Physiology of labor. Anesthesia in labor
Lecture by assist.prof. BerbetsAndriy
LABOR–is the physiology process whereby regular uterine activity causes progressive cervical dilatation and usually results in delivery of the fetus,
after 22 weeks of pregnancy
Labor is a physiologic process that permits
a series of extensive physiologic changes
in the mother to allow for the delivery of her fetusthrough the birth canal.
It is defined as progressive cervical effacement, dilatation, or both,-resulting from regular uterine contractions that occur at least every 5 minutes and last 30-60 seconds.
Classification of labor
PRETERM LABOR– delivery the fetusfrom the cavity of uterus in 22-36 weeks of pregnancy.
TERM LABOR- delivery the fetusfrom the cavity of uterus in 37-42 weeks of pregnancy.
Delayed labor- delivery the fetusfrom the cavity of uterus after 42 weeks of pregnancy.
Theories, which explain the mechanism of birth beginning
Forerunners of labor
The bottom of uterus is lowering
Insertion of pre-lying part
Krestellers cork is going away.
Reductions of woman’s weight.
Irregular muscular contractions of uterus.
Maturity of uterus’s neck
0-2 points – uterus’ cervix is “immature”
3-4 points – cervix is “mature but not enougph”
5-8 points– cervix is “mature”
І stage (cervical) – dilatation of the cervix(maximally 15hrs.)
ІІ stage (pelvic) – starts from complete dilatation of cervix to the delivery of baby (1-2 hrs.).
ІІІ stage(placental)- starts from the birth of baby till delivery of the placenta. (5-20 min.).
Uterine contractions –regular contractions of uterine musculature. Typically, contractions occur every 5-10 minutes and last for 20-25 seconds in the onset of labor. As labor pregresses, the contractions become more frequent, more intense, and last longer.
Characteristics of uterine contractions
Tonus – minimal pressure between contractions – 10-12 mm Hg.
Intensivity – difference between amplitude and basal tonus of uterus30-50-70mm Hg.
Frequency per 10 min – 3-4 за 10 min.
Duration – 35 - 93 sec.
Rhythm - intervals between contractions – equal.
Activity = intensivityхfrequency per 10 min = 280-340 Montevideo units
Bearing-down efforts (or pushing)
Is the periodic contractions of diaphragm, pelvic floor muscles and front abdominal which increase the force of uterine contractions.
They are started after complete cervix dilation, when the fetal head descends to the pelvic cavity.