For I am not ashamed of the gospel, for it is the power of God for salvation… Romans 1:16

Baby Development in the Womb

The development of the baby in the womb is an amazing and miraculous process. Throughout the entire course of development, the pre-born baby develops in different stages, as he or she gets ready to be delivered. It is important to remember though, that not all pregnancies are the same, and each baby develops at their own rate. The following information is just a quick overview, of what the development process is like.


The human embryo is identifiable as an individual, a specific human being on a molecular level with 23 pairs of chromosomes; containing all the genetic information such as: hair color, height, body shape, and much more. The placenta begins to develop and the umbilical cord, composed of two arteries and one larger vein, has formed and becomes a lifeline transporting nutrients, blood, and wastes to and from the embryo and placenta.


The placenta is fully developed and acts as a filter between the mother and child as well as providing the embryo with oxygen and removing carbon dioxide from the blood. The embryo also produces hormones to stop the mother’s menstrual cycle. The earliest version of the heart is formed at 20 days and will begin to beat somewhere around 25 days. The early formations of the brain and spinal cord are visible at this point. By the end of the fourth week, an astounding array of structures, including a highly functional circulatory system composed of three sets of blood vessels, pigment cells, and most of the bones and connective tissue for the face and neck begin to form.


During this time, profound changes are occurring in almost all the organ systems. The brain becomes subdivided into five parts- the same major divisions of the adult brain. The head is disproportionately large and the hands and legs form, first as flipperlike growths from the trunk, then developing elbows, fingers, and toes. The spine and spinal cord grows faster than the rest of the body at this stage- giving the appearance of a tail, however this disappears as the child continues to grow. In the face, the earliest recognizable traces of the future eyes, nose, and inner ears are readily distinguishable. At this time, the embryo is about three-quarters of an inch long, 40,000 times larger than when the baby began.


At eight weeks and roughly an inch and a half long, almost all the organs are forming. The skin is starting to thicken, although it is still transparent. Skin begins to fold over the eyes to make eye-lids. The unborn baby now has the ability to open his or her jaw, move the tongue, and even hiccup. Local stimuli may cause movements such as: squinting, opening the mouth, partial finger closure, and flexing of the toes. It is roughly around eight weeks where the lungs begin to develop and the intestines move from the umbilical cord into the abdomen of the child. At this time, the heartbeat is approximately 160 beats per minute and the brain equals almost half of the body’s total weight.

Years ago, while giving an anesthetic for a ruptured tubal pregnancy (at two months) I was handed what I believed to be the smallest human being ever seen. The embryo sac was intact and transparent. Within the sac was a tiny human male, swimming extremely vigorously in the amniotic fluid, while attached to the wall by the umbilical cord. The tiny human was perfectly developed, with long, tapering fingers, feet and toes. It was almost transparent as regards to the skin, and the delicate arteries and veins were prominent to the ends of the fingers. The baby was extremely alive and did not look at all like the photos and drawings of ’embryos’ which I have seen.

– Paul E. Rockwell, MD. (former director of Anesthesiology at Leonard Hospital)

Quote from: Handbook on Abortion (1979) by Dr. & Mrs. J.C. Willke. pg. 20

WEEKS 9–12

The child’s movements are now probably visible with an ultrasound, and soon the mother will be able to feel the kicks. Also, technology allows us to see the baby’s brain activity in response to pain or loud noises. Now that the vocal chords are complete, the child sometimes cries (silently). The child spends its time in cycles of sleep, drinking the amniotic fluid for nutrition, or excreting waste. At this time, soft fingernails and toenails are developing. In the mouth, 20 tiny baby buds are forming into teeth inside the gums. Many of the internal organs, such as the liver, have begun to function. However, the unborn child does not yet use its lungs, instead, oxygen is supplied by the placenta. At this point, body weight has increased by 75% and the almost completely developed heart resembles that of a newborn’s.

As early as eight to 10 weeks’ gestation,
and definitely by thirteen and a half weeks,
the human fetus experiences organic pain.
Dr. Vincent J. Collins,
 (former diplomat of the American Board of Anesthesiologist)

Quote from: V. J. Collins. (1976). Principles of Anesthesiology pp. 922-923.

During this time the hands and feet are becoming more functional and are beginning to take their natural proportions. As a result, the arms, legs, knees and elbows will move constantly. The baby may be able to put a thumb in it’s mouth, although the sucking muscles aren’t completely developed yet. The skin now becomes pink- although still transparent, and very fine hair called Lanugo, covers the baby’s body. Eyebrows and hair on the top of the head are beginning to grow, though the color may change after birth. The fully developed eye-lids have shut and will remain closed until about seven-months gestation. The baby may begin to show different expressions including a smile, frown, and grimace.


By the end of the fourth month, the baby will be somewhere around 4 ½ inches long, crown to rump. Awake or asleep, the baby moves 50 times or more each hour, flexing and extending its body, moving the head, face, and limbs, and exploring the amniotic sac by touch, perhaps even pulling on the umbilical cord. The baby moves around inside the sac seeking comfortable positions. The child will also be frequently hiccupping even though the mother may not feel it yet. At this point, the circulatory system is in full working order and the heart can be plainly heard. In fact, the baby’s heart is pumping up to twenty-five quarts of blood a day.

WEEKS 17–19

The nerve cells for each of the five senses – taste, smell, hearing, seeing and touch – are developing in their specialized areas of the brain. The baby will be able to recognize sounds and voices; and even though the eyes are still closed, a baby’s retinas can detect a small amount of light if the mother is out in the bright sun or under strong lights. The ears have moved to their final position and the vocal cords are formed. Oil and sweat glands now develop over the child’s body. A greasy, white substance called Vernix (Latin for “varnish”) covers the baby in a protective layer until it is born. The mother may now be able to feel the babies movements, called “quickening.” When the mother moves, the fetus will curl into a self-protective position. At approximately 5 ½ inches crown to rump, and weighing around 5-8 ounces, the baby is growing fast! As the child is growing, the womb and the umbilical cord are also growing thicker and stronger.


Though still small and fragile, the baby is growing rapidly and could possibly survive if born at this stage. The child’s sex organs are visible and the gender can be determined using an ultrasound device. The mother is transferring immune cells to the child, which will protect it until six months after birth, from viruses the mother has had already. Babies at 20 weeks’ gestation can be seen developing certain gestures and habits that persist into their postnatal years. Typically, until now, the baby has been measured from crown to rump, but from now until birth the child will be measured from crown to heel.

WEEKS 21–24

This is a time period of rapid growth! The child will continue to grow a centimeter a week and has gained about six ounces in muscle and bone mass. The lungs are developing “branches” and are producing cells that help the air sacs to inflate easily. The external skin has turned from transparent to opaque and a layer of fat is developing underneath for both insulation as well as food. The child has begun to produce it’s own white blood cells, also known as Leukocytes, which fight infections and diseases. Also, the child’s pancreas is developing rapidly and has already begun the production of insulin to break down sugars.

WEEKS 25–28

The baby now weighs between 1 ½ to 2 ½ pounds and is approximately measuring 13 ½ to 15 inches from head to toe. The baby’s nostrils are now open and the child is taking small breaths of amniotic fluid and the blood vessels of the lungs are now forming. The eyes begin opening and the optic nerve now functions. In fact, the eye is so sensitive to light that if a physician peers into the uterus with a telescope, the baby will try to shield its eyes with its hands. Also, the child’s response to sound is growing more consistent as a result of the developed network of nerves in the ears. The baby’s brain is quite active at this point in the pregnancy with more brain tissue developing and the grooves on the brain’s surface beginning to appear. The protective structures of the spine are now forming around the spinal cord. Although it is no longer than the average adult hand, it is now made up of 150 joints, 33 rings, and some 1,000 ligaments. From 27 weeks on the child finishes development and prepares for delivery.

WEEKS 29–31

In the last trimester, the baby prepares for its life outside the womb with more fat developing underneath the skin. The baby may soon slow up growing in length and drop head down, into the pelvic cavity awaiting its birth. Babies at this stage generally measure about 15 to 16 inches from crown to toe and weigh about 2 ½ to 3 ½ pounds and will continue to gain weight until birth. By 29 weeks, the head is in proportion with the rest of the body and is making room for the developing brain. The baby’s lungs and digestive tract are almost fully developed and the child’s bone marrow is now in charge of red blood cell production. A pint and a half to around a liter of amniotic fluid now surrounds the baby, but that volume decreases as he or she gets bigger and has less room in the uterus.


The baby’s arms, legs and body continue to fill out — and they are finally proportional in size to the head. Looking more like a newborn the child will measure close to 17 inches from crown to toe and weigh about 4 pounds. This is the most rapid period of body growth during the entire pregnancy, gaining up to half it’s birth weight between now and birth. The child now sleeps 90-95% of the day, and sometimes experiences REM sleep, when dreaming takes place.

The baby now weighs approximately 4 ½ to 5 ½ pounds and measures 17- 18 ½ inches head to toe. Plus, neurons and synapses are developing in huge numbers. By week 33, the eyes can now see dim shapes. Studies show that shining a bright light on the belly at this time can cause a baby’s heart rate to speed up or can cause the baby to turn towards the light in response. (Note: Exposing a pre-born baby or premature infant to bright light before it’s ready can damage its eyes.) Although the child’s hearing is fully developed, it may be paying closer attention to high-pitched tones. During these weeks, amniotic flux is at its highest level of the pregnancy and the baby’s head will move down into the mother’s pelvis as the baby gets into the right position for birth. The baby’s skull is still quite pliable and not completely joined, in part so he or she can ease out of the relatively narrow birth canal.

WEEKS 36–38

This marks the end of the normal gestational period. The baby now weighs anywhere between 6 and 7 1/2 pounds and measures approximately 18 ½ to 20 inches from head to toe and will continue to gain weight (about an ounce a day) until birth. Soon, as the wall of the woman’s uterus and abdomen stretch thinner and let in more light, the baby will begin to develop daily activity cycles. During these times the elbows, feet or head may protrude from the mother’s stomach when the child stretches and squirms about or tries “walking” around the womb by pushing off with its feet.