Physiological changes during
pregnancy
David Taylor
dcmt@liv.ac.uk
http://pcwww.liv.ac.uk/~dcmt/hpoa.pptx
Resources
• I have used
– Naish
– Kumar and Clarke
– Davidson’s
– And there are dozens of other web-based
resources
– www.medicinenet.com/pregnancy/article.htm#
has lots of pictures....
scenario
• After 3 months, when her menstrual period is
6 days late, Ms Garnett buys a testing kit.
They are pleased that it confirms pregnancy.
• “Don’t fuss, Mum. I’m pregnant – not ill…
feeling sick, lots of hormones, lots to decide,
and I’ve got my first appointment with the
doctor soon!”
Learning outcomes
• Outline the hormonal control of menstruation and the
menstrual cycle (with reference to the structure and
function of the pituitary and hypothalamus)
• Outline the key features of normal pregnancy including
physiological, immunological, biochemical, and
anatomical changes to the mother, and the main
hormonal controls (the endocrine system) on
maintaining pregnancy and developing breast function
and producing breast-milk, including the structure and
function of the breast
Hypothalamic-pituitary axis
• Understanding this is fundamental to
understanding endocrinology.
• We will be focussing on its effect on the
female reproductive organs,
• but remember that the hypothalamus is also
part of the limbic system.
Anatomical relations
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MRI scan of brain
removed for copyright
reasons
Kumar and Clarke,2009
7th edition
Fig 18.6
In more detail
This image, originally from the 1918 version of Gray’s Anatomy, is in the public domain
because its copyright has expired
Posterior pituitary
• The axons of hypothalamic neurones pass
down the infundibulum. Hormones formed in
the hypothalmus are transported by axonal
transport and are released from the nerve
terminals in the posterior pituitary into the
circulation (inferior hypothalamic artery).
• Examples of these hormones are
– Oxytocin (smooth muscle contraction)
– ADH (blood pressure)
ADH and Oxytocin
Stimulus
Inferior
Hypothalamic
artery
To target tissue
The others
Stimulus
Superior
Hypothalamic
artery
To target tissue
The hypophyseal portal system
1. Releasing/inhibitory hormones
2
3. Hormones to target tissues
Anterior pituitary hormones
Dopamine
VIP
TRH
Somatostatin
GRH
Dopamine
GnRH
PRL
TSH
GH
FSH/LH
ACTH
Mammary
glands
Thyroid
Liver and
others
Gonads
Adrenals
CRH
Focus on menstrual cycle
Early follicular
Pre-ovulatory
hypothalamus
hypothalamus
GnRH
GnRH
pituitary
FSH
pituitary
LH
FSH
LH
oestradiol
inhibin
follicle
oestradiol
Antral follicle
Focus on menstrual cycle
Pre-ovulatory
Early luteal
hypothalamus
hypothalamus
GnRH
GnRH
pituitary
pituitary
FSH
FSH
LH
oestradiol
Antral follicle
LH
progesterone
oestradiol
Corpus luteum
The menstrual Graph of hormonal changes
during menstrual cycle
cycle
•The growing
follicle produces
Oestradiol
•Which
enhances
FSH/LH release
•The Corpus
luteum produces
progesterone
removed for copyright
reasons.
Naish et al., 2009
1st edition
Fig 10.2
oestradiol
progesterone
• Endometrial
proliferation
• Genital development
and lubrication
• Breast proliferation
• Bone epiphyseal closure
and mineral content
• Brain
• Body fat
• Skin sebum
• Endometrial secretory
change
• Increased myometrial
contractility
• Thermogenesis
• Breast swelling
http://i497.photobucket.com/albums/rr332/hbomb1984/untitled.jpg
Hormone changes during pregnancy
• The syncytiotrophoblast produces hCG
– Human chorionic gonadrotrophin
• hCG binds to LH receptors, and maintains the
corpus luteum which produces progesterone
• As the placenta develops it takes over the
production of progesterone.
Cardiovascular changes in pregnancy
• Peripheral vascular resistance decreases
– progesterone decreases vascular smooth muscle
tone
– Oestrogen causes vasodilation through nitric oxide
– Placenta releases prostacyclin (vasodilator)
• Consequently blood volume, cardiac output
and GFR increase
• Blood pressure, plasma creatinine and urea
should decrease in 1st trimester.
Respiratory changes in prgnancy
• Progesterone increase body temperature,
therefore metabolic rate
– So oxygen consumption increases
• Progesterone increases sensitivity of central
chemosensors to CO2
– increasing tidal volume but not respiration rate
• Also physical changes in space available
means that more of the inspiratory reserve
volume is used.
GI changes in pregnancy
• Energy intake needs to increase by 1200kJ/day
• Smooth muscle tone and motility decreased
due to progesterone
– Constipation
– Increased transit time for food
• Acid reflux to the above and physical pressure
• Nausea and vomiting in 1st trimester are due
to rising levels of ovarian steriods
Brain adaptations
• Not really understood (progesterone
metabolites on GABA pathways?), but the
neuroendocrine response to stress is reduced
in pregnancy.
• Pituitary increases in size during pregnancy
– Due to increased prolactin and ACTH secretion
from AP
– And increased oxytocin production from PP
(where it is stored until progesterone levels drop)
Other endocrine changes
• T3 and T4 increase due to hCG, but remain
bound to plasma proteins
– Because oestrogen increases thyroxine-binding
globulin (TBG)
– Maternal bound T4 is a “reservoir” of thyroid
hormone for the foetus
• Foetus uses Calcium, which stimulates
maternal PTH output
– Increased absorption, reabsorption and
mobilisation of Ca2+
Learning outcomes
• Outline the hormonal control of menstruation and the
menstrual cycle (with reference to the structure and
function of the pituitary and hypothalamus)
• Outline the key features of normal pregnancy including
physiological, immunological, biochemical, and
anatomical changes to the mother, and the main
hormonal controls (the endocrine system) on
maintaining pregnancy and developing breast function
and producing breast-milk, including the structure and
function of the breast