Does maternal obesity explain trends in caesarean section rates? Evidence from a large Irish maternity hospital

BACKGROUND: A feature of contemporary obstetrics in wealthy countries has been both the continuing increase in caesarean section (CS) rates and the emergence of high levels of maternal obesity. AIMS: The purpose of this study was to examine whether the increasing CS rate in a large university maternity hospital was attributable in part to maternal obesity. METHODS: We studied all women who delivered a baby weighing ≥ 500 g from 2009 to 2014 in one of the largest maternity hospitals in Europe. Logistic regression techniques were employed to examine the contribution of trends in maternal BMI on the prevalence of CS. RESULTS: Obese women were more likely to be delivered by CS in 2014 than in 2009. Multivariate analysis shows that the increase in CS rates could not be explained by changes in obesity levels in either nulliparas or multiparas. The increase in CS rates during the 6 years was strongly associated with advancing maternal age, particularly for nulliparas. CONCLUSIONS: The study found that although the prevalence of being overweight or obese changed little over the period, the odds of having a CS if a woman is obese have increased for multiparas. For nulliparas, increasing CS rates were found to be strongly associated with an increase in maternal age over the period which is important because of the evidence that Irish women are choosing to defer having their first baby until later in life.