Induction in special situations
Previous caesarean section
Induction of labour in the setting of a previous uterine scar is not contraindicated but comes with increased risks. The main risk is uterine scar rupture, which brings with it high rates of morbidity and mortality for both mother and fetus.
The risk of uterine rupture is approximately 0.5% for women in spontaneous labour or when induced using mechanical methods (49-51). This risk increases to approximately 0.77% if induced with oxytocin alone or around 1% with prostaglandins (32). This risk is not increased in women who have also had a previous vaginal delivery, regardless of the method of induction. Using an intrauterine pressure catheter does not decrease the risk of rupture. According to the 2013 Cochrane review on induction with a previous caesarean section, there is insufficient evidence to recommend one agent over another for induction in this situation (52). Successful vaginal delivery in women undergoing a trial of labour after caesarean section is reduced from approximately 70% in those in spontaneous labour to 50% in women undergoing induction (49- 51). In conclusion, induction of labour with a prior caesarean section is not contraindicated, but carries markedly increased risks and so requires careful prior discussion with the woman.Intrauterine fetal death
IUFD rates vary throughout the world from around 5-6:1000 births in high-income countries to 30-40:1000 births in low- income countries (53). The causes are myriad and addressed in other chapters of this textbook. As discussed previously, the NICE guideline states that in the event of an IUFD when the mother is stable, it is suitable to offer expectant management versus immediate induction of labour. Since most women will deliver within 3 weeks of the fetal demise, this is a reasonable time period for expectant management as long as the mother continues to be stable.
The delivery method depends upon the gestational age, maternal preference, and maternal history of prior uterine scar. Throughout most of the second trimester a dilation and evacuation procedure may be offered. Many patients may be opposed to this option due to the damage to the fetus which is not only psychologically difficult but which also precludes a full autopsy. As with a termination of pregnancy, cervical preparation is important if the cervix is closed. The two most common methods are laminaria placed 12-24 hours prior to the procedure and misoprostol 400 mcg given sublingually or vaginally 3 hours prior to the procedure. The risks for infection, bleeding, and uterine perforation along with the level of difficulty of this procedure all increase with the gestational age. At higher gestational ages some practitioners will choose to use ultrasound guidance either during the procedure or after the procedure to confirm its completion. Tissue floating may also be employed, which is a process that involves examining the products of conception to ensure that the contents and quantity are consistent with the gestational age.
Induction of labour after IUFD using prostaglandins may be used at any stage of pregnancy. High-dose intravenous oxytocin can also work in the second and third trimesters but is less effective (54). Vaginal misoprostol is considered the best method of induction, and there is evidence that premedication with mifepristone 200 mcg decreases the time to delivery (55). Doses of vaginal misoprostol are higher than those at term. An expert group recommends doses of 200 mcg 6-hourly at 13-17 weeks, 100 mcg 6-hourly at 18-26 weeks, and 25 mcg 6-hourly above 26 weeks (56).
Induction of labour with an IUFD in a patient with a prior uterine scar is a controversial topic. According to the ACOG and the Royal College of Obstetricians and Gynaecologists, vaginal misoprostol use does not increase the risk of uterine rupture up to 28 weeks' gestation.
Beyond that, a halving of the misoprostol dose is suggested (54, 56). Caesarean delivery for an IUFD should be avoided as it causes significant risks to the mother such as infection, bleeding, and organ injury, and carries future pregnancy implications.Multiple pregnancy
Delivery of multifetal pregnancies depends on the type of twin pregnancy, the gestational age, fetal presentation, and general health of the twin pregnancy (58), and is covered in more detail in Chapter 20. In a diamniotic pregnancy without complications, vaginal delivery is a safe option if the presenting twin is cephalic and the gestational age is at least 32 weeks (58). Timing of delivery of the pregnancy is stratified by twin type. In uncomplicated dichorionic diamniotic pregnancies, induction is commonly arranged for 37-38 weeks if delivery has not spontaneously occurred, with monochorionic diamniotic pregnancies a week earlier (58). With higher orders of multiples, vaginal birth and induction of labour are safe options in the presence of an appropriately skilled provider and with an uncomplicated cephalic-presenting first fetus (59).
Methods of induction are the same as for singleton pregnancies. Prior low-transverse caesarean delivery is not on its own a contraindication to vaginal birth or induction in a multifetal gestation (60).
Failed induction
Induction of labour is performed with the goal of achieving a vaginal delivery. There is currently no consensus on the definition of a failed induction, but generally if a patient cannot be put into labour in the time period defined by the clinician as reasonable, this is considered a failed induction. In around 15% of women it is not possible to perform ARM even after cervical ripening with two doses of a prostaglandin (8). Management options at this point depend upon the urgency and indication for delivery. If a patient is of low risk and there is no medical urgency for delivery, medication can be resumed after a 24-48-hour hiatus.
If the clinical scenario is more urgent, alternative induction methods or a caesarean section may be indicated (8).Induction in settings with few resources
Induction indications in low-resource settings are similar to those in high-resource settings. However, due to the lack of technology in prenatal care, there are typically fewer inductions for fetal indications. Without readily available ultrasonography, for example, fewer cases of IUGR are diagnosed. Additionally, with limited resources for monitoring of the fetus or oxytocin infusion rates, induction is more hazardous for mother and baby. As a result, the threshold for induction is raised. When the level of acuity is high and the resources are limited each induction is a risk for everyone involved. In these settings the stillbirth rate may be doubled and the need for neonatal resuscitation is increased. The reasons for such a high rate of stillbirth are multifactorial and probably due to the lack of prenatal diagnostics, limited resources with very limited patient access, and low levels of health literacy.
The World Health Organization has published guidelines on induction of labour in low-resource settings (61). The evidence is similar to that provided previously, and they suggest a choice of oral misoprostol, Foley catheter plus oxytocin, or dinoprostone plus oxytocin depending on the local situations. The Foley catheter has the benefit of low cost and low rates of hyperstimulation, but requires a skilled practitioner for insertion and usually requires an oxytocin infusion. Oral misoprostol is a highly effective method of induction and has probably the best outcomes of any method irrespective of setting. Misoprostol solution or tablets can be given as 25 mcg 2-hourly. It is not commonly available in tablet form and so usually needs to be made up in solution (a detailed explanation is available at http:// www.misoprostol.org). It has the added advantages of being low cost, requiring no infusion apparatus, and can be continued at low dose (typically 5-20 mcg/hour) throughout labour in place of oxytocin (62). A recent randomized trial in hypertensive women in an Indian government hospital found that oral misoprostol was more clinically effective and more cost-effective than the Foley catheter (32). Both methods were followed by an oxytocin infusion under gravity control and the fetus was monitored using intermittent auscultation.