pregnancy Flashcards
describe the trimesters
0-13 weeks: spontaneous loss of pregnany common here
14-26 weeks: end of this trimester marks limit of infant survival
27-39 weeks
what is term?
39-40 weeks
around 280 days (40 weeks) since LMP
what are the main maternal changes?
- abdo changes seen from 2nd trimester
- inc. weight
- inc. blood clotting
- inc. vaginal mucous
- altered appetite
- altered joints
- inc. hormone levels
- dec. BP
- morning sickness
- altered emotion, brain function
when is the start of the pregnancy?
- from first day of last menstrual period
- embryologists and an obstetrician use different time scales
describe the IVF pregnancy timing
- fertilisation occurs 2-3 days before
- difference in time of 2/2.5 weeks from GA and GA in IVF pregnancy
what causes the inc. weight in mothers? how much?
- 10-15kg
- baby, placenta, amniotic fluid, inc. fluid retention, inc. stores
what hormones are inc.in mothers?
- hCG: peaks 1st trimester, dec. thereafter
- progesterone, oestrogens, lactogen: slowly inc. as pregnancy progresses
why is progesterone important?
- key to maintaining pregnancy
- progesterone antagonists = loss of pregnancy at all gestational stages
what is the source of progesterone?
- fertilisation –> 8 weeks: corpus luteum source via hCG
8+ weeks: placenta supplies progesterone
change over = luteo-placental shift
describe the oestrogen source
- fertilisation –> luteo-placental shift = corpus luteum
- 8+ weeks = complex interplay b/ foetal/maternal adrenals and placenta
describe this complex interplay
- human placenta doesn’t express enzymes needed to convert pregnenolone to androgens
- this occurs in foetal adrenals
- weak androgen produced (DHEA) sulphated to give DHEA-S
- DHEA-S is inactive so female foetus not exposed to androgens
- DHEA-S goes to placenta to be converted to 17-beta oestradiol
why are there low FSH and LH levels throughout?
high steroid levels suppress HPG-axis
why is there an inc. blood clotting tendency?
- protective against losing blood at delivery
when is blood pressure lowest?
- during 2nd trimester
- why pregnancy women should not stand for too long
why is there an inc. basal body temp?
- possible by progesterone
- mediated by foetal size
what causes the altered brain function?
high levels of steroid e.g. progesterone
what causes the altered appetite?
- due to height of fundus
- stomach may be impinged
- mother may need smaller meals
why is there altered flui balance and frequent urination?
- kidney functions change –> around 50% inc in plasma fluid volume by term
- inc, abdo size puts pressure on ballder
why are there altered joints?
- changes in pelvis to make connections more flexible to permit childbirth
why is there an altered immune system?
- production of factors: suppress maternal immune system from utero-placental interface
results in reduction of Th1 responses and inc. Th2 responses
describe placenta HLA
- placental HLA are almost invariant and very simple
- identify tissue as human but no other info
- HLA-G can suppress some leucocytes and down regulate maternal immune responses
define conceptus and embryo
conceptus: everything resulting from fertilised egg
embryo: baby up to week 8 of development
define foetus and infant
foetus: baby for rest of pregnancy
infant: after delivery
what are the weights of the baby in trimesters?
1st: 50g
2nd: 1050g
3rd: 2100g
give examples of the chromosomal abnormalities
- too few sex chromosomes = Turners
- too many sex chromosomes = Klienfelter’s
- too few autosomes = non-viability
- too many autosomes = trisomy 21
what are the 4 organs that have late development? why?
- lungs
- digestive system
- immune system
- brain
- have limited use in utero so late development
- problems developing here become apparent at birth
what are the functions of the placenta?
- exchange of nutrients and waste products
- connection/anchorage
- separation
- biosynthesis
- immunoregulation
describe the anatomy of the placenta
- primary subunit = placental villus that has branches
- provides large SA for exchange b/ maternal and foetal vascular systems
- veins = oxy blood, arteries = deoxy
- placenta carries out parallel function to lungs in pregnancy
what are cotyledons?
- maternal surface of placenta is sub-divided into cotyledons
- 30-60/ placenta
- each contains one or more villi
describe the development of the placenta
- approx 9 days post fertilisation, conceptus completely in maternal endometrium
- placenta originates from cytotrophoblasts layer
- cytotrophoblasts proliferate into syncytium to form columnar structure
- this becomes villous structure
- overall structure then doesn’t change but is modified
what are the levels of cytotrophoblasts at term?
fewer
so there can be a closer apposition b/ syncytium and placental capillaries
describe the contact of the conceptus with endometrial cells
- Early: conceptus contact with endometrial cells
- as it grows, conceptus makes transient contact w/ maternal capillaries
- rapidly cytotrophoblasts cells form capsule around conceptus
- this isolates it arounf 4 weeks PF
- decidual glands hypertrophy during 1st trimester to provide nutrients for placenta and baby
how long does the cytotrophoblast shell remain in place for?
until 8 weeks PF
blocks spinal artery formation
describe the blood supply formation
- 10-12 weeks GA, cytotrophoblast plugs break down and spiral arteries form to supply foetus w/ blood normally
what is the main risk time during pregnancy?
if placenta is not anchored properly, there is inc. pressure as it is exposed to maternal blood supply
can lead to detachment and a miscarriage
describe the spiral artery remodelling
- cytotrophoblast (ctb) cells remodel sprial arteries during 1st trimester until 16/18 weeks GA
- remodelling converts narrow bore spiral vessels into wide-bore vessels to transport more volumes of blood
- ctb cells replace vascular endothelium and VSMCs
- vessels here cannot respond to vasoconstrictors
what are the maternal risks of pregnancy?
- lie in labour and delivery
- remodelling of spiral artiers (vessels can lose a lot of blood after delivery)
- placenta checked to see if all been delivered, quite inflexible, any left in uterus may lead to ineffective uterine contractions
how is the loss of blood in labour reduced?
contractions of uterus after placenta delivery
what are the risks to the infant?
- defects to gametes
- loss of any autosome not compatible with life (miscarriage)
- changes in sex chromosomes is less severe
what are the risks to the placenta?
- incomplete anchorage in 1st trimester
- once pregnancy passes viability, early delivery problem
- infants born before 32w GA are greatest risk due to incomplete development of 4 organs
what is stillbirth?
death of infant within uterus, delivered without signs of life
how do you detect stillbirth?
- via monitoring of foetal well being
- US: monitor foetal movements
- foetal blood flow assessment: doppler US
