Effect of Regular Exercise in Prevention of Excessive Weight Gain in Pregnancy. A Single Blind Randomized Controlled Trial

Background:

Data from population-based surveys and longitudinal observational studies generally support that inactive men and women have higher body weight and BMI than physically active adults (US Departmentof Health and Human Services, 1996,Williamson et al., 1993,Sherwood et al., 2000,Anderssen et al., 2007). Studies examining the impact of exercise on maternal weight gain are varied and limited. Two different meta- analysis's found no difference in maternal weight gain between exercisers and non-exercisers (Kramer, 2002,Lokey et al., 1991). In a review from 2004 it is suggested that women who exercise before pregnancy and continue to do so during pregnancy tend to weigh less and gain less weight that controls (Siega-Riz et al., 2004). A recent study of Haakstad et al (Haakstad et al., 2007) found that women who continued to exercise regularly in the 3rd trimester had significantly lower total weight gain. In addition, women reporting high exercise frequency in the 3rd trimester ( ≥ 4 times per week), the proportion exceeding IOM's weight gain recommendations was significantly lower compared to women exercising less frequently (1-3 times per week)(Haakstad et al., 2007). These results indicate that there may be a dose-respons relationship, with higher levels of exercising being more effective than moderate and low levels for the prevention of high maternal weight gain.

So far, only few intervention studies aiming at weight management during pregnancy have been performed (Gray-Donald et al., 2000,Olson et al., 2004,Polley et al., 2002,Kinnunen et al., 2007). Moreover, most of these interventions have focused on how gestational weight gain may be altered through individual counselling combining diet and exercise habits, rather than supervised training. Search on PubMed revealed no randomized controlled trial where the main outcome was to investigate how the effect of supervised structured exercise may reduce the proportion of women gaining more weight than optimal. The aim of the present study is to assess whether a 12-week aerobic exercise program during pregnancy can prevent excessive gestational weight gain.

Method:

Participants This is a single blind randomized controlled trial to evaluate the effects of a structured, supervised aerobic exercise program on weight gain stabilization in primiparous pregnant women. Participants will be recruited via health practitioners (physicians, midwifes), articles and advertisement in the newspapers, official websites for pregnant women, through flyers and word of mouth. The aim is to include 100 women. With power = 0.85 and alfa = 5%, the present study is designed to detect a standardized difference in total weight gain of 0.6. Assuming that the standard deviation of weight gain is 5 kilos, then the actual weight gain has to be ∆= 3 kilos.