Labour Flashcards
What is the definition of term?
Baby delivered at 37-41 weeks gestation.
What is the definition of preterm?
Baby delivered at 33-37 weeks gestation.
What is the definition of post-term?
42 weeks of more.
What is the definition of very pre-term?
28-32 weeks.
What is the definition of early miscarriage?
First trimester.
What is the definition of late miscarriage?
Second trimester.
What is the definition of labour?
Fundally (from the fundus/top) dominant contractions coupled with cervical ripening and effacement (cervix becomes soft, flexible and open).
What are the stages of labour? (x4) !!!
- LATENT PERIOD: this occurs around 8 weeks before labour, and when the uterus begins intermittently and mildly contracting, in preparation for the main event. These uterine contractions are called ‘Braxton Hicks contractions’ or ‘contractures’. 2. CHANGES IN CERVIX AND MYOMETRIUM: describes the onset of uterine contractions associated with dilation of the os uteri aka cervix (from CERVICAL RIPENING (softening) and EFFACEMENT (shortening and thinning of the cervix)). The uterine contractions are coordinated myometrial contractions. 3. DELIVERY OF THE INFANT: The period of expulsive effort, beginning with complete dilation of the cervix and ending with the completed expulsion of the infant. 4. CALLED PLACENTAL STAGE: the period beginning at the expulsion of the infant and ending with the completed expulsion of the placenta and its membranes. Delivery of the placenta is associated with very powerful contractions of the uterus, leading to a rapid decrease in overall size – this is referred to as involution. Once the placenta has been delivered, this involution of the uterus is very important, as this is the primary process through which blood flow through the spiral arteries is stopped.
What hormone mediates uterine contraction after delivery of the placenta?
Oxytocin. Therefore, if contractions do not occur to stop blood loss, oxytocin can be injected to accelerate the process.
What is the physiological mechanism of cervical ripening and dilation? Three mediators?
Requires extensive remodelling (loss) of the extracellular matrix of the cervix so that it turns from rigid to soft (cervical ripening and effacement), mediated by Prostaglandin E2, interleukin-8 and matrix metalloproteinases (MMPs) – from leukocyte recruitment. This is therefore an inflammatory process.
What mediates the myometrium contraction in labour? (x3)
Prostaglandin F2alpha (E2) levels increase from foetal membranes, oxytocin receptor is upregulated, and contraction associated proteins increase.
What mediates the expulsion and rupture of foetal membranes? (x3)
Inflammatory processes in foetal membranes mediated by prostaglandins, interleukins, and MMPs – from leukocyte recruitment.
What transcription factor controls the inflammatory processes associated with cervical ripening and foetal membrane rupture in labour?
NF-kappaB – a pro-inflammatory transcription factor.
What are the possible causes of preterm delivery of a baby? (x4)
□ Intrauterine infection (strongly associated with pre-term labour because infections activate inflammation which mediates labour). □ Intrauterine bleeding. □ Multiple pregnancy. □ Maternal stress.
How is ‘term’ labour controlled? !!!
□ REMEMBER: Labour strongly resembles an inflammatory response in foetal membranes and cervix! □ CRH is made in the placenta and rises in the last three weeks of pregnancy. □ CRH increases amount of ACTH released from the baby’s pituitary gland, which stimulates production of cortisol in foetal adrenal glands. This cortisol goes back to the placenta and has a positive feedback effect on CRH production. □ Adrenal gland also produces steroids which mature foetal lungs. Foetal lungs mature by producing lung surfactant. The surfactant contains platelet-activating factor (PAF). □ Increased CRH and PAF levels stimulates expression of COX-2 which increases production of prostaglandins. CRH and PAF also stimulates production of pro-inflammatory IL-1beta which drives the continued production of molecules required for labour. □ Adrenal glands also stimulated to make precursor for oestrogens which are involved in the production of mediators for uterine contraction. □ Therefore, as the baby matures, there is an increase in the production of PRO-INFLAMMATORY MEDIATORS, which stimulate labour. Production of these mediators only when the baby is mature stimulates labour only when the baby is TERM.
