Pregnancy Calendar

Let's start with an understanding of your due date, the gestational age of your baby, and the stages of pregnancy.

First, some information about your baby's due date  Most babies are born between 38-42 weeks from the first day of your last menstrual period, with 40 weeks being the average. In actuality, only a small percentage of women actually deliver on their due date.  So, in general, 40 weeks after the first day of the last menstrual period is the estimated due date for the baby.

Now, about gestational age.  Gestational age is the age of the baby from the time of conception until the baby's birth.  It is typically measured in weeks and days. An early exam of the uterus and an early positive pregnancy test also help determine gestational age.  The most accurate way to determine gestational age is an ultrasound exam.  The baby can be measured with ultrasound as early as 5 or 6 weeks after the mother's last menstrual period.

Regarding the stages of pregnancy, a pregnancy is typically divided  into 3 periods of time, referred to as trimesters.  The first trimester includes months 0-3, the second trimester includes months 4-6, and the third trimester includes months 7-9.  These trimesters are discussed in detail on the page Pregnancy Stages. The information below will give you a quick overview of what is happening month-by-month as your baby develops.

Month # 1

The sperm and egg unite, the sperm fertilizes the egg,  and the fertilized egg attaches to the lining of your uterus. The fertilized egg begins to grow in the uterus, doubling in size every day. The placenta and umbilical cord begin to form. Your baby is enclosed in a sac of fluid that protects the baby.  The spinal cord develops and the bones of the spinal column begin to form. By the end of your first 6 weeks the baby has a head and trunk, is about 1/2 inch long and weighs less than an ounce.

Month # 2

By the end of the 2nd month, all of your baby's major body organs and body systems have begun to develop. The first bone cells appear, eyelids form and grow but remain shut, the inner ear  ankles, toes, wrists, fingers, and sexual organs are developing. The baby is now over 1 inch long and still weighs less than 1 ounce.

Month # 3

The baby is typically completely formed by the end of month #3. The fingers and toes are distinct and have soft nails. The baby's head is large compared to the rest of its body, the heart and kidneys are working and the baby's intestines have formed. At the end of the 3rd month the baby will weigh just over 1 ounce and will be approximately 4 inches in length.

Month # 4

Eyebrows and eyelashes begin to appear as do buds on the side of the head that will later develop into ears.  The baby's face continues to develop and the head makes up about half of the baby's size. The baby moves, kicks, sleeps, wakes,  and even swallows. By the end of the month #4, your baby will be 8-10 inches long and will weigh approximately 6 ounces.

Month # 5

The internal organs continue to mature, the baby is growing muscle, milk teeth will begin forming under your baby's gums, and body hair, including eyebrows and eyelashes, are starting to grow. Your baby develops regular sleep/awake cycles. At the end of month #5 the baby is about 10-12 inches long and will weigh about 1 pound.

Month # 6

The baby's skin is wrinkled and red. Your baby's brain is developing quickly. The baby's bones are becoming solid. At this point the baby is almost fully formed and looks like a miniature human. At the end of month #6, the baby will weigh about 1 to 1 1/2 pounds and be about 11- 14 inches in length.

Month # 7

Your baby's eyes can now open and close and can sense light. The baby kicks and stretches, can make grasping motions, and can suck their thumb.  By the end of month #6 the baby is usually about 15 inches long and weigh about 2 or 2 1/2 pounds.

Month # 8

Your baby's body continues to grow quickly with bones getting stronger, limbs fatter, and the skin develops a healthy glow. The brain is forming its different regions and is directing bodily functions. At the end of the 8th month the baby weighs about 4 pounds and is approximately 16-18 inches in length.

Month # 9

Your baby is gaining approximately 1/2 pound every week. Your baby is getting fatter and its skin appears less wrinkled. The baby will usually settle into the fetal position with its head down against the birth canal.

For a more detailed information visit the illustrated pregnancy calendar on Kidshealth and the website Pregnancy And Children.