The official pro-life organisation of the archepharchy of Kalyan - Mumbai, committed to all human life from conception to death.
Learn More

Fetal Development

There are many people who advocate for abortion who don’t know about fetal development. For some, all it takes to change their mind about the morality of abortion is the knowledge that a preborn baby’s heart starts beating at about 21 days or that babies in the womb can feel pain as early as 12 weeks. This won’t be the case for everyone – but you should know these basic facts about fetal development to use in your conversations about abortion.

The Milestones of Fetal Development

Week 1 -4

  • Conception occurs when the sperm fertilizes the egg.
  • Gender is determined by the sperm, which carries either an X or a Y chromosome. An X chromosome indicates a female baby, and Y denotes male.
  • The embryo implants itself on the wall of the uterus.
  • A neural tube forms; it will ultimately become the brain and spinal cord.
  • The circulatory system rapidly forms (including the umbilical cord), and the heart begins to beat toward the beginning of Week 3.

Week 5

  • Hands and wrist joints are forming.
  • All cranial nerves are now present, and limb nerves are forming.
  • Subtle movement begins.

Week 6

  • Brainwave activity has begun.
  • Arm and leg bones form, along with tooth buds.
  • Hands begin to move.
  • Eye lids are present and growing and a primitive nasal cavity forms.
  • Vital organs are continuing to form, including the kidneys, liver, pancreas, lungs, stomach, and intestines.

Week 7

  • The head rotates and legs move; the baby is also able to hiccup.
  • Hands can touch each other and fingers can overlap.
  • The heart, which began beating weeks ago, is nearly complete and is beating very quickly now (peaking between 165 and 170 beats per minute).
  • Feet begin to have tiny notches that will become toes, and knee joints form.

Week 8

  • Hair appears around eyebrows and in the mouth.
  • Urine production and release begins.
  • Joints are similar to those of an adult.
  • Right- and left-handedness begins to emerge.
  • Fingers and toes are webbed and short but continuing to grow.
  • Eyelids are completely fused together.

Week 9

  • Weight increases 75% this week.
  • The head is now much larger than the rest of the body.
  • The baby can suck thumb and move tongue.
  • Early vocal cords are present and the baby begins to yawn.

Week 10

  • Fingernails and toenails start to grow, and unique fingerprints are now present.
  • Bones are beginning to solidify.
  • Eyes now roll down reflexively.
  • Buds form that will eventually be secondary teeth.

Week 11

  • Nose and lips are completely formed; complex facial expressions begin.
  • Reproductive organs are well-formed and gender can now be seen on ultrasound.
  • Intestines absorb water and glucose.
  • Weight increases 60% this week.

Week 12

  • Hands touch mouth up to 50 times an hour.
  • Bile production begins in liver.
  • Bowel movements begin.
  • There are taste buds all over mouth.

Week 13

  • Teeth, as well as other tissues, are growing.
  • Cilia are lining airways.
  • Most of the body is sensitive to touch.

Week 14

  • Facial features become more defined.
  • Body grows faster than the head.
  • Fingers and toes are fully formed, nails continue to grow.
  • Baby can make facial expressions.

Week 15

  • Skeleton continues to harden.
  • Baby begins to move limbs more actively.
  • Skin is still thin and translucent.
  • External genitalia are distinguishable on ultrasound.

Week 16

  • Baby can make sucking motions.
  • Lanugo (fine hair) starts covering the body.
  • Heart pumps 25 quarts of blood per day.
  • Muscles are developing for movement.

Week 17

  • Baby’s skeleton is now visible on ultrasound.
  • Fat begins to deposit under the skin.
  • Baby can hear sounds from outside the womb.
  • Movements become more coordinated.

Week 18

  • Hearing improves; baby may respond to sound.
  • Eyebrows and head hair appear.
  • Digestive system starts functioning.
  • Baby’s limbs are in proportion to the body.

Week 19

  • Vernix caseosa (protective skin coating) begins forming.
  • Rapid brain development occurs.
  • Baby’s movements may be felt by mother (“quickening”).
  • Sleep-wake cycles begin.

Week 20

  • Midpoint of pregnancy; fetus measures about 6.5 inches.
  • Sex can be clearly determined on ultrasound.
  • Swallowing and sucking skills improve.
  • Lanugo covers most of the body.

Week 21

  • Baby’s movements become stronger.
  • Digestive system produces meconium.
  • Skin is thin but developing fat layer underneath.

Week 22

  • Hair on head continues to grow.
  • Eyebrows and eyelashes are forming.
  • Lungs continue to develop, preparing for breathing.

Week 23

  • Skin appears wrinkled due to thin fat layer.
  • Fingernails reach fingertips.
  • Hearing continues to improve.

Week 24

  • Alveoli (air sacs) form in lungs.
  • Baby gains more body fat.
  • Eyes are developing pigment.
  • Baby may respond to familiar voices.

Week 25

  • Baby’s movements are stronger and more coordinated.
  • Hair and eyebrows continue to grow.
  • Immune system starts developing.

Week 26

  • Baby may open eyes and respond to light.
  • Lungs continue to mature.
  • Baby begins to store fat under the skin.

Week 27

  • Brain grows rapidly; neurons form connections.
  • Baby can move arms and legs with more coordination.
  • Fetal sleep patterns develop.

Week 28

  • Third trimester begins.
  • Eyes can blink and sense light changes.
  • Body gains more fat and smooths wrinkles.
  • Baby may practice breathing motions.

Week 29

  • Muscles continue to strengthen.
  • Baby’s head starts growing faster to support brain development.
  • Movements become stronger, mother feels kicks more distinctly.

Week 30

  • Skin becomes less translucent as fat increases.
  • Bone marrow produces red blood cells.
  • Baby may respond to sounds with movement.

Week 31

  • Fat continues to accumulate under the skin.
  • Baby can coordinate hand and eye movements.
  • Bone development continues.

Week 32

  • Lanugo begins to shed.
  • Baby’s body fills out with fat for warmth after birth.
  • Movements may become restricted due to limited space.

Week 33

  • Baby’s head moves down into pelvis in preparation for birth.
  • Immune system strengthens further.
  • Baby practices breathing and sucking.

Week 34

  • Skin is smooth and less wrinkled.
  • Lungs continue to mature.
  • Baby can respond to sound, touch, and light.

Week 35

  • Baby gains weight rapidly.
  • Body is plump, and movements are strong.
  • Fat continues to store under skin for warmth.

Week 36

  • Baby is considered “early term.”
  • Movements may feel more confined due to limited space.
  • Lungs and organs are fully developed and ready for birth.

Week 37

  • Baby is considered “full term.”
  • Head may descend further into pelvis.
  • Skin is soft and smooth, with body fully formed.

Week 38

  • Baby continues to gain weight, mainly fat.
  • Organs are fully mature.
  • Movements may be slower due to space restriction.

Week 39

  • Baby is fully developed and ready for birth.
  • Head engages in the pelvis for labor preparation.
  • Body fat continues to increase for temperature regulation after birth.

Week 40

  • Full-term birth occurs.
  • Baby’s organs, muscles, and reflexes are ready for life outside the womb.
  • Lanugo and vernix caseosa mostly disappear.
  • Baby typically weighs between 5.5 to 8.8 pounds and measures about 19-21 inches.

Be the Voice For the Voiceless

Stand with us and support this mission through your generous donation, helping us bring hope, dignity, and life-affirming education to many.

Give