Nationality was considered as the exposure, and women were categorised into four groups, namely, Lebanese, Syrian, Palestinian and migrant women of other nationalities who are mainly domestic workers (online supplemental table 3). Other than maternal age, ICD-10-CM codes and nationality, all other variables were imputed by classification using ML methods. Caesarean section in the current pregnancy was generated using a combination of ICD-10-CM codes and classification. Other characteristics extracted from the ‘free-text’ were gestational age, parity, consanguinity, smoking, current number of caesarean sections, diabetes, hypertension and episiotomy. Primary caesarean section was defined as performing the caesarean section for the first time.
Maternal outcomes extracted from the ‘free-text’ included diabetes, hypertension disorders during pregnancy (including pregnancy induced hypertension and preeclampsia), placenta abruption, placenta praevia, placenta accreta spectrum, hysterectomy, uterine rupture and blood transfusion. Infant outcomes extracted were preterm birth (<37 weeks of gestational age), very preterm birth (<32 weeks of gestational age) and intrauterine fetal death (IUFD). Use of caesarean section was calculated as a proportion by dividing the number of caesarean sections by the total number of maternities for each nationality. Serious complication of pregnancy was a composite outcome that included preeclampsia, hysterectomy, placenta accreta spectrum, placenta praevia, blood transfusion, placenta abruption and uterine rupture.