Spontaneous Vaginal Delivery

 

 

Introduction

Labour is a series of repetititive uterine contractions, lasting 30-60 seconds, associated with progressive cervical dilation and effacement of the cervix. Term is 37-42 weeks, with preterm before and postterm after.

Can be associated with "bloody show", diarrhea (because of prostaglandin), or rupture of membranes.

 

Care begins with assessment and admission to hospital. As this can be an uncertain and fearful time, a caring attitude of the admitting health care professional is critical to set the stage for what is to come.

Assessment of progress should be done with a sterile gloved hand. In areas where perinatal infection rates are high, soaking the gloved hand in 0.25% chlorhexidine solution can be helpful.

 

 

Supplies Required

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Evaluating Labour

 

 

As food will not pass through the gut during labour, food should be avoided, especially if general anesthetics are possibly to be used. However, low-fibre, low-fat meals or drinks likely pose little hazard, and may in fact prevent ketoacidosis. (O'Sullivan et al, 2009).

 

The following should be monitored during the first stage:

• pulse, temperature, and blood pressure every 2 hours
• assess frequency, strength, and intensity of uterine contractions
• monitor fetal heart rate every 15 minutes
• assess cervical dilatation every 4 hours to determine progress and descent of presenting part
• discuss ongoing analgesic needs
• determine position of head

 

Progress is again dependent on the three P's:

• power of contractions
• passage
• passenger: flexion or position can be enhanced using manual, vacuum, or forceps technique

 

 

Six Cardinal Mechanisms of Labour

Descent

• occurs prior to onset and then throughout labour, with other mechanisms superimposed on it
• occurs at greater rate during latter part of 1st stage and 2nd stage

Flexion

• present before labour to some degree due to natural muscle tone
• further encouraged during labour by resistance from cervix, walls of pelvis, and pelvic floor
• optimizes presenting diameter of head

Internal Rotation

• head enters transversely and then rotates so that occiput is turned towards symphysis pubis (OA, occiput anterior position)
• 20% of the time, the head rotates OP, occiput posterior, though at least 75% of fetuses will rotate back as labour progresses

Extension

• to follow the path of the vagina, as the head moves under the symphysis it needs to move from flexion to extension
• make sure there's not too much extension
• crowning - when the largest diameter of the head is encircled by the vaginal opening, occurs during extension

External Rotation/Restitution

• the delivered head now rotates back to the transverse position, as it originally was, realigning the head with the back and shoulders

Delivery/Expulsion

• as descent continues, anterior shoulder delivers under the symphysis pubis, followed by the posterior shoulder. The rest of the body quickly follows

 

 

Stage III

• delivery of baby and placenta; duration avg 5-10 min; range 0-30 min
• signs of placental separation:
  • gush of blood from vagina
  • ubbilical cord lengthening
  • fundus of uterus moves up into abdomen
  • uterus becomes firm and globular
• watch closely for postpartum hemorrhage
• inspect cervix, vagina, and perineum for lacerations and repair if necessary
• inspect placenta to ensure complete removal

 

 

 

Used during delivery

IV oxytocin is effective within 30-60 seconds

IM oxytocin is effective in 3-4 minutes.

Its duration of action is 5-15 mins.

hyperstimulation

fetal heart decel

hyponatremia occurs really only after dose of 40 mIU/min

 

 

 

Perinatal Bloodwork

 

 

 

Resources and References

O'Sullivan G et al. 2009. Effect of food intake during labour on obstetric outcome: randomised controlled trial. BMJ. 338:b784