Maternal Physiology , Labour and Lactation Flashcards
Why do women get Morning Sickness in pregnancy
Feature of early pregnancy because of the human chorionic gonadotrophin secreted by the trophoblast.
Diminishes after first trimester
Explain what happens to CO in pregnancy
Cardiac output increases to 130-140% by 20 weeks gestation.
What happens to BV in pregnancy
Blood volume rises by 20% mostly at the second half of the pregnancy. rises almost 40% by the the end of pregnancy
What happens to O2 consumption and CO2 production in pregnancy
O2 consumption and CO2 production increase. Therefore VO2 and VCO2 increases to keep up with demand of fetal metabolism.
What happens to BMR in pregnancy
15% increase in BMR
What happens to GFR and NA/H20 reabsorption in pregnancy
- Renal reabsorption of NaCl and H2o is elevated by high levels of maternal sex steroids having aa mineralocorticoid like effect.
- GFR is raised indirectly by increased CO and directly to limit fluid retention
When can frequency of urination increase during pregnancy
During the third trimester when the fetus might be pressing on the bladder
What are pregnant women prone to be deficient of
Iron and Calcium
Explain the increased nutritional demands in pregnancy
Energy and protein intake of an average diet is adequate but mineral and vitamin intake is not. Additional 1 g of iron is needed and calcium
What happens if there is a calcium deficiency in pregnancy
Deminiralising of maternal bones
What is the usual weight gain during pregnancy and why
Weight gain : 10 kg 1- fetus : 3.5 kg 2- breast development : 1 3- placenta and amniotic fluid : 2.5 increased body weight in mother : 3.5 kg
What mechanical effects could be caused due to where the fetus is in the abdomen
1- Dyspnoea late in pregnancy
2- acid reflex
What is the average duration of pregnancy
270 days ( 284 from last menstruation )
Explain Parturition
Birth happens in 3 stages
1- dilation of cervix
2- explosion of fetus
3- delivery of placenta
Explain the preparation stage of parturition
During last trimester
1- cervix softens and dilates
2- pubic symphysis becomes more flexible
3- smooth muscle of uterus becomes more excitable and connected via gap junctions ( under estrogen levels )
4- prostaglandin production increases and oxytocin receptors rise
5- CRH production increases that has a positive feedback on placenta , increasing fetal ACTH and cortisol.
Why is increase of cortisol vital in the last trimester
Cortisol is vital to maturity of fetal respiratory system and preparation of change in environment.
When is the fetus ready to be born
After CRH production has been increased
How many stages of labour are there
3 stages
Explain the 1st stage of labour
Lasting 8-24 hours
1- canal trough cervix is dilated by babies head pushing down by myometrial contractions
2- stretch causes reflex release of oxytocin from posterior pituitary that acts on myometrium to increase contraction and thus increase cervical stretch
3- 1st stage lasts until 10cm dilation of cervix
Explain the 2nd stage of labour
Lasting 30-90 min
1- Once cervix is 10cm dilated head of baby exiting cervix will trigger reflexes to contact abdominal muscles
2- Reflex contractions could be reinforced voluntarily by pushing ( not necessary though )
3- Contraction expels baby out of vagina
Explain the 3rd stage of labour
Delivery of the placenta that shears off wall of contracted uterus. Because the uterus is contracted there is usually minimal blood loss.
What is lochia and why does it happen
Regression of decidual endometrium giving discharge post birth called lochia.
Due to the dramatic drop of estrogen and progesterone levels after loss of placenta.
When do breasts fully develop in pregnancy
During the third trimester , at 20 weeks women is able to produce milk but prevented by high levels of estrogen and progesterone until birth.
How do breasts develop to secrete milk ( explain hormones )
Breasts develop to secrete milk under influence of estrogen and progesterone from placenta.
1- estrogen promotes duct development
2- progesterone enlarges terminal secretory portions of glands
3- prolactin ( from mom ) and human chorionic somatomammotropin ( from placenta ) develop enzymes for milk production
How mechanical stimulation of nipple causes breastfeeding
1- suckling stimulates hypothalamus via spinal cord afferents
2- causes secretion of prolactin via anterior pituitary by decreasing Prolactin inhibitor hormone secretion
= initiates and maintains milk production ( endocrine )
3- nipple stimulation will increase oxytocin from hypothalamus that contracts smooth muscle surrounding secretory alveoli = milk expelled into mouth of infant ( neurological )
What is the advantage of suckling being a neuroendocrine reflex
It has to be an instantaneous process, and well controlled. Easier to do that if it’s not just neuro controlled
How Can breastfeeding act as an unreliable contraceptive
Prolactin inhibits gonadotrophin production, which inhibits FSH and LH
Why is breastfeeding not a reliable contraceptive
Because breastfeeding is pulsatile , if women misses a feed then gonadotrophin will not be inhibited.
What are the components of breast milk
1- Triglycerides 2- carbohydrates : lactose 3- protein 4- vitamins 5- calcium 6- phospate
What is secreted after the first few days by the breasts
Colostrum what has more protein and less fat and glucose than normal breast milk. Contains lactoferrin ( antibacterial ) and maternal antibodies ( IgA ) for immunity
