Pregnancy Stages – Week by Week

pregnancy stages

Pregnancy is a beautiful journey, a miracle of growth of life inside you. Through this tool, you can discover the science of pregnancy from conception, through the three trimesters. The pregnancy stages are detailed week by week and you can easily discover the progress in growth of your baby.

The baby development process is universal. Life flourishes within you. And, it is you who brings it in to this world. You carry forward the legacy of the universal creator.

So, Congratulations if you have stepped in to this journey. For a detailed information on pregnancy symptoms, tips, diet and tests, you can refer this link.

I thank you because you made me. You knit me in your womb. Your eyes could see me as an embryo. You wrote my days beautifully. You gave me a place where I was safe while I was being created. I could feel your joy of having me and your pain too. Thank you for bringing me in this world. Thank you Mom.

Love, Baby

Do check out our other tools: the Due Date & Conception Date calculator to determine your expected due date, the pregnancy by week calculator to determine how far you are in your pregnancy and the pregnancy milestones and the Ovulation Calculator to estimate your most fertile days.

The Pregnancy Stages


Pregnancy Week by Week

Stages of your Baby's development

Pregnancy is a beautiful journey, a miracle of growth of life inside you. Through this tool, you can discover the science of pregnancy from conception, through the three trimesters. The pregnancy stages are detailed week by week and you can easily discover the progress in growth of your baby.

The baby development process is universal. Life flourishes within you. And, it is you who brings it in to this world. You carry forward the legacy of the universal creator.

So, Congratulations if you have stepped in to this journey.

Week 1-4: The Conception

Week 1: the week of your last menstrual period

This is the week of your last menstrual period. The first day of menstrual bleeding is considered the official start date of pregnancy and the 40 weeks of pregnancy are calculated by this date.

Week 2: Fertilization

Every month, about three to 10 eggs receive a hormonal signal that cues them to mature and prepare for ovulation. At the same time, the uterus is forming a blood rich lining that is called the endometrium. This will thicken, upon fertilization, to form a sack strong enough to carry and cushion your baby throughout the entire pregnancy.

Week 3: Cells Join, Divide - New life begins

Once a month around the 14th day, one of the eggs travels down into the fallopian tube. This is ovulation. If in the next 36 to 48 hours, just one of the millions of the sperms can get all the way from the vagina through the uterus and into the fallopian tube to penetrate the egg, the egg will become fertilized. Sperm can live for up to 5 days in this environment, therefore making pregnancy possible for up to 5 days after intercourse.

Week 4: Implantation

The fertilized egg immediately begins dividing and floats down into the uterus. Upon fertilization, your little one is set as a boy or a girl.

Ladies, this is one that you can not take credit for since it is up to the sperm to determine the gender of your baby. Sperm carries either a "X" (girl) chromosome or a "Y" (boy) chromosome. The gender of your baby is predetermined by the father's sperm chromosomes.

Week 5-8: Your baby is an embryo consisting of two layers of cells from which all her organs and body parts develop

Week 5-7: the embryotic stage begins
"the heart begins to beat"

The amniotic fluid is being built up. The embryo grows from a tiny speck about 2mm - the size of a pin head. By the end of the week the embryo will have more than doubled in size to about 4-5mm. The egg has now completely grown into the mucous membrane of the uterus which covers the egg, the umbilical sac and the amniotic fluid cavity. A fibrin clot closes the hole to the uterus cavity. The placenta is developing. The embryo starts receiving oxygen and nutrition through the placenta.

Week 8: Baby starts to practice moving

The embryo measures about 18 mm (3/4 inch) in length. Their arms and legs are growing and location of the elbows and toes are visible.. The feet and hand buds have appeared. Starts to practice moving (not felt by mom till week 20). The stomach is being made from part of the gut.
The face is beginning to take shape. Your baby's mouth and nostrils are starting to develop. Teeth begin to develop under the gums. The eyes can now be seen as small hollows on each side of the head.

Week 9 - 12: Your baby is now about the size of a kidney bean and is constantly moving. He has distinct, slightly webbed fingers.

Week 9: Fingers and Toes form

The embryo has grown to measure 30 mm (1.2 inches) in length. The fingers and toes are well defined. Cartilage and bones begin to form. The upper lip as well as the nose tip are being formed. The tongue begins to develop and the larynx is developing. The eyelids are developed, although they stay closed for several months. The main construction of the heart is complete.

Week 10: Embryo is now a Fetus

From this week until birth, the developing organism is called a fetus. The fetus is now the size of a small cherry. The feet are 2mm long (one tenth of an inch). The neck is beginning to take shape. The body muscles are almost developed. Baby has begun movement. While still too small for you to feel, your little one is wriggling and shifting. The jaws are in place. The mouth cavity and the nose are joined. The ears and nose can now be seen clearly. Fingerprints are already evident in the skin. Nipples and hair follicles begin to form.

Week 11: Neurons multiply

The fetus CRL is about 1.5 inches (35mm) in size. The fingers and toes have completely separated. The taste buds are starting to develop. Baby has tooth buds, the beginning of the complete set of 20 milk teeth. Baby can swallow and stick out his or her tongue. Whole body except tongue is sensitive to touch. Cartilage now calcifying to become bone. If it is a boy, the testicles are starting to produce the testosterone hormone.

Week 12: Fingernails and toenails appear

The fetus is now about 2.5 inches (6cm) length and weighs about 0.7 ounce (20 g). The feet are almost half an inch (1cm) long. The fetus starts moving spontaneously. The face is beginning to look like a baby's face. The pancreas is functioning and producing insulin. Fingernails and toenails appear. The baby can suck his thumb, and get hiccups.

Week 13 - 16: By now your baby is around 7 to 8 centimetres (3 inches) long and weighs about the same as half a banana. Her tiny, unique fingerprints are now in place.

Week 13: Baby flexes and kicks

The fetus has grown to about 3 inches (8cm) long. Weight approximately 1 ounce (25 grams). Bone is beginning to replace cartilage and the ribs are appearing. The nose and chin are well defined. Movements can be measured. The child will begin to learn to suck its thumb. The child can open and close its mouth. The external genitalia are well defined making it is possible to determine the baby's gender.

Week 14: Hormones start up

The fetus is 3 and half inches (9cm) long. Weight is about 1 and half ounces (45 grams). The eyes are slowly moving towards the center of the face. The nose is more pronounced. The ears are fully developed. The cheekbones are visible. The first hair is appearing. The kidneys are producing urine. In girls, the ovaries are moving down towards the pelvis. In boys, the prostate gland is developing. Fingerprints are already evident in the skin. For girls, the ovaries move into the pelvis.

Week 15: Bones and muscles grow

Baby is now over 4 inches (10cm) long and weighs about 2.5 ounces (75 grams). He or she can move its arms and make a fist. Fingernails and toenails are present. Baby's skin is still very thin.

Week 16: Facial expressions are possible

The fetus measures nearly 5 inches (12cm) from head to buttocks. The fetus weighs about 3.5 ounces (100 grams). The fetus is covered with a protective soft down to regulate its temperature. Fat begins to form underneath skin. Baby hears external voices, sleeps and dreams.

Week 17 - 20: Your baby is now about 13 centimeters ( 5.5 inches) long and weighs 140 grams (5 ounces). His skeleton is starting to harden from rubbery cartilage to bone.

Week 17: Fat accumulates

The umbilical cord is growing thicker and stronger. Fetus weight is just over 5 ounces (150g). Baby is about 5 inches (14cm) long crown to rump and would be about 9 inches (23cm) head to toe, if it could stretch out. The retina has become sensitive to light. The first stools (meconium) are now beginning to accumulate.

Week 18: Baby begins to hear

The fetus is now 6 inches long and weighs 7 ounces. The fetus measures about 15cm and weighs almost 200 grams. They can hear sounds and may be startled by loud noises. Mother can recognize their active and rest periods. The skin is building a protective wax layer (vernix).

Week 19: Genitals recognizable

Fetus is around 6.5 inches (17cm) and 9 ounces (250gm). Your placenta continues to grow and nourish the baby. Features of your baby's heart, should be visible during an ultrasound. Your baby's genitals are distinct and recognizable. Scalp hair has sprouted and continues to grow.

Week Twenty: The halfway point

Baby is 17cm long crown to rump, and weighs about 310 grams. The baby can hear and recognize the mother's voice. The mother will probably start feeling the first fetal movements. The toenails and fingernails are growing. The growth of hair on the rest of the body has started. The skin is getting thicker. The heart can now be heard with a stethoscope.

Week 21 - 24: Eyebrows and eyelids are now in place. Your baby would now be more than 27 centimeters (10.5 inches) long if you stretched out her legs.

Week 21: Nourishment evolves

Length is now measured crown to heel. The fetus has grown to 10.5 inches (27 cm) - 12.7 ounces (360 grams). It is now gaining weight steadily, with fat being added to the body. Bone marrow has started making blood cells. Their small intestine is starting to absorb sugars.

Week 22: Taste buds develop

The fetus reacts to loud sounds. Baby starts having a regular sleeping and waking rhythm. The mother's movements can wake her baby. Taste buds are forming on your baby's tongue. The baby is 28cm long (crown to heel) and weighs over 450 grams. The weekly weight gain has increased to around 70 grams.

Week 23: Sense of balance develops

He or she measures over 28cm and weighs up to 550 grams. The baby is over 11 inches tall, weighs about a pound. The eyebrows are visible. The child can successfully suck. Bones located in the middle ear harden.

Week 24: Practices breathing

The child is now gaining around 3 ounces (90 grams) a week. Baby weighs about 600 grams and is 30cm (crown to heel) long. The eyelids can be seen very clearly. If born at this stage, is officially considered viable, they may well be able to survive with appropriate medical support.

Week 25 - 28: Your baby weighs about a 660 grams (1.5 pounds). His wrinkled skin is starting to smooth out as he puts on baby fat

Week 25: Exploration continues

Baby is around 13.5 inches in length and weighs 1 and half pounds. Bones are becoming solid, hands are now fully developed. The brain is growing rapidly, the brain cells are starting to mature. The sexual organs are fully developed.

Week 26: Second trimester ends

The baby measures 14 inches long and weighs over 1.7 pounds. The feet are 2 inches (5cm) long. Hands are very active. The baby's eyes begin to open around this time.

Week 27: Eyes can open

The fetus weighs almost 2 pounds now and is about 14.5 inches long. Baby now weighs about 875 grams and is 36.5 cm in length. The head is over 2.5 inches (7cm) in diameter. Your baby's hearing continues to develop. The eyes can blink, open and close.

Week 28: May recognize your voice

The fetus has its own regular intervals for sleeping and being awake. The weight has increased to 1000 grams and is 37.5cm in length. The feet are just over 2 inches (5.5cm) long. The hair on the head are now clearly visible. The milk teeth have developed under the gums. The eyes are starting to move in their sockets.

Week 29 - 32: By now, your baby is more than 40 centimetres (15 inches) long. She can open and close her eyes and probably see what's around her.

Week 29: Movement is more forceful

Your baby now weighs about 2 and a half pounds (1150gm) and is about 15 inches (38.5cm) long from head to heel. Brain is busy developing billions of neurons. Baby's muscles and lungs are continuing to mature. The fetus can taste and respond to pain. The milk teeth have developed under the gums.

Week 30: Baby puts on pounds

Baby measurements are 16 inches and weighs about 3 pounds. The head is almost 3.5 inches (8cm) in diameter. The feet are nearly 2.5 inches (6cm) long. The wrinkled skin is becoming smoother now. In boys, the testicles have moved down to the groin. The baby controls its own body temperature.

Week 31: Baby detects light

Baby weighs 3.5 pounds and measures 16.5 inches from the head to heel. The eyes have now completely opened and are responding to light and darkness. A loud noise near you may cause your little one to jump.

Week 32: Reproductive development continues

The baby is 17 inches (43cm) long and weighs 4 pounds (1.8 kilograms). The diameter of the head is almost 4 inches (10cm). Under the skin the fat layer is getting thicker. The toenails and fingernails are completely formed. In boys, the testicles will be descending from the groin down into his scrotum.

Week 33 - 36: Your baby now weighs around 2.2 kilos (4.7 pounds). His layers of fat are filling him out, making him rounder, and his lungs are well developed

Week 33: Lanugo is disappearing

The baby is now 4.4 pounds (2 kg) and around 17.5 inches (44cm) in length. The diameter of the head is about 8.5cm. The baby fuzz, lanugo, is disappearing. Your baby drinks about a pint of amniotic fluid a day. You may gain a pound a week (500g) for the rest of your pregnancy. Half of your weight gain will go directly to your baby.

Week 34: Rapid growth continues

Your baby now is approximately 18 inches long and weighs about 5.25 pounds. Your child has now an excellent chance of survival outside the womb. Fat accumulations plumps up the arms and legs this week. Eyes opened when awake and closed when sleeping. The fingernails are now completely formed.

Week 35: Reflexes are coordinated

Your baby is now about 18.5 inches in length and weighs over 5.5 pounds. The body is growing round due to developing fat layers. Your baby's reflexes are coordinated. Lungs are almost fully developed. About 90% of babies born this week survive.

Week 36: Baby may drop into the birth canal

The baby is about 19 inches (48 cm) long. Weight is around 6 pounds (2.7 kg). The baby's body is becoming chubby as fat layers build. Between now and birth they may gain about an ounce (30g) a day. You may feel contractions of the womb, called Braxton Hicks contractions.

Week 37 - 40: Your baby is almost due. At birth, the average baby is more than 51 centimeters (20.5 inches) long from head to toe and weighs approximately 3.4 kilograms (7.5 pounds), but babies vary widely in size at this stage

Week 37: Baby is full term

Typically, baby now measures 19.5 inches (50 cm) from the head to the heel. Baby weighs up to 7 pounds or 3 kilograms. The head diameter is over 3.5 inches (9cm). The water could break at any time. If it does happen, see a doctor immediately.

Week 38: Development is complete

Baby is about 20 inches (51 cm) and weighs about 7.5 pounds (3.4 kilograms). The soft down, which covered the body throughout the pregnancy, is now disappearing. The body fat is continuing to build up. The wrinkled skin is becoming 'baby' smooth. The baby may have reached its final birth position. Most babies are born head first with only about 3 percent coming out feet first.

Week 39: Very close now

The average baby is about 20 inches (51 cm) and weighs about 7.5 pounds (3400 grams). The baby has reached its final birth position. It will be cramped inside your uterus for much movement. Your baby will continue to punch and kick but lower in your abdomen, under your pelvis. The head is about 4 inches (10 cm) in diameter. Most of the baby's downy coating of lanugo has now disappeared.

Week 40: Your due date arrives

You have now reached the time of delivery. All systems are developed and ready to go. Now it is just a matter of time. Baby is about 20 inches (51cm) and weighs approximately 7.5 pounds (3.5 kg). The head has a diameter of about 4 inches (10 cm). The contractions could begin at any moment. Congratulations!

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