Several common positions become risky as pregnancy progresses, primarily because the growing uterus can compress major blood vessels, strain weakened abdominal muscles, or put pressure on your spine and pelvis. The most important one to know: after 28 weeks, avoid lying flat on your back for extended periods. But sleeping position is only part of the picture. Certain exercise positions, lifting techniques, and even the way you sit or stand can affect both your comfort and your baby’s wellbeing.
Why Lying on Your Back Becomes a Problem
When you lie flat on your back, the weight of your uterus presses directly on the inferior vena cava, the large vein that carries blood from your lower body back to your heart. This compression reduces the amount of blood returning to your heart, which can lower your blood pressure and decrease blood flow to the placenta. The result is sometimes called supine hypotensive syndrome, and it can leave you feeling dizzy, nauseous, or short of breath.
UK national guidelines recommend that women be advised against sleeping on their backs after 28 weeks of pregnancy, citing evidence linking the supine position to increased risk of stillbirth and smaller-than-expected babies. Before 28 weeks, the uterus generally isn’t heavy enough to cause significant compression, so back sleeping earlier in pregnancy is less of a concern.
The practical fix is side sleeping, with the left side often recommended because it keeps the vena cava completely unloaded. A pillow between your knees and another behind your back can keep you from rolling over during the night. If you wake up on your back, don’t panic. Simply shift to your side. The risk is associated with prolonged time in the supine position, not brief moments.
Stomach Sleeping: Safer Than You’d Think
Many pregnant women assume lying face down is dangerous, but research from a pilot study published in BMC Pregnancy and Childbirth found that with appropriate pillow support, the prone position is feasible and comfortable even for women near term. In the study, participants tolerated it well for short periods of about five minutes. Pregnancy alone is not a reason to consider the prone position unsafe.
That said, comfort is the real limiting factor. By the second trimester, most women naturally find it too awkward to lie on their stomachs. If you do want to lie face down for a massage or brief stretch, a body pillow with a cutout for your belly can make it workable. Just know that longer durations haven’t been well studied, and the position did cause a slight increase in maternal heart rate in the research that exists.
Exercise Positions That Increase Abdominal Pressure
Certain core exercises create high intra-abdominal pressure that can worsen diastasis recti, the separation of the two sides of the abdominal wall that commonly develops during pregnancy. The key warning sign is “coning,” a visible ridge or bulge that forms along the midline of your stomach during exertion. If you see coning during any movement, stop immediately and find a modification.
Full planks are a common culprit. If you can’t breathe normally during a plank, feel excessive pressure in your abdomen, or notice coning, switch to a knee plank or an elevated plank with your hands on a chair or wall. If those still cause issues, skip planks entirely and work on other deep core exercises like pelvic floor engagement or modified bird-dogs.
Traditional crunches, sit-ups, and double leg lifts also fall into the high-pressure category and are generally best avoided from the second trimester onward. The goal isn’t to stop working your core altogether. It’s to choose exercises that strengthen without forcing the abdominal wall apart.
Yoga Poses to Skip
Three categories of yoga poses deserve extra caution during pregnancy: inversions, closed twists, and prolonged supine poses.
- Inversions like headstands, handstands, and shoulderstands put the extra weight of the placenta, amniotic fluid, and baby above your diaphragm. This compresses your breathing, increases pressure on your heart, and raises the risk of losing your balance as your center of gravity shifts.
- Closed twists such as revolved side angle and revolved triangle pose twist the torso in opposing directions, restricting blood flow and compressing the abdomen against the uterus.
- Supine poses held for extended periods carry the same vena cava compression risk as back sleeping, particularly from the second trimester onward. Brief transitions through a back-lying position are generally fine, but holding a pose like savasana flat on your back for several minutes is worth modifying. Lying on your left side or propping your upper body at an angle are simple alternatives.
Lifting: How Much and How
Clinical guidelines based on the NIOSH lifting equation break recommendations into two pregnancy periods: before 20 weeks and 20 weeks or later. The maximum recommended weight for an ideal lift (infrequent, close to the body, no twisting or stooping) is 51 pounds. But real-world lifting rarely looks ideal. If you’re holding something far from your body, that limit drops to around 20 pounds. After 20 weeks, all recommended limits decrease further because your growing belly increases the distance between the object and your spine, putting more strain on your lower back.
Two specific lifting positions are flagged as especially risky regardless of weight:
- Lifting from the floor with your hands below mid-shin level. This requires deep bending that strains the lower back and pelvic floor.
- Overhead lifting, which shifts your already-altered center of gravity even further, increasing postural instability and the risk of falls.
If you need to pick something up, bend at the knees rather than the waist, keep the object close to your body, and avoid twisting as you stand. After 20 weeks, consider asking for help with anything heavy or awkwardly shaped.
Prolonged Standing and Sitting Posture
Standing continuously for long stretches, particularly over eight hours, is associated with chronic venous insufficiency, lower back pain, foot pain, and an increased risk of preterm birth. If your job requires standing, take seated breaks every 30 to 60 minutes, wear supportive shoes, and use a small footstool to alternate resting each foot.
Sitting posture matters too, especially if you’re dealing with pelvic girdle pain. The key principle is keeping your hips higher than your knees. When your knees sit higher than your hips (as happens in deep, soft couches or low car seats), it tilts your pelvis backward and increases strain on the pubic joint and lower back. If you use an exercise ball for sitting, make sure it’s large enough that your hips remain above knee level. When standing up from any seated position, keep your back and knees aligned rather than twisting to one side.
Sexual Positions in Late Pregnancy
Sex during pregnancy is safe for most people, but certain positions become uncomfortable or impractical as the belly grows. Lying flat on your back for extended periods carries the same vena cava concern as back sleeping, making missionary-style positions less comfortable in the third trimester.
Being on all fours can work well in early and mid-pregnancy, but during the last two months, the spinal curvature combined with a heavy belly can cause the cervix to be hit more directly during penetration, which some women find painful. Being on top gives you control over depth and angle, but in the third trimester, deep penetration may irritate the cervix or cause light bleeding if you’re already sensitive. Standing sex tends to become difficult simply because of balance and the physical bulk of a late-pregnancy belly.
The common thread is that positions allowing you to control depth, avoid lying flat, and stay comfortable are the best choices as pregnancy progresses. Side-lying positions, where both partners face the same direction, tend to remain comfortable throughout all three trimesters.
Heat Exposure During Physical Activity
While not a body position per se, it’s worth noting that exercising in high heat and humidity poses a real risk during pregnancy, especially in the first trimester. Elevated core body temperature from sources like hot tubs and saunas has been linked to an increased risk of neural tube defects. Normal exercise doesn’t typically raise core temperature into the danger zone, but exercising in hot environments while wearing restrictive clothing can push you closer to that threshold. Loose-fitting clothes, good hydration, and avoiding outdoor exercise during peak heat are simple precautions that make a real difference.