The growth of your baby

How Baby Grows

Pregnancy is a time of major change. From the very start, your baby-to-be (fetus) alters your body and the way you live. For your entire pregnancy, the baby depends on you for all the things it needs to grow and thrive.

Although each pregnancy is unique, the growth and development of a fetus take place in a fairly uniform pattern. A woman’s egg is fertilized by a man’s sperm in the fallopian tube. During the next few days, they travel through the fallopian tube to the uterus where the embryo implants and starts to grow.

The cluster of cells or embryo that reaches your uterus will become the fetus and the placenta (or afterbirth). The placenta functions as a life-support system during pregnancy. It delivers oxygen, nutrients, and hormones from mother to fetus.

The First Month

(1-2cm in length)

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  • The fertilized egg attaches to the lining of the uterus. Some of these cells will grow into a baby. Other cells will form the placenta.
  • Arms and legs begin to form.
  • Brain and spinal cord begin to form. Heart and lungs begin to develop.
  • The heart begins to beat near the end of this month.


The Second Month

(2-3cm in length)

  • Eyelids form, but remain closed.
  • The inner ear begins to develop.
  • Bones appear. Ankles, wrists, fingers, and toes form.
  • The genitals begin to develop.
  • By the end of the month, all major organs and body systems have begun to develop.


The Third Month

(approx. 10cm in length)

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  • Buds for future teeth appear.
  • All internal organs are formed, but are not fully developed.
  • Fingers and toes continue to grow.
  • Soft nails begin to form. Bones and muscles begin to grow.
  • The intestines begin to form.
  • The backbone is soft and can flex.
  • The skin is almost transparent.
  • The hands are more developed than the feet.
  • The arms are longer than the legs.


The Fourth Month

(approx 15cm in length)

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    • Eyebrows, eyelashes, and fingernails form.
    • Arms and legs can flex. External sex organs are formed.
    • The skin is wrinkled and the body is covered with a waxy coating (vernix) and fine hair (lanugo).
    • The placenta is fully formed.
    • The outer ear begins to develop.
    • The fetus can swallow and hear.
    • The neck is formed.
    • Kidneys are functioning and begin to produce urine.


The Fifth Month

(approx 25cm, 400-500g)

  • The sucking reflex develops.
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  • If the hand floats to the mouth, the fetus may suck his or her thumb.
  • He or she is more active.
  • You may be able to feel him or her move.
  • The fetus sleeps and wakes regularly.
  • Nails grow to the tips of the fingers.
  • Gall bladder begins producing bile, which is needed to digest nutrients.
  • In girls, all her eggs have formed in the ovaries.
  • In boys, the testicles begin to descend from the abdomen into the scrotum.


The Sixth Month

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(approx 30cm, 500-750g)

  • Real hair begins to grow.
  • The brain is rapidly developing.
  • The eyes begin to open. Finger and toe prints can be seen.
  • The lungs are fully formed, but not yet functioning.


The Seventh Month

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(approx 35cm in length, 1-1.2kg)

  • The eyes can open and close and sense changes in light.
  • Lanugo begins to disappear.
  • The fetus kicks and stretches.
  • The fetus can make grasping motions and responds to sound.



The Eighth Month

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  • With its major development finished, the fetus gains weight very quickly.
  • Bones harden, but the skull remains soft and flexible for delivery.
  • The different regions of the brain are forming. Taste buds develop and the fetus can taste sweet and sour.
  • The fetus may now hiccup.



The Ninth Month

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  • The fetus usually turns into a head-down position for birth. The skin is less wrinkled.
  • The lungs mature and are ready to function on their own. Sleeping patterns develop.
  • The fetus will gain about 1/2 pound per week this month.


Conversion Chart

1 inch = 2.54 centimeters
1 ounce = 28 grams 1 pound = 453.59 grams
The Uterus Grows With Pregnancy