1
OB Exam 2
LABOUR AND CHILDBIRTH:INITIATION OF LABOUR
pg.45
It is believed that labor is influenced by: uterine stretch from the fetus and amniotic fluid
volume, progesterone withdrawal to estrogen dominance, increase oxytocin sensitivity, and
increased release of prostaglandins
Estrogen to progesterone
o During the last trimester estrogen increases and progesterone decreases
The number of oxytocin receptors in the uterus increases at the end of pregnancy
Increased levels of estrogen also lead to increased sensitivity to oxytocin
With increasing oxytocin levels in the maternal blood along with increasing fetal cortisol
levels that synthesize prostaglandins, uterine concentrations are initiated
Oxytocin also aids in stimulating prostaglandin synthesis
Prostaglandins lead to additional contractions, cervical softening, gap junction induction,
and myometrial sensitization leading to progressive cervical dilation
Uterine contractions have two main functions: dilate the cervix and to push the fetus
through the birth canal
Signs of Approaching Labor pg. 456
Lightening occurs when the fetal presenting part begins to descend into the true pelvis
o The uterus lowers and moves into a more anterior position
o The woman will usually notice her breathing becomes much easier and there is
decreased gastric reflux
o She may complain of increased pelvic pressure, leg cramping, dependent edema in the
lower legs, low back discomfort, increase in vaginal discharge and urination
o In primiparas, lightening can occur 2 weeks or more before labor beings and in
multiparas, it may not occur until labor
Braxton Hicks Contractions may be experienced throughout the pregnancy
o Felt as tightening or pulling sensation on top of the uterus
o Occur primarily in abdomen and groin and gradually spread downward before
relaxing
o Irregular contractions that can be decreased by walking, voiding, eating, increasing
fluid intake, or changing position
o Usually last about 30 seconds but can last up to 2 minutes
o As birth gets closer, the uterus becomes more sensitive to oxytocin and the
frequency and intensity of these contractions increases
o If the contractions last longer than 30 secs and occur more than 4-6x/hr, the woman
should contact her HCP so she can be evaluated for preterm labor
Backache
Bloody show
, 2
o At the onset of labor or before, the mucous plug that fills the cervical canal is
expelled as a result of cervical softening and increased pressure of the presenting
part
Downloaded by ANTONY KIMANI ()
, 3
o These ruptured capillaries release a small amount of blood that mixes with mucus
resulting in the pink tinged secretions known as the bloody show
Spontaneous Rupture of Membranes
o Rupture of membranes with loss of amniotic fluid prior to onset of
labor premature rupture of membranes (PROM)
o The majority of women will begin labor within 24 hours
o The rupture can result in either a sudden gush or a steady leakage of amniotic fluid
o A continuous supply of amniotic is produced even though some is lost
o After the amniotic sac has ruptured, the barrier to infection is gone and ascending
infection is possible
o There is also a danger of cord prolapse if engagement has not occurred
Increased Energy Level
o Some women have a sudden increase in energy before labor
o Sometimes this is referred to as nesting because the mother will use this time to
prepare for the baby and spend time with other children
o Usually occurs 24-48 hours before the onset of labor
o Thought to be the result of an increase in epinephrine released caused by decreased
progesterone
Weight loss loses 1-3lbs
True vs. False Labor pg. 457
False labor irregular uterine contractions are felt but the cervix is not affected
o False labor, prodromal labor, Braxton Hicks
True labor contractions occurring at regular intervals that increase in frequency,
duration, and intensity
o Bring about progressive cervical dilation and effacement
Example: if a woman comes in and she goes from 2cm to 3 cm then back to 2cm and stays
that way for hours, you would send her home because it’s not progressing
Cervical Dilatations and Effacement
Dilatation is the opening of the cervix
Effacement is the thinning of the cervix
, 4
Downloaded by ANTONY KIMANI ()
OB Exam 2
LABOUR AND CHILDBIRTH:INITIATION OF LABOUR
pg.45
It is believed that labor is influenced by: uterine stretch from the fetus and amniotic fluid
volume, progesterone withdrawal to estrogen dominance, increase oxytocin sensitivity, and
increased release of prostaglandins
Estrogen to progesterone
o During the last trimester estrogen increases and progesterone decreases
The number of oxytocin receptors in the uterus increases at the end of pregnancy
Increased levels of estrogen also lead to increased sensitivity to oxytocin
With increasing oxytocin levels in the maternal blood along with increasing fetal cortisol
levels that synthesize prostaglandins, uterine concentrations are initiated
Oxytocin also aids in stimulating prostaglandin synthesis
Prostaglandins lead to additional contractions, cervical softening, gap junction induction,
and myometrial sensitization leading to progressive cervical dilation
Uterine contractions have two main functions: dilate the cervix and to push the fetus
through the birth canal
Signs of Approaching Labor pg. 456
Lightening occurs when the fetal presenting part begins to descend into the true pelvis
o The uterus lowers and moves into a more anterior position
o The woman will usually notice her breathing becomes much easier and there is
decreased gastric reflux
o She may complain of increased pelvic pressure, leg cramping, dependent edema in the
lower legs, low back discomfort, increase in vaginal discharge and urination
o In primiparas, lightening can occur 2 weeks or more before labor beings and in
multiparas, it may not occur until labor
Braxton Hicks Contractions may be experienced throughout the pregnancy
o Felt as tightening or pulling sensation on top of the uterus
o Occur primarily in abdomen and groin and gradually spread downward before
relaxing
o Irregular contractions that can be decreased by walking, voiding, eating, increasing
fluid intake, or changing position
o Usually last about 30 seconds but can last up to 2 minutes
o As birth gets closer, the uterus becomes more sensitive to oxytocin and the
frequency and intensity of these contractions increases
o If the contractions last longer than 30 secs and occur more than 4-6x/hr, the woman
should contact her HCP so she can be evaluated for preterm labor
Backache
Bloody show
, 2
o At the onset of labor or before, the mucous plug that fills the cervical canal is
expelled as a result of cervical softening and increased pressure of the presenting
part
Downloaded by ANTONY KIMANI ()
, 3
o These ruptured capillaries release a small amount of blood that mixes with mucus
resulting in the pink tinged secretions known as the bloody show
Spontaneous Rupture of Membranes
o Rupture of membranes with loss of amniotic fluid prior to onset of
labor premature rupture of membranes (PROM)
o The majority of women will begin labor within 24 hours
o The rupture can result in either a sudden gush or a steady leakage of amniotic fluid
o A continuous supply of amniotic is produced even though some is lost
o After the amniotic sac has ruptured, the barrier to infection is gone and ascending
infection is possible
o There is also a danger of cord prolapse if engagement has not occurred
Increased Energy Level
o Some women have a sudden increase in energy before labor
o Sometimes this is referred to as nesting because the mother will use this time to
prepare for the baby and spend time with other children
o Usually occurs 24-48 hours before the onset of labor
o Thought to be the result of an increase in epinephrine released caused by decreased
progesterone
Weight loss loses 1-3lbs
True vs. False Labor pg. 457
False labor irregular uterine contractions are felt but the cervix is not affected
o False labor, prodromal labor, Braxton Hicks
True labor contractions occurring at regular intervals that increase in frequency,
duration, and intensity
o Bring about progressive cervical dilation and effacement
Example: if a woman comes in and she goes from 2cm to 3 cm then back to 2cm and stays
that way for hours, you would send her home because it’s not progressing
Cervical Dilatations and Effacement
Dilatation is the opening of the cervix
Effacement is the thinning of the cervix
, 4
Downloaded by ANTONY KIMANI ()
