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 mistrial 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.
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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!
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.
Your baby is constantly moving, though you can’t feel it.  your baby is now 1/2 of an inch long.
Baby’s elbows and fingers can be seen. Some reports show that your 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?
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 and weighs
almost 1/8 of an ounce. The developing ears and nose are visible and 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.
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?
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 and 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.”
Your little one’s teeny toes can curl, baby’s brain is growing furiously, and her 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!
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 weigh 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.
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.
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.
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.
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.
Baby has now almost doubled its weight to 7 ounces. The skeleton is hardening and calcifying
and 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.
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.
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.
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.
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.
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.
 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.
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.
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.
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.
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 rhythmic breathing and regulate body temperature.
Your baby is also developing billions of neurons in her brain and adding more body fat in preparation
for life in the outside world. 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.
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.
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 her face.
(Normal adult vision is 20/20.)
Meanwhile, you may be battling mood swings, clumsiness, and fatigue.
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.
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 or 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.
 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.
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.
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.
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.
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.
Your baby has really plumped up and weighs about 6.8 pounds and is over 19 1/2 inches long.
your wee one now has a firm grasp, which you’ll soon be able to test when you hold his or her hand
for the first time! Your baby’s organs have matured and are ready for life outside the womb.
Your baby is full term this week and waiting to greet the world!
your baby continues to build a layer of fat to help control his or her body temperature after birth,
but it’s 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.
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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