• Incidence;
  • obesity;
  • pregnancy;
  • rates;
  • trends

Objective  The aim of this study was to identify trends in maternal obesity incidence over time and to identify those women most at risk and potential-associated health inequalities.

Design  Longitudinal database study.

Setting  James Cook University Hospital maternity unit, Middlesbrough, UK.

Sample  A total of 36 821 women from 1 January 1990 to 31 December 2004.

Methods  Trends in maternal obesity incidence over time were analysed using chi-square test for trend. Demographic predictor variables were analysed using multivariate logistic regression, adjusting for confounding factors after testing for multicollinearity. National census data were used to place the regional data into the context of the general population.

Main outcome measure  Trends in maternal obesity incidence. Demographic predictor variables included ethnic group, age, parity, marital status, employment and socio-economic disadvantage.

Results  The proportion of obese women at the start of pregnancy has increased significantly over time from 9.9 to 16.0% (P < 0.01). This is best described by a quadratic model (P < 0.01) showing that the rate is accelerating; by 2010, the rate will have increased to 22% of this population if the trend continues. There is also a significant relationship with maternal obesity and mothers’ residing in areas of most deprivation (odds ratio [OR] = 2.44, 95% CI = 1.98, 3.02, P < 0.01), with increasing age (OR = 1.04, 95% CI = 1.04, 1.05, P < 0.01), and parity (OR = 1.17, 95% CI = 1.12, 1.21, P < 0.01).

Conclusions  The incidence of maternal obesity at the start of pregnancy is increasing and accelerating. Predictors of maternal obesity are associated with health inequalities, particularly socio-economic disadvantage.