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Labor Induction

¢Â Labor induction
1. Indication
: Membrane rupture without spontaneous onset of labor
: Maternal hypertension
: Nonreassuring fetal status
: Post-term gestation
* Relative indications
: History of rapid labor and/or Distant residence from the obstetrical facility

2. Contraindication
1) Uterine contraindication : prior disruption (e.g. classical incision or uterine surgery), placenta previa
2) Fetal contraindication : macrosomia, some fetal anomaly (e.g. hydrocephalus, malpresentations)
3) Maternal contraindication : related to maternal size, pelvic anatomy, and selected medical condition (e.g. active genital herpes)

3. Complications
: ¡èincidence of chorioamnionitis and cesarean delivery

4. Preinduction cervical ripening
=> Bishop score

* ¡Ã9 : usually successful in the active labor induction
* ¡Â4 : unfavorable cervix

1) Pharmacological techniques
(1) Prostaglandin E2 (dinoprostone)
: 50%Á¤µµ 24hr À̳»¿¡ active labor µé¾î°¨
: indication - Bishop score ¡Â 4
: PGE2Åõ¿©¿Í oxytocin½ÃÀÛ °£ÀÇ optimal intervalÀº Á¤ÇØÁöÁö ¾Ê¾ÒÁö¸¸, PGE2 Åõ¿©ÈÄ 6~12hrÀÌÈÄ¿¡ oxytocin Åõ¿©Çϱ⸦ ±ÇÀå
: side effects
- uterine hyperstimulation
; ¡Ã6 contractions in 10 minutes for a total of 20 minutes
: 1% for intracervical gel(0.5mg), 5% for intravagnial gel (2-to 5-mg)
: º¸Åë Åõ¿© ÈÄ 1hr³»¿¡ ¹ß»ý
- fever, vomiting, diarrhea : negligible in low dose





(2) Prostaglandin E1 (misoprostol ; Cytotec)
: vaginal°ú oral Åõ¿©ÀÇ È¿°ú´Â ºñ½Á
- vaginal misoprostol
; 25 §¶ q 3-6hr
: uterine rupture in women with prior uterine surgery ¹ß»ý°¡´É(6%)
- oral misoprostol
: 100 §¶ oral dose = 25§¶ vaginal dose

2) Mechanical techniques
(1) Balloon catheter : infusion of extra-amnionic normal saline
(2) Hygroscopic cervical dilators : laminaria
(3) Membrane stripping
: inserting the index finger as far through the internal os as possible and rotating twice through 360¡Æto separate the membranes from the lower segment
: ¨ø°¡ 72hr³»¿¡ spontaneous labor¿¡ µé¾î°£´Ù.
: ROM, infection, bleedingÀÇ risk´Â Áõ°¡ÇÏÁö ¾Ê´Â´Ù.

¡Ø °¢ techniques°£¿¡ ºñ±³ study´Â Àû°í ¾î¶² ¹æ¹ýÀ̵çÁö benefitÀº ÀÖ´Ù.

5. Labor induction and augmentation
=> Oxytocin
1) Definition
(1) Induction : stimulation of contractions before the spontaneous onset of labor, with or without ruptured membranes
(2) Augmentation : stimulation of spontaneous contraction that are considered inadequate because of failure of progressive dilatation and descent

2) Techniques for IV oxytocin
* Goal : uterine activity that is sufficient to produce cervical change and fetal descent
: avoiding uterine hyperstimulation and/or nonreassuring fetal status
- Contraction >5 in a 10-minute period or 7 in a 15-minute period
=> Continuous contraction monitoring ÇÊ¿ä
- Hyperstimulation ¹ß»ý½Ã, half-life°¡ 5ºÐ À̹ǷΠÅõ¿© Áß´ÜÇϰí ÁöÄѺ¸¸é µÈ´Ù.
- Dose regimen

- Risks vs Benefits
: uterine rupture - ±Ù·¡¿¡´Â µå¹°Áö¸¸, uterine surgery¸¦ ¹Þ¾Ò´ø °æ¿ì ¹ß»ýÇÒ ¼ö ÀÖ´Ù
: antidiuretic effect - amino-acid homology similar to arginine vasopressin
- water intoxication¿¡ ÁÖÀÇ


- Uterine contraction pressure
: cervical change¾øÀ» ¶§ oxytocin stimulationÀ¸·Î 2½Ã°£µ¿¾È 200 Montevideo unitÀÌ»óÀÇ contraction ¹ß»ý½Ã¿¡´Â arrest¸¦ Áø´ÜÇÒ ¼ö ÀÖ´Ù.

3) Amniotomy (= artificial rupture of the membranes)
=> cord prolapse ÁÖÀÇÇϰí fetal heart rate monitoringÀ» Çϸ鼭 ½ÃÇàÇÏ¿©¾ß ÇÑ´Ù.
(1) Elective amniotomy
: AROM with the intention accelerating labor
: 5cm Á¤µµÀÇ cervical dilatation »óÅ¿¡¼­ amniotomy¸¦ ½ÃÇàÇϸé spontaneous labor 1-2½Ã°£ ´ÜÃà
(2) Amniotomy induction
: amniotomy alone or combined with oxytocin > oxytocin alone
: early amniotomy°¡ labor¸¦ ´õ ´ÜÃà½Ãų ¼ö ÀÖÁö¸¸, chorioamnionitis(23%), cord compression(12%)ÀÇ ¹ß»ý °¡´É¼ºÀÌ ³ô´Ù.
(3) Amniotomy augmentation
: induction°ú ¸¶Âù°¡Áö·Î labor arrest¿¡¼­ oxytocin°ú ÇÔ²² labor ½Ã°£À» ´ÜÃà½ÃŰ´Â È¿°ú°¡ ÀÖÁö¸¸, chorioamnionitisÀÇ À§Çèµµ°¡ Áõ°¡ÇÑ´Ù.