To examine pre-conception dietary patterns in pregnant asthmatic women and to identify associations between maternal diet and asthma control during pregnancy.

Cross-sectional study. Pre-conception food frequency data were collected retrospectively. Asthma control was assessed using the Global Initiative for Asthma guidelines. Dietary patterns were derived using factor analysis. Binary logistic regression analyses were used to test the association between uncontrolled asthma and each dietary pattern (Z-score), with values presented as odds ratio and 95 % confidence interval.

Antenatal clinic in a tertiary hospital, Adelaide, Australia, May 2009–July 2013.

One hundred and fifty-eight asthmatic pregnant women.

Three dietary patterns were identified: (i) ‘high protein/fruit’ (strong food group loadings for fish, meat, chicken, fruit); (ii) ‘high fat/sugar/takeaway’ (takeaway foods, crisps, refined grains); and (iii) ‘vegetarian-type’ (vegetables, fruit, soya milk, whole grains). A 1 sd increase in score on the high fat/sugar/takeaway pattern was associated with increased likelihood of uncontrolled asthma (adjusted OR=1·54; 95 % CI 1·07, 2·23; P=0·022). Women with uncontrolled asthma (n 115) had higher energy-adjusted intakes of saturated fat, monounsaturated fat, carbohydrate, sugar and fibre compared with women with controlled asthma (n 43, all P≤0·05).

Pre-pregnancy dietary patterns may influence maternal asthma control. Our work highlights the importance of achieving a healthy diet before pregnancy that is low in saturated fat, sugar and takeaway foods, and therefore higher in lean meats, poultry and fish, as well as fruits, vegetables and whole grains. A healthy dietary pattern should be encouraged in all asthmatic women who are of childbearing age, and should additionally be promoted before pregnancy and beyond.