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Development Stages Of a Pregnancy . Abram Martens, Bryan Van Belle, Ben Crooks and Davis Konynenbelt. www.mamanyc.net. www.orwelltoday.com. The First Trimester. The first twelve weeks of pregnancy; f ertilization to the end of the third month.
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Development Stages Of a Pregnancy Abram Martens, Bryan Van Belle, Ben Crooks and Davis Konynenbelt www.mamanyc.net www.orwelltoday.com
The First Trimester The first twelve weeks of pregnancy; fertilization to the end of the third month. The fetus develops from a zygote to an embryo that is approximately the size of a goose egg. It will be roughly 9 cm long and weigh about 60 grams. www.nature.com www.turtlebayandbeyond.org
O – 1.5 Weeks Day One: The sperm and egg unite and fertilization occurs and a zygote is formed. The zygote has 46 total chromosomes, 23 from the sperm and 23 from the egg. Days 2-7 the zygote undergoes cleavage. This means that the cell divides, but the size of the zygote does not change. The zygote is implanted in the uterus. www.nature.com
1.5 Weeks • The amnion and the yolk sac begin to form. • The amnion is a membrane sac that covers the blastula (early embryo). It fills with embryonic fluid. This fluid insulates and protects the blastula. • The yolk sac is the site of early red blood cell formation, and contributes to the primitive digestive tract later on. Nelson Biology 20-30 Textbook
2 Weeks The formation of primary germ layers begins. This process is called gastrulation. The two layered blastula develops into a three layered gastrula. The inner cells of the blastula elongate, and form a narrow line of cells. Some cells migrate inwards, and the form three layers; the ectoderm (outer layer), mesoderm (middle layer) and the endoderm (inner layer).
The Gastrula Nelson Biology 20-30 Textbook
3 Weeks This is the start of the Embryonic Development period. The central nervous system begins to develop (this includes the brain and the spinal cord). Heart development begins and the heart’s beating starts. Nelson Biology 20-30 Textbook
4-7 Weeks • Week 4-5: • Embryo is now roughly 1 cm long and weighs less than 1 gram. • The early development of the eyes begins. • Buds of the arms and legs start to form. Ears, lips and nose formation begins as well. • Basic formation of brain and spinal cord is begun. • Weeks 6-7: • Teeth and the palate start to develop. • The exterior genitalia begin to form.
8-11 Weeks Now roughly the size of a chicken’s egg, the embryo weighs around 4 grams and is about 2 cm long. Hands and feet are visible. In males, testosterone starts to be produced. At this point, the baby is very reactive to his/her environment. The 9th week is the start of the Fetal Development period. Nelson Biology 20-30 Textbook
12 Weeks The embryo is now around 9 cm long and weighs about 60 grams. The placenta is well established and weighs more than the baby. Nelson Biology 20-30 Textbook
The Second Trimester Apparently “the easiest three months” Covers week 14-24 www.mayoclinic.org www.myhealth.alberta.ca
Week 14-16 Week 14: The sex of the baby becomes apparent Week 15: Skeleton of the child begins to form, arms have reached their birthing length www.blogspot.com
Week 16 Length: 5.5” Weight: 0.4lbs The baby can now move Eyes face forward, slowly move Heart beat can be heard www.i-am-pregnant.com
Week 17-20 • Week 17: Baby begins to accumulate fat deposits • Week 18: The child begins to hear sound with ear development • Week 19: VernixCaseosadevelops • Hair-like substance for protection • Week 20: Movements can be felt www.whattoexpect.com www.assets.huggies-cdn.net
End of Second Trimester Second Trimester finishes at week 24 Prenatal visits increase to every 2 weeks Length: 8.5” Weight: 1.5lbs www.babyzone.com
3rd Trimester Final growth occurs Organs mature Baby grows to size of placenta Size and weight increase www.pregnancyweekbyweek.co
28th Week If lungs developed baby can survive 35 cm (14 in) long and 1.1 kg (2.5 lbs) About 10-20% survival rate if born www.netmums.com
32nd Week Turning to face down Skin turning wrinkly and red Baby the same size as placenta About 41 cm (16 in) and 1.68 kg (3.7lbs) 50% survival rate www.doctorberlin.com
36th Week Fingernails on fingertips Some fat grows on outside About 46cm (18in) long and 2.5kg (5.5lbs) 94% survival rate www.citranatal.com
40th week Full term About 51 cm (20 inches) long and 3.4 kg (7.5 lbs) www.doctorberlin.com www.pregnancy.about.com
Other Sources Cited Ritter, Bob, Douglas Fraser, and K. L. Burley. Nelson Biology: Alberta 20-30. Toronto: Thomson Nelson, 2007. Print. https://www.youtube.com/watch?v=sqpmzEefWrk