Pregnancy Flashcards
What are the features of the 1st trimester?
- Most risky part
- Miscarriage risk highest
- N+V “morning sickness”
- Hard to tell someone is pregnant
- Increased urinary frequency - hormones alter kidney function
What are the risks of the 1st trimester?
- High miscarriage risk (esp weeks 10-12 when placenta becomes less anchored as cytotrophoblast plug breaks down)
- Incomplete anchorage of placenta
- Defects in gamete production - too many/few chromosomes: Turner’s (XO), YO inviable, Kelinfelter’s XYY, Down’s trisomy 23, loss of autosome = fatal)
- Major congenital abnormalities
- Functional defects + minor congenital abnormalities
- Spina bifida
- Cleft palate
What is the 1st trimester?
Weeks 0-13
What are the features of the 2nd trimester?
- Urinary frequency normalises
- Mother starts to feel baby moving
What are the risks of the 2nd trimester?
- Stillbirth
- Increase in maternal blood clotting tendency
- Drop in BP –> maternal fainting
What is the 2nd trimester?
Weeks 14-26
What are the features of the 3rd trimester?
- Increased urinary frequency as uterus pushes on bladder
What are the risks of the 3rd trimester?
- Increase in maternal blood clotting tendency
- Gestational diabetes
- Preeclampsia
- Preterm labour
- Preterm premature rupture of membranes
- Placental previa + placental abruption
- Intrauterine growth restriction
- Malpresentation (breech, etc.)
What is the 3rd trimester?
Weeks 27-39
What is the main purpose of the 2nd trimester?
?
What are the maternal changes associated with pregnancy?
Increased:
- Weight
- Hormone levels/ altered endocrine system
- Blood clotting tendency
- Basal body temp
- Breast size
- Vaginal mucus production
- N and V
Decreased:
- Blood pressure
Altered:
- Brain function
- Appetite
- Fluid balance + urination frequency
- Emotional state
- Joints
- Immune system
What are the main purposes of the 3rd trimester?
?
How does the placenta develop?
- From single layer of cells in blastocyst
- Cells proliferate + differentiate
- Expands iteratively
- Cytotrophoblast shell limits blood (oxygen) supply to embryo during early developing to reduce no. of oxygen free radicals
Day 9 PF:
- Blastocyst implants into decidualising endometrium
- Surrounded by inner cytotrophoblast and outer synctiotrophoblast which has fluid filled spaces called lacunae
Day 13-20 PF:
- STB bumps into maternal blood supply
- Slow flow of blood into lacunae
- CTB begins to invade into the STB to form a primary villus and trophoblastic shell
Day 21- 28 PF:
- CTB eventually reaches outside to cut off maternal blood supply
- Creating a low oxygen tension environment (~3%)
End of 1st TM:
- Fewer CTB so that syncitium and placental capillaries can be close together
- During first trimester, endometrial glandular hypertrophy
- Histotrophic nutrition
- 8 weeks PF CTB plugs as maternal spiral arteries start to break down
How is steroidogenesis an example of the three-way interaction in pregnancy?
- Maternal adrenals, placenta, foetal adrenals and foetal liver all involved
- Maternal adrenals make DHEA-S and cortisol from maternal LDL-cholesterol
- Maternal LDL-cholesterol –> prenenolone –> progresterone in placenta
- Placental pregnenolone –> foetal adrenals –> DHEA-S –> foetal liver –> 16aOH DHEA-S
- Foetal liver DHEA-S + 16aOH-DHEA-S –> placenta
- Maternal cortisol –> placenta –> cortisone
- Maternal DHEA-S + foetal liver DHEA-S –> placenta –> oestrone 17B oestradiol
- Foetal 16aOH-DHEA-S –> oestriol in placenta
Define conceptus
Everything resulting from fertilised egg - baby, placenta, foetal membranes, umbilical cord
