Over the past few decades, there has been an increasing trend towards caesarean sections across the globe. A good induction protocol will help avoid the need for a caesarean section and hence reduce the section rates in avoidable indications thereby reducing the morbidity and mortality. The process of induction involves a comprehensive assessment of indication, appropriate choice of method and skillful execution to attain the final goal of obstetrics, the delivery of a healthy baby with a healthy mother.
Induction implies stimulation of contractions before the spontaneous onset of labour, with or without ruptured membranes.
When the cervix is closed and uneffaced, it will often commence with cervical ripening, a process that generally employs prostaglandins to soften and open the cervix. Augmentation refers to enhancement of spontaneous contractions that are considered inadequate because of failed cervical dilation and fetal descent.
The culmination of normal pregnancy involves three stages: prelabour, cervical ripening and labour. These occur as a continuum rather than as isolated events.
In developed countries, up to 25% of all deliveries at term, now involve induction of labour. In developing countries, the rates are generally lower but, in some settings, they have been found be as high as 30%.
Two previous analyses by Guerra and colleagues of labour induction in Latin America were based on WHO Global Survey(WHOGS) data and found an induction rate of 11.4%, of which16.7% were elective (2). Premature rupture of membranes was the most frequent medical indication in all countries. However, elective induction was the most common overall indication and was associated with increased uterotonic use, ICU admission, hysterectomy, greater anesthesia/analgesia use and delayed commencement of breastfeeding.
Inductions were more frequently in urban and tertiaryfacilities in Africa, whereas this was not significantly different inAsia.Induction without medical indicationaccounted for lessthan 2% of deliveries in all countries, except for Sri Lanka (27.8%),
Japan (8.5%), India (3.6%) and Thailand (3.5%). In Africa,PROM (27.3%) was the mostcommon indication, while in Asia47.2% wereelective. Oxytocin alone or oxytocin in combination with other non-drug method are most common indication in Africa and Asia.Inductionsuccess (inductions resulting in a vaginal birth) was 83.4% in Africaand 81.6% in Asia. The most successful method was oxytocin only in Africa (86.1%) and oxytocin, misoprostol/misoprostol/anotherprostaglandin and a non-drug method in Asia (86.3%).
Cervical ripening is the most important factor for the outcome of induction of labour. In the 1st trimester, 50% of the dry weight of the cervix is tightly aligned collagen, 20% smooth muscle and the rest is ground substance composed of elastin and glycosaminoglycans (Chondroitin, dermatan sulphate and hyaluronidase)The proportions of muscle cells varying from 30% in the internal OS to 6% in the external OS.During labour, hyaluronidase increases from 6 to 33%,whereas dermatan and chondroitindecrease. Collagenase and elastase enzymes increase, as do the vascularity and water content.Increased production of interleukin-1-beta, tumor necrosis factor -alpha and interlukin-8,increase in PgE2, relaxin and progesterone antagonists occurs.