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Charlotte Lozier Institute

Phone: 202-223-8073
Fax: 571-312-0544

2776 S. Arlington Mill Dr.
#803
Arlington, VA 22206

The
Voyage of Life
Weeks 0 and 1
Week 2
Week 3
Week 4
Week 5
Week 6
Week 7
Week 8
Week 9
Week 10
Week 11
Week 12
Week 13
Week 14
Weeks 15 & 16
Weeks 17 & 18
Weeks 19 & 20
Weeks 21 & 22
Month 6
Month 7
Month 8
Month 9
Birth

Week 10

Fingers, toes, and right-handedness

Human Prenatal Age
  • Post-conception week 8
  • Days of life 56-62
  • Gestational Week 10
Highlights

  • The unborn baby has grown from a single cell into nearly one billion cells forming over 4,000 distinct structures in the body.1

  • Toes and fingers are free to wiggle,2 and the baby may already prefer one hand.3

  • The unborn baby can roll within the amniotic sac, touch his face, and make breathing movements.4

Week 10 marks the end of the embryonic period. In just 8 weeks, the baby has grown from a single cell into nearly one billion cells. More than 90% of the approximately 4,500 named structures in the adult body form during the embryonic period—an extraordinary transformation from one cell to a complex human being.5

What can the unborn baby feel and do at 10 weeks?

By 10 weeks, the unborn baby starts touching his face. He can move each arm and leg independently6 and will even show a preference for the right or left arm.7 The baby uses arm and leg motions to shift his position within the womb.8 9 Later, these movements will help him settle head-down for birth. For now he has ample room to move. He can roll within the amniotic sac and often rests horizontally.10 He  generally moves in little bursts of activity lasting roughly a minute.11 Nearly every baby observed for more than an hour hiccups and makes distinct arm movements at least once—small but unmistakable signs of active life.12

At the same time, nerve receptors in the skin detect gentle touch. The eyelids and palms respond to a light stroke.13 If something brushes his nose or forehead, he turns away. But, if something brushes his mouth or chin, he turns toward it. 14 These early reflexes will one day guide him to his mother’s breast.

This composite image rendered from light-guided endoscopy recordings shows an embryo alive in the uterus at 8 weeks following [tooltip anchor="fertilization"]Sperm-egg fusion[/tooltip] (or 10 weeks gestation). This baby is already touching his face, hiccuping, and responding to gentle touch. (Image Credit: <a href="https://erf.science/#high-resolution">Education Resource Fund</a>)
This composite image rendered from light-guided endoscopy recordings shows an embryo alive in the uterus at 8 weeks following fertilization (or 10 weeks gestation). This baby is already touching his face, hiccuping, and responding to gentle touch. (Image Credit: Education Resource Fund)
At 10 weeks, nearly every unborn baby observed for more than an hour hiccups and makes distinct arm movements at least once—small but unmistakable signs of active life.15
Brain development

At 10 weeks of pregnancy, the brain is still extremely large and makes up ~43% of the unborn baby’s total weight.16 For comparison, the brain is only 10-15% of the newborn’s body weight17 18 and 2% of an adult’s body weight.19

The baby’s brain is still mostly smooth, but as early as 10 weeks, it begins to form its characteristic fissures and grooves, called “sulci.”20 Bumps called “gyri” will begin to develop in later weeks.21 Furthermore, this week the cerebellum, which will coordinate movement, starts to form.22

At 10 weeks, the baby’s brain makes up about 43% of the body’s weight—far larger proportionally than at any other stage of life. (Image Credit: Science Source)
At 10 weeks, the baby’s brain makes up about 43% of the body’s weight—far larger proportionally than at any other stage of life. (Image Credit: Science Source)
How do the eyes develop?

Rarely does biology reveal anything more extraordinary than the journey from one cell to a complex human organism. The eye quintessentially exemplifies this process, creating transparent structures in precisely correct places.23

The human eye starts forming very early, 22 days after conception.24 Tiny grooves form on the brain, which bulge out and then fold in on themselves, create the basic shape of the eye. Part of this structure becomes the light-sensitive retina, which turns light energy into neural signals, while another part forms a protective layer called the retinal pigment epithelium.25 26

At the same time, a thick patch of the outer cell layer called the lens placode folds inward to form the lens, which helps focus light. Cells around the eye create the transparent cornea, the white part called the sclera, and the blood vessels. The connection between the eye and brain later becomes the optic nerve. By 10 weeks most structures in the eye have formed but need time to mature.27

Over the next few months, the different parts of the eye grow. Eyelids, tear glands, and eye muscles also develop. By week 10, the muscles that move the eye are starting to form,28 and the eyelids fuse shut for three to four months.29 By about seven months gestation, the eye responds to visual input, and researchers can measure brain responses to light.30 The eye continues maturing and visual acuity continues improving for the first four years of childhood.31

Fingers and toes

By the start of gestational week 10, the fingers and toes are free to wiggle. Starting around 6 weeks of pregnancy, a baby’s hands begin as limb buds sprouting from the sides. Around weeks 7 and 8, these buds begin to flatten and fan out forming paddle-shaped hand plates. Cells near the tips grow faster, while a wave of programmed cell death, called apoptosis, carves away the spaces between the future fingers. This natural sculpting process separates the five distinct fingers, though in week 9 they still look webbed.32

By 10 weeks of pregnancy, the basic shape of the hand is recognizable: thumbs have rotated into position, joints begin to form, and tiny muscles and nerves start connecting. The fingers and toes are free to wiggle.33 From this point on, the hands continue to grow — developing fingerprints, nails, and the ability to grasp and move each finger separately. Long before birth, the baby may even suck his thumb.34

Note how the skin is opaque on the toes. The fingers are separate and the toes are free to wiggle. (Image Credit: <a href="https://www.priestsforlife.org/graphic-images/index.aspx?gid=1&sid=1">Priests for Life</a>)
Note how the skin is opaque on the toes. The fingers are separate and the toes are free to wiggle. (Image Credit: Priests for Life)
The human heart at 10 weeks of pregnancy. At 10 weeks, the unborn baby’s heartbeat already shows electrical patterns similar to a newborn’s.[citation text="Sameni, R., & Clifford, G. D. (2010). A review of fetal ECG signal processing; issues and promising directions. The open pacing, electrophysiology & therapy journal, 3, 4. https://pmc.ncbi.nlm.nih.gov/articles/PMC3100207" href=" https://pmc.ncbi.nlm.nih.gov/articles/PMC3100207/"] (Image Credit: Science Source)
The human heart at 10 weeks of pregnancy. At 10 weeks, the unborn baby’s heartbeat already shows electrical patterns similar to a newborn’s.35 (Image Credit: Science Source)
The fully functional fetal heart

By gestational week 10, the heart has developed all four chambers, functioning valves, and a working electrical system to coordinate contractions.36 In fact, it has the same electrical wave components as a newborn’s heart.37 The unborn baby’s heart is pumping blood just like a newborn’s heart, although the fetal circulatory system is uniquely designed to work with the placenta. In fact, most of the blood bypasses the lungs, which do not supply oxygen until birth.38 Instead, the umbilical vein brings oxygen-rich blood and nutrients from the placenta to the baby. The umbilical arteries carry low-oxygen blood and waste from the baby to the placenta.39

When does the digestive system start working?

In gestational week 10, the digestive system starts working. The stomach and pancreas start making digestive hormones like insulin.40

Furthermore, the intestines start creating villi. These tiny finger-like projections increase the surface area where the blood can absorb nutrients from the fluids in the intestines41.

After an adult swallows food, muscle contractions in his esophagus and intestines help propel the food forward in a process called peristalsis. The circular muscle, which aids in peristalsis, surrounds the esophagus at 10 weeks gestation.42. Peristalsis can begin as early as week 14 in the baby’s large intestine,43 but is sporadic until the last month of pregnancy44. This is because the unborn child does not usually poop before birth, except in cases of fetal distress during labor45

What is the amniotic sac?

The amniotic sac is a fluid-filled sac that surrounds and protects the developing baby.  This sac consists of a thin but tough pair of transparent membranes, which envelopes the baby until shortly before birth. The inner membrane, called the amnion, contains the amniotic fluid and the baby. The amnion does not have any blood vessels of its own. The other membrane, called the chorion, keeps the amnion safe and is part of the placenta. The chorion contains fetal blood vessels.  The volume of amniotic fluid increases slowly, reaching 30 milliliters around 12 weeks, 350 milliliters around 22 weeks and up to 1 liter by the time the baby is born.46

Amniotic fluid enters the developing baby through the skin, lungs, and digestive system. Given that the baby also starts urinating into the amniotic fluid around 13 weeks gestation,47 the amniotic fluid must be kept clean. In fact, the water content of the amniotic fluid changes every three hours!48

This baby and his placenta are surrounded by the amniotic sac, a fluid-filled sac designed to protect and nourish the growing child. (Image Credit: <a href="https://www.priestsforlife.org/graphic-images/index.aspx?gid=1&sid=1">Priests for Life</a>)
This baby and his placenta are surrounded by the amniotic sac, a fluid-filled sac designed to protect and nourish the growing child. (Image Credit: Priests for Life)
How does amniotic fluid circulate?

Amniotic fluid constantly circulates as the baby develops. It circulates in at least four major ways:

  1. Before the fetal skin thickens, water and gases from the amniotic fluid pass through the skin to the baby.49
  2. Amniotic fluid is absorbed by the fetal intestines as the baby swallows. About half of the amniotic fluid is filtered by the fetal kidneys and returns to the amniotic sac as urine while the other half is exchanged with the mother at the placenta.50
  3. Large amounts of water pass through the amniochorionic membrane at the placenta to keep amniotic fluid in balance with fetal circulation.51
  4. Amniotic fluid is absorbed by the baby’s respiratory tract as the baby “inhales.”52  The amniotic fluid might be absorbed directly by the lungs; it’s also possible that the fluid in the lungs contributes to the amniotic fluid volume.53 Fetal breathing has been observed as early as 10 weeks gestation.54
Continued development at 10 weeks gestation

At 10 weeks of pregnancy, in the third month, the baby’s face continues to take shape. The upper lip is still forming as the left and right sides join together. Inside the mouth, the hard and soft palate fuse, while the nostrils and the structures that divide the nasal passages continue to grow. These changes help create the familiar features of the face.55

The baby continues growing and preparing for life after birth. The earliest breathing movements were detected at 10 weeks gestation,56 57 58 59 although breathing becomes a lot more frequent in week 13.60 helping the lungs grow and develop specialized cells.61 The baby continues to grow rapidly—about 1 millimeter per day62 63—and by the end of the week weighs about 2.5 grams, roughly the weight of a penny.64

A chart titled Pregnancy Timeline shows pregnancy months with their corresponding weeks: Month 1 (weeks 1-4), Month 2 (5-8), Month 3 (9-13), Month 4 (14-17), Month 5 (18-22), Month 6 (23-27), Month 7 (28-31), Month 8 (32-35), Month 9 (36-40).
Dive Deeper
Right and Left-Handedness
At 10 weeks, it is possible to determine left-handedness or right-handedness...
Read More
Eye Formation
The eyes begin forming 22 days after conception...
Read More
Back to The Voyage of Life
Sources
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  2. ^ Torchia, M.G., and Persaud, T.V.N (2025). The Developing Human, Clinically Oriented Embryology. Elsevier. 12th ed.
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Learn more about Gestational Age

Credentialed scientists reviewed all the material on The Voyage of Life for accuracy. Ages are listed in gestational weeks, measured from the first day of the mother’s last menstrual period, unless otherwise noted. This standard medical practice differs from post-conception age, used by embryologists and medical textbooks cited here, which starts at conception, about two weeks later.

Medical art animation was used to provide a schematic representation of fetal development, with some features, including timing, not to scale. The animation was chosen as an ethically uncompromised guide to fetal development. There are many real human images at each developmental age showing the most accurate fetal forms throughout development. A concerted effort was made to use images and material in which the human embryo or fetus did not undergo any known harm.

Page last updated on May 7, 2026
Sperm-egg fusion
Sperm-egg fusion