The stages of Life Before Birth
You and everyone you know began your lives by successfully completing the journey before birth described in Your Life Before Birth. Read on to learn more about your journey and to better understand why the prenatal experience is so important for everyone.
Welcome to the amazing world inside the womb where every tiny baby grows and prepares for life after birth. It's also the place where bonding between mother and child begins and where each little one's lifelong health is partly established.
This page are referenced from the start of fertilization, not the beginning of a woman's last menstrual period (LMP). To calculate the equivalent, from a woman's LMP, add two weeks to the fertilization ages provided here.
A time of preparation
The nine months of pregnancy truly is a time of preparation for life after birth. With rare exception, virtually everything that a newborn baby can do has been practiced over and over again for weeks or months before birth.
A bond like no other
From the time of fertilization (or conception), the developing baby and mother seamlessly work together and communicate with one another in numerous and complex ways that are still not fully understood. Pregnancy is the ultimate expression of selfless teamwork as mother and child do everything, share everything, and experience everything together as they jointly pursue a healthy full-term pregnancy and safe delivery.
As you might expect, a mom’s health and well-being are closely intertwined with the health and well-being of her child. With few exceptions, what is good for mom is good for her baby, and what is good for her baby is good for mom. Likewise, what is harmful to mom is harmful to her baby, and what is harmful to her baby is harmful to mom.
The exceptional teamwork between mother and child begins almost immediately. The first pregnancy hormone, called early pregnancy factor, appears in mom's blood as early as 24 hours after fertilization. This hormone starts preparing her body to meet her baby’s needs.
Prenatal growth and development influence lifelong health
Research over the past 30 years has uncovered many ways in which a baby’s prenatal environment and growth pattern influence life-long health.
To cite just a few examples, babies experiencing impaired prenatal growth face an increased risk of heart attack, stroke, hypertension, and Type II diabetes later in life. Tobacco exposure during pregnancy is associated with an increased risk of certain behavior disorders as well as obesity, diabetes, and diminished lung function.
Human fertilization
The single-cell human embryo is created when fertilization begins.
Single-cell embryo
This single-cell embryo shows the male and female pronuclei (the two round structures) meeting in the center. Each pronuclei contains the DNA of one parent. [Carnegie Stage 1b human embryo]
Human development and human life begin simultaneously
There are a number of unassailable scientific facts that you should know about human fertilization and the single-cell human embryo. All are important. Despite unequivocal scientific evidence, some remain controversial.
Fertilization, or conception, marks the beginning of human development; the start of a brand new, unique, genetically distinct human being; and the true onset of pregnancy.
The living, single-cell human embryo formed at fertilization is a new human life at the first stage of human development. Because of the controversy, this topic deserves some further discussion. Defining the start of human life as occurring at some point later than fertilization ignores and contradicts longstanding scientific fact. This is very simply understood. Only a continuously living embryo can divide from one cell into two, two cells into four cells, and so on throughout pregnancy. It is equally true that a dead embryo cannot grow, cannot divide, cannot change, cannot consume oxygen, cannot produce carbon dioxide, cannot replicate DNA, and cannot become alive at some future time. As a scientific question, to argue that the human embryo or fetus comes alive at some point beyond fertilization is to support a modern version of the theory of spontaneous generation. Proponents of this once-popular theory believed that living things could form from dead matter years.
The distinction about when human life and human development begin is more than an academic or theoretical question. It has health implications. Once fertilization is underway, the fragile early embryo is susceptible to damage from the surrounding environment, which includes exposure to toxins present in mom’s uterine tube or intra-uterine environment.
An amazing skill set
In addition to the ability to work closely with mom, the simple-appearing, single-cell human embryo directs its own development throughout life using the instruction set present in its own DNA.
Multiplying and Dividing
about 24 hours, the single-cell embryo divides into two cells, then four cells, and so on. This begins the incredible transformation from single-cell embryo to precious newborn.
Early human blastocyst
This early blastocyst is about 4 days post-fertilization. The cells of the inner cell mass are destined to form the embryo's body. Note that the protective shell is still in place.
Mature human blastocyst
This more mature blastocyst is about 5 days post-fertilization. The outer cells will help form the placenta. Note that the protective shell (zona pellucida) is gone.
For normal development to proceed, the blastocyst must escape its protective coating. When viewed under the microscope, this process is called "hatching." The protective coating of the human embryo developing naturally inside the womb is believed to break down and fall apart, rather than "hatch" as seen here.
Early hatching blastocyst
Here we see the embryo "escaping" the confines of the zona pellucida.
The great escape
Here you can again see the human embryo freeing itself from its protective shell.
The Rapidly Developing Beating Heart
By 22 days, the heart begins to beat... and quickly resembles the heart of a newborn. The first sign of heart development occurs at about 20 days. By 22 days, the tube-shaped heart begins to beat. Almost immediately, the heart begins changing shape as seen below. As we will see time and time again, the developing human begins performing new functions at what seems to be the earliest possible opportunity.
The rapidly maturing heart
Once the tubular-shaped human heart forms, it changes shape almost immediately. It is essentially fully formed within 21 days
The circulation
Here you can see her beating heart in slow motion just 4½ weeks after fertilization. Do you see how her heart changes color as blood enters and leaves its chambers with each beat? The heart begins to beat at just about the earliest possible time that it could beat. By 4 weeks, blood circulated by this tiniest of all hearts is delivering life-sustaining oxygen and nutrients to various parts of the brain and body. Note the precision with which this little heart does its vital work!
The brain and beating heart
The brain, heart, and liver are the most prominent structures at this stage.
The four-chambered beating heart
If you look closely, you can see contraction activity in all four heart chambers. Note how the liver fills the abdomen. The large red blood vessel that appears to be entering the liver is the umbilical vein within the umbilical cord. It is bringing oxygenated blood from the placenta to the baby. Thanks, mom
Movement and Brainwaves
6 weeks, the baby begins to move and will turn away if lightly touched on his face. Brainwaves have been recorded as early as 6 weeks and 2 days.”
Movement begins
Movement begins just 5½ to 6 weeks after fertilization.It is one of our earliest activities and one of the most natural things we can do. The baby's ability to sense and respond to a light touch on the face represents the first evidence of a working reflex pathway. You may be surprised to know that movement before birth is necessary for normal development of the nerves, bones, and joints. In fact, without movement early in pregnancy, normal joint formation would be impossible. Movement is vital to human health, starting long before birth and at all ages thereafter.
The 7-Week Embryo
From poo: “By 7 weeks, the baby begins turning her head and moving her hands.
Actively engaged
Active motion in the womb begins many weeks before mom can feel it. Here you can see the frontal portion of the brain, the beating heart, and active head rotation with both hands in motion at about 7 weeks following fertilization. Once again, you can see how the liver completely fills the abdomen. Once movement begins, it doesn’t take long for many other movements of increasing complexity to emerge. These movements include coordinated muscle activity inside the body. Peristalsis is the complex traveling wave of coordinated muscle relaxation and contraction of the intestinal wall, which propels swallowed nutrients through the digestive tract. Peristalsis begins in the large intestine at 8 weeks and in the small intestine at 9 weeks.
Fingers and Toes, Amazing Eyes
Idividual fingers are emerging from his hand plates… and his eyes are developing rapidly.
The origin of fingers and toes
Distinct fingers and toes emerge from the hand and foot plates over about 10 or 11 days, starting at about 6 weeks after fertilization. It is well established that the cells between the individual fingers and toes, having served their purpose, will self-destruct through a process of planned (programmed) cell death.
Upper and lower limb buds
The upper and lower limb buds make their first appearance at approximately 26 and 28 days, respectively. Here again, humble-appearing limb buds quickly produce magnificent structures.
Hand plate and wrist
With the passage of just 7 days, the hand and wrist regions are distinct and the hand plate is shaped like a round pancake. The marginal vein is well seen here outlining the hand plate. Now, even more dramatic changes are about to unfold.
Hand plate
As the fingers just start to emerge, the rounded hand plate begins to flatten between the digital rays, giving the appearance of a collection of straight lines. Each digital ray will give rise to the bones of the finger (or thumb) and the corresponding metacarpal bone.
Fingers
By 7½ weeks, the tissue between the fingers is gone. Individual fingers now have the freedom to move independently. Note how thick the pads of the fingers [see arrow] are in the hand of this 8-week embryo.
Eyes
The eyes at 7 weeks are well formed but still not complete. The optic nerves are forming behind each eye, along with several layers of the retina. Several muscles that attach to and move each eye are emerging as well.
The maturing lens
The developing lens (lens vesicle) is the most prominent feature at this stage. The lens will eventually become transparent. Its job is to bend (refract) light in order to project sharp, focused images onto the retina of objects nearby and far away. Leg movements are also seen... along with the startle response.
The human heart beats approximately 54 million times before birth. that is just the beginning, as EHD further estimates that the human heart beats in excess of 3.2 billion times over a typical 80-year lifesInvestigators have recorded an electrical tracing of the human heart at 7½ weeks following fertilization. By this age, the conducting system within the heart is very well developed, and the EKG tracing has a very similar appearance to EKG tracings obtained from newborns and even adults. By 7½ weeks, the baby’s fingers are separate. His hands begin to touch in the midline... as do his feet.
As his hand plates grow, the cells between the emerging fingers (and toes) undergo planned (programmed) cell death to create separation between the fingers. The baby’s hands can now reach and touch one another in the midline (with the feet doing likewise). This marks the beginning of exploring his world through the touch of a finger.
Here you can see her beautiful right eye surrounded by her emerging eyelids. The human eye at this stage shows considerable similarity to the newborn and adult eye. Here you can see the developing lens and anterior chamber, behind which the relatively large posterior chamber is seen.
Eyelids
The eyelids are now just appearing. This is a rare chance to appreciate how advanced the eye appears at 7½ weeks, right before the eyelids begin to temporarily fuse together. The overbite is typical and temporary at this stage.
Within the posterior chamber of the eye, you can see the dark pigment of the human retina. Though not yet in final form, it has already been in place for weeks! You can also clearly see the early upper and lower eyelids. At this point, the eyelids begin to rapidly cover the entire surface of the eye and will soon fuse together.
The Amazing 8-Week Embry
The sheer number of newly identifiable permanent body parts that emerge during the 7-day period from 7 weeks (or 49 days) to 8 weeks (56 days) is astounding. Despite the baby’s small size and young age, a whole new level of exquisite detail emerges as numerous individual ligaments, tendons, muscles, nerves, and blood vessels become identifiable for the first time.
The arteries of the hand
The arteries that supply the hand provide an excellent example of the exquisite detail present in the 8-week embryo. This screen shot captures the tiny arteries that supply the hand and fingers.
Hand arteries
The arteries that supply the palm of the hand and fingers are seen in this movie clip. The arterial pattern seen here precisely mimics the pattern found in newborns and adults. (Note the thick pad on the thumb and the elbow.)
By 8 weeks, the baby’s brain is so complex that parts of it closely resemble the brain of a newborn. Parts of the brainstem (the base of the brain closest to the spinal cord) and the arterial blood supply of the brain appear very similar to those found in the newborn. Because the human brain is so advanced by 8 weeks, some experts believe brain function is likely already underway.
Preparing for first breath and first cry
Breathing movements before birth help blood return to the heart and prepare the breathing muscles for their vital duties after birth. At 8 weeks, breathing motions are observed only 2% of the time. As the baby matures, these motions are seen roughly 30%–40% of the time.
A full-term newborn baby has the ability to draw in her first deep breath and release her first cry because she has prepared for this moment for 30 weeks! Her many hours spent practicing breathing motions has also given her the endurance to continue breathing.
Right- and left-handedness
Ultrasound studies have shown that 75% of babies demonstrate a definite preference to move their right hands, starting 8 weeks after fertilization. The remaining babies are split into two equal groups, with one group preferring to move their left hands and the other group showing no preference.
Eyelids
Here you can see the near-complete fusion of the eyelids. Within a few days, the white fusion line seen here will extend across the entire right eye. You can also see the light-colored collar bone adjacent to the lower right jaw and the right ear.
Appreciating what has been accomplished
In just 8 weeks, the remarkable single-cell embryo has blossomed into one billion cells, which have already formed an estimated 4,000 body parts and a dozen body systems.
The astonishing transformation in just 8 weeks is incomprehensibly complex and, considering the incalculable number of steps involved, amazingly error free.
One immediate consequence of this dramatic developmental progress is that now more than ever, the overall form of the 8-week human embryo closely resembles the overall shape of a newborn baby despite still being a tiny fraction of a newborn’s size.
This undeniable similarity is not coincidental. Rather, it is the inevitable consequence of the fact that the 8-week embryo and the newborn baby each possess thousands of the exact same body parts, and those parts are arranged in almost exactly the same way. With these facts in mind, a similar external appearance should be expected.
The Fetal Perio
The fetal period begins 8 weeks and one day after fertilization and continues until birth. 9 weeks, the baby begins to suck his thumb, swallow, sigh, and stretch. His face, hands, and feet now sense and respond to light touch.”
Active motion
The nose is normally plugged up until about 13 or 14 weeks. Note the subtle side-to-side motions of the fingers (0:05–0:06), the coiled umbilical cord (0:07), and the fused eyelids (0:11).
The early fetus continues to respond to her environment in new ways. Swallowing is a complex function that is added to the growing list of abilities being practiced before birth.
With nearly every major nerve pathway in place between the skin and the spinal cord and even to parts of the brain, the baby is already extraordinarily advanced and enters a period of rapid growth.
Yawning begins by 9½ weeks. By 10 weeks, he practices walking motions and his fingerprints begin to form.
Yawning
A yawn is no simple thing. It involves an unusually deep inspiration with slight lifting of the head, followed by a deep expiration.
Fancy footwork
The fancy footwork you see here is, of course, just the beginning. Coordinated walking motions begin long before birth, but they become more difficult to practice as the baby grows, as room inside the womb becomes extremely limited before birth.
The begining of danceWalking and dancing motions begin long before birth!Fingerprints
Fingerprints are unique identifiers and they are forming by 10 weeks.
Fingernails and toenails are also beginning to grow.
By 11 weeks, the baby's mouth and lips are fully formed and she continues to grow much larger.
There are approximately 30 muscles involved with facial expression. By 11 weeks, the baby begins to coordinate many of these muscles to make various expressions. By 12 weeks, the baby opens and closes her mouth, and moves her tongue. Her hands are fully formed.
Roof of the mouth (hard palate)
The roof of the mouth already closely resembles that seen in the newborn. The midline "fusion" line shows where the left and right sides fused together. You can also see a glimpse of the inside of the right cheek.
The tongue and roof of the mouth
The nervous system continues to mature. By 13 weeks, her ability to detect a light touch extends everywhere except parts of her scalp.
She now begins to store fat. The emergence of fat deposits helps the baby to fill out. Fat represents stored energy and helps the baby regulate body temperature after birth. As pregnancy continues, the baby continues to grow and acquire new skills. Hearing, sleep-wake cycles, and responding to sound and light, forming taste preferences, recognizing mom’s voice, and more, are all a routine part of the fascinating prenatal journey.”
It was not that many years ago that doctors believed smiling did not begin until 6 weeks after birth. We now know that smiling, like so many other typical human behaviors, is well rehearsed, starting long before birth. Pregnancy is indeed a time of preparation for life after birth. It is also a time to celebrate and anticipate the joys, wonders, and challenges that come with every new life.
Newborn Baby
This little buddy is ready for whatever comes next. Thanks again, mom. You are amazing.
The Amazing Placenta and Umbilical Cord
The placenta serves as the vital interface between mother and child. It produces hormones, helps regulate the baby's body temperature, supplies oxygen, removes carbon dioxide, and more.
Umbilical cord details
The umbilical vein brings freshly oxygenated blood to the growing baby from the placenta. Here you can see the striking color difference between the larger umbilical vein and the two smaller umbilical arteries. You can also see several placental vessels in the background
Base of the umbilical cord
Loops of intestine are temporarily stored outside the body next to the base of the umbilical cord. This completely normal process is necessary because the massive liver nearly fills the entire abdomen.
The origin of rhythm
Every time this baby's heart beats, it creates a visible pulsation throughout the umbilical cord.