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Start of last period
The first day of your last period is when pregnancy "starts" although the eg had not yet been fertilized. This date is what the baby'sdue date will be based off of. -
Period: to
week by week fetal development
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Fertilization
TThe egg can only be fertilized when the woman is ovulating (when the egg is traveling down the fallopian tube). Day 14 of pregnancy is when ovulation occurs and the sperm can fertilize the egg. -
Clevage
Once the egg is fertilized, it wil begin a proccess called cleavage. Cleavage is when the fertilized egg rapidly divides before it even attaches to the endometrium of the uterus. -
Implantation
By this time, The growing embryo has grown to a 50-60 cell cluster. At around this time is when the embryo will implant to the uterine wall. -
Embryo
During week 5, the amniotic fluid is being built up and the growing embryo begins recieving oxygen and nutrients through the placenta. By this time the embryo has grown to about 4-5mm. -
The Heart
During week 6 of pregnancy, the embryo's heart forms and begins to beat. At this time the embryo has grown to about the size of a raisin. -
Organs and Extremities
At week 7, the embryo begins to develop funtional organs such as the lungs, liver, and pancreas. It will also develop buds that will grow into arms and legs. -
Movement
The embryo will practice movement during the 8th week of pregnancy. It also forms facial features and a stomach. -
Bones develop
During this stage of development, the fetus develops cartilage and bones. The heart is now completely finished developing. -
Fetus
At the start of week 10, all organs of the embryo should be identifyable therefore the embryo is now called a fetus. Fingerprints are already evident and hair and muscles begin to develop. -
Genitals
At this time the fetus had started developing genitals although it is still too early to tell it's gender. The brain is also rapidly growing and is producing up to 250,000 new neurons a minute. -
Behavior
At this time, the fetus' brain is completelt developed and it can suck its thumb and get hiccups. Finger and toenails appear and the fetus' facial profile begins looking like a newborn's. -
Gender
The fetus' genitals are becoming more defined and it may be possible to identify its gender. At this time the fetus is begining to form more bone instead of cartilage including the ribcage. -
Hormones
During week 14, the fetus begins producing hormones. For girls, the ovaries begin to move down into the peliv cavity while boys develop a prostate gland. -
Taste Buds
The fetus has now developed taste buds and can taste any food the mother eats. The bones and muscles continue to grow through this week and the mother may be able to feel soft kicking. -
Facial Expressions
Since the muscles have developed, The fetus can now make simple facial expressions suck as squinting or frowning. At this time the fetus can also breathe and have dreams. -
Fat
At week 17 the fetus will begin storing fat. The umbilical cord has become thicker and stronger to support the growing fetus' nutrition needs. At this time, the fetus' retina has become sensitive to light. -
Sound
The fetus' ears are now fully developed and can hear sounds and may even be startled by a loud noise. The fetus also has a recognizable sleep pattern, similar to that of a newborn. -
Development
The genitals have become fully recognizable at this time. Girls have around 6 million eggs which will reduce to around 1 million by birth. -
Midpoint
The skin begins to thicken at this point. Hair and nails have also began growing throughout the rest of the body. -
Nourishment
The fetus' bone marrow has started producing blood cells. Beofre this point, The spleen had been producing most of the blood cells. Their small intestine has also developed enough to begin absorbing sugar. -
Weight Gain
The growing fetus will begin to gain around 70 grams a week. At this point in time, the fetus should weight around 1 pound. -
Balance
The fetus' ears should be fully developed now which gives them a sense of balance. Pigment in the skin has also started forming. The fetus now looks like a newborn but much thinner. -
Viability
If the fetus were to be born during this week, it would be considered viable by doctors. Also around this time, Sweat glands will begin to form in the fetus' skin and it will continue to practice breathing. -
Nerves and Ligaments
The ligaments of the spine and other structures are developing at this time along with the nerves throughout the body. Babies born at 25 weeks have a 50% chance of survival. -
End of Second Trimester
The second trimester ends at week 26. At this stage the fetus can begin to open its eyes and suck its thumb. Sucking its thumb is a good way for the fetus to strengthen its cheek and jaw muscles. -
Start of 3rd Trimester
The fetus now appears how it would if it were born. If born at this time, it has an 80% chance of survival. -
Voice Recognition
By this time the fetus is able to recognize the mothers voice and their heartbeat will slow upon hearing it. If born now, there is a 90% chance that it will survive. -
Senses
At week 29, the fetus can taste and respond to pain. It has also developed milk teeth under the gums -
More Development
By week 30 the fetus can control its own body temperature and if the baby is a boy, the testicles have dropped to the groin area -
Maturing Organs
The fetus is almost fully developed at this point. growth in this week will focus on maturing these organs -
Becoming Cramped
The fetus is now becoming more cramped inside the uterus as it becomes more mature. During week 32 a male's testicles are moving from the groin down into the scrotum while a female's clitoris becomes more prominent. -
Lanugo Dissappears
At week 33 the "baby fuzz" languno will begin to dissappear and be replaced with hair. The fetus may be inhaling up to a pint of amniotic fluid a day and excreting the same amount. -
Up-side Down
around week 34 of pregnancy the fetus should flip up-side down so the head is pointing toward the birth canal. The fetus' skin is becoming less wrinkled and it is building up immunities to mild infections. -
Coordination
The fetus' movements have become more coordinated. Although the baby has gained a significant amount of weight, it still does not have enough fat to keep warm outside of the uterus at this time. -
Drop Into Birth Canal
The fetus may start dropping into the birth canal inpreparation for labor. Oftentimes it stays like this for days or weeks until it is born. -
At Term
Week 37 is when a pregnancy is considered at term. At this point the baby is gaining up to an ounce a day and develops a regular daily cycle. -
Complete Development
Development has been completed by week 38 and the only thing left for the fetus to do is gain weight and wait. -
Week 39
The fetus' head is approximately 4 inches wide at this point. The baby can be born at any second. -
Due Date
The bones of the baby's head are soft to help ease the journey down the birth canal. Once the baby takes its first breath, the umbilical cord immediately stops working and all oxygen is forced to travel to the baby's lungs.
