Effectiveness on Gestational Weight Gain of Pregnant Women of Motivational Interviewing on Diet and Lifestyle: a Randomized Controlled Trial

It is widely recognized that nutrition, metabolism and physical activity during pregnancy play a central role in several aspects of the health and well-being of pregnant women and their offspring. Pre-pregnancy Body Mass Index (BMI) and Gestational Weight Gain (GWG) are important predictors of maternal and neonatal health outcomes. In particular, excessive maternal pre-pregnancy BMI (BMI ≥ 25) and GWG outside the range recommended by the Institute of Medicine (IOM), may put mothers at risk of complications during pregnancy and delivery and can affect the short and long-term health of the offspring. They are also predicting factors of postpartum weight retention and long-term risk of offspring overweight or higher BMI. Similarly to obesity, also maternal pre-pregnancy underweight can cause negative health effects with short and long-term consequences for the mother and the foetus.

The most recent scientific evidence acknowledges the complex interplay between factors that influence the nutritional status and GWG of pregnant women, suggesting the need for multifaceted interventions that include counselling approaches, implemented during routine antenatal care for broad public health benefits. In particular, interventions based on health-related behavioural changes such as motivational interviewing (MI), used to address motivation, self-efficacy and self-regulation, have shown to have high chances of success. MI is a person-centred technique for communication that is effective for overcoming ambivalence and eliciting motivation for change.

The starting hypothesis is that inadequate GWG at the end of pregnancy may bear some relation with dietary habits and lifestyle before and during pregnancy and that MI might be effective in initiating and sustaining behavioural changes, including weight control. The study will compare a group of pregnant women, randomly assigned to receive, as part of the hospital-based prenatal care program, a behavioral intervention based on the MI methodology focused on dietary habits and lifestyle, with a group of women randomly assigned to the standard prenatal care program. It is expected that the dietary habits of women in the MI group will change as a result of the intervention, and that the resulting effective management of weight gain during pregnancy will contribute to improved maternal and neonatal outcomes.