Introduction
Since 19851, the World Health Organization (WHO) has considered the ideal caesarean section (CS) rate to be between 10% and 15% with the crude rate of CS proposed as a global indicator to evaluate the quality of obstetric care. However, since then, CS rates have gradually increased, raising concerns on the potential negative effects on mother and infant health, and many efforts have been made to reduce the number of unnecessary interventions. In 2001 Robson2 proposed the “Ten Group Classification System” (TGCS), a totally inclusive and mutually exclusive classification system that divides the obstetric population into 10 groups with the aim of comparing caesarean section rates over time in one single unit and among different units, to improve perinatal care. In 20173 the WHO has endorsed the TGCS, proposing that it should be considered “a global standard for assessing, monitoring and comparing CS rates within healthcare facilities over time, and between facilities”. A relatively recent review4 of the literature that included 73 papers on the use of the Robson classification in more than 33 million women in 31 countries showed that, despite its valuable utility, among the limitations reported by users, there was a failure to take into account the indication to the CS and the characteristics of both the mother and the fetus, which can significantly influence the CS rate (e.g. maternal age or fetal growth, to name just a few). Consequently, it is possible to find different CS rates in the same Robson group, in relation to different countries, but also in the same institution, in relation to different types of women. These differences may influence the comparison among hospitals or inside the same hospital if the population characteristics change. Maternal age, immigrant status, body mass index and diseases (for instance, gestational diabetes mellitus or hypertension), or neonatal birthweight and the use of obstetric analgesia are not taken into consideration by the TGCS but they potentially influence the CS rate. Our hypothesis is that these factors may influence the probability of giving birth by caesarean section, within each individual Robson group.
Therefore, the purpose of our study was to evaluate which obstetric and maternal-fetal variables affect the CS rate within the individual Robson groups and to verify any differences between the groups. As secondary results we analysed the time course of the CS rate for the Robson groups over a period of 24 years.