Analysis of Longitudinal Studies

Philip Sedgwick
Reader in medical statistics and medical education
Centre for Medical and Healthcare Education, St George’s, University of London, London, UK

Louise Marston
Research Statistician

February 6, 2015

A randomised controlled trial investigated whether a low glycaemic index diet in pregnancy reduced the incidence of macrosomic (large for gestational age) infants. Participants were an at risk group—women without diabetes, in their second pregnancy, who had previously given birth to an infant weighing more than 4000 g. The intervention consisted of a low glycaemic index diet from early pregnancy; the control was no dietary intervention. The primary outcome measure was birth weight, and the secondary outcome was gestational weight gain from baseline (measured at 24, 28, 34, and 40 weeks). Treatment groups were compared at each gestational age using the independent samples t test⁽¹⁾.

The researchers reported that a low glycaemic index diet in pregnancy did not reduce the incidence of large for gestational age infants in women at risk of fetal macrosomia. It did, however, have a significant effect on gestational weight gain. At each measured gestational age, except for 24 weeks, the intervention group gained significantly less weight than the control group^(T1) .

Click here to view the answer

Cite this as: BMJ 2013;346:f363

This post is based on an article published in "Endgames" an educational series from The BMJ. Other Endgames articles are available here. Copyright BMJ Publishing Group 2013.