How your baby grows in the womb

  • By Team TDO

Congratulations to the mom-to-be. It must feel great having two hearts beating inside you. Do you know how this life is developing, hair by hair, toe by toe?

We take you on the journey right from the eruption of the egg till the breaking of water at the time of your delivery.Scroll down to the week of the pregnancy you are in to know the progress of your baby’s development

First trimester

The first three weeks: To make it simple, imagine a war under sea. The egg erupts from the follicle in the female around the 14thday of the menstrual cycle. In the next12-24 hours, one sperm swims up the uterus to the fallopian tube to penetrate the egg, combining their genetic material and becomes the champion.

As the sperm from the male merges with the egg from female, a zygote, or yolk, is formed. This marks the appearance of baby in the womb. The egg or ovum has x chromosomes. The sperm has x and y chromosomes. If sperm carries x to fertilize the egg, the baby will be a girl, and if it carries y to fertilize egg, it will be a boy.

In the initial stages of development, the baby looks like a ball of cells multiplying rapidly. It lodges itself into the uterus. The placenta, a cord that joins baby and mom, starts forming and releases the hormone HCG.

Week 4: The baby is the size of poppy seed. It is called as embryo. The amniotic sac, a protective fluid filled sac, surrounds the baby. The placenta is not yet active. This week marks the beginning of development of the baby's organs.

Week 5: The baby, about the size of a sesame seed, develops in three layers. Ectoderm forms the skin, hair, nails and breasts. Mesoderm forms a tiny heart, which starts beating this week. Lung, intestine, urinary system, liver, pancreas develop from the endoderm. Brain, spinal cord, backbone, nerves are all formed.

Week 6: The baby is now size of a lentil. The nose, mouth and ears begin to develop this week. The baby heart beats twice as fast as the mom's. Intestines and pituitary gland are developing along with bones and muscles.

Week 7: This week is marked by emergence of hands and feet from the developing arms and legs. The baby is now about a size of cherry and about 1.2cm in length. The bone marrow starts forming in this week. Intestinal loops bulge into the umbilical cord and exchange nutrients.

Week 8: Eyelids are formed over the eyes. Tiny finger and toe buds pop out from the hands and feet. Breathing tubes form and stretch to lungs. The baby is now approximately the size of a kidney bean and is having a merry time within by moving around and swimming in the sea.

Week 9: The baby is 2.5 cm long. Eyes are completely formed and the eyelids closed. The heart fully divides into four chambers and valves start forming. Tiny teeth begin to form. Placenta is fully developed. Sex organs are seen, but gender can't be determined.

Week 10: The baby is about 3cm long. Important part of development is almost complete by now. Organs like kidneys, liver, brain, and intestine start to function, however, they develop throughout pregnancy. Baby can now swallow fluid and kick.

Week 11: Baby is about 3.8 cm now. Gum buds are formed and few bones begin to harden. Kicking, stretching, and swimming become common and regular. However, moms can't feel them yet.

Week 12: This week shows remarkable changes as the baby starts moving its fingers and toes, flexing wrists, and even begins to move eye muscles and mouth. Kidneys start to excrete urine into the bladder. The baby is now 5 cm long or about the size of a lime.

Second trimester

Week 13: Tiny fingers are marked by fingerprints. Organs and veins become visible through the skin. Size is about 7.5cm and sex organs are quite developed.

Week 14: Baby is now almost 9cm long and 40g. The baby can now suck its thumb. Facial expressions like frowning develop.

Week 15: Baby is 10 cm. Legs become longer than hands and can be moved. Lungs develop further. Taste buds are developing, along with sensitivity to light. But the eyes are still closed.

Week 16: The baby starts growing very rapidly now. It is now 11 cm long and 100 grams. Head becomes erect, legs develop further, toenails begin to grow, and scalp starts shaping up. Pumping of blood by heart has already begun.

Week 17: The baby weighs about 150 gm and is 12 cm long. Soft cartilage of skeleton turns bony. Umbilical cord – a cord connecting to the placenta – becomes strong and thick. Sweat glands begin to develop.

Week 18: Baby is now almost 14 cm. Ears are placed at their appropriate position. A protective covering around the nerves begins to form. Genitals and sex organs are further developed.

Week 19: Specialized areas for smell, taste, hearing, vision, and touch are developing in the brain. The baby can hear now. It is 15 cm long and weighs about 250g.

Week 20: Baby is now 300 grams. It starts swallowing more, as the digestive tract develops and also produces a by-product of digestion called Meconium. This accumulates in the intestine and is passed at birth or after birth as first stools.

Week 21: The baby is about 26 cm long. Full-blown kicks and shakes can be felt now. Eye brows and lids are formed. Vagina begins to form in baby girls.

Week 22: Almost 28 cm, the baby looks like a tiny doll now with more defined eyelids, eyebrows and lips. Tooth buds are growing from the gums. Fine hair called lanugo and tiny wrinkles are formed on the skin.

Week 23: Blood vessels in the respiratory system are developing to prepare the baby for breathing after birth. Loud noises can be picked up by the baby as it twists and turns and swims in the womb. The baby weighs about half a kilo now.

Week 24: Baby weighs slightly more than 500g and almost a foot long. Brain, taste buds, and lungs develop further rapidly this week.

Third trimester

Week 25: The baby is now 34cm in length and 650g in weight. The wrinkled skin disappears as fat formation takes place underneath. More hair growth takes place.

Week 26: The baby is 36cm. Ears are well developed to hear the parents talk. Breathing movements are more distinct. Testicles descend in scrotum in the next 2-3 days in baby boys.

Week 27: Baby weighs 900g and is 37cm. It is able to open and close eyes and suck fingers. A regular pattern of sleeping and waking up develops. Brain is very active by now.

Week 28: Here is the reason to celebrate.The baby is now 1kg. Eyesight is developing and it is able to blink eyes to the light passing through womb. Baby has more body fat forming.

Week 29: Weight is slightly more than 1kg and the baby is 38cm long.It is growing rapidly with lungs and muscles maturing, and size of head growing bigger to accommodate the developing brain.

Week 30: Eyesight continues to develop as baby becomes 1.3kg and 40cm.

Week 31: The baby weighs 1.4kg and can move head from side to side. Arms, legs, and body become rounded with required fat accumulation below skin. The baby’s movements increase a lot.

Week 32: The baby now takes a lot of space in womb as it weighs 1.7 kg and is 42 cm long and will gain almost half of its total birth weight in the next few weeks. Nails and hair are grown and skin is soft and smooth.

Week 33: The baby’s skeleton is rapidly hardening, and wrinkles are vanishing. Skull bones aren't fused and can overlap to aid easy passage of head through birth canal at delivery. Weight is 1.8 -2 kg and length is 43 cm from head to heel.

Week 34: Baby is plumper with those fat layers forming. This develops temperature regulation. Lungs and brain are maturing. Weight has gone up to 2.2kg.

Week 35: Baby is already 45cm long and 2.3kg. It has less space left in womb to move, but number of kicks remains the same. Kidneys are fully developed and some liver function has started.

Week 36: Basic development is completed by now and baby is inside the womb to pack on some more weight at the rate of 28-30 grams per day. Baby is now 45- 47 cm long and sheds hair and waxy protective substance called vernixcaseosa covering the skin.

Week 37: Now the baby is considered full-term. He is about 48 to 50cm and weighs almost 3kg. The respiratory system is matured and ready to breathe outside the womb. Some babies even have head full of hair at birth.

The fascinating journey comes to an end. And now you have a bawling baby in your arms. We hope you enjoyed reading about just how this miracle of life came to be.