Month One of Pregnancy
The amniotic sac is a water-tight sac that forms around the fertilized egg. It helps cushion the growing embryo throughout pregnancy.
The placenta also develops at this point in the first trimester. The placenta is a round, flat organ that transfers nutrients from the mother to the baby, and transfers waste from the baby.
By the end of the first month of pregnancy, your baby is around 6-7mm (1/4 inch) long - about the size of a grain of rice!
Second month of trimester 1
Month Two of Pregnancy
Your baby's facial features continue to develop. Each ear begins as a little fold of skin at the side of the head. Tiny buds that eventually grow into arms and legs are forming. Fingers, toes, and eyes are also forming in the second month of pregnancy.
The neural tube (brain, spinal cord, and other neural ti**ue of the central nervous system) is well formed. The digestive tract and sensory organs begin to develop. Bone starts to replace cartilage. The embryo begins to move, although the mother cannot yet feel it.
By the end of the second month, your baby, now a fetus, is about 2.54cm (1 inch) long, weighs about 9.45g (1/3 ounce), and a third of baby is now made up of its head.
Third month of trimester 1
Month Three of Pregnancy
By the end of the third month of pregnancy, your baby is fully formed. Your baby has arms, hands, fingers, feet, and toes and can open and close its fists and mouth. Fingernails and toenails are beginning to develop and the external ears are formed. The beginnings of teeth are forming. Your baby's reproductive organs also develop, but the baby's gender is difficult to distinguish on ultrasound. The circulatory and urinary systems are working and the liver produces bile.
At the end of the third month, your baby is about 7.6 -10 cm (3-4 inches) long and weighs about 28g (1 ounce).
Second Trimester Symptoms
The span from week 13 to week 27 of pregnancy is called the "honeymoon period" for good reason: Typically, nausea subsides, emotions even out and sex drive returns. It's also the time when you'll start to feel the baby's first movements.
In the second trimester of pregnancy -- months 4, 5, and 6 -- your baby's fingers and toes are well-defined. His eyelids, eyebrows, eyelashes, nails, and hair are formed, and teeth and bones are becoming denser. Your baby can even **** his or her thumb, yawn, stretch, and make faces.
The nervous system is starting to function at this point in pregnancy. The reproductive organs and genitalia are now fully developed, and your health care provider can see on ultrasound if you are having a boy or a girl. Your baby's heartbeat may now be audible through an instrument called a Doppler.
By the end of the fourth month, your baby is about 6 inches long and weighs about 4 ounces.
More on the 2nd trimester
Month 5 of Pregnancy
Hair is beginning to grow on your baby's head, and lanugo, a soft fine hair, covers his or her shoulders, back, and temples. This hair protects your baby and is usually shed at the end of the baby's first week of life.
You may begin to feel your baby move, since he or she is developing muscles and exercising them. This first movement is called quickening.
By the end of the fifth month of pregnancy, your baby is about 10 inches long and weighs from 1/2 to 1 pound.
More the 2nd trimester
Month 6 of Pregnancy
By the end of the sixth month, your baby is about 12 inches long and weighs about 2 pounds. His or her skin is reddish in color, wrinkled, and veins are visible through the baby's translucent skin. Baby's finger and toe prints are visible. The eyelids begin to part and the eyes open.
If born prematurely, your baby may survive after the 23rd week of pregnancy with intensive care.
Month Seven of Pregnancy
At the end of the seventh month of pregnancy, fat begins to be deposited on your baby. Your baby is about 36 cm (14 inches) long and weighs from about 900 - 1800g (two to four pounds). Your baby's hearing is fully developed and he or she changes position frequently and responds to stimuli, including sound, pain, and light.
If born prematurely, your baby would probably survive after the seventh month of pregnancy.
Month Eight of Pregnancy
Your baby, who is now about 46cm (18 inches) long and weighs as much as about 2.27 kg (five pounds), will continue to mature and develop body fat reserves. You may notice that your baby is kicking more. Baby's brain is developing rapidly at this time, and he or she can see and hear. Most internal systems are well developed, but the lungs may still be immature.
Month nine of trimester 3
Month Nine of Pregnancy
Towards the end of the third trimester, your baby continues to grow and mature. His or her lungs are nearly fully developed. Your baby's reflexes are coordinated so he or she can blink, close the eyes, turn the head, grasp firmly, and respond to sounds, light, and touch.
Your baby's position changes to prepare itself for labor and delivery. The baby drops down in your pelvis, and usually his or her head is facing down toward the birth canal.
By the end of this pregnancy month, your baby is about 46- 51cm (18 to 20 inches) long and weighs about 3.2kg (seven pounds).