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Aim
To present the mechanisms and outcomes of the major physiological changes which occur during the course of pregnancy.
Content
Multiple changes occur to the mother in pregnancy. These changes are anatomical, physiological, biochemical, psychological. These changes are designed to:
- to nurture the fetus in an optimal environment
- to protect the mother from the risks imposed by the pregnancy
- to prepare the mother for the delivery process
- to prepare the mother for breast feeding.
All changes are completely reversible, in that after a mother stops breastfeeding, there are no physiological markers from which to note that she has a child other than residual stretch marks on her abdomen and final changes in breast development which appeared in the early stages of pregnancy. Physiological changes are mainly under the control of pregnancy associated hormones. Hormones can emanate from the:-
- Placenta: Human Chorionic Gonadotrophin, Human Placental Lactogen, Progesterone, SP1, Inhibin, Relaxin, Placental Associated Plasma Proteins A,B C,D (PAPP A,B,C,D)
- Feto-Placental Unit: Oestrogens
- Endometrium: Prolactin
- Mother: Cortisol, MSH, Renin/Angiotensin/Aldosterone
Changes to the mother occur in relation to fetal size. If a mother is having a multiple pregnancy, then changes will be greater than for a singleton pregnancy. For a singleton pregnancy a woman will, on average, gain 12_ kg over the pregnancy, a weight gain which is contributed to not only by the fetus, placenta and amniotic fluid, but by increases in fat deposits, interstitial fluid and breast tissue. Hormonal changes and intermediary metabolism make the mother more dependent on fat stores leaving glucose stores for fetal utilisation. All the organs within the mother have to adapt to pregnancy. There is a greater stress put on the cardiovascular system, the respiratory system, the renal system, the immune system. The physiological adaptations within the mother due to hormonal influence more than compensate for the extra stresses placed on the systems by the pregnancy.
Further reading:
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"Physiological Changes In Pregnancy" by Hytten & Chamberlain
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