4.1 The incidence of failed induction of labor.
The study has found the incidence of failed induction of labor in women delivering at Jinja Regional Referral Hospital to be 35.33%. This finding aligns closely with similar studies conducted in various settings. For instance, a study conducted at Kenyatta National Hospital, Kenya, reported an incidence range of 38% (13). Similarly, a WHO study across eight Latin American countries documented a pooled incidence of 30% (14), while research at Kathmandu Medical College found a rate of 34.6% (15).
However, the incidence observed in this study deviates from rates reported in other regions. For example, research conducted at Mbarara Regional Referral Hospital in Western Uganda indicated a lower incidence of 22.7% (16), and studies at Harare Maternity Hospital in Zimbabwe and in Northern Tanzania reported rates of 24.9% (8) and 19% (9) respectively. Several factors may contribute to these variations. Variances in the definition of fIOL play a crucial role; for instance, Kajabwangu and coleagues (16) defined failure of induction as the inability to achieve the active phase of labor within 12 hours, whereas other studies may have employed different criteria. Additionally, differences in study design, sample size, and population characteristics can influence incidence rates. Notably, the retrospective nature of the Tanzanian study (8), which defined fIOL based on cesarean section, and the inclusion criteria of gestational age ≥37 weeks in the Harare study may have contributed to the observed differences.
Moreover, methodological disparities, such as data collection techniques, also impact outcomes. In this study, a hybrid approach utilizing interview-administered questionnaires and patient records was employed, whereas many other studies relied solely on secondary data from patient files, potentially leading to differences in data completeness and accuracy (8).
Comparisons with studies conducted in other settings further highlight discrepancies in fIOL rates. Studies at Jimma University Specialized Hospital (17) and Adama Referral Hospital (18) reported lower rates of 21.4% and 29.6% respectively. These differences may stem from variations in study settings and the methods employed for labor induction. For instance, the use of different induction methods, such as combinations of artificial rupture of membranes (ARM) and oxytocin in other studies, contrasts with the predominant use of misoprostol in the current study setting. These discrepancies underscore the multifactorial nature of fIOL and emphasize the importance of context-specific research to inform clinical practice effectively.
4.2 Predictors of failed induction of labor.
Understanding the factors that predict failed induction of labor (fIOL) is essential for identifying high-risk groups and tailoring interventions accordingly. In this study, parity, pre-induction Bishop Score, birth weight, and BMI emerged as predictors of fIOL.
4.2.1 Parity:
The analysis revealed that nulliparous women had a significantly higher likelihood of failing induction compared to primi/multiparous women. Specifically, nulliparous women exhibited a twofold increased risk of fIOL. This finding is comparable to previous research conducted in various settings aOR=2.34 (16), aOR=1.79 (9), aOR=1.5 (7). The increased risk among nulliparous women may be attributed to their unfavorable pre-induction cervical status, which is less responsive to ripening methods compared to multiparous women. Additionally, multiparous women may have increased myometrial sensitivity and contractility, enhancing their response to oxytocin and facilitating labor progression.
4.2.2 Pre-induction Bishop score:
A low pre-induction Bishop score was significantly associated with an increased likelihood of fIOL. Specifically, women with a Bishop score <6 had a 2.5 times higher risk of fIOL compared to those with a score ≥6. This finding aligns with previous studies conducted in Uganda (16), Ethiopia (7), Tikrit-city Iraq (19) and (8). It highlights the importance of cervical status in predicting induction success. An unfavorable cervix, characterized by parameters such as dilation, effacement, position, and consistency, hampers cervical stimulation and labor progression, contributing to induction failure.
4.2.3 Birth weight:
The study identified a strong association between birth weight ≥3.5kg and fIOL. Mothers with fetal weights ≥3.5kg had a 1.2 times higher likelihood of induction failure compared to those with lower fetal weights. This association is consistent with findings from other studies done in Pakistan (15), Thailand (20), and Tanzania (9). It can be attributed to factors such as poor fetal descent, malposition, and malpresentation in larger babies, hindering optimal application of the fetal head to the cervix and impeding cervical effacement and dilation.
4.2.4 Body Mass Index (BMI):
Elevated BMI (≥30kg/m2) was significantly associated with an increased risk of fIOL. Women with a BMI ≥30kg/m2 had a 1.7 times higher risk of induction failure compared to those with lower BMI values. This association has been observed in other studies done in Zimbabwe (8) and Tanzania (9). It may be attributed to mechanical obstruction caused by adipose tissue accumulation in the abdomen and pelvis among obese women. Additionally, obesity can disrupt cervical moisture and collagen content, further impeding fetal descent and cervical effacement and dilation.