Pregnancy Flashcards
What maternal changes might occur in the first trimester of pregnancy
Altered brain function, hormones, fluid balance and immune system
What maternal changes might occur in the second trimester of pregnancy
Increased blood volume and blood clotting tendency
Decreased blood pressure
Altered fluid balance
What maternal changes might occur in the third trimester of pregnancy
Increased weight
Altered joints
Describe the endocrine changes during pregnancy
hCG peaks around week 9 then rapidly falls
Progesterone, oestrogens (oestriol) and placenta lactogen increase throughout pregnancy 100-1000 fold compared to levels in non-pregnant women
What is the conceptus
Everything resulting from the fertilised egg (baby, placenta, fetal membranes, umbilical cord)
Distinguish between embryo, foetus and infant
Embryo – the baby before it is clearly human
Fetus – the baby for the rest of pregnancy
Infant – less precise, normally applied after delivery
Describe the overall timing of maternal and placental changes during pregnancy
Maternal changes occur throughout
Placental changes are complex, mostly occurring in the first half
At how many weeks can a baby be born and survive without modern Neo-natal ICU and how is this affect by the unit
26 weeks
With unit - pushed back to 22
When in pregnancy is risk of miscarriage greatest
before 13 weeks i.e. first trimester
Define the features of the first trimester (0-13 weeks) of normal human pregnancy
The most dangerous time for the foetus
95% of pregnancies that survive the first trimester → term
Most “embryology” takes place in this period – complex
Focus on structural development not growth
Define the risks of the first trimester (0-13 weeks) of normal human pregnancy
Chromosomal abnormalities → miscarriage
Most susceptible to insult → congenital abnormalities
Placental problems → miscarriage, pre eclampsia
What is viability
the foetus can survive if born
Define the features and risks of the second trimester (14-26 weeks) of normal human pregnancy
Safest time for the baby and the mother Fetal weight increases from 50g – 1000g Uterine stretch Progesterone levels continue to increase Estrogens increase
What is the main purpose of the second trimester
The foetus becomes viable in this trimester
What is viability limit and survival rate at 25 weeks
Viability limit = 24 weeks
At 25 weeks = 50% survival
Without intensive care required = end of trimester (26-27 weeks)
Define the features and risks of the third trimester (27-39 weeks) and list the main purposes of this phase
GROWTH (loads, increases by 2 kg)
Maturation of brain, immune system, lungs and digestive tract (BILD)
Problems with these systems if baby is born prematurely
Highest risk to mother during this time
Labour, haemorrhage
List the main placental functions
Separation between maternal and fetal system
Exchange nutrients and waste products
Biosynthesis
Immunoregulation of whole of pregnancy
Connection: placenta must anchor the pregnancy in place
Identify the main features of the maternal side of the placenta
Pieces of tissue with separation between them (cotyledon) , number of them doesn’t matter for the growth and development of baby
Large cotyledon is in the centre of placenta (2-3cm) and smaller out
The gaps between cotyledon contains maternal tissue = decidua. Usually stays behind after birth
Very strong contact with vascular system on this side
Identify the main features of the foetal side of the placenta
Disc shaped structure
The side baby will be facing and the umbilical cord which will connect to the fetus
Blood vessels are carrying nutrients from maternal system to baby insertion point near the centre
Fetal membranes thinner in placenta and surrounds the disc
Umbilica cord is very hard and can cause damage to baby if it gets tangled
Describe the vasculature of the placenta
Spiral arteries - provide blood supply to foeto-placental unit
Placental villous trees -Massive surface area
Umbilical vessels - As in lung, vein = oxygenated blood, arteries – deoxygenated blood
Countercurrent flow
Explain how the placenta develops
Starts as a layer of single cells in the blastocyst
These proliferate and differentiate
Form simple branched structure, expands iteratively
What occurs in spiral artery remodelling
arteries become wide bore = greater exchange of nutrients
High volume blood supply in trimesters 2 and 3, when infant growth is greatest.
How is pregnancy normally “Counted” and why is this system used
The last day of the last menstrual period is used as the basis of pregnancy timing
As this can be identified easily
What are the key features of the placenta
Very highly branched structure, provides a large surface area (~11m2).
Very effective for transport of molecules between maternal and fetal circulations.
Anchors the placenta (and baby) securely for 9 months.
Intimate contact between maternal and placenta tissues – immunology
What doe cytotrophoblasts do in placental development
Cytotrophoblast shell limits blood (oxygen) supply to embryo during early development
Explain how the placenta develops
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