Pregnancy Flashcards
What does “conceptus” refer to?
Everything resulting from fertilised egg: Baby Placenta Foetal membranes Umbilical cord
In the UK, what gestational age is attempt at revival made if they are born pre-term?
24 weeks
In which trimester is spontaneous loss of pregnancy common?
1st
In the absence of an ICU cot, what is the absolute limit of gestational period for survival of a pre-term baby?
26-27 weeks
With an ICU cot, what is the absolute limit of gestational period for survival of a pre-term baby?
22-23 weeks
Which gestational weeks are considered “term”?
37-41
Summarise the hormonal changes during the first trimester
hCG peaks
Oestrogens, Progesterone + placental lactogen begin to increase in parallel with growing placenta
How do levels of progesterone and oestrogens in pregnancy compare with menstrual cycle levels?
They greatly exceed those in the normal menstrual cycle
Describe the levels of LH and FSH throughout pregnancy
Very low as high levels of Oestrogens + Progesterone suppress the HPG axis
Which hormone must be at very high levels to allow pregnancy to continue? What can low levels or an antagonist cause?
Progesterone
Low levels/ antagonist leads to loss of pregnancy
Which hormone is associated with morning sickness?
hCG
Peaks in 1st trimester
Recall 2 possible mechanisms for the altered immune response in pregnancy
- Endogenous immunosuppressant production at utero-placental interface
Decreasing Th1 responses
Increasing Th2 system - Placental HLA-G expression
Provides immunological signal that shows tissue is human
Recall 3 major maternal changes in the 3rd trimester
- Loosening of pelvic joints
- Weight gain of 10-15kg
- Increased urination frequency
Recall the source of progesterone throughout pregnancy
Till 8 weeks: Corpus luteum, production driven by hCG
Placenta can also produce P, but small size means small contribution
Post 8 weeks: Luteo-placental shift
Recall the source of oestrogens throughout pregnancy
Till 8 weeks: corpus luteum
Following LPS: maternal pregnenolone is converted by foetal andrenals to DHEA-S
Placenta converts DHEA-S to 17-B-oestradiol
Fetal liver converts DHEA-S to precursor, placenta converts to Oestriol
To where does the placenta anchor in the uterus?
Decidua
Describe the development of the placental blood supply during pregnancy
- Cytotrophoblast columnar structure forms + branches into villous sprouts
- At 8 weeks: cytotrophoplast plug breakdown; spiral artery formation
- During 2nd + 3rd trimesters there is increased branching, placental diameter = 5–> 20cm
What is the gestational age limit for a foetal death to be considered “miscarriage”?
23 weeks
How is still birth risk assessed?
Foetal movement on ultrasound
What makes the foetus so vulnerable in the first trimester?
Abnormal chromosomal make-up (excess/ deficient chromosomes)
Incomplete anchorage of placenta (increase in pressure can lead to detachment
Depending on type of gain or loss of chromosomes, what consequences are seen in the infant?
Autosomal loss: inviable
Autosomal gain: Chr.21 Trisomy Down Syndrome
Sex Chr. gain: Viable with variability
Sex Chr. loss: Turners syndrome / inviable
Why is placental anchorage essential for maintaining pregnancy?
Cytotrophoblast plugs break down, so spiral arteries provide main supply of nutrients to the developing placenta + fetus.
If not fully anchored to maternal decidua, the increase in pressure on exposure to the maternal arterial supply can detach the placenta + lead to miscarriage
What is the major risk in the second trimester?
Early delivery due to:
Labour starting before term
Deteriorating maternal or fetal health, such that delivery is required to save life of mother, fetus, or both
Why are infants born before 32 weeks GA at greater risk of stillbirth?
Development of lungs, digestive system, brain + immune system is incomplete
