4 million deliveries per year in the US
Highest pregnancy rates seen in 25-29 year old females
Latent
Passage of cervical mucous plug
Slow dilation to 6 cm
Active
Rapid cervical dilation from 6 cm to 10 cm
~8 hours in primiparous and ~5 hours in multiparous
Passage of cervical mucous plug
Slow dilation to 6 cm
Rapid cervical dilation from 6 cm to 10 cm

Cervix fully dilated
Urge to push
Expulsion of infant
~20 - 50 minutes

~20 minutes
>18 minutes increases risk of postpartum hemorrhage with >30 minutes conferring very increased risk
>18 minutes increases risk of postpartum hemorrhage with >30 minutes conferring very increased risk

1st hour after placental delivery
Period of time with highest risk for postpartum hemorrhage
Emergent delivery
IVF maintenance
Umbilical cord prolapse
Resuscitative hysterotomy
Breech delivery
Neonatal resuscitation
Shoulder dystocia
Delayed sequence intubation