(10.1) Birth Flashcards
State the aim of each stage of birth giving.
- First: Creation of birth canal
- Second: Expulsion of foetus
- Third: Expulsion of placenta
How is the birth canal enlarged during pregnancy?
- Oestrogen > Progesterone at end of pregnancy -> Endometrium produces Prostaglandin
- Prostaglandin -> + [Ca2+]i smooth muscle cells -> + force of Myometrium contraction
- Prostaglandin -> Ripening -> + Cervix stretchiness
- Pacemakers -> contraction -> Myometrium pushes foetal head -> Cervix stretches
- Stretched Cervix -> Ferguson feedback -> + Hypothalamus -> + Posterior Pituitary -> + Oxytonin
- Oxytonin -> - Action Potential Threshold -> + frequency of Myometrium contraction
What type of molecule is Prostaglandin? Where is it produced? What stimulates its production?
- Biological active lipid
- Endometrium
- Oestrogen > Progesterone at late pregnancy
Which types of Prostaglandin play major roles at aiding labouring? What are their main actions?
- PG E2 & F2x
- [Ca2+]i smooth muscle cells -> + force of Myometrium contraction
- Ripening of Cervix -> + stretchiness
How is the production of Oxytonin stimulated? Where is it produced?
- Ferguson Reflex: +ve feedback from stretched cervix -> Hypothalamus
- Produced by Posterior Pituitary Gland
How is the Amniotic Fluid released at birth?
Stretched Cervix -> raptures Fetal Membrane -> Release
What factors determine the maximum size of birth canal except from the expansion of soft tissues.
- Softening of ligaments by Progesterone
- Pelvic Inlet: 10.5cm, antero-postrior shorter
- Pelvic Cavity: 12cm, round
- Pelvic Outlet: 11cm, medial-lateral shorter
Briefly describe the common positional changes of the foetus during labouring.
- Flexion of head ~9.5cm & Rotation of head
- Head stretches vagina & perineum (risk of tearing)
- Delivery of head & Rotation of shoulder
- Delivery of shoulder & the rest follows
Describe the contraction of Uterus, how it aids the expulsion of foetus?
Brachystasis = relaxation less than contraction -> shortening of smooth muscle fibres -> pushes presenting part of foetus down to cervix
Suggest causes of failure in labouring.
- Inadequate contraction of myometrium
- Inadequate birth canal e.g. bony pelvis / rigid peritoneum
- Foetus too big / Fetal breech position
How might you give the mother to help her uterus to contract?
Prostaglandin & Oxytotic drugs
How is the Placenta expelled?
- Contraction of uterine -> shortened fibres -> expels
Expulsion of Placenta may cause severe haemorrhage, how is it prevented? What is the normal amount of blood flow to Placenta?
- Persist contraction of Uterus 5-15 mins after birth -> compress blood vessels
- 500-800ml /min (10-15% of cardiac output)
What is the first line treatment of postpartum haemorrhage?
Oxytotic drugs -> + uterine contraction -> compress blood vessels
How can you monitor the state of the foetus during labouring?
Fetal scalp electrode
What is C section? Briefly describe how it is performed. In what situation is it normally performed?
- Cesarean Section
- Suprapubic Incision at Linia alba & Anterior Rectus Sheath -> retracted Rectus muscles laterally
- Placenta Previa: implantaion at lower uterus, over cervix
What is the full name of C section? State two forms of operative delivery other than C section.
- Cesarean Section
- Forceps delivery
- Vacuum Extraction
What term is used to describe birth that occurs at
Spontaneous abortion = not ture abortion, but unlikely that the foetus would survive
When is the foetus normally born? What is it called if born before that?
- 37-42 weeks
- Pre-term
Which hormone helps to increase the size of pelvic inlet before earlier in pregnancy and how?
- Progesterone
- Softens Sacrotuberous & Sacrospinous ligaments
Describe the contraction of myometrium before labouring, in early and late pregnancy. What are their purposes?
- Early: frequent, less forceful (not noticeable)
- Late: less frequent, forceful (may cause pain, aka Braxton Hicks)
- Practice contraction to help with cervical effacement etc
Which hormone inhibits the uterine to contract?
Progesterone
Why do you get Lordosis towards end of pregnancy?
- Foetal weight
- Relaxins + other hormones -> stretchy ligaments including vertebral ligaments
What anatomical landmark is used to access foetal head position in the birth canal?
Foetal frontanelles
What is Epidural anaesthesia?
- Insertion from the back
- Blocking T9-S4
What are the boundaries of the Pelvic Inlet?
- Pubic symphysis & Superior pubic rami anteriorly
- Ilio-pectineal line laterally
- Sacral promontory posteriorly
