Induction of Labour

Updated : September 24, 2024

Induction of labour is an obstetric intervention that is very common and artificially initiates the process of labor onset. Sice 1990, the rates of induction have almost doubled. There exists a wide varaiation in rates of IOL globally, which can be attributed to variability in guidelines and lack of consensus on clinical practice guidelines regarding IOL. Estimating the proportion of neonates who are born with IOL nowadays would be about 25% across high-income countries. The percentage of these across low and middle-income countries is geneally much lower.

There are indications depending on the medical and obstetrical history of patient regarding early term, late-term, post- term, and late preterm delivery. IOL is done when it is believed that the chances for the fetus and or mother will be better given that the pregnancy will otherwise be allowed to proceed until labor begins naturally, a technique referred to as expectant management. The recommendadtion of ACOG (American College of Obstetricians and Gynaecologists) for the timing is well documented and extensive, and the following are the most common clinical indicators of delivery:

Oloigohydraminous at 36 0/7- 37 6/7 weeks of gestation.
There seemed to be restriction to fetal intrauterine growth with no abnormal Doppler in the pregnancy and the timing for this was between 38 0/7 and 39 6/7 weeks.
Intrauterine growth retardation in the fetus with no flow velocity in end diastole, time of examination was 34 weeks gestation zero days.
Intrauterine growth restriction characterized by the presence of reversed end-diastolic flow and the timing was done at 32 0/7 weeks of pregnancy.
In case if patient was not on antihypertensive therapy, was diagnosed with chronic hypertension, and the timing was between 38 0/7 to 39 6/7 weeks of gestation.
Gestational hypertesnion at the age of 37 0/7 weeks of gestation or at the time of diagnosis if before thus.
Severe preeclampsia with features of severe maternal end organ dysfunction or uncomplicated preeclampsia at 34 0/7 weeks gestation or if diagnosedd earlier, at the time of diagnosis.
GDM (gestational diabetes), exercise, or diet, at the gestational age of 39 0/7- 40 6/7 weeks.
PPROM (preterm prelabor rupture of membranes) at a gestational period of 34 0/7 weeks or at the time of diagnosis if diagnosed later, Late- term with the timing at 41 0/7- 41 6/7 weeks of gestation.
Chorioaminonitis
IUFD (intrauterine fetal demise)
Abruptio placentae

Induction of labor may also be indicated in cases of distance from hospital, psychosocial indications, or risk of rapid labor. In these cases, the presence of maturity of fetal lung should be documented. Availability of a mature fetal lung test result in the absence of appropriate clinical circumastances is not an indication for delivery before 39 weeks of gestation.

The following are the contraindications for these procedures:

Transverse fetal presenttaion
Active herpes infection
Umbilical cord prolapse
History of previou classical C-section
Placenta previa or Vasa previa
History of myoectomy that breached endometrial cavity

Induction of labor is a medical procedure that stimulates uterine contractions before spontanoeus labor, often due to maternal or fetal health concerns. Key outcomes include increased likelihood of vaginal delivery, risk of Cesearean section, shorter duration of labor, increased medical interventions, infectin risk, urinary hypersimulation, and postpartum hemorrhage. Fetal outcomes include improved health, increased risk of prematurity, respiratpry issues, NICU admission, and birth trauma. Inductions at or after 39 weeks are associated with better outcomes for both motehr and baby, with a lower risk of C- section. Indications for inducion include post-term pregnancy prelabor rupture of memebranes, maternal health conditions, fetal health concerns, preeclampsia, and chorioamnionitis. The ACOG recommedns that elective inductions noyt be performed before 39 weeks unless medically indicated.

There are two main ways of conducting labour, i.e., pharmaoclogical and mechanical. Cervical ripening agents are primarily used when the Bishop score is unfavorable, less than eight. A double- balloon device or a foley catheter, such as a Cook catheter, is introduced via the endocervical canal for mechanical cervical ripening. Synthetic dilators, Osmotic dilators, and Laminaria are also used in cervical ripening and are introduced into the cervical os.

The pharmacological methods of laboir induction include oxytocin and synthetic prostaglandins. Prostaglanidns are indicated in the ripening o fteh cervix, while misoprostol- prostaglandin E1 and dinoprostone-prostaglandin E2 are used in different disages and via different routes. However, prostaglandins should be used cautiously in women who have had a low transverse cesarean section due to the risk of rupture of the uterus. Oxytocin is given intravenously in different doses.

The artificial membrane rupture, also called as Amniotomy, can be combined with pharmacological or mechanical methods of induction.

Patient preparation

The Bishop scoring system evluates the cervix during IOL, with a favourable score of eight or more likely to result in a vaginal delivery. Helathcare providers should review this information with pregnant women to help them understand the process. Before starting IOL, all pregnant women shoul dhave consented and understand all benefits, fetal and maternal risks, and alternatives for this process. Risks of IOL include the need to perform a C-section, an opertaive vaginal delivery, tracing non- reassuring fetal heart rate, postpartum hemorrhage and chorioamnionitis.

During the consent process and while preparing women for IOL, it is encourged to review different methods of inducing labor. A 2016 randomized control trial found that a combination with misoprostol or a Foley with syntocinonin, had a faster median time to delivery compared to those who received only Foley catheter or misoprostol.

Cesarean section rates and indications for perfoming CS should be reviewed with all pregnant women before consenting to IOL. The ARRIVE trial in the United States demonstratedd a significanlty lower CS rate in the induction group and statistically lower adverse effects.

Patient position

The patient’s position during induction of labor (IOL) is crucial for comfort and effectiveness of procedures. Common positions that are also used include the lithotomy position, which offers good access for catheter insertion and administration of an agent, such as misoprostol or dinoprostone, the semi-Fowler’s more tolerable for longer times in positions that are moderately comfortable, and side-lying for oxytocin administration.

Upright or mobile positions are encouraged during the active phase of labour to aid in labor progression and fetal descent. The lithotomy position is similar to the cervical ripening and can also be used in amniotomy. Regular changes of position with the use of pillows or supports can enhance comfort.

Induction of labor takes into consideration various factors so that the process is likely to result in optimum outcomes on the part of both the mother and fetus. Maternal indications include maternal health conditions, fetal health concerns, and post-term pregnancy. Assessment of the cervix using using the Bishop score measures the degree of readiness for labour. Unfavourable cervices require cervical ripening agents, while more favourable cervices require direct methods of induction. In general, induction is recommended at or beyond 39 weeks, unless there are compelling medical reasons to do it earlier. Methods include mechanical methods, like foley catheeters, pharmacological methods like prostaglandins, or amniotomy. Maternal preference and informed consent are very important, as well as regard for hospital protocols and resources. Monitoring the contractions and overall well being. Labour management should include labor progress, assessment of fetal and maternal well-being, and planning for possible complications by healthcare providers.

The process of induction for cervical dialtion involves mechanical dilation using a double-balloon catheter, laminaria, or a Foley-catheter. The balloon is inflated with normal saline to exert pressure on the internal os, resulting in faster induction and lessneed for syntocinon. The devices are typically removed when 3cm to 4cm of cervical dialtion is achieved. Misoprostol is used for cervical ripening, with doses ranging from 25 to 50 mcg. Prostaglandins are also used, with higher doses recommended for intrauterine fetal demise. Syntocinon is administered intravenously, with dosing titrated to cause contractions. Amniotomy with an “amnio hook” can be performed at any time the cervix is dilated, considering factors like head engagement, pain level, fetal station, and patient preference.

Complications

As labor is increasingly induced, the safety of induction methods is increasingly important. Mechanical methods, which are wiely available, low-cost, with little side effects, amy be safer for the baby. However, pharmacological methods can cause complications like postaprtum hemorrhage, uterine tachysystole, and intrapartum vaginal bleeding.

Induction of Labor – StatPearls – NCBI Bookshelf (nih.gov)