Fetal Development

*First Trimester*

 Before a woman even misses her menstrual period, if an egg has been fertilized,
this is what occurs in a normal pregnancy, you’ll ovulate, and if egg meets sperm,
you’ll be on your way to pregnancy! After fertilization and implantation, we outline
your baby’s journey in the womb below from the earliest stages of development
when moms-to-be discover they are pregnant up to and including
what is considered to be full term at 4o weeks.
Did you know that in just 21 days following your last minstrial period,
your baby’s heart is beating quickly and the intestines are forming?
Your budding son or daughter’s earlobes, eyelids, mouth, and nose are also taking shape.
This tiny new cell, smaller than a grain of salt contains all the genetic information for
every detail of the newly-created life including the colour of the hair and eyes, the intricate
 fine lines of the fingerprint, the physical appearance, gender, height, and skin tone.
Your tiny embryo is growing like crazy and you may be noticing pregnancy discomforts
like sore breasts and fatigue. Your baby’s heart is the size of a poppy seed and is the
very first organ to function. The first signs of brain development are evident, and the
foundation for every organ system is already established and beginning to develop.
pregnancy-week-6-webbed-hands_4x3.jpg.pagespeed.ce.9pKomA0-PO (1)
 6 weeks after LMP
LMP being-last menstrual period 
Your baby’s nose, mouth, and ears are beginning to take shape. You may be having
morning sickness and spotting. Baby continues to grow rapidly and measures 1/8 of an
inch long. The basic structure of the entire central nervous system (brain and spinal cord)
has formed. Eyes are developing, and the arm and leg buds are now visible.
Your baby’s beating heart can be seen on an ultrasound scan
and is already beating about 100-120 times per minute!
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 7 weeks after LMP
Your baby – still an embryo with a small tail – is forming hands and feet.
Your uterus has doubled in size.
Your baby is now 1/3 of an inch long and is making its own blood.
Depending on the baby’s gender, the testicles or ovaries are beginning to form.
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 8 weeks after LMP
Your baby is constantly moving, though you can’t feel it.  your baby is now 1/2 of an inch
long. Baby’s elbows/fingers can be seen. Some reports show that baby can move its trunk
and limbs. Lungs begin to develop. Taste buds are forming on the tongue, tooth buds
for “baby teeth” are taking shape in the jaw and eyelids are beginning to form.
Did you know that at 8 weeks your baby can respond to touch by reflex?
pregnancy-week-9-finger-touch-pads_4x3.jpg.pagespeed.ce.7L59H_b2NZ
 9 weeks after LMP
Nearly an inch long now, your baby is starting to look more human. You’ve probably
 noticed your waist thickening. your baby measures 3/4 of an inch long & weighs
almost 1/8 of an ounce. The developing ears and nose are visible & there is
pigment in the retina. Nipples can now be seen on the chest. The limbs and fingers are
growing rapidly, and the bones in the arms are beginning to calcify and harden.
pregnancy-week-10-fingernails_4x3.jpg.pagespeed.ce.ZMl-OW3JsW
 10 weeks after LMP
Your baby has finished the most critical part of development!
Organs and structures are in place and ready to grow. Babys’ brain is growing rapidly.
Each minute it produces almost 250,000 new neurons! The upper and lower portions of
the arms and legs are clearly seen, as well as the fingers and toes. By now the external ears
are fully developed. If you are carrying a baby boy, he begins to produce the male
hormone, testosterone. Did you know that for the first time in development,
the brain can make the muscles move on purpose?
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 11 weeks after LMP
Your baby’s hands will soon open and close into fists, and tiny tooth buds are appearing
underneath the gums. Because your baby has all of the major organ systems & is a distinctly
recognizable human being, he or she is no longer referred to as an embryo,
but is known as a fetus, a Latin word for “young one.”
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12 weeks after LMP
Your little one’s teeny toes can curl, baby’s brain is growing furiously, and baby’s kidneys
are starting to excrete urine. Baby is about 2 inches long and can yawn and suck.
Baby’s eyelids are formed and closed to protect the developing eyes.
The kidneys begin to produce urine. During the next several weeks, his or her body
will grow rapidly, increasing in weight 30 times and tripling in length!
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 13 weeks after LMP
It’s the last week of the first trimester! Your baby now has exquisite fingerprints and is
almost 3 inches long. Baby is very active in the womb however, mom may not be able to
feel baby’s movements just yet. Fingerprints are forming on your baby’s tiny fingertips,
her veins and organs are clearly visible through her still-thin skin, and her body is starting
to catch up with her head – which makes up just a third of her body size now.

 *Second Trimester*

At the beginning of the second trimester, babies are about 3 1/2 inches long and

weighs about 1 1/2 ounces. Tiny, unique fingerprints are now in place, and the
heart pumps 25 quarts of blood per day. As the weeks go by, your baby’s skeleton
starts to harden from rubbery cartilage to bone, and baby develops the ability to hear.
You’re likely to feel kicks and flutters soon if you haven’t already.
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14 weeks after LMP
Your baby’s tiny features are making different expressions. And you may be feeling
more energetic and less nauseated. Your baby is coordinated enough to find his or her thumb
and suck it. Fingernails and toenails are beginning to grow.
Baby is also able to swallow and urinate.
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15 weeks after LMP
Your growing baby now measures about 4 inches long, crown to rump, and weighs in at
about 2 1/2 ounces. His or her legs are growing longer than their arms now, and baby can
move all of his or her joints and limbs. Although your baby’s eyelids are still fused shut,
your little one can sense light. If you shine a flashlight on your tummy, for instance,
your baby’s likely to move away from the beam. There’s not much for your baby to taste
at this point, however, your baby’s is taste buds are forming.
Have a stuffy nose? It’s a surprising pregnancy side effect.
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16 weeks after LMP
Baby’s heart beats between 110 and 180 times per minute and pumps about 26 gallons
of blood each day. Baby’s gender might be seen on the ultrasound. If your baby is a girl,
millions of eggs are forming in her ovaries. Get ready for a growth spurt. In the next
few weeks, your baby will double his weight and add inches to his length.
pregnancy-week-17-skeleton_4x3.jpg.pagespeed.ce.Fi9cHHleB_

17 weeks after LMP

At almost 5 inches in length and weighing nearly 4 ounces, baby can coordinate
the movements of his or her arms and legs. Your baby’s skeleton is changing from
soft cartilage to bone, and the umbilical cord is growing stronger and thicker.
pregnancy-week-18-ears_4x3.jpg.pagespeed.ce.9yufE27NsI

18 weeks after LMP

Baby has now almost doubled its weight to 7 ounces. The skeleton is hardening
and calcifying is visible on ultrasound. Reflexes such as blinking and frowning are
now developed. Baby has its own unique fingerprints and toe prints. Your baby’s genitals
are developed enough to see on an ultrasound. By the 18th week, the fetal movement
known as “quickening” can usually be felt by the mother.
pregnancy-week-19-hair_4x3.jpg.pagespeed.ce.u4lZHcVBL6

19 weeks after LMP

Go ahead and sing: Your baby may be able to hear you!
And if your sides are aching, it could be round ligament pain.
Hungry? An increase in appetite is normal now.
pregnancy-week-20-fetal-movement_4x3.jpg.pagespeed.ce.RANdVwkpyb

20 weeks after LMP

Congratulations, you’re at the halfway mark in your pregnancy! Baby is now 10 inches long
from head to heel and weighs 11 ounces. Your baby has a unique wake and sleep patterns
and even has a favorite position to sleep in.  Your pregnancy is beginning to “show”.
Your baby is swallowing more now and producing meconium.
Studies show that babies can feel pain at 20 weeks and possibly even earlier.
pregnancy-week-21-eyelid_4x3.jpg.pagespeed.ce.grCs1Y_wzf
21 weeks after LMP
Feeling your baby move?
Those early flutters will turn into full-fledged kicks. Your baby’s eyebrows and lids
are present now, and if you’re having a girl, her vagina has begun to form. You’re probably
feeling pretty comfortable these days. You’re not too big yet, and the usual discomforts
associated with early pregnancy are, for the most part, gone.
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22 weeks after LMP
If your baby is male, his testicles are beginning to descend from the abdomen to the scrotum.
Hair is visible on baby’s head and body. From now until about 32 weeks your baby feels
pain more intensely than any other time in their development.
Your baby is starting to look like a miniature newborn.
And your growing belly may be turning into a hand-magnet.
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23 weeks after LMP
When you’re on the move, your baby can feel the motion. With her sense of movement well
developed by now, your baby can feel you dance. And now that she’s more than 11 inches
long and weighs just over a pound, you may be able to see her squirm underneath your
clothes. Baby’s rapid eye movements began which is an activity associated with dreaming.
Your baby may have a blink-startle response resulting from sound applied to the mother’s
abdomen. Some babies born at this stage of development are able to survive.
Pretty soon, you may notice swelling in your ankles and feet.
pregnancy-week-24-lung-development_4x3.jpg.pagespeed.ce._Q-p6frloD
24 weeks after LMP
 Blood vessels in your baby’s lungs are developing and baby inhales amniotic fluid in
preparation for breathing. The sounds that your baby’s increasingly keen ears pick up are
preparing him or her for entry into the outside world. Your baby’s hearing has developed
to the point that he or she can recognize your voice, breathing, and heartbeat.
Your baby is long and lean and your growing
uterus is now the size of a soccer ball.
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25 weeks after LMP
Head to heels, your baby now measures about 13 1/2 inches. Baby’s weight is about
1 1/2 pounds and beginning to exchange the long and lean look for some baby fat.
Your baby’s wrinkled skin will begin to smooth out and he or she will start to look more
and more like a newborn. Your baby is also growing more hair, and if you could see it, you’d
 be able to discern the color and texture. Your own hair may be looking extra lustrous, too.
pregnancy-week-26-ear-nerves_4x3.jpg.pagespeed.ce.dB2ZVXtNxx
 26 weeks after LMP
Your baby now weighs almost 2 pounds and besides reacting to sounds outside your
womb, baby’s eyes now respond to light. Baby has permanent teeth buds in the gums.
Eyelashes and eyebrows are well formed, and the hair on your baby’s head is growing longer.
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27 weeks after LMP
Feel a tickle? It may be your baby hiccupping.  Chalk up any tiny rhythmic movements you
may be feeling to a case of baby hiccups, which may be common from now on. Each
episode usually lasts only a few moments, and they don’t bother her, so just relax
and enjoy the tickle. Baby is sleeping and waking at regular intervals, opening and closing
his or her eyes, and perhaps even sucking her fingers. With more brain tissue developing,
your baby’s brain is very active now.

*Third Trimester*

Babies weigh about 2 1/4 pounds by the start of the third trimester. They can blink
their eyes, which now sport lashes. And their wrinkled skin is starting to smooth out
as they put on baby fat. They’re also developing fingernails, toenails, and real hair
 (or at least some peach fuzz), and adding billions of neurons to their brain. Your blossoming
baby will spend his or her final weeks in utero putting on weight. At full term, the
average baby is more than 19 inches long and weighs nearly 7 pounds.
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28 weeks after LMP
Welcome to your last trimester! With the support of intensive care, a baby born
at this stage is capable of breathing air. Your baby’s brain is developed enough to
coordinate neurons, rhythmic breathing and regulate body temperature.
Baby is also developing billions of neurons in his or her brain and
adding more body fat in preparation for life in the outside world.
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29 weeks after LMP
Your baby’s muscles and lungs are continuing to mature, and your baby’s head is growing
to make room for his or her developing brain.  Because your baby’s bones are soaking up
lots of calcium, be sure to drink your milk or find another good source of calcium, such as
cheese, yogurt, or enriched orange juice. This trimester, about 250 milligrams of calcium
are deposited in your baby’s hardening skeleton each day.
pregnancy-week-30-amniotic-fluid_4x3.jpg.pagespeed.ce.9PJuYtJLzx
30 weeks after LMP
Your baby now weighs almost 3 pounds and is just over 15 inches in length. A pint and a half
of amniotic fluid surrounding your baby, but that volume will shrink as he or she gets bigger
and takes up more room in your uterus. Baby’s eyesight continues to develop, though it’s
not very keen; even after birth, your baby will keep his or her eyes closed for a good part
of the day. When your baby does open them, he or she will respond to changes in light but
will have 20/400 vision – which means she can only make out objects a few inches
from his/her face. (Normal adult vision is 20/20.)
Meanwhile, you may be battling mood swings, clumsiness, and fatigue.
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31 weeks after LMP
This week, your baby measures over 16 inches long. He or she weighs about 3 1/3 pounds
and is heading into a growth spurt. your baby can turn his or her head from side to side,
and baby’s arms, legs, and body are beginning to plump up as needed fat accumulates
underneath your baby’s skin. You’ve probably noticed your baby moving a lot too, so you
may have trouble sleeping because your baby’s kicks and somersaults keep you up.
Take comfort: All this moving is a sign that your baby is active and healthy.
You may be feeling Braxton Hicks contractions, too.
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32 weeks after LMP
Your baby is plumping up! By now, your baby weighs 3 3/4 pounds and is about 16.7 inches
long, taking up a lot of space in your uterus. You’re gaining about a pound a week and
roughly half of that goes right to your baby. He/she will gain a third to half of her birth
weight during the next 7 weeks as your baby fattens up for survival outside the womb.
Your baby now has toenails, fingernails, and real hair or at least respectable peach fuzz.
Her skin is becoming soft and smooth as she plumps up in preparation for
birth. Meanwhile, your expanding uterus may cause heartburn and shortness of breath.
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33 weeks after LMP
 This week your baby weighs a little over 4 pounds and has passed the 17-inch mark.
Your beloved wee one is rapidly losing that wrinkled, alien look, and his or her skeleton
is hardening. The bones in your baby’s skull aren’t fused together, which allows them
to move and slightly overlap, thus making it easier for your baby to fit through the birth
canal. The pressure on the head during birth is so intense that many babies are born with
a cone-head–like appearance. These bones don’t entirely fuse until early adulthood,
so they can grow as his or her brain and other tissue expands during
infancy and childhood. With your baby now weighing a little over 4 pounds,
you might be waddling – and having trouble getting comfy in bed.
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34 weeks after LMP
Your baby now weighs about 4 3/4 pounds and is almost 18 inches long.
  Your little one’s central nervous system is maturing, and his or her lungs are continuing
to mature as well.  Your baby’s head is covered in hair and their fingernails have reached
the tip of his or her fingers. If you’ve been nervous about preterm labor, you’ll be
happy to know that babies born between 34 and 37 weeks who have no other health
problems generally do fine. They may need a short stay in the neonatal nursery and may
have a few short-term health issues, but in the long run, they usually do as well as full-term
babies.  At this stage, dizziness and fatigue may be slowing you down.
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35 weeks after LMP
Your baby doesn’t have much room to maneuver now that he’s over 18 inches long and tips
the scales at 5 1/4 pounds. Because it’s so snug in your womb, he or she isn’t likely to be doing
somersaults anymore, but the number of times your baby kicks should remain about the same.
Your little one’s kidneys are fully developed now, and his or her liver can process some
waste products. Most of your baby’s basic physical development is now complete. He or/she
will now spend the next few weeks putting on weight. Your baby is too snug in your
womb to do somersaults, but you’ll still feel frequent – if less dramatic – movements.
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36 weeks after LMP
Your baby is still packing on the pounds – at the rate of about an ounce a day and now
weighs almost 6 pounds and is more than 18 1/2 inches long. He or she is shedding most
 of the downy covering of hair that covered your little one’s body, as well as the vernix
caseosa, the waxy substance that covered and protected your baby’s skin during the
nine-month amniotic bath. Your baby swallows both of these substances, along with
other secretions, resulting in a blackish mixture called meconium that will form the
contents of her first bowel movements. You may feel pressure as your baby “drops”
down into your pelvis as you approach your due date.
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37 weeks after LMP
Your due date is very close now, but doctors don’t consider your baby “full term” until
39 weeks. Spending the next two weeks in the womb allows your baby’s brain and lungs
to fully mature. So if you’re planning to have a repeat c-section, for example, your doctor
will schedule it for no earlier than 39 weeks unless there’s a medical reason to intervene
earlier. Many babies have a full head of hair at birth, with locks from 1/2 inch to
1 1/2 inches long.  And then, of course, some babies sport only peach fuzz. At this point, your baby weighs 6 1/3 pounds and measures a bit over 19 inches, head to heel.
Your baby’s brain and lungs are continuing to mature.
You may have more vaginal discharge and occasional contractions.
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38 weeks after LMP
Your baby has really plumped up and weighs about 6.8 pounds and is over 19 1/2 inches long.
Baby now has a firm grasp, which you’ll soon be able to test when you hold his /her hand
for the first time! Your baby’s organs have matured and are ready for life outside the womb.
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39 weeks after LMP
 Your baby is likely to already measure about 20 inches and weighs a bit over 7 pounds.
The outer layers of your baby’s skin are sloughing off as new skin forms underneath.
If your water breaks, call your healthcare provider.
40 weeks after LMP
It’s hard to say for sure how big your baby will be, however, the average newborn weighs
about 7-8 pounds and is about 20 inches long. your baby’s skull bones are not yet fused,
which allows them to overlap a bit if it’s a snug fit through the birth canal during labor.
This so-called “molding” is the reason your baby’s noggin may look a little pointy after
birth. Rest assured that this is normal and temporary. Don’t worry if you’re still pregnant,
it’s common to go past your due date, be patient as
only 4% of babies are born on their actual due dates.

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