placenta/pregnancy 3 Flashcards
beta- hCG
human chorionic gonadotrophin
produced exclusively by the syncytiotrophoblast of the preimplantation blastocyst and placenta
is detectable in the maternal blood/urine within days of implantation
can be used as an indicator for the health of the pregnancy
functions of hCG
binds to the LH/hCG receptor and thus transmits similar signals to LH
luteal support:
- hCG has strong leutotrophic properties and is importnat in stimulating the production of P4 and E2 by the ovary in first 6-8 weeks of pregnancy
- stops regression of corpus luteum
The corpus luteum doubles in size about a month into pregnancy under the influence of hCG
what causes estrogen and progesterone to be secreted and its effect
corpus luteum secretes E2 and P4 from the signals coming from the placenta in the form of hCG
- prevents menstruation
- maintains endometrium as a decidua
hCG levels in multiple pregnancies
women with multiple pregnancies have increased levels of hCG
- this is because of the increased amount of syncytiotrophoblast in twin pregnancy
other than in multiple pregnancies where else can high levels of hCG be found
trophoblastic tumours
- choriocarcinoma and hydatidiform mole
- also in some testicular tumours
hCG importance in male pregnancies
in having LH-like activity that stimulates testosterone synthesis by the leydig cells of the testis in male fetuses
progesterone in pregnancy and its importance clinically
is synthesised by the syncytiotrophoblast of the placenta
therefore ovaries can be removed without disrupting the pregnancy from the time that the placenta takes over P4 production (instead of the corpus luteum) = 6-10 weeks
functions of progesterone
- maintains uterine quiescence (P4 is a SM relaxant)
- along with E2 it converts the uterine environment to one that is conducive with pregnancy
- P4 receptors are expressed by both glands and stromal cells in the decidua
is the decidua essential for implantation
no, this can be verified by ectopic pregnancies
however it is important for providing nutrients prior to the maternal blood supply
oestrogen changes during pregnancy
theres a 1000 fold increase in E2 during pregnancy
how is oestrogen produced during pregnancy
cholesterol is taken up in the maternal blood and converted into P4 in the syncytiotrophoblasts (placenta). P4 then taken up by the fetal circulation to the fetal adrenals and liver. In those organs androgens are created by 17 alpha hydroxylase. Then shuttled back to the placenta where they’re aromatised to estrogens
- (aromatisation occurs in syncytiotrophoblasts)
cardiovascular adaptations during pregnancy (& preeclampsia)
occurs 9-10 weeks gestation
increased CO
-increased SV and pulse rate
reduced peripheral vascular resistance
preeclampsia = higher than ‘normal’ PVR
preeclampsi
maternal hypertension after the 20th week of gestation accompanied by protein in the urine
- affects most maternal organs
- triggered by something from the placenta (only cure is to deliver)
- exaggerated inflammatory response leading to vascular dysfunction
- loss of normal peripheral vascular resistance
apart from haematological changes whats causes cardiovascular changes during pregnancy
angiotensin II is a vasoconstrictor which causes the arterioles to contract and increase BP
- its levels increase in pregnancy
- uteroplacental unit produces RAS
nitric oxide synthetase is increased in pregnancy
-NO causes arterial wall relaxation and dilation
haematological changes during pregnancy and clinical importance
increased BV
- plasma volumes and BV both increase but at different rates
haematocrit declines as plasma volume increases at a higher rate than cell mass
important to remember when taking blood test results from pregnant women that the normal values change for pregnant population
