Exercise in pregnancy tracker

The number everyone quotes, and where it comes from

One hundred and fifty minutes a week is the figure, and it is unusually well agreed. The UK Chief Medical Officers publish it in their pregnancy-specific physical activity guidelines. ACOG repeats it, tracing it to the US physical activity guidelines. WHO's 2020 recommendations say the same. It is one of the few numbers in pregnancy advice where the major bodies have converged rather than diverged.

What matters as much as the total is the instruction to spread it across the week. Three fifty-minute sessions beat one long Sunday. Ten-minute blocks count, and three of them count as thirty, which is the framing that makes the target reachable for someone who is exhausted, nauseated or working full time.

There is no heart-rate limit, and there has not been for a long time

This is the question that brings most people to a page like this, and it deserves a straight answer: no current guideline sets a maximum heart rate for exercise in pregnancy. The "keep it under 140" rule circulated widely in the 1980s and 1990s, was withdrawn, and was never replaced with another number.

ACOG sets out the reasoning. Heart-rate responses to exercise in pregnancy are blunted in some women and normal in others, so the same reading means genuinely different things in different bodies at different gestations. Prescribing to a number would be prescribing to noise.

What replaced it is perceived exertion. ACOG puts moderate intensity at 13 to 14 on the Borg scale, described as "somewhat hard". If you prefer something you can use without a chart, the talk test does the same job: if you can hold a conversation while you exercise, you are almost certainly not overexerting. If you can sing comfortably, you can push harder. If you cannot get a sentence out, ease off.

What the evidence actually shows

The old worries have not held up. ACOG's summary is that concerns about regular physical activity causing miscarriage, poor fetal growth, musculoskeletal injury or premature delivery "have not been substantiated for women with uncomplicated pregnancies", and that in the absence of complications, physical activity in pregnancy is safe and desirable.

The benefits side is where the evidence has strengthened. Regular aerobic activity in pregnancy is associated with lower rates of gestational diabetes, lower rates of gestational hypertensive disorders, fewer caesarean births, and faster postpartum recovery. It is also linked to lower rates of depressive disorders in the postpartum period, which is not a small thing.

Physical inactivity, by contrast, is recognised as an independent risk factor for maternal obesity and related pregnancy complications. The framing in the guidance is not "exercise is permitted"; it is that inactivity carries its own risks.

Starting from nothing is explicitly supported

If you were not active before pregnancy, the guidance does not tell you to wait. ACOG describes building towards moderate-intensity exercise for at least 20 to 30 minutes a day on most or all days of the week, starting low and increasing gradually. The 150 is a destination, not an entry requirement.

The rule that does apply to newcomers is about intensity rather than existence. Women who habitually did vigorous activity before pregnancy can generally continue it, including into the third trimester. Starting vigorous training in pregnancy is a different proposition, and the sensible progression is to add minutes before adding intensity.

The two modifications the guidance is specific about

After around 20 weeks, avoid long periods lying flat on your back. The weight of the uterus can compress the vein returning blood to the heart, which reduces venous return and can cause light-headedness. This is a positioning adjustment rather than a reason to stop core work; most exercises have a side-lying or inclined version.

And stay well hydrated and out of high heat and humidity, particularly in the first trimester. ACOG notes that exposure to heat from sources such as hot tubs, saunas or fever has been associated with an increased risk of neural tube defects, while adding that exercise itself would not be expected to raise core body temperature into that range. Loose clothing, water, and not choosing the hottest hour of the day cover it.

When to stop and ask

Stop exercising and get advice if you have vaginal bleeding, regular painful contractions, fluid leaking from the vagina, chest pain, calf pain or swelling, shortness of breath before you have started, dizziness, headache or muscle weakness affecting balance.

And the boundary a tracker cannot see: there are obstetric and medical conditions in which aerobic exercise is genuinely contraindicated, and others where the programme needs individualising. If you have one of those, the plan should come from your maternity team. A percentage on a screen is a prompt for that conversation, not a substitute for it.

The bits the 150 minutes leaves out

Two things sit outside the aerobic target and get forgotten. Muscle-strengthening activity on two days a week is part of the same guidance, and it matters more in pregnancy than at other times because strengthening abdominal and back muscles can reduce the low back pain that more than 60% of pregnant women experience.

Pelvic floor exercises are named specifically in the UK guidance and are recommended daily. They do not count towards the 150 minutes, they take a couple of minutes, and they are the single highest-return thing on the whole list for continence after birth. This tracker counts them separately for exactly that reason.