Sitting for long periods of time when pregnant could increase the risk of maternal diabetes.
The ethics of running clinical trials on pregnant women where the control group is considered likely to have a negative health impact are, understandably, not considered ethical.
As such, information regarding the amount of physical effort a pregnant woman should undertake during pregnancy is sparse.
Because of this knowledge gap, recommendations as to the amount of activity a pregnant woman should take are largely guesswork- albeit educated and reasonable guesswork.
There is a sensible, general consensus that at least some physical activity is better than none, but the negative impacts of prolonged sitting down during pregnancy had not, until now, been measured.
The risks of a sedentary lifestyle
A sedentary lifestyle is already known to have negative health implications, which differ from a lack of exercise. In other words, spending a large amount of time sitting down is a risk factor itself, separate from a lack of moderate to vigorous physical activity.
Long periods of inactivity have been linked to diabetes, obesity, heart disease and mental health issues.
Previous studies on the general population have shown that sedentary lifestyles have an effect on metabolism, bone mineral content, vascular health, increased plasma triglyceride levels, decreased levels of high-density lipoprotein cholesterol and decreased insulin sensitivity.
Compared with our parents or grandparents, people are far more likely to spend protracted amounts of time sitting down. This is due to a number of factors, including changes in the types of jobs people do (desk job versus farming), entertainment (computer games versus jump rope) or transport (cycling and walking versus cars and trains).
In 1970, around 20% of employed Americans had relatively sedentary jobs and 30% were in jobs requiring high energy output. In 2000, the figure of employed people in light activity jobs had risen to 40%, and high energy roles were down to 20%.
The risks of inactivity during pregnancy
This latest research was conducted by Nithya Sukumar at the University of Warwick in the UK and presented at the Society for Endocrinology's annual conference.
The study used data from questionnaires completed by 1,263 pregnant women. The participants were asked questions relating to their levels of physical activity and general emotional well-being. These questionnaires were conducted during the first trimester and the later stages of the second trimester.
After controlling for BMI, socio-economic status and age, the results showed that women who suffered depression symptoms were more likely to spend longer amounts of time being stationary.
The study also found that women who remained more sedentary carried out less moderate to vigorous physical activity during their second trimester. These women gained significantly more weight between the first and second trimester.
Thirdly, the research team found that, at 28 weeks, the more sedentary pregnant women had higher blood glucose levels, giving them an increased risk of developing gestational diabetes.
Sukumar's take-home message from these findings is twofold; firstly, earlier interventions in pregnant women's mental well-being could be of benefit and help prevent physical deterioration later in the pregnancy.
Secondly, Sukumar is eager to promote physical activity within pregnant women to lessen the risk of diabetes:
"Gestational diabetes can increase the risk of birth complications for the mother and baby and so it is important we minimize this risk by reducing the time that pregnant women spend sitting down."
As for recommendations, co-lead author Dr. Ponnusamy Saravanan believes that encouraging women to take breaks from sitting might be an easier health policy to implement than an attempt to increase women's activity during pregnancy.