Birth (Parturition)Three stages of Labour

1. Dilation of the cervix

2. Stage of Expulsion

3. The Afterbirth

• During the final 3 months, uterus undergoes weak irregular contractions

• When they are about 30 min apart this marks the beginning of labour

1st Stage- Dilation of the Cervix

• Onset of labour to complete dilation• 8-9 hrs (1st child) 4hrs (subsequent children)• Waves of contractions from top of uterus down

to cervix (like peristalsis)• With each contraction, muscle fibres of the

uterus shorten and pull on the cervix• This shortens the cervix until it no longer

protrudes into the vagina, and begins to open• Dilation allows foetus to move deeper into the

mothers pelvis

• Cervix is fully dilated at approx 10 cm

• The uterus, cervix and vagina from a single curved passage (birth canal)

• Voluntary contractions of the ab. Muscles aid the uterine contractions

• Full dilation marks the end of this stage

2nd Stage- Stage of Expulsion

• Often begins with breaking of the waters

• Lasts 20 min – 2 hrs

• Contraction of the uterus and abs, push the foetus through the vagina

• Babies head turns towards woman’s back

• Head advances with contraction and retracts in between

• Mothers pulse increases and she usually breaks out in a sweat

• Eventually head stretches the vagina and perineum

• Once emerged the head turns to face the woman’s hip, this allows the shoulders & body to pass through the birth canal

• As foetus passes through the birth canal it’s head may be pushed out of shape due to semi movable joints

• Head resumes normal shape after a few days

• Head first in 90% of births

• Head acts as a wedge

• Foetus may breath before birth is complete

3rd Stage- The Afterbirth

• Baby is still connected to amnion, chorion and placenta, which is still in the uterus

• Umbilical is clamped, tied in 2 places and cut• Arteries & vein retract before or immediately

after the cut• After a few days the chord dries up and the

navel is left

• At birth baby is covered in a waxy material called Vernix

• Vernix protects the babies skin from infection ( most removed)

• Uterus continues to contract, approx 5 min later afterbirth is expelled

• Uterine contractions squeeze shut uterine blood vessels minimising blood loss and blood clots form

• In the past infection was common

• Expulsion of the afterbirth can be sped up by medication