Risk factors for Caesarean delivery after induction of labour among nulliparous women at term Abstract

Selina Tsz-Ching LEE, Winnie Wai-Yan YEUNG, Kwok-Yin LEUNG
Department of Obstetrics and Gynaecology, Queen Elizabeth Hospital, Hong Kong
Objectives: To determine risk factors for Caesarean section after induction of labour (IOL) at term among nulliparous women, and to develop and validate a predictive model.
Methods: We retrospectively reviewed records of all nulliparous women with term, singleton, cephalic pregnancies and induction of labour from 1 January to 31 December 2017 in Queen Elizabeth Hospital. The cervix was examined on admission using the Modified Bishop Score for cervical dilatation, effacement, position, consistency, fetal station. Women with unfavourable cervix received cervical priming. Those with favourable cervix proceeded to induction of labour by combining artificial rupture of membrane and oxytocin infusion. Risk factors for Caesarean delivery were identified using univariable analysis and multivariable logistic regression. A nomogram was constructed using the independent risk factors. A receiver-operating characteristics curve and the area under the curve were generated to assess the discriminative power of the predictive model. An external validation was performed.
Results: A total of 1557 women who were nulliparous and had term, singleton, cephalic pregnancies and induction of labour were included for analysis. 1426 (91.6%) of them were of Chinese ethnicity. Of the 1557 women, 473 (30.4%) underwent Caesarean delivery and the remaining 1084 women delivered vaginally. In the multivariable logistic regression, independent risk factors for Caesarean delivery were maternal age (odds ratio [OR]=1.04, p=0.005), baseline height (OR=0.954, p=0.001), final body mass index (OR=1.11, p=0.001), and need for cervical priming (OR=1.32, p=0.033). The discriminative power of the predictive model was assessed by the area under the curve, which was 0.661 for the study cohort and 0.613 for the external validation set of 142 women.
Conclusion:Among Hong Kong nulliparous women with induction of labour at term, independent risk factors for Caesarean delivery were older maternal age, lower baseline height, higher final body mass index, and more need for cervical priming. The predictive model based on these risk factors can calculate the probability of Caesarean section for counselling these women.
Hong Kong J Gynaecol Obstet Midwifery 2020; 20(1):27–31
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