Lecture 3a: Pregnancy and Physiological Changes Flashcards
When are follicles matured?
During ovulation
What is the release of a mature follicle (and the egg within it) triggered by?
a surge in luteinizing hormone (LH)
Where does a mature egg go once released?
Once released from ovary the egg goes into the fallopian tube
How many sperm make it to the egg cell (if intercourse at proper timing occurs)?
Only a few hundred of up to 300 million make it to the egg cell
What is a zygote?
When a sperm successfully penetrates the egg - genetically complete
What happens after a zygote is successfully made?
undergoes series of cell divisions called cleavage - divisions increase the number of cells not overall size of embryo (mitosis)
What 3 phases of cleavage does the zygote undergo?
2 cell stage, 4 cell stage, 8 cell stage
What does a zygote become once divided?
After several divisions, it is composed of about 16 cells. At this stage, it is referred to as a morula - 16 cell stage
When Does the Zygote Become an Embryo?
After 10 days
When is the morula formed?
Around 4 days after fertilization
What happens to the morula?
continues to divide, fluid begins to accumulate between the cells, marking the transition into a blastocyst
When does the blastocyst form?
Around 6 days after fertilization
What happens to the blastocyst cells?
More than 100 cells. Fills with fluid and cells seperate into 2 groups
What is the structure of a blastocyst?
Trophoblast = outer layer
Embryoblast (ICM) = cluster of cells inside the blastocyst
What happens to trophoblast cells?
develop into the placenta
What happens to the embryoblast cells?
develop into the fetus
When does implantation occur?
Around 10 days after fertilization
When does pregnancy begin?
At conception
What is EDD?
Estimated Date of Delivery
When is EDD?
Typically counted from first day of last menstrual period (LMP); 40 weeks from LMP or 38 weeks after conception
When is the first trimester?
Conception to 12th week
When is the second trimester?
13th to 28th week
When is the 3rd trimester?
28th to birth
What is considered pre-term? (premature)
less than 37 weeks
What is considered term?
37-42 weeks
What is considered post-term (postmature)?
more than 42 weeks
How many births occur on the due date?
Less than 10%
How many births occur within a week of the due date?
50%
How many births occur within 2 weeks of estimated due date?
90%
When is the baby considered an embryo?
0-8 weeks
When is the baby considered a fetus?
8 weeks onwards
What is the baby referred to at birth?
Neonatal/newborn/neonate
What is the baby considered 1 week onwards after birth?
Post neonatal
When is it considered a miscarriage?
Before 20 weeks
When is it considered a fetal death/stillbirth?
After 20 weeks
What is the survival rate at 24 weeks?
Around 50%
When is considered very preterm?
<34 weeks
When is considered perinatal?
20 weeks - 1 week old
Is the placenta an organ?
Yes - a temporary organ
When does the placenta start forming?
At implantation of the blastocyst
When is the placenta fully formed?
By 18-20 weeks; continues to grow throughout pregnancy
How much does the placenta weigh at birth?
about 0.5kg
What does the placenta carry from mother to the fetus?
Oxygen, nutrients and antibodies
What does the placenta carry from fetus to the mother?
Waste materials including CO2
The placenta takes over the hormonal role of what?
Ovary
How is the placenta connected to the embryo/fetus?
By umbilical cord
What is HCG?
Human Chorionic Gonadotropin (hCG)
What is the role of HCG?
- What the body uses to recognise whether the pregnancy is viable
- Works to prevent the body from releasing more eggs
- Works in combination with other hormones to control pregnancy state
What is the structure of the umbilical cord?
1 umbilical vein + 2 umbilical arteries
What is the role of the umbilical vein?
provides oxygenated blood
What is the role of the umbilical arteries?
removes deoxygenated blood
What are teratogens?
Any agent that can disturb the development of an embryo or fetus
What can teratogens cause?
May cause a birth defect in the child or halt the pregnancy
What are the classes of teratogens?
- Radiation
- Maternal infections
- Chemicals
- Drugs
When is a baby not susceptible to teratogenesis?
0-2 weeks
What are major congenital anomalies?
significant structural or functional abnormalities that are present at birth and can have a serious impact on an individual’s health, development, or functional abilities
When do major congenital anomalies occur?
3-8 weeks (main embryonic period)
What are functional defects?
abnormalities in the way an organ or system in the body functions, even if its structure appears normal
What are minor anomalies?
less severe physical abnormalities that are usually less likely to cause significant health problems compared to major congenital anomalies
When do functional defects and minor anomalies occur?
9-40 weeks (fetal period)
When does major CNS development occur?
3 weeks
When does major eye, heart and limb development occur?
4-5 weeks
When is the highly sensitive period for NTDs?
The first 3-4 weeks
When is the highly sensitive period for developing mental retardation during pregnancy?
7-16 weeks
