Pregnancy Calendar

One of the frequent questions a woman wants answered is "How far along is my pregnancy?" or "When am I due?"  Your health care provider will estimate the gestational age of your baby at one of your first prenatal appointments. While this is just an estimate (only about 5% of babies are born on their estimated due date), it is important to know the approximate gestational age when monitoring your pregnancy.

The following has been adapted from the websites listed at the bottom of the page.

It is important to remember that your due date is only an estimate most babies are born between 38 and 42 weeks from the first day of your last menstrual period (LMP).  Only a small percentage of women actually deliver on their due date.

A pregnancy is divided into trimesters: the first trimester is from week 1 to the end of week 12, the second trimester is from week 13 to the end of week 26, and the third trimester is from week 27 to the end of the pregnancy.

To help you follow some of the concerns and changes you may encounter during your pregnancy this section is divided into month-by- month segments. Additional information about months 1-3 is provided  on the page first trimester, months 4-6 on the page second trimester, and months 7-9 on the third trimester.

What is gestational age?

Gestational age is the age of an unborn baby.  It is measured in weeks and days, not in months.  Since the precise date of conception is seldom known, the age is based on the date of the mother's last menstrual period.  Forty weeks after the first day of the last menstrual period is the estimated end of a normal term pregnancy, or due date. 

The gestational age of a baby may be calculated from the date of your last period.  If you are sure of this date and have regular periods, your due date is estimated to be 40 weeks from the first day of your last period.  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 a reliable date for the last menstrual period confirmed by an ultrasound exam.  The baby can be measured with ultrasound as early as 5 or 6 weeks after the mother's last menstrual period. 

First Month

About 5 to 7 days after a sperm fertilizes an egg, the egg attaches to the lining of the uterus. This process is called implantation. The fertilized egg then begins to grow in the uterus, doubling in size every day. At this stage of development the baby is called an embryo.

Shortly after implantation the placenta and umbilical cord begin to form. The placenta and umbilical cord provide nourishment and oxygen to your baby and carry away the baby's wastes. Your baby is enclosed in a sac of fluid, called the amniotic sac, to protect the baby from bumps and pressure.

In another week the baby has a spinal cord. A few days later, five to eight bones of the spinal column (vertebrae) are in place. Nerve development is beginning. By the end of your first 6 weeks of pregnancy, your baby has a head and trunk, is about 1/2 inch long and weighs a fraction of an ounce.

During your first month of pregnancy, you may experience fatigue and sleepiness, frequent urination, nausea, vomiting, heartburn, indigestion, bloating, food aversions or cravings, and/or breast changes. These pregnancy symptoms vary from woman to woman. You may experience all of them, just a few, or none of them. Emotionally, you may feel irritable, have mood swings, may act irrationally, and be quick to cry. These emotions are similar to those experienced by women who have premenstrual syndrome. It is also common to have a variety of feelings about being pregnant, including misgivings, fear, joy, and elation.

Second Month

Your baby's development is very rapid during the second month. By the end of the second month, all of your baby's major body organs and body systems, including the brain, lungs, liver, and stomach, have begun to develop. The first bone cells appear during this time. Eyelids form and grow but remain sealed shut. The inner ear is forming. Ankles, toes, wrists, fingers, and sexual organs are developing.

At the end of the second month of pregnancy, your baby looks like a tiny human infant. If it is a boy, the penis will begin to appear. The baby is a little over 1 inch long and still weighs less than 1 ounce. From now on the baby is called a fetus.

Third Month

Your baby will be completely formed by the end of the third month. Your baby may have begun moving its hands, legs, and head and opening and closing its mouth, but he or she is still too small for you to feel this movement.

The fingers and toes are now more distinct and have soft nails. The baby's hands are more developed than the feet and the arms are longer than the legs. Your baby's head is quite large compared to the rest of its body. Hair may have started to form on the head. Tooth buds have formed under the baby's gums. Vocal cords develop around the 13th week of pregnancy. Your baby's heart has four chambers and beats at 120 to 160 beats per minute. Kidneys are now developed and start draining urine into the bladder. Intestines have formed outside of the baby (on the umbilical cord) because they can not fit inside the baby. By the end of this month, the umbilical cord, which carries nutrients to your baby and takes wastes away, will be fully formed. At the end of your third month, your baby will weigh just over 1 ounce and will be about 4 inches long.

Additional information about months 1-3 is provided  on the page first trimester.

Fourth Month

The baby's skin in pink and somewhat transparent. Eyebrows and eyelashes begin to appear in this month. Buds on the side of the head begin to form into the outer ear. The baby's face continues to develop. The tail has disappeared from the fetus and the head makes up about half of the baby's size. The baby's neck is long enough to lift the head from the body.

The baby moves, kicks, sleeps, wakes, swallows, and passes urine. You may start to feel a slight sensation in your lower abdomen (called quickening). This feels like bubbles or fluttering. When you feel the baby's movement, write down the date and tell your health care provider. This helps determine when your baby is due. By the end of the fourth month, your baby will be 8 to 10 inches long and will weigh about 6 ounces.

Fifth Month

The internal organs are maturing. Your baby's fingernails have grown to the tips of the fingers. Fat is now being stored beneath your baby's skin. Your baby is also growing muscle and is getting stronger every day. The blood cells take over for the liver the job of producing blood. Your baby's gall bladder will become functional, producing bile that is necessary for digestion. Milk teeth will begin forming under your baby's gums. Body hair, including eyebrows and eyelashes, are starting to grow.

Your baby sleeps and wakes at regular intervals. You will find that your baby is much more active now. He or she turns from side to side and head over heels. Your baby may suck its thumb.

At the end of the fifth month, you baby will be about 10-12 inches long and will weigh about 1 pound.

Sixth Month

This month continues to be a period of rapid growth. Your baby's skin is wrinkled and red. It is covered with lanugo (fine, soft hair) and vernix (a substance consisting of oil, sloughed skin cells and lanugo). Real hair and toenails are beginning to grow. Your baby's brain is developing rapidly. Fatty sheaths which transmit electrical impulses along nerves are forming. Meconium, your baby's first stool, is developing. A special type of fat (brown fat) that keeps your baby warm at birth is forming. Baby girls will develop eggs in their ovaries during this month. The baby's bones are becoming solid.

Your baby is almost fully formed and looks like a miniature human. However, because the lungs are not well developed and the baby is still very small, a baby cannot usually live outside the uterus at this stage without highly specialized care. By the end of the sixth month, Your baby will be around 11 to 14 inches long and will weigh about 1 to 1 1/2 pounds.

Additional information about months 4-6 is provided  on the page second trimester, and months 7-9 on the third trimester.

Seventh Month

Your baby's eyes can now open and close and can sense light changes. The lanugo is starting to disappear from the baby's face. Your baby's hearing is getting better. He or she can now hear the outside world quite well over the sound of your heartbeat. The baby exercises by kicking and stretching. He or she can also make grasping motions and likes to suck its thumb.  By the end of this month, your baby will be approximately 15 inches long and weigh about 2 or 2 1/2 pounds. If the baby was born now, its chances of survival are better than last month.
 
Eighth Month

Your baby's body continues to grow quickly. The bones are getting stronger, limbs are fatter, and the skin has a healthy glow. The brain is now forming its different regions. The brain and nerves are directing bodily functions. Taste buds are developing. Your baby may now hiccup, cry, taste sweet and sour, and respond to pain, light, and sound. If you are having a boy, his testicles have dropped from his abdomen where they will then descend into his scrotum.  Your baby will be about 16 to 18 inches long and will weigh about 4 pounds at the end of this month.

Ninth Month

Your baby is now gaining about a 1/2 pound each week. Your baby is getting fatter and its skin is less rumpled. He or she is getting ready for birth and is settling into the fetal position with its head down against the birth canal, its legs tucked up to its chest, and its knees against its nose.

Your antibodies to disease are beginning to flow rapidly through the placenta.  The rapid flow of blood through the umbilical cord keeps it taut which prevents tangles.

Your baby is beginning to develop sleeping patterns. Your baby will continue to kick and punch although it will move lower in your abdomen to under your pelvis (this is a process called "lightening"). You will also feel your baby roll around as it gets too cramped inside your uterus for much movement. Your baby's lungs are now mature and your baby will have a great chance of survival if born a little early. The bones of baby's head are soft and flexible to ease the process of delivery through the birth canal.

Your baby is now about 20 inches long and weighs approximately 6 to 9 pounds. Your baby may be born anytime between the 37th and 42nd week of pregnancy. Click on this link for more on labor and delivery.

Additional information about months 7-9 is provided  on the page third trimester.