**4. Outcome of labor induction**

Induction of labor (IOL) is done with the main aim of initiating labor without its true time to save the health of the mother and unborn fetus and minimizing severe obstetric complications related to unnecessary cesarean section [2]. However, this artificial initiation of labor is not without its own risks and is associated with adverse maternal and perinatal outcomes such as postpartum hemorrhage [18], hyperstimulation of the uterus that can result in uterine rupture, chorioamnionitis, endometritis [9], fetal hypoxia, maternal fluid intoxication [19], stillbirth [5], severe birth asphyxia [20], increased medical interventions, increased hospital costs [3], abnormal fetal heart rate patterns, maternal water intoxication if oxytocin is used, delivery of a preterm infant due to incorrect estimation of dates, and cord prolapse [8, 21]. Induction of labor also influences the woman's childbirth experience, and it has more

discomfort and pain. For these abovementioned reasons before starting IOL, all pregnant women should have consented to the process and understand all benefits, maternal and fetal risks, and alternatives to IOL. Furthermore, reviewing indications for cesarean section, operative vaginal delivery should be discussed prior to offering IOL.

Furthermore, even after induction is done knowing all these risks, it might not achieve the intended labor and vaginal birth, and it may result in failed induction. However, while there is a well-accepted definition of IOL, the definition of a successful or failed induction of labor (FIOL) is less certain [22–24]. Most studies define FIOL as an inability to achieve vaginal delivery or birth through cesarean section (CS) [25– 27]. Nevertheless, others suggest a variety of criteria such as mode of delivery (vaginal versus cesarean) and certain time intervals within which active phase of labor is achieved or adequate number of uterine contractions is achieved for diagnosing FIOL [3, 28, 29]. Some protocols also define it as failure to achieve regular (e.g., every 3 min) uterine contractions and cervical change after at least 6–8 h of the maintenance dose of oxytocin administration, with artificial rupture of membranes [30]. American College of Obstetricians and Gynecologists (ACOG) recommends diagnosing and doing cesarean section for a failed IOL if vaginal delivery is not achieved for 12– 18 hours after administrating oxytocin and performing amniotomy [16].

### **5. Pre-induction assessment**

As mentioned before, although the goal of labor induction is to achieve a successful vaginal delivery, induction exposes women to a higher risk of a CS and other complications than spontaneous labor. To minimize these risks and complications, thorough examination of the maternal and fetal condition is required before undertaking labor induction [31]. Indications and contraindications for induction should be well reviewed and discussed with the patient along with the alternatives, risks, and benefits of labor induction. Confirmation of gestational age and evaluation of fetal lung maturity should also be performed. Labor induction should be performed at a location where personnel who are familiar with the process and its potential complications are available. Availability of uterine activity and electronic fetal monitoring (EFM) is also recommended for any mothers receiving uterotonic medications [2, 32].

In spite of this, existing evidence points out that the failure rate of IOL is increasing worldwide [33, 34]. As a result, a variety of maternal and fetal factors as well as screening tests have been suggested to predict labor induction success. Maternal factors include: parity (prior vaginal delivery), body mass index (BMI), and maternal age. Fetal factors include: estimated fetal weight, gestational age, and fetal presentation. Clinical pelvimetry, transvaginal ultrasound (TVUS) assessment of the cervix, and biochemical markers [including fetal fibronectin (fFN) and insulin-like growth factor binding protein-1 (IGFBP-1) [31, 35, 36]]. The other main factor that determines the success of induction is the status of the cervix (Bishop score) before induction is commenced. For this reason, before undertaking induction of labor, pre-induction assessment for the fulfillment of the prerequisites, particularly bishop score, is required.

#### **5.1 Cervical ripening and Bishop score**

One of the main factor that needs to be examined and documented before labor induction is cervical status using Bishop score, which is one of the most important

factors for predicting the likelihood of success in labor induction [31, 37]. The Bishop score is a pre-labor pelvic scoring system that is commonly used in clinical practice as a predictor of the success for induction [38].

It was first developed in the 1960s by Dr. Edward Bishop. Initially, the system tabulates a score based on 5 determinants (the station of the presenting part and four characteristics of the cervix) [39]:

1.Dilation,

2.Effacement,

3.Consistency, and

4.Position.

Each component attributes a value from 0 to 2 or 3 points each (for a maximum score of 13). However, in 1966, Burnett modified the scoring scheme so that each variable was assigned a maximum value of 2 points (for a maximum score of 10) [40].

If the Bishop score is high, which is often considered to be a score of 8 or above, the likelihood of vaginal delivery is similar whether labor is spontaneous or induced [41]. In contrast, a low Bishop score, which is a score of 5 or less, is considered to be unfavorable, and if an induction is indicated, cervical ripening agents may be utilized [37, 38, 41]. A score from 6 to 7 is considered to be intermediate [30, 32].

Several studies have shown an increased rate of failed induction and CS when women are induced with an unfavorable cervix (12–16). Xenakis's prospective study of 597 pregnancies stratified found the highest risk of CS and failed induction in those with low Bishop scores [25].

### **6. Method of induction and cervical ripening**

When deciding undertaking induction of labor after fulfilling the requirements for induction, the next step will be deciding which methods will be used to achieve it. Depending on different conditions, there are different types of induction methods that could be utilized. These methods are grouped as medical and surgical. Medical method of induction are methods that use pharmacological products to achieve artificial labor initiation, while surgical methods use non-pharmacological methods [2, 3, 31, 32].

#### **6.1 Medical method**

#### *6.1.1 Prostaglandins*

Prostaglandins are a group of physiologically active endogenous compounds found in the myometrium, decidua, and fetal membranes during pregnancy. Its administration results in the dissolution of collagen bundles and an increase in submucosal water content of the cervix, resulting in changes of cervical connective tissue that are similar to those observed in early labor [2, 3, 31, 42]. It also causes direct stimulation of myometrial contraction by stimulating receptors in the uterus [38].

PG formulations analogues were have been used since they were first synthesized in the laboratory in 1968. They could be used for both induction and as a cervical ripening agent, but they are more effective when used for cervical ripening with increased success of vaginal delivery rates within 24. However, the overall risk of cesarean section will not change, and they have an increased risk of uterine hyperstimulation and FHR changes [43].

Although they can be given intravenously and by oral routes, local administration of PGs in the vagina or the endocervix is the route of choice because of fewer side effects and acceptable clinical response [31].

There are different types and preparations of PG available for both induction of labor and cervical ripening.

**Prostaglandin E2** (PGE2): Also known by the name dinoprostone, it is a naturally occurring compound involved in promoting labor, by causing contractions in the myometrium via direct stimulation and softening and dilatation in the cervix, dissolving the collagen structural network of the cervix [38, 42].

Prostaglandin E2 is available in 3 different preparations as a cervical ripening agent:

• Intravaginal 1 mg and 2 mg gel (Prostin), and
