A new study now suggests that running during pregnancy is actually safe.
Women who jog while pregnant are not more likely to have babies born prematurely or of a low birth of its kind, said the study.
The study says that infant wellbeing is unaffected regardless of how far their mothers ran or if they did so throughout all three trimesters.
Speaking about it, lead author Professor Andrew Shennan, from King's College London, said that women can continue accustomed exercise during pregnancy, and they would encourage this to ensure a healthy outcome for both her and her baby.
A previous study has already suggested that high-intensity running affects the cervix and therefore foetal wellbeing, however, the scientists of the current research argue this trial assessed just six pregnant athletes, not average runners.
Around one-third of pregnant women are unsure whether it is safe to continue running when expecting, according to a poll by the charity Tommy's.
Guidelines recommend 30 minutes of moderate daily exercise for most pregnant women to reduce their risk of weight gain, pre-eclampsia and gestational diabetes.
According to professor Janice Rymer, vice president for education at the Royal College of Obstetricians and Gynaecologists said that the new study shows that, in the majority of cases, it is safe for both the mother and the baby if a woman who runs regularly continues to do so during her pregnancy.
Results further suggest pregnant runners are more likely to require forceps or a vaccum device during labour, which may be due to their greater pelvic floor muscle tone.
In addition, those who never run during their pregnancies are on average 2.3kg (5lbs) heavier than those who continue to do so.
The findings were published in the journal BMJ Open Sport & Exercise Medicine.
