- Onset of labor is due to oxytocin stimulation, estrogen stimulation, progesterone withdrawal, and prostaglandin secretion, fetal secretion of cortical steroids, aging of placenta, and increasing uterine pressure.
- Prodromes to labor are:
- Lightening - the settling of the fetal head into the inlet of the true pelvis; may not occur in multiparas.
- Show - the release of cervical plugs consisting of mucous, blood streaked vaginal discharge.
- Spontaneous Rupture of membrane - sudden gush of clear fluid from the vagina.
- Excess energy - "nesting instinct" feeling of extremely energetic.
- Braxton Hick's contractions increased.
- Loss of 1-3 lbs from water loss resulting from fluid shifts produced by changes in progesterone and estrogen levels.
- Uterine contraction - true labor contractions starts at the back and sweep across the abdomen, increasing in intensity and frequency.
