Pregnancy, labour and lactation Flashcards
How does cardiac output change in pregnancy?
Increases to 30-40% by 20 weeks gestation. BV rises by 20% (mostly in 2nd half)
How do VO2 and VCO2 change during pregnancy?
Increase in same time period with demands of foetal metabolism- 15% increase in BMR and rise in resp minute volume of similar magnitude
How is renal reasborption of NaCl and H2O altered in pregnancy?
elevated by mineralocorticoid like effects of maternal sex steroids
GFR also raised both directly and indirectly by increased CO, to limit resulting fluid retention
3rd trimester foetus pressing on bladder > inc urination
How are nutritional demands affected by pregnancy and their effects?
^ demands, mineral and vitamin intake need increased but energy and protein average is adequate.
Iron deficiency anaemia common, and calcium deficiency in foetus corrected by demineralising m. bone
dyspnoea, acid reflux common
What is the role of relaxin in parturition? (birth)
Cervix softens and dilates, pubic symphysis becomes more flexible
How does the uterine muscle change?
Oestrogen stiumulated ( ^ levels), SM more excitable and more connected by gap junctions. Prostaglandins and oxytocin receptors ( SM contractor) ^
How is foetal CRH production affected?
^, driving placental CRH up
-Foetal ACTH and cortisol producted in positive feedback
Cortisol prepares for drastic change in environment, foetus picks when to be born by ^ its CRH production
what is the first stage of labour?
Dilation- canal through cervix dilated by action of babies head by myometrial contraction.
Reflex release of oxytocin from PP, acts on myometrium to ^ contraction, ^ cervical stretch and amplifies contractions. PGs also inc MM C, relaxin role
what is the second stage of labour?
Expulsion- head exits cervix triggering reflexes, contract abd. muscles helping expulsion
Reinforced voluntarily by consciously pushing with them
What is the third stage of labour?
Delivery of the placenta- shears off wall of contracted uterus- usually minimal blood loss as uterus contracted.
Dramatic drop in maternal O+P due to loss of placenta- leads to regression of Dec. endometrium, post birth discharge (lochia)
Lactation
^ placental oestrogen and progesterone influence milk secretion
Oestrogen- duct development
Progesterone- englarges secretory alveoli
Prolactin (ant. PG) and human chorionic somatomammotrophin from plac. develop enzymes, ready around 20 weeks.
Suckling reflex
Suckling > spinal cord afferents > hypothalamus > dec PIH > ant p, prolactin > milk secretion (sec. epi)
And
Post. pituitary, oxytocin > milk ejection (myoepi. cells)
How does suckling itself cause release of prolactin
Mech. stimulation of nipple > prolactin, decreasing prolactin inhib. hormone secretion.
Components of breast milk
Triglycerides, carbohydrates (lactose) protein, vitamins, calcium,
