Advanced maternal age and the risk of cesarean birth: a systematic review.
BACKGROUND
The increasing pregnancy rate at advanced maternal age is contemporaneous with the increasing rate of cesarean birth. Several studies have found that advanced maternal age is a risk factor for cesarean birth. The objective of this systematic review was to assess the relationship between advanced maternal age and cesarean birth among nulliparous and multiparous women.


METHODS
To identify relevant studies, we searched the literature for articles published from January 1, 1995 to March 1, 2008, using Medline, EMBASE, PsychINFO, and CINAHL. We also hand-searched the bibliographies of retrieved articles to identify additional related studies. We included all cohort studies and all case-control studies that examined this association in developed countries. The Cochrane Collaboration's Review Manager software (5.0) was used to summarize the data.


RESULTS
Twenty-one studies met the inclusion criteria and were included in the review. All studies demonstrated an increased risk of cesarean birth among women at advanced maternal age compared with younger women, for both nulliparas and multiparas (relative risk varied from 1.39 to 2.76). Because we found extreme heterogeneity (both statistical and clinical) among the included studies, we did not provide a pooled estimate of the risk of cesarean birth.


CONCLUSIONS
All included studies illustrated an increased risk of cesarean birth among older women. Fifteen studies adjusted this association for potential confounders, which suggests that a valid and independent association is likely to exist between advanced maternal age and cesarean birth. However, the associated factors for this increased risk are not totally understood in the literature.
Bayrampour
Hamideh
H
Faculty of Nursing, University of Manitoba, Winnipeg, Manitoba, Canada.
Heaman
Maureen
M
D000328:Adult; D001723:Birth Rate; D002585:Cesarean Section / Q000706:statistics & numerical data*; D002908:Chronic Disease; D015331:Cohort Studies; D019992:Databases as Topic; D019049:Developed Countries; D005260:Female; D006801:Humans; D008423:Maternal Age; D010298:Parity; D011225:Pre-Eclampsia; D011247:Pregnancy; D011256:Pregnancy Outcome; D018566:Pregnancy, High-Risk; D012307:Risk Factors