labour and delivery Flashcards
what is labour?
Presence of regular painful uterine contractions becoming progressively stronger and more frequent, accompanied by effacement (cervix undergoes changes – thin, and has contact with the baby) and progressive dilatation of the cervix and descent of the presenting part
how does labour start?
starst with bloody mucoid show
what is the function of the mucus plug?
seals the uterus to prevent infection getting to the fetus
why does the amniotic sac rupture?
bc the head of the fetus is against the cervix –> as uterus contracts, amniotic fluid is expelled
how should the amniotic fluid look?
should be clear - may contain bits such as dead cells, fetal urine etc.
how does labour end?
Ends with baby coming out along with other products of conception
what are Braxton Hicks contractions?
uncoordinated contractions of the uterus around 6-4 weeks before end of gestation
what causes Braxton Hicks contractions?
progressive hormonal changes - oxytocin from mum and baby, oestrogen, relaxin and prostaglandin
progressive mechanical changes
what does relaxin do?
made by the placenta to relax connective tissue of the cervix and causes softening of the pubic symphysis to allow it to move further apart
what do prostaglandins do?
causes contraction of the uterus
what does progesterone do?
inhibits uterine contractility during pregnancy –> prevents expulsion of fetus prematurely
what does oestrogen do?
increases the degree of uterine contractility –> increases number of gap junctions between adjacent smooth muscle
how do levels and ratio of oestrogen and progesterone change over the course of pregnancy?
secreted in progressively greater quantities throughout pregnancy
Increased ratio of oestrogen to progesterone at 7 months - Oestrogen continues to increase while progesterone stays the same or declines
what is the Ferguson reflex?
positive feedback mechanism involving oxytocin
explain how the ferguson reflex happens
- baby’s head stretches cervix –> feedback on mother’s pituitary
- mother secretes oxytocin
- baby makes own oxytocin
- oxytocin travels to uterine muscle and stimulates contractions –> pushes baby down and stretches cervix
- also stimulates placenta to make prostaglandings
- oestrogen induces more oxytocin receptors
- cycle is repeated until the baby is born
how are abdominal muscles involved in labour and how are they activated?
• Abdominal muscles are activated by neurogenic reflexes to contract and their contraction aids the expulsion of the baby
what effect does baby’s oxytocin have on the mother?
gets across placenta and directly stimulates smooth muscle in the myometrium to contract. Upregulates the oxytocin receptor
how many stages of labour are there?
4
how many stages in the first stage of labour and what are they?
latent phase
active phase
transition phase
how far is the cervix dilated in the latent phase?
0-4cm
what happens during the latent phase of labour?
- Duration not easily determined bc there isn’t much to show for it
- Often long, especially in women having their first baby
- Contractions last 30-60 second and are 5-20 mins apart
how far is the cervix dilated in the active phase?
4-10cm
what happens in the active phase of labour?
- Cervix dilates at the rate of about 0.5 – 1 cm/hour
- May be faster in multiparous women or slower in first
- Average duration of this phase – 12 hrs
- Contractions last 45-60 seconds and are 2-5 mins apart
describe the transition phase contractions?
Transition contractions last 60-90 seconds and are 2-3 mins apart
when does the second stage start?
at full dilation of the cervix - 10cm
what is the second stage of labour?
pushing
describe the contractions in the second phase of labour
o Contractions last 45-90 secs and 3-5 mins apart
what happens in the 3rd stage of labour?
- After baby is delivered, placenta and amniotic membrane need to be delivered
- Usually within 30 mins
what happens in the 4th stage of labour?
• Last from delivery of placenta until postpartum condition of woman stabilises (up to a week afterwards)
o 1-2 hours after delivery
• Uterus will continue to contract which help the uterus to return back to normal size over the next few days.
at what rate does the cervix decrease in size during the 4th stage of labour?
descends 1 cm each day for about 10 days
what is the widest and narrowest part of the pelvis?
Pelvic inlet is the widest bit, ischial spines are narrow
what does left occiput anterior mean?
Means that baby’s head is slightly off centre in the pelvis with back of the head toward the mother’s thigh. Baby is face down when it comes out
what does left occiput transverse mean?
When back of baby’s head points directly at the mother’s thigh
why is left occiput transverse more painful?
bc the head doesnt fit into the bony pelvis as well
what do fetal stations measure?
Ischial spines can be palpated through the skin. Head can be felt and measured in relation to the ischial spines
what is the baseline of the fetal stations?
ischial spines - 0
when is the fetal station negative?
• If the presenting part is higher than the ischial spine the station has a negative number
when is the fetal station positive?
• Positive means that the presenting part has passed the ischial spine
at what fetal station is the outlet?
+4cm
what is cervical ripening?
increased softening, distensibility, (effacement and dilatation of the cervix)
how does cervical ripening occur and why?
• Due to changes in the biomechanical properties of cervical tissue
o Rearrangement and realignment of collagen and an increase in the ground substance when compared early pregnant cervix.
o Allows for a thinner cervix which is more able to dilate
what is cervical ripening under the control of?
o Prostaglandins – produced in uterus o Oestrogens o Progesterone and antiprogesterones o Relaxin – produced by the placenta. Causes softening and thinning of the cervix o Inflammatory mediators o Nitric oxide o Apoptosis
what is the bishops score?
• A method of measuring whether a pregnancy and labour is progressing at a normal rate or if there’s a need to induce
what does the bishops score take into consideration?
Cervix dilation, cervical length, consistency, position and head station
what does a bishop score of less than 5 suggest?
score of 5 or less suggests labour is unlikely to start without induction
what does a bishop score of 9 or more suggest?
indicates that labour will most likely commence spontaneously
what happens during birth?
- engage: baby’s head is engaged
- flex and descent - positive feedback
- full dilation of cervix
- internal rotation of head then extension
- external rotation so the shoulders can come out
- expulsion
- cord is tied off
- placenta needs to be removed
