Trends in caesarean section and instrumental deliveries in relation to Body Mass Index: a clinical survey during 1978 - 2001

BACKGROUND: During the last 20 years the rate of CS has increased in Sweden as it has in many other countries. The proportion of pregnant women suffering from a high BMI has also increased rapidly during the same time period. It would therefore be of interest to study both how and if these two observations are related to each other. The aim was therefore to study trends in mode of caesarean section (CS) and instrumental deliveries among women in three BMI groups over a time span of almost 25 years with special focus on the observed body weight of pregnant women. METHOD: The design is a retrospective cohort study using medical records of consecutively delivered women at two delivery wards in South East Sweden during the years 1978, 1986, 1992, 1997 and 2001. RESULTS: No significant time-trends were found for CS and instrumental delivery within each BMI-group for the time period studied. The proportion of women with BMI ≥ 25 delivered by means of CS or instrumental delivery increased quite dramatically from 1978 to 2001 (χ(2 )test for trend; p < 0.001 for both CS and instrumental deliveries). The mean birth weight in relation to BMI and year of study among women delivered by means of CS decreased, a trend that was most evident between 1997 and 2001 (F-test; p = 0.005, p = 0.004, and p = 0.003 for BMI < 20, 20-24.9, and ≥ 25, respectively). CONCLUSION: Overweight and obese pregnant women constitute a rapidly growing proportion of the total number of CS and instrumental deliveries. Planning and allocation of health resources must be adjusted to this fact and its implications.