Maternal changes in pregnancy (repro)

Question 1

Maternal changes in pregnancy

Answer 1

• major changes in multiple systems
• causative factors: high levels of steroids, mechanical displacement, foetal requirements
• pregnancy is a physiological event
• systems usually return to normal after delivery, but not all

Question 2

Maternal system in pregnancy

Answer 2

• to diagnose abnormality in pregnancy, changes in the changes need to be detected
• however pregnancy may exacerbate a pre existing condition
• uncover hidden or mild condition

Question 3

Changes in the system

Answer 3

Changes designed to cope with several main events:

• increase in size of uterus
• increased metabolic requirements of uterus
• structural and metabolic requirements of foetus
• removal of foetal waste products
• provision of amniotic fluid
• preparation for delivery and puerperium

Question 4

Systems in which changes occur

Answer 4

• energy balance
• respiratory system
• cardiovascular system
• gastrointestinal system
• urinary system
• endocrine system

Question 5

Hormones that cause most of the change

Answer 5

Placental peptides:
- hCG 
-hPL
- GH
Maternal steroids:
- placenta takes over ovarian (CL) production around week 7
Placental and foetal steroids:
- progesterone
- oestrogen
- oestriol 
Maternal and foetal pituitary hormones:
- GH
- thyroid hormones
- prolactin
- CRF

Question 6

Effects of placental steroids

Answer 6

• renin/angiotensin system
• respiratory centre
• GI tract
• blood vessels
• uterine myometrial contractility

Question 7

Gain in weight

Answer 7

Total weight gain 12.5-13kg:

• foetus plus placenta: 5kg
• fat and protein: 4.5kg
• body water: 1.5kg (excluding intravascular, interstitial, intracellular)
• breasts: 1kg
• uterus: 0.5-1kg
• ideally keep to less than 13kg
• failure to gain or sudden change needs monitoring

Question 8

Energy balance

Answer 8

need to increase energy:

• output - to cope with increased respiration and cardiac output
• storage - for foetus and for labour and puerperium

gain in fat and protein stores is 4-5kg:

• increased consumption and reduced use
• mainly laid down in anterior abdominal wall
• utilised later in pregnancy and puerperium

Question 9

Basic metabolic rate

Answer 9

rises by:

• 350 kcal/day mid gestation
• 250 kcal/day late gestation
• these are 75% foetus and 25% uterus

9 calories = 1g fat therefore 40g fat for 350kcal ie 1 large mars bar

Question 10

Glucose

Answer 10

• need increased availability in 2nd trimester
• active transport across placenta as foetal energy source
• foetus stores some in liver

1st trimester maternal reserves:
- pancreatic beta cells increase in number
- plasma insulin increases
- fasting serum glucose decreases (laid down as stores and used by muscle)
2nd trimester foetal reserves:
- hPL causes insulin resistance ie less glucose into stores results in increased availability in serum glucose (more crosses placenta) but can cause diabetes

Question 11

Total water gain

Answer 11

• foetus
• placenta
• amniotic fluid
• oedema (lungs, connective tissue ligaments, leakage, swollen ankles)
• uterine muscle
• mammary gland
• plasma volume (sodium retention, resetting of the osmostat, decrease thirst threshold, decrease in plasma oncotic pressure (albumin))

Question 12

Respiration

Answer 12

oxygen consumption is increased

process:

• increases respiratory centre sensitivity to CO2 and thoracic anatomy changes so ribcage is displaced upwards and ribs flare outwards
• causes woman to breathe more deeply
• minute volume increases 40%
• arterial PO2 increases 10% and PCO2 decreases 15-20%
• this facilitates gas transfer and O2 increases and CO2 decreases in the mother

Question 13

Maternal blood

Answer 13

• maternal plasma volume increases 45%
• red cell mass increases 18%
• increased efficiency of iron absorption from gut
• Haemodilution is apparent anaemia as concentration of Hb falls
• changes in white cells and clotting factors makes blood hypercoagulable (increases fibrinogen for placental separation, but increased risk of thrombosis)

Question 14

Foetal blood

Answer 14

• foetal blood has increased Hb and altered in type
• leads to increased O2 binding
• therefore O2 given up by maternal Hb
• smoking increases maternal carboxy-Hb which is more permanent and reduces the increased binding
• leads to foetal hypoxia

Question 15

Cardiovascular system (heart)

Answer 15

Expanding uterus:
- pushes heart round
- changes ECG and heart sounds
Increased cardiac output:
- increased heart rate and stroke volume
- begins as early as 3 weeks to max 40% at 28 weeks
- for maternal muscle and foetal supply

Question 16

Cardiovascular system (vessels)

Answer 16

• increased cardiac output and vasodilation by steroids leads to reduced peripheral resistance
• increased flow to:
• uterus
• placenta
• muscle
• kidney
• skin
• Neoangiogenesis, including extra capillaries skin (spider naevi) to assist in heat loss

Question 17

GI tract

Answer 17

steroids:

• affect appetite and thirst
• reduced GI tract motility (causing constipation)
• relax lower oesophageal sphincter (causing acid reflux)
• large uterus causes small frequent meals and acid reflux

Question 18

Dietary supplementation of folic acid

Answer 18

• folic acid helps with DNA production, growth and blood cells in the uterus, placenta and foetus
• supplementation advised 5mg/day up to week 12
• deficiency linked to spina bifida (neural tube defect)

Question 19

Urinary system

Answer 19

• urinary tract dilates and relaxes, increased UTI may persist
• kidney has increased blood flow which leads to increased filtration rate
• this leads to increased clearance of creatinine, urea and uric acid
• Early pregnancy: the uterus is enlarging but it is within the pelvis compressing the bladder leading to frequency
• Mid pregnancy: the uterus is lifted out of the pelvis leading to normal micturition
• At term: the head of the foetus descends into the pelvis leading to frequency

Question 20

Changes in uterus

Answer 20

• huge increase in muscle mass
• huge increase in blood flow
• placenta and uterus (1/6 of total)
• dimensions of uterus go from 5x7.5x2.5 and 100ml to 24x28x21 and 14000ml
• isthmus becomes softened and elongated during pregnancy
• lower uterine segment formed from isthmus
• upper part of cervix incorporated from 34 weeks

Question 21

Changes in cerviz

Answer 21

• primary function is to retain the pregnancy
• increase in vascularity
• tissue softens from 8 weeks (changes in connective tissue and begins gradual preparation for expansion)
• proliferation of glands:
• mucosal layer becomes half of mass
• great increase in mucus production
• protective ie anti-infective

Question 22

Return to normal

Answer 22

• dramatic and rapid fall in steroids on delivery of placenta
• most endocrine-driven changes return to normal rapidly
• uterine muscle rapidly looses oedema but slowly (never returns to pre-pregnancy size)
• removal of steroids permits action of raised prolactin on breast

Question 23

Glossary

Answer 23

• Trophoblastic invasion - During implantation and subsequent trophoblast invasion, fetal trophoblast cells and maternal uterine tissues (endometrium and myometrium) come into intimate contact with each other.
• Placental hormone production - The placental hormone (Human Chorionic Gonadotropin, HCG) is present in the mother’s body during pregnancy. Its structure and effect resemble the luteinizing hormone (LH) that is secreted from the pituitary gland.
• Vasodilatation - The dilatation of blood vessels, which decreases blood pressure.
  Effective circulating volume - The volume of arterial blood effectively perfusing tissue.
• Physiological adaptation - Internal systematic responses to external stimuli in order to help an organism maintain homeostasis.
• Gestational diabetes - Any degree of glucose intolerance with onset or first recognition during pregnancy.
• Pre-eclampsia - A condition in pregnancy characterized by high blood pressure, sometimes with fluid retention and proteinuria.