Heat During Pregnancy: What’s Safe

Heat on your lower back or shoulders is generally fine during pregnancy, on a low setting for short sessions. Heat on your belly, and anything that raises your whole body temperature, is where the caution sits.

The distinction that matters

• Local heat warms one patch of skin and the muscle under it. A heat pad on your lower back does this. It doesn’t change your core body temperature.
• Whole-body heat raises your core temperature. Hot tubs, saunas, very hot baths and hot yoga do this. Advice in pregnancy is to avoid these, particularly in the first trimester, because a sustained rise in core temperature has been linked with a higher risk of certain birth defects.

A heat pad on your back is the first kind, not the second. On how far a pad’s warmth actually reaches, see what heat does under the skin.

Where a pad is reasonable

• Lower back. The most common pregnancy ache, especially later on as your centre of gravity shifts.
• Hips and the back of the pelvis. Pelvic girdle pain is common and often eases with warmth. Where it sits out on the side of the hip, see outer hip pain.
• Neck and shoulders.
• Calf and leg muscle aches, if there’s no swelling or tenderness in one calf (see the warning below). Night cramps are covered in calf cramps at night.

Lowest setting, cover on, 15 minutes, then move gently. Don’t lie on top of the pad.

Where not to use it

• Your abdomen. Keep the pad off your bump at any stage. See heat and tummy pain.
• Over a caesarean wound that hasn’t fully healed. See heat after a C-section and heat after surgery.
• Anywhere you have reduced sensation, including from a recent epidural or spinal.
• While you sleep. Pregnancy is tiring and dozing off with a pad on is easy to do. See is it safe to sleep with a heating pad on?

Skin can also be more sensitive during pregnancy, so start lower than you normally would and check afterwards. The full list is in who should not use a heating pad.

Comfortable positions

From the second trimester, avoid lying flat on your back for long.

Side-lying works well: lie on your left side, knees bent, a pillow between them and one supporting your bump, with the pad over your lower back. Sitting upright in a firm chair with the pad behind you is the other easy option.

What else helps pregnancy back and pelvic pain

• A warm (not hot) shower, with the water on your back
• Walking and swimming, if you’re used to them
• A pregnancy support belt for pelvic pain
• Keeping your knees together when getting out of bed or a car
• A physiotherapist who works in women’s health, who can assess you properly. Ask them exactly how they want the heat used.

Call your doctor or midwife if…

• You have any tummy pain, cramping or tightening. That needs assessing, not a heat pad.
• You have vaginal bleeding or fluid loss
• One calf is swollen, warm or tender. Pregnancy raises the risk of blood clots, and heat and massage are the wrong response. Get seen the same day.
• Back pain comes with fever, or burning when you pass urine
• You have a bad headache with vision changes or swelling of the face and hands
• You notice reduced movements from your baby

Check with your own doctor or midwife before using heat regularly, especially if your pregnancy is being monitored for any reason.

Afterwards: heat after a C-section, warm compresses for blocked ducts and mastitis, and new parent neck and shoulder pain.

Clinically reviewed by: Nigel Chua (Hand Occupational Therapist) & Louise Yow (Physiotherapist). This article is general information, not a diagnosis. electricheatpad.com sells electric heat pads.