Long-term changes in cesarean delivery and recurrence in Norwegian
nulliparous women, 1967-2014: A population-based study
Abstract
Objective: To describe long-term changes in Cesarean Delivery (CD) and
estimate CD recurrence risk across five decades. Design:
Population-based cohort study Setting: Norway, 1967-2014 Sample: A total
of 951,895 nulliparous women with their singleton, cephalic, term
deliveries were followed through their first and second births. Methods:
Data from the Medical Birth Registry of Norway was used to describe CD
by maternal age (years): <20 (reference), 20-24, 25-29, 30-34,
35-39 and >=40 and onset of labor: spontaneous (reference),
induced and pre-labor CD. Based on seven risk factors, women were
grouped as lower (no factors) - and higher-risk (one or more factors).
Risk estimates were stratified by periods: 1967-1982, 1983-1998 and
1999-2014. Multivariable regression models were used to estimate
relative risk (RR) with 95% confidence interval (CI). Results: CD in
the first birth increased across periods from 3.3% to 10.2% and from
8% to 20.5% in lower- and higher-risk women, respectively. The
increase in CD was only found among women < 35 years. Compared
to women with spontaneous onset, the RR of CD in lower-risk women with
induced onset of labor increased from 3.8 (95% CI 3.6-4.0) to 5.9 (95%
CI 5.7-6.2) across periods. Overall CD recurrence risk was 57.9%, but
relative recurrence risk was lower in the last than in the first period.
Conclusion: Overall CD risk increased over time in Norwegian women
<35 years both in lower- and higher- risk groups, while it was
stable or decreased in older women. CD recurrence risk declined across
47 years in Norway.