Parturition & Lactation Flashcards
What are 4 roles of progesterone during pregnancy?
- Thickens endometrium throughout pregnancy
- Prevents ovulation
- Stimulates growth of maternal breast tissue, preventing lactation
- Strengthens pelvic wall muscles in preparation for labour
In assisted reproduction, what is the role of progesterone?
- 1st trimester progesterone supplementation support early pregnancy by reducing miscarriage
- Reduces risk of pre-term delivery
What hormones are prominent in the third trimester?
- Oestrogen, which results in an increase in prostaglandins that affect uterine contractility + cervical ripening
- Progesterone levels decrease
What is oestriol?
A weak oestrogen that promotes uterine growth + prepares body for giving birth
What is Braxton-Hicks contractions?
- Sporadic uterine contractions (false labour)
- Increase in oxytocin
What 3 stages can parturition be divided into?
1 - Onset of contraction, dilation + shortening of cervix
2 - full dilation of cervix to delivery of baby
3 - delivery of placenta
Describe the first stage of parturition.
- Cervical effacement (ripening of cervix)
- Contractions retract the cervix + lower part of uterus to form a continuous birth canal with the vagina
- Cervix needs to undergo changes to make it softer + more flexible (cervical remodelling)
- Needed for dilation + expulsion of foetus
What does cervical remodelling involve?
- Softening
- Ripening
- Dilation & labour
- Post partum repair
- Prostaglandins + relaxin
- Possibly Nitric Oxide (NO)
When does stage 1 of parturition end?
When cervix is fully dilated
Describe the second stage of parturition.
- Parturition
- Period from full dilation of cervix to expulsion of neonate (baby)
- A few days prior to parturition, stomach ‘sinks’ as pelvic ligaments relax + baby settles lower in uterus
- Mammary glands enlarge as colostrum is produced
- Requires contractions of uterine myometrium that are sufficiently strong to expel foetus
What hormone is produced to prepare a woman for birth?
Ovary + placenta produce relaxin
What does relaxin do?
Relaxes ligaments in pelvis + softens and widens cervix to allow passage of foetus
What other hormones increase to promote labour?
Oestradiol
Prostaglandins
Prolactin
What does a breech birth refer to?
Any other part of the body, other than the head, approaches cervix first
What are 2 triggers for parturition?
1- High oestrogen (oestadiol)
- Stimulates expression of oxytocin receptors in myometrium
- Increase in receptors makes myometrium more responsive to oxytocin
- Oxytocin stimulates synthesis of placental prostaglandins
2 - Oxytocin + prostaglandin stimulate smooth muscle contraction
- Pressure of head in contact with cervix triggers release of oxytocin from pituitary gland
- Oxytocin stimulates uterine contractions (labour)
- When contractions start, head of foetus is pushed against cervix, stimulating more contractions + more oxytocin to be released (+ feedback)
- Contractions consequently increase in intensity + frequency
- As foetus moves through cervix, stretch receptors in vagina activate neural reflexes that trigger abdominal wall contractions
Describe the third stage of parturition.
- Exoulsion of the placenta
- Oxytocin falls after birth
- Secondary surge triggers series of uterine contractions that separates placenta from myometrium
- Myometrium continues to contract to constrict uterine blood vessels supplying placental attachment site
- Prolactin stimulates milk synthesis + secretion
What is thought to be the role of Corticotropin Releasing Hormone?
- Establish positive-feedback loops that initiate parturition + labour
- Interacting with oestrogen, adrenal steroids, prostaglandins + oxytocin
- Timing of birth by regulating control of contractile properties of myometrium
- May contribute to initiation of labour by acting indirectly to enhance foetal ACTH (adrenocorticotropic hormone) and adrenal cortisol production
- Stimulates production of foetal adrenal DHEA-S
What is CRH secreted by?
Foetal portion of placenta
What is the role of cortisol in parturition?
Prepares foetal lung for extra-uterine life
What is the role of DHEA-S?
- Induces myometrial oxytocin receptors, thereby preparing the uterus for parturition, in late gestation
- Used by placenta to produce oestrogen
How is the delivery date more accurately predicted currently?
Based on maternal CRH levels as early as the end of 1st trimester
How is labour induced?
- Vaginal infusions of prostaglandins
- Oxytocin then used to rigger myometrial contractions to induce parturition
Are oxytocin levels during c-sections higher or lower?
Lower due to the lack of cervical + myometrial contractions
What is the issue with reducing less oxytocin during c-sections?
Oxytocin involved in mother offspring bonding + preparation for lactation - lead to maternal problems
What are some foetal changes at parturition?
- Foetal circulation doesn’t involve lung because O2 is provided through placenta
- 2 ventricles pump in parallel + shunts divert most circulation away from developing lungs to placenta
- 3 shunts bypass lungs, divert blood from left to right side of heart + bypass most of hepatic system
Describe foetal circulation
- Blood oxygenated in placenta
- Oxygenated + nutrient-enriched blood from placenta returns to foetus through left umbilical vein
- A little blood enters liver but most bypasses hepatic system through ductus venosus + enters inferior vena cava
- From vena cava, blood enters right atrium.
- Most is shunted directly to left atrium through foramen ovale, bypassing right ventricle
- From left atrium, blood enters left ventricle + is delivered to foetal tissues via aorta
- Oxygenated depleted + nutrient-poo foetal blood is returned to placenta via right + left umbilical arteries
- A small amount of blood in right atrium enters right ventricle + goes to lungs but most of blood bypasses lungs through ductus arteriosus
How and why do the shunts close at birth?
- Placental blood flow ceases + lung respiration begins in neonate
- Decreases in prostaglandins + changes in blood pressure forces septa against shunts, closing them off
- Shunts must close at birth to establish normal adult circulation
What is it called if the foramen ovale fails to close?
Patent foramen ovale
What happens if the ductus arteriosus closes prematurely?
- Increased pressure on right ventricle = pulmonary hypertension
- If left untreated = foetal death
What happens if the ductus venous fails to close?
Hepatic dysfunction
Describe foetal respiration
- Ahead of parturition, foetus makes resp movements that move amniotic fluid into + out of lungs
- Foetal corticosteroids stimulate the production of pulmonary surfactant (a phospholipid attached to a protein) that reduces surface tension of pulmonary fluid in lungs
What happens if insufficient surfactant is produced?
- Result in problems with lung expansion at birth (idiopathic respiratory distress syndrome
- In premature infants, lung maturation can be improved by injections of corticosteroids in mother
What is tachypnea?
Abnormally rapid breathing
What occurs is normal removal of fluid does not take place?
- Happens in c-sections
- Baby’s lungs may not develop properly
- Transient Tachypnea of newborn (TTN)
What does puerperium mean?
Post partum
What is uterine involution?
When the uterus shrinks to normal size after parturition
How long does it take for hormone levels to return to normal after parturition?
4-6 weeks
What is lochia?
Vaginal discharge containing blood, mucus + uterine tissue
What do marsupials have instead of a placenta?
Enlarged yolk sac
What is a kangaroos gestation period?
31-36 days
Give birth to embryonic, immature young that climb to a nipple in pouch + attach to it
What is diapause?
- E.g. a doe, usually have 3 offspring at the same time
- Delaying development of fertilised egg if environmental conditions are unfavourable or until older joey vacates pouch
Describe the anatomy of the breast
- Made up of fat + breast tissue
- Nerves, blood vessels + connective tissue
- Has a number of lobules that branch out from nipple
- Each lobule holds tiny, hollow sacs (alveoli) where milk is secreted + stored
Describe lactation during gestation
- Elevated placental oestrogen stimulates milk duct development
- Elevated placental progesterone stimulates alveoli formation
What hormones stimulate + synthesise enzymes essential for milk production by alveolar epithelial cells?
Prolactin + Human Placental Lactogen (hPL)
What is the role of prolactin and hPL?
- Stimulate + synthesis enzymes essential for milk production by alveolar epithelial cells
- Promote foetal groeth by stimulating secretion of insulin-like growth factors (IGF-1 and 1GF-2)
Where is milk synthesised in breasts?
Epithelial cells
What 2 hormones are essential for maintaining lactation?
Prolactin + oxytocin
What hormones are released through suckling?
Oxytocin + prolactin
What does oxytocin and prolactin do when young is suckling?
- Causes smooth muscle contraction that ejects milk
- Prolactin stimulates synthesis of more milk to replace milk ejected
What does the breast produce prior to milk production?
Colostrum
A thick, yellowish fluid + is only produced for a few days
Gradually replaced by milk
What does colestrum contain?
- Protein
- Fats
- Vit A
- Immune cells (lymphocytes)
- Antibodies such as IgA, IgG and IgM
- Growth factors, such as insulin-like growth factors (IGF-1 and IGF-2)
What is meconium?
New-borne first stools
Contains excess bile + waste products from when still in uterus
Colostrum has a laxative effect to help expel this
What are the advantages of breast feeding?
Reduced risk of:
- Asthma
- Autoimmune diseases
- Type 1 diabetes
- Some cancers, e.g. Lymphoma
What are the disadvantages of bottle feeding?
- Digestive tract infections
- Respiratory tract infections
What are the advantages of breast-feeding for the mother?
- Oxytocin hastens involution (shrinking of uterus)
- Prolactin inhibits GnRH
- Helps lose weight
