Phys: Pregnancy, Labour and Lactation

Question 1

What physiological changes occur in the body during pregnancy?

Answer 1

• Morning sickness
• Increased CO and BV
• Increased O2 consumption and CO2 production
• Increased ventilation
• Increased BMR
• Increased GFR/Na+ and H20 reabsorption (net fluid retention)
• Increased nutritional demands
• Weight gain (fetus, breasts, BW)

Question 2

What is parturition?

Answer 2

Birth

Question 3

What changes occur in the body to prepare for parturition?

Answer 3

• Relaxin secreted in last 3 months to soften and dilate cervix and make pubic symphysis more flexible
• Uterine muscle becomes more excitable and connected by gap junctions (oestrogen stimulated ), prostaglandins increase vascularity, oxytocin receptors increase for smooth muscle contraction and initiation of labour
• Fetal CRH production increases, drives placental CRH up - increases fetal ACTH and cortisol - respiratory maturation - determines birth timing

Question 4

Describe the changes in the body during parturition.

Answer 4

3 stages

1. Dilation - increased oxytocin sensitivity - myometrial contraction - cervical stretch - spinal afferents activate hypothalamus which activates post. pituitary to produce more oxytocin
2. Expulsion - head exiting cervix activates powerful abdominal contractions + “bearing down” helps
3. Delivery of placenta - placenta shears off uterine wall, low blood loss as uterus already contracted

• lochia (vaginal discharge for first few days after birth)

Question 5

Which hormones are involved in lactation?

Answer 5

• Oestrogen (duct development)
• Progesterone (secretory alveoli)
• Human chorionic somatomommotrophin (enzymes that secrete milk)

Question 6

Describe the suckling reflex.

Answer 6

• Mechanical stimulation of the nipple
• Spinal cord afferents
• hypothalamus (reduces PIH)
  Increases prolactin release from ant. pituitary (milk secretion) and oxytocin from post. pituitary (milk ejection)

Question 7

What is the advantage of the suckling reflex being a neuroendocrine reflex?

Answer 7

Instantaneous production of milk when stimulated (neuro) but whole organ effect (hormonal)

Question 8

Why are you less likely to fall pregnant during breastfeeding?

Answer 8

• Prolactin inhibits gonadotrophins (GRH)
• therefore, no LH or FSH produced
• but breast-feeding must be regular

Question 9

What are the components of breast milk?

Answer 9

• triglycerides, carbs, protein, vitamins, calcium, phosphate
• in first few days, secretion termed colostrum
• Colostrum: more protein, less fat and lactose, lactoferrin (antibacterial), maternal IgA - passive immunity