Caesarean Sections Linked to Older Pregnancies

(July 4, 2008) - Delaying childbirth (Read about "Childbirth") has substantially contributed to recent rises in caesarean section rates, according to a new study. The reason - the older a woman gets the weaker her contractions.

Researchers examined more than 500,000 cases between 1980 and 2005 to determine the association between maternal age and the outcome of labor. Alongside a major increase in the number of caesareans, they found striking changes in the age of mothers over the study period.

The proportion of women aged 35-39 entering their first pregnancy increased seven-fold, while there was a ten-fold increase for women aged 40 or older. At the same time, the caesarean rate more than doubled. The researchers estimate that 38 percent of these additional procedures would have been avoided if the maternal age distribution had remained static.

Hypothesizing that there was a biological cause, the team went on to study samples of the myometrium, muscle from the middle of the uterine wall, taken from 62 women undergoing elective caesarean procedures.

They found that advancing age was associated with impaired uterine function, in particular a reduced degree of spontaneous contraction and change in the type of contraction. The reduction is thought to result in poor progression of labor and thus the increased rate of caesarean section.