Maternal Adaptation To Pregnancy

Maternal Adap Tation T
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How is ventilation increased?
Progesterone is thought to indirectly act on the respiratory centre which increases tidal volume and resp rate which results in a 20% increase in consumption.
What 3 factors affect weight gain?

1/3 - foetus, amnion and placenta
1/3 - uterus and breast, blood and tissue fluid
1/3 - increased fat stores for lactation
Why does plasma volume increase?
There is fluid retention due to the high concentration of salt retaining hormones such as progesterone, oestrogen and prolactin.
Why does the Hb concentration increase?
The bone marrow produces more RBC's in response to increased oxygen consumption.
Why does BP stay the same?
Because the increase in CO due to increased SV, HR, and blood volume is offset by decreased TPR due to vasodilation.
Does urine output increase of decrease?
It increases due to the increased excretory load.
Is there salt loss?
No, because the salt loss due to the 60% increased GFR and the salt losing hormones is compensated by the RAA system which produces aldosterone which reabsorbs salt.
How is the uterus prevented from contracting during pregnancy?
The membrane of myometrial cells is hyperpolarised which means that it is not near the threshold for unwanted contractions.
What are braxton-hicks contractions?
Myometrial cells gradually depolarise towards term, and they near the contraction threshold. From around two weeks to term ryhmical braxton-hicks contraction can be felt by the mother.
What role do acid mucopolysaccharides play in the softening and stretching of the cervix.
Oestrogen and relaxin causes them to retain water which decreases the adhesion between collagen fibres which softens the dilates the cervix.

What is role of a) the corpus luteum (b) the chorion of the placenta in oestrogen and progesterone production.

a) Secretes oestrogen and progesterone for the first 3-4 months of pregancy
b) Secretes oestrogen and progesterone from about 3-4 weeks until birth.
List 4 functions of progesterone

1. Prevents myometrial contractions
2. Prevents menstruation
3. Prevents ovulation
4. Development of breast tissue in preparation for lactation
List 2 functions of oestrogen

1. Relaxation of pubic sympthesis
2. Works along with hPL to prepare the breasts for lactation
Where is relaxin produced and what does it do?
It is produced in the corpus luteum and then the chorion of the placenta. It causes relaxation of the pubic symphysis and the sacroiliac and sacrococcygeal ligaments. It also plays a role is dilation of the cervix.
Where is human placental lactogen produced?
Chorion in proportion to the size of the placenta
List four function hPL

1. Prepare mammary tissue for lactation
2. Stimulate maternal growth - protein synthesis
3. Alter metabolism - decrease maternal GLU use to preserve for foetus.
4. Liberate fatty acids from adipose for maternal ATP.
Where is corticotrophin releasing hormone produced and what does it do.
It is released by the chorion and its production increase throughout pregnancy and it is thought to act as a clock which determines birth. It also stimulates the release of cortisol which develops lungs and surfactant synthesis.
Describe the pattern of human chorionic gonadotrophin release.
It is released by the chorion and it peaks around week 9 then declines as placenta assume role of corpus luteum
List two functions of hCG and what regulates its release.

1. Maintains the corpus luteum
2. Immunosuppressive
Release stimulated by FSH and LH

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