Parturition

Question 1

Labour

Answer 1

Physiological process by which foetus, placenta and membranes are expelled through the birth canal after viability of the foetus (22 weeks gestation). Characterised by regular and painful uterine contractions with cervical changes (effacement and dilatation) that concludes in progressive labour.

Question 2

Physiology of Labour

Answer 2

• Corticotrophin-releasing hormone (CRH) from the foetal hypothalamus stimulates release of Adrenocorticotropic Hormone (ACTH) from the foetal pituitary. This acts on the foetal adrenal gland which releases cortisol to act on the placenta and secrete oestrogens.
• When cortisol binds to the receptors in the placenta, it causes an increase in interleukins 1, 6 and 8, decrease in progesterone, increase in oestrogen, increase in prostaglandins and increase in oxytocin. It also causes a release of CRH which acts on the foetal hypothalamus, creating a loop.
• Meanwhile in the mother, the oxytocin production leads to increase in myometrial receptors (prostaglandins and oxytocin), increase in gap junction, increase in decidual prostaglandin F2 and increase stretch receptor number and sensitivity. Leads to uterine contractions and labour.

Question 3

Preterm Gestation Period

Answer 3

24-37 weeks gestation

Question 4

Term Gestational Period

Answer 4

37-42 weeks gestation

Question 5

Post term Gestational Periods

Answer 5

after 42 weeks gestation

Question 6

Estimated Date of Delivery

Answer 6

• dates or scan (Last menstrual period (first day of last period) + 9 months + 7 days)
• 280 days (40 weeks)

Question 7

Fundal Height

Answer 7

Fundal height is measured in cm from the pubic crest to the top most portion of the uterus. After 20 weeks, it often matches the number of weeks you have been pregnant.

Question 8

Foetal Lie/Presentations

Answer 8

• Longitudinal Lie - Vertex or Breech presentation
• Oblique lie
• Transverse lie - shoulder presentation
• Abnormal presentations include face, brow, breech and shoulder.
• Cephalic lie - most normal presentation with occiput presenting first at pelvis.

Question 9

Diagnosis of Labour

Answer 9

• History - labour pains, show, sudden loss of fluid from vagina.
• Abdo exam - uterine contractions: frequency (3/10), duration (40-60s), severity (pressure >80mmHg).
• Pelvic exam - cervical dilatation, effacement, consistency, position, level of presenting part.

Question 10

Stages of Labour

Answer 10

• 0 - Quiescent uterus - maintained by progesterone and relaxin - inhibitors: progesterone, prostacyclin, relaxin, nitric oxide, parathyroid hormone-related peptide (corticotropin-releasing hormone and human placental lactogen).
• 1 - Uterine ‘awakening’, initiation of parturition, extending to complete cervical dilatation - increase in gap junction connectivity (prostaglandins), increase in oxytocin receptor numbers (oestrogen) - uterotropins: oestrogen (progesterone, prostaglandins, CRH).
• 2 - Active labour, from complete cervical dilatation to delivery - oxytocin release triggered by the Ferguson Reflex, prostaglandins - Uterotonins: oxytocin and prostaglandins
• 3 - From delivery to the expulsion of the placenta and the final uterine contractions - involution: oxytocin and thrombin.

Question 11

Cervical Ripening

Answer 11

• Effacement - shortening and thinning of a cervix to get ready for childbirth and allow it to happen.

Question 12

Positive Feedback Loop of Oxytocin during Labour

Answer 12

Head of baby pushes against cervix > nerve impulses from cervix transmitted to brain > brain stimulates pituitary gland to secrete oxytocin > oxytocin carried in bloodstream to uterus > oxytocin stimulates uterine contractions and pushes baby towards cervix > repeat.

Question 13

Uterine Contractions

Answer 13

• Prostaglandins
• Oxytocin
• Relaxin
• Stretch Response

Question 14

Oxytocic Drugs

Answer 14

• Promote uterine contractions
• Induction of augmentation of labour
• Active management of labour
• Treatment of uterine atony and postpartum haemorrhage.

Question 15

1st Stage of Labour

Answer 15

• Latent phase - under 4cm. ~20hrs. Irregular contractions - every 5-30mins for ~30s.
• Active phase - 4cm-10cm (10cm is full dilatation), rupture of membranes. Regular contractions every 3-5mins which last 1+min (4-6cm) and then progress to intense contractions (6-10cm) which occur every 0.5-2mins and last 60-90 secs. They can overlap. Rupture of membranes e.g. rupture of amniotic sac.

Question 16

2nd Stage of Labour

Answer 16

• 3 P’s
• Flexion - uterine contractions push the foetus downwards, while the cervix resist to this change resulting in increased flexion of the head. (Normally fully flexed - chin on chest, rounded back, flexed arms and legs).
• Foetal Stations - foetal presenting part in relation to mother’s ischial spine. -5 station = pelvic inlet. Station 0 = ischial spine (engagement). Flexion then occurs, then internal rotation where the foetal shoulders internally rotate 45 degrees. Station 4 = where there is extension of the head when passing under pubis symphysis. Station 5 = emerge from vagina (restitution - head externally rotatesso shoulders can pass through the pelvic outlet and under the pubis symphysis). Expulsion - anterior shoulder slips under pubic symphysis followed by posterior shoulder followed by rest of body.

Question 17

Episiotomy

Answer 17

Surgical cut made during childbirth to aid a difficult birth and prevent rupture of tissues. Medio-lateral or midline.

Question 18

3rd Stage of Labour

Answer 18

• Delivery of the placenta. Uterus contracts firmly and the placenta starts to separate from the uterine wall and carefully removed to make sure there are no placental remnants left in the uterus.
• Signs of placental separation include lengthening of cord, gush of blood, uterus becomes hard, mobilde from side to side and height rises to umbilicus.

Question 19

Intrapartum Monitoring

Answer 19

• Mother - contractions, cervix dilation, vital signs, drugs given, descent
• Foetal - Pinnard stethoscope, doppler foetal heart rate, CardioTocoGram (CTG)

Question 20

Foetal Pole

Answer 20

The fetal pole is the first direct imaging manifestation of the fetus and is seen as a thickening on the margin of the yolk sac during early pregnancy. It is often used synonymously with the term “embryo”.

Question 21

3 P’s of Childbirth

Answer 21

• Power - forceful strength of contractions
• Pelvis/Passage - birth canal anatomy including size and shape of woman’s bony pelvis and resistance of soft tissue.
• Passenger - the baby, particularly its lie and presentation.

There are 2 more P’s which have been introduced but not mentioned in the lecture - Psyche (women’s expectations of the birthing process and how anxiety can lengthen labour) and Preparation.