Changes in Pregnancy Flashcards
Functions of the Placenta
- Anchoring Foetus and establishing Foeto-Placental Unit
- Organ of Gaseous Exchange
- Transfer of Substances to and from Foetus
- Barrier against Infection
- Endocrine Functions
Functions of the Placenta: Barrier against Function
o Effective against most Maternal blood-borne Bacterial Infections
o Syphilis, Parvovirus, Hepatitis B and C, Rubella, HIV and CMV able to cross
o Also serves as barrier against Maternal immune system (NB: IgG able to cross)
Functions of the Placenta: Endocrine Function
o Human Chorionic Gonadotrophin (produced by Syncytiotrophoblasts; Detectable from 6 days after Fertilisation
▪ Crucial for persistence of the Corpus Luteum post-fertilisation, which is the
source of Progesterone prior to Placenta development
▪ Concentrations reach peak at 10 – 12 weeks, and plateau for remainder
o Other hormones produced include Oestrogen, Progesterone and Human Placental Lactogen (Reduced Maternal Insulin Sensitivity =Increased Blood Glucose, Increased Lipolysis =Increased Blood FFA, Breast Growth)
Why do physiological changes happen in pregnancy?
- Early changes in part due to metabolic demand from Foetus, Placenta and Uterus, mostly regulated by Oestrogen and Progesterone and other Pregnancy Hormones
- Late changes are more anatomical in nature, due to Mechanical pressure from Gravid Uterus
Role of Progesterone in Pregnancy
Progesterone – First 35 days by Corpus Luteum; Subsequently by Placenta
o Smooth Muscle Relaxation (GI, Ureters, Uterus) and Body Temperature
o Prevents Preterm labour; Used in prevention
Role of Oestrogens in Pregnancy
Primarily Oestradiol (90%)
o Breast and Nipple Growth, Pigmentation
o Promotion of Uterine Blood Flow, Myometrial Growth and Cervical Softening
o Increased Sensitivity and Expression of Myometrial Oxytocin receptors
o Increased Water Retention and Protein Synthesis
Role of Human Placental Lactogen in Pregnancy
Similar Structure and Function to Growth Hormone
o Modification of Maternal Metabolism to promote energy supply to Foetus
o Increased Insulin Secretion as well as Resistance – Promotes higher maternal Lipolysis and Blood Glucose for Foetus
Changes in Pituitary Gland in pregnancy
Enlarges mainly due to changes in Anterior Lobe; Increased Prolactin level
(likely due to Oestrogen influence), Inhibited GnRH secretion, Increased ACTH production
o Posterior Pituitary – Releases Oxytocin principally during first stage of Labour and
during Suckling to promote breast milk expression
Thyroid Changes in Pregnancy
Increased Renal Clearance of Iodine (due to Haemodynamic changes) causes Relative Iodine
deficiency, leading to Thyroid enlargement in response
o Followed by Increased Thyroid Binding Globulin production doubled – Hence, initial Thyroid Hormone rise falls to non-pregnant normal range
o NB: Thyroid Hormone, Iodine, Anti-thyroid Drugs and Thyroid Abs can cross Placenta
Haemodynamic Changes in Pregnancy : Red Cells
Increased plasma volume
Red cell mass increases
Relative haemodilution results in drop in haemoglobin concentration
Haemodynamic Changes: White Cells
- Increased WCC; Mostly Neutrophils, peaking at 32 weeks; Massive Neutrophilia occurs during Labour; Profound Drop in Eosinophils during Labour
- Depressed Lymphocyte Function and Cell-Mediated Immunity
Haemodynamic Changes: Clotting
- Platelet count falls slightly during pregnancy; Function unchanged
- Hypercoagulable state – Raised Clotting factors, especially Fibrinogen; ESR up to four-fold
Cardiovascular changes:
Most significant occurring within 12 weeks
Raised Cardiac Output
Increased cardiac volume
Drop in PVR due to prostaglandins
BP drops by 10 – 20mmHg in Mid-pregnancy, returns to normal at term
o Vasodilation and Hypotension triggers RAAS
Respiratory Changes
Diaphragm rises
Increased tidal volume
Breathlessness more common: lower maternal partial pressures co2
Reproductive System Changes: Uterus
Increase in weight
Muscle hypertrophy
Increased uterine blood flow and arterial calibre
