Exercise in the second and third trimester: positions, balance and effort

For many people, the second trimester feels like coming up for air. Nausea often fades, energy returns, and movement starts to feel good again. Then, as the bump grows through the third trimester, the questions change: which positions are still comfortable, how to stay steady on your feet, and how hard is hard enough.

This guide covers the main adjustments for the middle and later months of pregnancy, with what the research says and what Eggsports does in its own sessions.

Is it safe to lie on your back to exercise after 16 to 20 weeks?

When you lie flat on your back later in pregnancy, the weight of the uterus can press on the vena cava, the large vein that returns blood to the heart. The IOC expert group explains that being motionless or exercising on your back may reduce blood return and cause low blood pressure in 10 to 20% of pregnant people.^[2] ACOG gives the same advice for everyday life: avoid lying flat on your back or standing still for long periods, as both can make your blood pressure drop for a short time.^[6]

Where guidelines disagree is on when this starts to matter:

• The WHO advises avoiding activities on your back after the first trimester.^[1]
• The Canadian guideline recommends changing position if you feel light-headed, nauseous or unwell when exercising flat on your back.^[5]
• The IOC expert group says side effects are more likely after 28 weeks, and that some studies found no adverse effects from exercising on the back for two to three minutes at a time.^[3]
• The NHS suggests that in later pregnancy you avoid lying flat on your back for more than a few minutes.^[7]

The reason for the different answers is simple: there isn't much research. A systematic review concluded there was not enough evidence to say whether exercising on your back is safe or should be avoided.^[4] Eggsports takes a cautious middle path: from week 16, our sessions leave out exercises lying on your back or on your front.

You don't need to give up the exercises you like. The IOC group suggests tilting your upper body to about 45 degrees, or moving the exercise to side-lying, sitting or standing.^[3]

If you ever feel dizzy, sick or short of breath on your back, roll onto your side, rest for a moment, and sit up slowly.

How does pregnancy change your balance?

ACOG describes the changes clearly. The extra weight at the front of your body shifts your centre of gravity and puts stress on your joints and muscles, especially in your pelvis and lower back, which makes you less stable and more likely to fall. Pregnancy hormones also relax the ligaments that support your joints, which makes them more mobile and more prone to injury.^[6]

This is why the guidelines are wary of activities where a fall is likely. The Canadian guideline recommends avoiding activities with physical contact or a danger of falling, such as horse riding, downhill skiing, ice hockey and gymnastics, and suggests avoiding non-stationary cycling as pregnancy progresses.^[5] It also recommends a warm-up and cool-down for every session, because relaxed ligaments may affect your range of movement.^[5]

Practical changes that help:

• Keep a hand on a wall, chair or rail during single-leg or standing exercises.
• Widen your stance in squats and hinges.
• Swap walking lunges for supported split squats.
• Choose a stationary bike over a road bike, and an even path over rough ground.
• Slow down transitions, especially getting up from the floor.

Eggsports applies this throughout pregnancy by leaving out exercises with a high balance demand, and from the third trimester it also leaves out those with a moderate balance demand.

Is high-impact exercise okay in the second and third trimester?

ACOG says experienced runners and racquet-sports players may be able to keep doing these activities in pregnancy, after discussing them with their doctor.^[6] At the same time, it suggests avoiding jerky, bouncy or high-impact motions because of looser joints.^[6] The NHS notes that as your bump grows, you may find other types of exercise more comfortable, such as switching from running to brisk walking, and that swimming can take pressure off your muscles and joints.^[7]

Impact also loads the pelvic floor, and the IOC expert group notes that pregnant athletes are not protected from leaking or prolapse.^[3] If you notice leaking, heaviness or pelvic pain when you run or jump, that's a sign to switch to lower impact for now and to keep up your pelvic floor exercises. Our pelvic floor exercise timer can help you make them a habit. Pelvic pain while walking or on stairs may be pelvic girdle pain, which our guide to pelvic girdle pain covers in detail.

How hard should you exercise later in pregnancy?

The Canadian guideline recommends moderate-intensity activity throughout pregnancy and describes the talk test: you're at a comfortable intensity if you can keep up a conversation, and should ease off if you can't.^[5] On a 0 to 10 scale of effort, the WHO puts moderate activity at around 5 or 6.^[1]

Heart rate can be a useful extra signal, but it has limits. The IOC expert group found that perceived effort doesn't track heart rate closely in pregnancy, with heart rate often higher than people expect from how hard they feel they are working.^[2] That's another reason to lean on the talk test and how you feel. Our pregnancy exercise intensity guide combines both.

What about harder efforts? A systematic review of 15 studies found that vigorous exercise continued into the third trimester did not affect birth weight and appears safe for most healthy pregnancies.^[8] The Canadian guideline is more cautious, recommending high-intensity activity only in a monitored environment and supervision from an obstetric care provider for anyone exercising well above the guidelines.^[5]

Heat is worth respecting. The WHO advises avoiding activity in excessive heat, especially with high humidity, and staying hydrated.^[1] A review of heat studies in pregnancy found that no participant reached the core temperature of concern, and identified limits that kept people comfortably below it.^[9]

Which positions work best in the third trimester?

In the third trimester, Eggsports favours standing, seated and side-lying exercises. All fours can work well too, as long as your wrists and knees are comfortable. ACOG also reminds us that standing still for a long time can make blood pool in the legs and feet, so keep gently moving between exercises.^[6]

You can check which week you're in with our pregnancy week calculator. If you lift weights, our guide to lifting weights while pregnant has trimester-specific swaps, and our guide to core training in pregnancy explains how to adapt ab work as the bump grows.

When should you slow down or stop?

These are ACOG's warning signs for stopping exercise in pregnancy.^[6] The NHS adds that it's important to listen to your body, not push yourself too hard, and stop if you feel uncomfortable, too hot or unwell.^[7]

The later months are also when contractions and fluid loss become things to watch for. Our guide to warning signs to stop exercising explains each sign and what to do. If you're earlier in pregnancy, see exercise in the first trimester, and for the full picture, our complete guide to exercise during pregnancy.