Maternal Physiological Changes in Pregnancy

Question 1

Human chorionic gonadotropin (hCG)

Answer 1

– Peptide hormone
– Synthesised by trophoblast cells of embryo under direction of progesterone and oestrogens
– Prevents involution of corpus luteum at end of menstrual cycle

Question 2

Nausea & vomiting experienced by pregnant women during first 12-14 weeks

Answer 2

– Precise cause not known but it does seem to parallel rising levels of hCG secretion by syncytiotrophoblasts

Question 3

Human placental Lactogen (hPL)

Answer 3

– Human Chorionic somatomammotropins
(hCS1 & hCS2)
– Polypeptide hormones structurally related to GH and prolactin secreted by placenta
– Synthesised by syncytiotrophoblast cells of placenta
– Promote development of maternal mammary glands
– es insulin sensitivity and utilization of glucose by mother
– Play role in release of free fatty acids from mother’s fat stores

Question 4

the placenta produces

Answer 4

large quantities of hormones secreted by syncytiotrophoblast cells

Question 5

Progesterone

Answer 5

– Development of uterine endometrium & role in nutrition of early embryo (decidual cell development)
–  contractility of pregnant uterus – reducing spontaneous abortion
– Helps oestrogens prepare mother’s breasts for lactation

Question 6

• Oestrogens (proliferative effects

Answer 6

– Enlargement of mother’s uterus
– Enlargement of mother’s breasts and growth of ductal structure
– Enlargement of external genitalia
– Relaxation of pelvic ligaments
• Sacroiliac joints become limber
• Symphysis pubis becomes elastic

Question 7

Placenta is imperfect endocrine organ

Answer 7

– Cannot manufacture adequate cholesterol
– Lacks 2 crucial enzymes for synthesising estrone & estradiol (brown background)
– Lacks enzyme for synthesising estriol (brown background)

Question 8

what does the mother and what does the foetus supply

Answer 8

• Mother supplies most of cholesterol as LDL particles
• Foetal adrenal gland and liver supply 3 enzymes that placenta lacks
• Foetus cannot synthesise oestrogens as it lacks enzymes to catalyse last 2 steps (blue background)

Question 9

Medial preoptic area (mPOA) plays central role in

Answer 9

regulating maternal behaviour

Question 10

Relaxin produced by

Answer 10

corpus luteum In early pregnancy it stimulates oxytocin (OT) and vasopressin neurons

Question 11

Cardiovascular Changes

Answer 11

• Cardiac output (CO) increaseses in 1st trimester (30-40%) and then only slowly during 2nd and 3rd trimesters (30-50% at term)
– Due to increase in SV (10-20%) and HR (from 70 to 80-90 bpm)

Question 12

Mean arterial pressure (MAP) usually

Answer 12

decreases during 2nd trimester and then increases during 3rd trimester although it remains at or below normal.
– Due to decrease in PVR, due to vasodilating effects of progesterone & estradiol and expansion of placental circulation

Question 13

Blood Volume Changes

Answer 13

• Maternal blood volume increases during pregnancy
• Blood volume increases in 1st trimester, expands rapidly in 2nd trimester and rises at lower rate in 3rd trimester, then plateaus in last few weeks of pregnancy (45% in singleton and 75-100% in twin/triplet pregnancies)

Question 14

what is the survival advantage of an increase in maternal blood volume

Answer 14

– decrease in blood viscosity improve placental
perfusion
– Reserve during haemorrhage
• RBC increases by 18-25%, may be due to  in erythropoietin - WBC also 

Question 15

why is there an increase in blood volume

Answer 15

•  in blood volume due to  in plasma volume and number of erythrocytes
• Proposed mechanism is elevated progesterone and oestrogens cause vasodilation leading to  in PVR &  in renal perfusion (‘underfill’)

Question 16

Endothelial Changes

Answer 16

• During pregnancy high oestrogen levels stimulate NO production
• Relaxin from corpus luteum causes vasodilation by blocking endothelin induced vasoconstriction

Question 17

Pre-eclampsia

Answer 17

• Placental problem involving an increase in BP (>140/90 mmHg), proteinuria (after 20 weeks) and oedema
• May involve failure of the second wave of trophoblast invasion that normally impairs the capacity of material spiral arterioles to constrict (12-16 weeks)
• Treatment – delivery of baby

Question 18

risk factors for Pre-eclampsia

Answer 18

– Previous pregnancy with pre-eclampsia
– >40 yrs old
– Family history
– Obesity
– Primigravida

Question 19

clinical features of pre-eclampsia

Answer 19

– Head ache
– Visual disturbance
– Epigastric pain
– Oedema

Question 20

Increased vascular resistance in placenta in preeclampsia causes:

Answer 20

– Hypertension in the mother

– Renal arteriolar endothelial damage causes oedema, glomerular damage and proteinuria (‘acute atherosis’)

Question 21

Eclampsia

Answer 21

• Extreme hypertension (e.g. 180/120)
• Increased intracranial pressure, seizures, coma
• Significant risk of cerebral haemorrhage

• Interventions:
– Magnesium sulphate
– Antihypertensives
– Rapid delivery
– Careful fluid balance