Caesarean section in nulliparous women of advanced maternal age has been reduced in Sweden and Norway since the 1970s: a register-based study

Abstract

Objective: To investigate rates of caesarean delivery in Sweden and Norway from 1973 to 2008 in relation to advanced and very advanced maternal age.

Design: Register study.

Setting: Sweden and Norway.

Sample: All nulliparous women aged over 30 years with a singleton pregnancy, with the fetus in a cephalic presentation, and delivering at term between 1973 and 2008 were evaluated. The study population comprised 329 824 women in Sweden and 127 810 women in Norway.

Methods: Data from the national Medical Birth Registers were used to describe caesarean section rates in three age groups: 30-34 years (reference group); 35-39 years (advanced age group); and ≥ 40 years (very advanced age group). Logistic regression analyses estimated the risk in each age group over four decades, in each of the two national samples.

Results: Caesarean delivery decreased from 1973-1979 to 2000-2008 in the two oldest age groups in Sweden (35-39 years, OR = 0.53, 95% CI = 0.50-0.58; ≥ 40 years, OR = 0.36, 95% CI = 0.30-0.43) and Norway (35-39 years, OR = 0.61, 95% CI = 0.54-0.68; ≥ 40 years, OR = 0.45, 95% CI = 0.34-0.58), but increased in women aged 30-34 years. The caesarean delivery rate in the two oldest groups peaked in the second half of the 1970s. Regardless of time point, the caesarean delivery rate was always highest in women aged ≥ 40 years, followed by women aged 35-39 years and lowest in women aged 30-34 years.

Conclusions: Caesarean delivery in nulliparous women of advanced and very advanced age peaked by end of the 1970s in Sweden and Norway. The subsequent reduction was contemporaneous with the introduction of electronic fetal monitoring and a more consistent use of the partogram, suggesting that more effective surveillance of labour increased the chance of a vaginal birth in these high-risk women.