Caesarean section in nulliparous women in spontaneous labour at term: trends and obstetric factors over a 10-year period.

BACKGROUND: Nullipara with a singleton pregnancy and cephalic presentation in spontaneous labour at term (Group 1 Robson Ten Group Classification System) (TGCS) represent a significant proportion of the antenatal population. Caesarean section (CS) rates among this group vary internationally and greatly influence overall CS rates. OBJECTIVE: To determine CS rates for Group 1 Robson TGCS from 2014 to 2023 and examine trends, timing of CS procedures during labour, and demographic influences. STUDY DESIGN: Retrospective analysis of prospectively collected data from a university teaching hospital in Ireland. Among 28,264 deliveries, 10,038 were nullipara with 4,523 in Group 1 Robson TGCS. Outcomes measures included CS rates, timing (CS in first or second stage), CS indications, maternal age, BMI, birth weight, and public vs private care. Descriptive statistics, chi-square testing for proportions and trend and multinomial logistic regression analyses were performed. RESULTS: The CS rate in Group 1 Robson TGCS was 15.2%, increasing from 13.5% in 2014 to 18.6% in 2023 (P < 0.01). Rates of CS procedures increased in the first (P = 0.01), but not the second stage of labour. CS rates for suspected fetal compromise or poor progress remained stable, though oxytocin augmentation increased. Maternal age < 25 years reduced CS risk, while higher BMI (25.0-29.9, OR 1.55, 95% CI 1.25-1.92, P < 0.001; 30-34.9, OR 1.81, 95% CI 1.32-2.48, P < 0.001; 35.0-39.9, OR 1.78, 95% CI 1.04-3.06, P < 0.05; ≥40, OR 2.47, 95% CI 1.04-5.83, P < 0.05) and birthweight, ≥4kg, (OR 2.295 95% CI 1.78-2.95, P < 0.001) increased odds. Private care was associated with a higher odds of CS (OR 1.47 95% CI (1.08-2.01), P < 0.05). CONCLUSION: CS Rates in Group 1 Robson TGCS increased over 10 years, primarily in the first-stage of labour. Maternal age, BMI, birthweight, and private obstetric care were significant associated factors.