Physiology of Pregnancy Flashcards
What is the range of a normal pregnancy in humans?
37 - 42 weeks in humans, with 40 weeks being the average
What is the span in weeks of each Trimester?
T1: 01 - 12
T2: 13 - 26
T3: 27 - 40
When does a pregnancy officially start?
From the day of the Last Menstrual Period
If the Pregnancy starts from the Last Menstrual Period, when does conception and implantation occur?
Conception is at Week 3
Implantation is at Week 4
Braxton-Hicks contractions are experienced in which trimester(s)?
Third trimester
The maternal heartbeat increases by how much during pregnancy?
60 to 76 beats per minute
The maternal blood pressure changes how, during a pregnancy?
BP remains unchanged, however mother may become hypervolaemic. There may however be a small drop in blood pressure mid gestation
Although the mother may become Hypervolaemic during a pregnancy - why is there a fall in Haematocrit?
The RBCs do not increase as much as the plasma, hence the fall in Haematocrit
How does the Foetal heartbeat change during a pregnancy?
It rises up until the first trimester, then falls to a steady 140 bpm
During which trimester is there the greatest foetal growth?
During the second trimester
The Luteal Phase of the Ovarian cycle is analogue to what phase of the Uterine cycle?
Secretory Phase
During what phase of the Ovarian cycle, does Implantation occur?
Luteal Phase
Describe what happens during Implantation to the point where Histrotrophic support is established
- The Blastocyst hatches from the Zona Pellucida, and the glycolayx of the Uterus is lost
- The trophoblast interdigitate with cells of the epithelia, allowing integrin binding to occur
- Cells of the epithelia change morphology, with the nuclei moving to basolateral surface to accomodate implantation
- The trophoblast interdigitates the epithelia, destroying the stromal cells beneath -(decidualisation)
- Trophoblast differentiates into syncytotrophoblast and cytotrophoblast
- Within the syncytotrophoblast, lacunae form which provides histrotrophic support
The epiblast becomes the…?
Ectoderm
The hypoblast becomes the…?
Endoderm
What forms between the ectoderm and endoderm?
Mesoderm
Describe what happens when there is Cessation of Histrotrophic support and Haemotrophic support begins
- Maternal spiral arteries will terminate at the Lacunae
- Primary villi begin forming from conceptus extending into the syncytiotrophoblast
- The villi grow into the lacunae
- Maternal spiral arteries remodel, allowing blood to pool into the lacunae of the syncytiotrophoblast
The villi of chorionic syncytiotrophoblast penetrate the uterus by which week?
Week 5
Is the Placenta, fetus or maternal derived?
Fetus derived
How does foetal blood carry 20-50% more oxygen than maternal blood?
Foetal haemoglobin (alpha2, gamma2) has a higher affinity for oxygen than Adult haemoglobin
How does the placenta transport fats and sugars across to the foetus?
Glucose: via GLUT 1, 3, 4, 12 transporters
Fats: via LPL
What is the precursor for Progesterone?
Pregnolone
How much does the heart increase in size by during pregnancy?
12%
What is Chadwick’s sign?
Blue-ish hue of vagina / labia, due to increased vascularisation
During pregnancy, what respiratory changes are there?
- 4cm elevation of diaphragm
- 16-20% more oxygen consumed
- Thoracic breathing
How does Progesterone stimulate the breast during pregnancy?
Growth of alveoli / lobules
How does Oestrogens stimulate the breast during pregnancy?
Stimulates growth of milk ducts
How does HPL (Human Placental Somatomammotropin) stimulate the breast during pregnancy?
Mimics prolactin and GH, causing breast / nipple / aerola to enlarge
