Pregnancy and labour Flashcards
What is pregnancy?
- Pregnancy (or gestation) refers to the sequence of events that begins with fertilisation, proceeds to implantation, embryonic and foetal development and ideally concludes at birth (usually 389-40 weeks after the last menstrual period in a full-term pregnancy)
What are the developments during pregnancy?
- Prenatal period refers to the developmental phases
- The embryonic period from fertilisation to 8 weeks gestation
- The foetal period that begins from week 9 until birth
- The embryonic period is the most critical stage of development, as most of the organs and systems form in this phase
- Zygote > embryo > foetus
What is a healthy pregnancy?
Healthy pregnancy
* 40 weeks
* Also known as 280 days
* Also known as three trimesters
What are the TCM patterns of pregnancy?
TCM patterns:
* Stomach and Liver heat: internal heat due to stasis in the penetrating vessel
* Liver Qi Xu: emotional stress
* Stomach Qi Xu: imbalance in the penetrating vessel causing “rebellious Qi”
* Empty cold: internal cold due to long term yang xu (poor diet, overwork).
What is labour?
- Labour is the process of giving birth
- Occurs within 15 days of the calculated due date which is 280 days from the last menstrual period.
- In the last few weeks of pregnancy, complex interactions between the foetal and placental hormones increases oestrogen and diminished the inhibitory effects of progesterone on uterine contractions.
What is Phase one of labour?
STIMULATING FOETAL HORMONE PRODUCTION PHASE 1
* Rising corticotrophin-releasing hormone (CRH) levels by the placenta causes the foetus anterior pituitary gland to secrete adrenocortiocotrophic hormone (ACTH).
* This stimulates the foetus adrenal glands to produce cortisol and dehydroepiandrosterone DHEA.
What is phase 2 of labour?
DHEA to oestrogen, prostaglandins and relaxin PHASE 2:
* Increased myometrium (muscle lining of uterus) sensitivity to oxytocin (the hormone driving contractions during labour).
* Prostaglandin production by the placenta, causing enzymes to digest collagen fibres in the cervix (softening and shortening the cervix) and triggers contractions.
* During this time, relaxin from the placenta assists in dilating (opening) the cervix.
* Consequently, uterine contractions increase.
What is phase 3 of labour?
TRUE LABOUR: Phase 3
* True labour occurs when uterine contractions occur at regular intervals
* The intervals between contractions reduces, the contractions intensify
* Control of labour contractions occur via a positive feedback cycle, until birth of the infant.
What are the signs of true labour?
SIGNS OF TRUE LABOUR:
* The cervix dilates to 10cm and a show develops which is a blood containing mucous. It’s discharged from the cervical canal
* Other signs include localisation of pain in the back which is intensified by walking.
* In false labour, pain is in the abdomen at irregular intervals. There is no “show’ or cervical dilation.
What is the positive feedback loop during labour?
- Contractions of the wall of the uterus force the baby’s head or body into the cervix > increasing > controlled condition: stretching of the cervix. The baby moves deeper into the birth canal which distends (stretches the cervix).
- Receptors: stretch-sensitive nerve cells in the cervix. Response: contractions intensify the stretching of the cervix which results in the secretion of more oxytocin. Input > nerve impulses.
- Control centre > brain. Effectors: oxytocin is carried by the blood to the uterus where it stimulates the myometrium to contract more forcefully. Output > brain interprets input and releases oxytocin.
- Effectors: muscles in the wall of the uterus. Neurosecretory cells in the hypothalamus are stimulated and release oxytocin from the posterior pituitary gland. Contract more forcefully.
- Response: baby’s body stretches the cervix more. Stretch receptors in the cervix send sensory signals to the brain. Interruption of the cycle. The birth of the baby decreases stretching of the cervix.
- Increased stretching of the cervix causes the release of more oxytocin, which results in more stretching of the cervix.
What are the stages of labour?
Dilation
Expulsion
Placental
What happens during the dilation stage?
DILATION STAGE
* Dilation (average 6-12 hours) is the first stage of labour. It involves contractions of the uterus and dilation of the cervix to 10cm.
* This stage may result in spontaneous rupture of amniotic sac. If not, it is intentionally ruptured prior to expulsion.
What is the expulsion stage?
EXPULSION
* Typically between 10 mins to several hours, involves the baby moving through the birth canal.
What is the placental stage?
PLACENTAL STAGE
* The placental stage is after expulsion of the infant. It takes 5 – 30 minutes after delivery, until the placenta or after-birth is expelled by forceful uterine contractions.
* It is essential that the placenta is checked and completely intact and there are no leftover parts inside the uterus.
* As the placenta tears away from the endometrium, there is active constriction of the blood vessels which prevents excess blood loss and reduces the possibility of haemorrhage.
What hormonal changes occur at birth?
Progesterone:
* Inhibits uterine contractions during pregnancy. Levels decrease towards the end of gestation.
DHEA:
* Converted into oestrogen by the placenta. Rising CRH by placenta stimulates the production of DHEA in the foetus
RELAXIN:
* Dilates the uterine cervix during labour. Increases flexibility of pubic symphysis.
OXYTOCIN
* Stimulates uterine contraction during labour. Uterine muscle fibres form gap junctions with each other.
OESTROGEN
* Overcomes inhibiting effects of progesterone. Increases the number of oxytocin receptors on uterine muscles. Stimulates placenta to make prostaglandin.
