Pregnancy Calculator

Find out what happens to mother and baby during the first, second, and third trimesters of pregnancy.

First Trimester


1 Week Pregnant

This is the week of menstruation when the uterus sheds much of its thick lining. Pregnancy is measured from the first day of the last menstrual period.

2 Weeks Pregnant

The uterine lining begins to thicken and a surge of hormones from the brain prompts the ovaries to release a mature egg which is drawn into the Fallopian tube.

3 Weeks Pregnant

The egg meets sperm and is fertilized. The egg undergoes cell division and forms a hollow sphere called a blastocyst which implants in the wall of the uterus.
Preg Test 1-1

4 Weeks Pregnant

The blastocyst continues to implant more deeply into the uterine lining and flattens into two layers. The yolk sac nourishes the embryo until the placenta takes over.
Week 5

5 Weeks Pregnant

The embryo is shaped like a comma and forms a neural tube—the start of the baby’s brain, nervous system, and spine—and the beginnings of a heart.

6 Weeks Pregnant

The baby’s heart begins to beat, some bones and muscles begin to develop, the basic features of the baby’s face—eyes, ears, upper and lower jaws—appear.

7 Weeks Pregnant

The brain and nervous system are developing quickly and becoming more complex. Legs and arms begin to bud, and the umbilical cord forms.

8 Weeks Pregnant

The baby now has eyes and eyelids as well as fingers and toes which are webbed. The hands are held over the heart which beats at 150 beats per minute.
A female physician checks a female patient's breathing in an exam room

9 Weeks Pregnant

The embryonic “tail” at the bottom of the spine disappears, the head grows larger than the rest of the body, and digestive systems begin to develop.

10 Weeks Pregnant

All of the major organs and systems are formed and working. The fingers and toes have now separated. Inside the baby’s mouth, 20 tooth buds begin forming.
A male doctor sitting in front of a computer talks with a female patient wearing a black baseball cap

11 Weeks Pregnant

The developing baby is now categorized as a fetus rather than an embryo. The baby’s head is now round and proportionally large — one-third of the body’s total length.

12 Weeks Pregnant

The features of the baby’s face are now formed and arranged with the eyes having moved from the side of the head to the front. Toenails and fingernails begin to form.

Second Trimester

A woman checking her weight on the scale

13 Weeks Pregnant

The second trimester of pregnancy begins, and the baby continues to grow rapidly with the body beginning to catch up to the size of the head.

14 Weeks Pregnant

Soft downy hair called lanugo begins to cover the baby’s face and head. The neck is now more defined and the vocal cords have formed.

15 Weeks Pregnant

The fetus is more active and coordinated. Arms and legs move vigorously (some have even been seen sucking their thumbs). The circulatory system is working well.

16 Weeks Pregnant

Proportions of the baby’s body change as the skeleton and muscles develop. The head is more erect, and the baby begins to have facial expressions.
A female physician consults with a female patient in a clinic exam room

17 Weeks Pregnant

The baby’s joints—knees, elbows, ankles, wrists—are all formed and working. The baby also has a repertoire of simple reflexes like swallowing and blinking.
A female nurse in blue scrubs talks with a female patient in a clinic exam room

18 Weeks Pregnant

The fetus begins to look more and more baby-like with ears that stand out from the side of the head, well-formed nostrils, and a more proportioned face.
A pregnant woman is examined by her physician

19 Weeks Pregnant

The bones of the inner ear have hardened through ossification which may allow the baby to begin hearing things inside the womb.
A male physician consults a pregnant patient sitting in an exam chair

20 Weeks Pregnant

The baby has reached the halfway point and is about 6.5 inches long and weighs about 10 ounces. Its body is covered with a protective coating called vernix.

21 Weeks Pregnant

Motor neurons in the brain are more developed, and the baby’s movements are more controlled and conscious—it can scoot, flip, and wiggle in the amniotic sac.

22 Weeks Pregnant

The baby’s senses are developing—it can touch, hear, and taste. Soft, fur-like lanugo covers the baby’s body, and the scalp may start sprouting hair.

23 Weeks Pregnant

The baby is now approximately 7.5 inches long and weighs one pound. The fetus has begun to build a layer of fat, but the skin still hangs loosely and is wrinkled.

24 Weeks Pregnant

The fetus’s own bone marrow beings to help the placenta make blood cells, and lungs are developing surfactant which prevents lung collapse when the baby exhales.


25 Weeks Pregnant

The fetus begins to put on more fat. The wrinkles on the skin smooth out and the cheeks plump slightly. Hair on the baby’s head may take on color and texture.

26 Weeks Pregnant

The baby can now detect light and hear things outside the womb such as music and voices. It can also now detect if it is right side up or upside down.
Week 27

27 Weeks Pregnant

The fetus practices breathing movements drawing amniotic fluid into its lungs. These inhale and exhale movements strengthens muscles for the baby’s first breaths.

Third Trimester

Week 28

28 Weeks Pregnant

The baby’s brain develops folds and grooves, fat continues to build as the baby grows, and it can now open and close its eyes.
Week 29

29 Weeks Pregnant

The baby’s skeleton is assembled, and the bones continue to harden. The baby has now filled much of the uterus and can be felt kicking and moving.
Week 30_v2

30 Weeks Pregnant

The baby is having a major growth spurt as arms, legs, and torso are filling out. The baby now weighs about three pounds (about as much as a butternut squash).
Week 30

31 Weeks Pregnant

The baby continues to practice opening and closing its eyes. The eyes are sensitive to light, but the ability to see color and focus will come after birth.
week 32

32 Weeks Pregnant

By 32 weeks, many babies have a full head of hair and eyebrows. The lanugo hair that covered the body for many weeks begins to shed.
Week 33

33 Weeks Pregnant

While the skeleton is hardening, the baby’s skull is still very pliable so that the plates of the skull can overlap as the head moves through the birth canal.
Week 34

34 Weeks Pregnant

The baby alternates periods of rest or sleep with more active periods and now has smooth skin and fingernails that extend to the fingertips.
Week 35

35 Weeks Pregnant

Weight gain is now happening rapidly at a rate of one ounce per day. Things are getting cramped in the uterus, and amniotic fluid has decreased.
Week 36

36 Weeks Pregnant

The baby now weighs just under 6 pounds (the size of a mini watermelon) and has fuller cheeks and a rounder appearance overall.

37 Weeks Pregnant

The lanugo hair and waxy vernix that once covered the baby’s body are mostly gone. The baby now has a layer of fat and can grasp with its fingers.

38 Weeks Pregnant

The baby is now considered full-term, but the brain and nervous system are still developing (and will continue to develop through childhood).

39 Weeks Pregnant

At 39 weeks, most babies weight about seven pounds. Growth is much slower now, but the layer of fat continues to build. Hair and fingernails are also growing.

40 Weeks Pregnant

The estimated due date (EDD) is this week. Pay attention for uterine contractions that are regular, gradually get closer together, last longer, and increase in intensity.


The baby is now fully developed and ready to be born. This doesn't always mean he or she will come on time. Labor induction may be needed to help your baby enter the world.