You and your baby take an incredible nine-month journey together before you get to meet face to to face. Here’s a quick guide to what’s happening as your baby grows into a person ready for independent life.

by Christina DiMartino

From the time your child is born until she reaches adulthood, you can etch a mark on that specially designated wall to chart her growth. But before you even meet your child, parenting starts with an incredible nine-month journey. And during that time your baby is in your womb, there’s no way to precisely record her week-to-week or month-to-month development. 

Sutter Health is a community-based, not-for-profit network of doctors and hospitals serving Northern California. Its system includes specialists in high-risk pregnancy and care for premature babies. It reports that the growth of your baby is a continuous process that often conveys a sense of awe. To help you understand your baby’s rapid growth while in the womb, it provides a breakdown by the three trimesters, including fetal development milestones. (Sizes and weights are approximate.)

First trimester

At the end of four weeks, your baby is about a quarter of an inch long. The heart, digestive system, backbone, and spinal cord begin to form, and the placenta is starting to develop. The fertilized egg is now 10,000 times larger than it was at conception.

At the end of the second month, the baby has grown to 1-1/8 inches long. The heart is functioning, and the eyes, lips, tongue, ears and teeth are forming. If the baby is a boy, the penis begins to appear. The baby is moving but is still too small for you to feel.

At 12 weeks, the baby is 2-1/2 to 3 inches long and weighs from 1/2 to 1 ounce. It has a recognizable form. Nails are starting to develop, and earlobes are formed. Arms, hands, fingers, legs, feet and toes, and most organs and tissues are also developed. The eyes are almost fully formed. You and your doctor can now hear the baby’s heart rate with a special instrument called a Doppler.

Second trimester

At the end of the fourth month, your baby is 6-1/2 to 7 inches long and weighs about 6 to 7 ounces. The baby is developing reflexes, such as sucking and swallowing, and may begin sucking her thumb. Tooth buds are developing, sweat glands are forming on palms and soles, and fingers and toes are well defined.

It’s an exciting time because your baby’s gender is now identifiable. His skin is bright pink, transparent, and covered with soft, downy hair. Although recognizably human in appearance, the baby would not be able to survive outside the mother’s body.

By the end of month, five things are even more exciting inside of your womb. Your baby is now 8 to 10 inches long and weighs about 1 pound. Hair has begun to grow on his head, and soft wooly hair called lanugo covers his body. Internal organs are maturing, and eyebrows, eyelids and eyelashes appear. You will likely begin to feel some fetal movement about now.

Third trimester

At six months, your baby’s weight is 1-3/4 to 2 pounds, and length is between 11 and 14 inches long. Eyelids begin to part and eyes open for short periods of time. The baby can now hiccup. The skin is covered with a protective coating called vernix.

At month seven, the baby’s taste buds have developed. Fat layers are forming and organs are maturing. The skin is still wrinkled and red. The baby weighs from 2-1/2 to 3-1/2 pounds, and is between 14 and 16 inches long. If born at this time, the baby would be considered premature and require special care.

Month eight brings rapid overall growth, including the brain. Your baby is 16-1/2 to 18 inches long and weighs about 4 to 6 pounds. Except for the lungs, most body organs are now developed, and the kidneys are mature. Movements or “kicks” are strong enough to be visible from the outside. The baby’s skin is less wrinkled, and fingernails extend beyond the fingertips.

Nine months have passed, and your baby is fully developed. She can now survive outside of your body. On average, she is 19 to 20 inches long and weighs 7 to 7-1/2 pounds. She is settling down lower in your abdomen to prepare for birth. She may seem less active, but don’t worry. She’s just getting ready for your big push.

 

Christina DiMartino has been a freelance and assignment writer since 1985. She is a researcher, interviewer, writer, editor, and manuscript collaborator with a repertoire of clients from around the world.

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