnant. In just 40 short weeks, your baby will grow from the size of a tiny seed to the size of a plump watermelon. The size of your baby will vary from person-to-person and pregnancy-to-pregnancy. Here, Jonathan D. Herman, M.D., shares the average for each week.
Your fertilized egg, known as a zygote, is a ball of 32 cells that's about the size of a poppy seed. It's at this stage that the cells separate into three distinct layers from which your baby's internal organs and skin will develop.
The ball of cells now resembles a tadpole and is as big as a peppercorn. The creation of the brain, spinal cord, heart, and blood vessels is already well under way.
Your little one has tripled in size and is protected by amniotic fluid. Although he's grown by leaps and bounds, he's still only about the size of a pomegranate seed.
Your baby is about the size of a raspberry. His hands and feet have webbed fingers and toes. Soon this extra tissue between his digits will be reabsorbed to reveal individual fingers and toes.
Baby's Length: about 0.63 in.
Baby's Weight: less than 0.04 oz.
Note: From week 8 through week 20, measurements are taken from crown to rump.
Your baby has graduated from embryo to fetus—and is now about the size of a cherry. The digestive tract and reproductive organs are formed, but it's still too early for even a skilled technician to tell whether you're having a boy or a girl.
Your baby is almost three inches long now, about the size of a plum. Fingernails, toenails, and bones are forming, and a fine layer of hair covers most of her body.
As you enter your second trimester, your baby is the size of a peach. All of her internal organs formed during the first trimester, and they will continue to mature from now until she's born.
Your baby is now the size of an apple. His brain now controls all the muscles in her body; he is able to move. Yes, he'll even do somersaults! But if this is your first baby, you probably won't feel him moving for several more weeks.
Your baby is now about the size of a mango. His legs are now longer than his arms, and he'll start giving you "hello" jabs at regular intervals, which you may be able to feel if this is your second or third pregnancy. First-time moms still might not feel anything for a few more weeks.
Your baby is the size of a papaya. Her lungs are developing rapidly, and they will begin making a protein called surfactant, which will help her breathe independently once she's born.
Your baby is as long as an ear of corn. Her nostrils are opening now for "practice breathing"; she'll go through the same motions of real breathing but inhale amniotic fluid instead of air.
Your baby is the size of an acorn squash. He's developing a firm grasp and may reach out and grab the umbilical cord. He can also stick out his tongue!
Your baby is the size of a large cabbage. She has cycles of sleeping and waking. After 30 to 90 minutes of snoozing, she may give you a kick to let you know she's awake.
Your baby is the size of a Napa cabbage. Because her taste buds are developed, she may acquire a preference for the foods you eat, which she samples when she swallows amniotic fluid.
Your baby is the size of a pineapple. Lanugo, the fine hair that covered her entire body and helped keep her warm as she developed, is starting to disappear, but there might still be patches of it on her shoulders and back.
Your baby is the size of a cantaloupe. Her bones are fully developed by now, and she's turning her head, pirouetting, and moving her body from side to side.
Your baby is as long as stalk of Swiss chard. Because he's running out of room in your uterus, he mostly stretches and wiggles, instead of delivering big kicks.
Your baby now weighs as much as a small pumpkin. At this point, he has shed most of that white creamy substance called vernix and the fine, fur-like hair called lanugo that has covered his skin since the middle of your second trimester.
By the time she's born, your baby may be watermelon-size. You're expecting to give birth this week, but don't worry if your baby decides to stick around a little longer. Many first babies are late, and she'll be worth the wait—we promise!
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