Pregnancy and postpartum running
Evidence: moderate
National obstetric guidance supports continuing moderate exercise, including running, through most uncomplicated pregnancies, and a graded return afterwards. The headline advice is well established, but the specific timelines and screening criteria rest largely on clinical consensus rather than trial evidence, and the picture is highly individual.
Not medical advice
This is a general knowledge base, not medical advice. Pregnancy and the postpartum period are medical, and decisions about running through them must be made with your own doctor, midwife and physiotherapist, who know your history and your pregnancy. The guidance below is general information only. If you are pregnant, recently gave birth, or have any complication, get individual clearance before acting on anything here.
Most women who run before pregnancy can keep running through it, and starting moderate activity in pregnancy is also safe for most. The two questions that matter are whether a particular pregnancy is uncomplicated, which is a clinical judgement, and how to scale the running as the body changes.
What the guidance says
In the absence of obstetric or medical complications, physical activity in pregnancy is safe and beneficial, and women should be encouraged to continue or begin it (ACOG 2020). The standing recommendation is around 150 minutes per week of moderate-intensity aerobic activity. Women who were habitually doing vigorous aerobic activity before pregnancy, including runners, can carry on (ACOG 2020). Benefits include better cardiovascular fitness and a lower risk of conditions such as gestational diabetes, with no good evidence that moderate exercise harms an uncomplicated pregnancy.
That permission is conditional. There are absolute and relative contraindications, certain heart and lung conditions, some forms of bleeding or placental problems, and pre-eclampsia among them, for which a clinician will advise against aerobic exercise (ACOG 2020). There are also warning signs that mean stopping and seeking care: vaginal bleeding, regular painful contractions, fluid leaking, calf pain or swelling, chest pain, dizziness, headache, muscle weakness affecting balance, or breathlessness before exertion (ACOG 2020). These are not training problems to push through; they are reasons to call a clinician.
Physiological changes that affect running
Pregnancy changes the body in ways that bear directly on running. Resting heart rate and blood volume rise, so a given pace costs more cardiovascular effort, which makes perceived exertion a more useful guide than old pace targets (ACOG 2020). Weight gain and a shifting centre of mass alter gait and balance, raising the load through the pelvic floor and the risk of losing footing. Connective tissue becomes more lax, partly under hormonal influence, which may affect joint stability. Thermoregulation matters more, so avoiding overheating and staying hydrated become priorities (ACOG 2020). The core and pelvic floor carry steadily more load as pregnancy advances.
The usual pattern is that volume and intensity fall as pregnancy progresses, and many women switch some or all running for lower-impact activity in later pregnancy. How far and how fast is highly individual and best decided session by session with clinical input, not by a fixed schedule.
Returning to running after birth
The postpartum return is where caution matters most. Tissues that were loaded and sometimes injured during pregnancy and delivery, the pelvic floor and the abdominal wall above all, need time and graded reloading before they tolerate the repeated impact of running. The widely used guidance recommends no return to running before about 12 weeks postpartum, and a criteria-based check of pelvic-floor and abdominal recovery, strength and load tolerance before resuming impact, whatever the mode of delivery (Goom et al. 2019). Assessment by a pelvic-health physiotherapist before returning to running is a central recommendation (Goom et al. 2019). Symptoms such as leaking, heaviness or pain on impact are signs to stop and be reassessed, not to train through. These are timeline-and-criteria starting points from clinical consensus, and individual recovery varies widely.
This return is slower and more tissue-led than a return from a typical running injury, but the underlying principle, reintroduce load gradually and let the tissue set the pace, is the same one that governs any return to running.
Energy availability and breastfeeding
The postpartum period also raises the risk of low energy availability. Recovery, and breastfeeding in particular, add a substantial energy cost on top of training, so a runner can slip into a deficit without intending to. Chronic low energy availability is the root cause of RED-S, which harms bone, hormones and recovery, and underfuelling during a return to running undermines the very tissue repair the return depends on. Eating enough to cover training, recovery and any breastfeeding is part of returning safely, and is worth discussing with a clinician or registered dietitian.