What Mattress Firmness Is Best During Pregnancy?

The question of mattress firmness during pregnancy does not have a single answer because the right firmness changes as pregnancy progresses. A surface that feels right in the first trimester may be too firm by week 30, when hip cushioning becomes a genuine need. Understanding why that happens makes it easier to find the right starting point and know what to adjust.

How pregnancy changes what firmness does

Firmness ratings describe the surface feel of a mattress. What that feels like depends partly on you, specifically your weight, body shape, and sleep position. Pregnancy changes all three of these over time.

In the first trimester, your body is largely the same as before pregnancy. Firmness preferences from before pregnancy usually still apply.

By the second trimester, the center of gravity has shifted forward. Most women have transitioned to side sleeping or are being advised to. Hip width and the prominence of the greater trochanter (the bony protrusion at the top of the femur) become the primary pressure concern. A mattress that was fine to back sleep on may be too firm for side sleeping on that same hip.

By the third trimester, weight has increased significantly, often 25 to 35 pounds above baseline. Heavier bodies compress mattress surfaces more, which means a medium-firm mattress that felt supportive earlier in pregnancy may feel harder as body weight increases its contact with the surface.

Research: Body weight and contact area directly influence interface pressure at the hip and shoulder during side sleeping. Pressure increases as a function of body weight relative to surface compliance, meaning a given firmness will feel effectively firmer as pregnancy weight increases. (Jacobson BH, Sleep Health, 2010)

Firmness by trimester

First trimester: Whatever you were comfortable with before pregnancy, with one caveat. If you are a stomach sleeper, start thinking about transitioning to side sleeping now. Stomach sleeping becomes impractical by 12 to 16 weeks, and starting the habit earlier is easier than making an abrupt switch when sleeping on your stomach becomes uncomfortable.

Second trimester: Medium (around 5 to 6 on a 10-point scale) for most women. Side sleeping is now the primary position, and the hip needs enough give to cushion the greater trochanter and iliac crest without sinking through. Back sleepers who have not yet transitioned should do so now. If you were on a firm mattress before pregnancy, this is the trimester where it often starts to cause hip and shoulder soreness.

Third trimester: Medium to medium-soft (around 4 to 6) for most women. The combination of increased weight, round ligament discomfort, and the need to change positions frequently all favor a slightly more giving surface. The hip pressure point is now more prominent, and the mattress needs to cushion it across longer periods without bottoming out.

Firmness by sleep position

Most of this guide assumes side sleeping, because that is the recommended position from the second trimester onward. But position preferences vary, and some women move between positions through the night.

Side sleeping: Medium to medium-soft. Hip and shoulder need to sink into the surface. Lumbar region needs to be supported in neutral position, not hanging in a gap between hip and shoulder. A pillow between the knees takes torque off the pelvis regardless of firmness.

Back sleeping (first trimester only): Medium-firm. The goal is lumbar support and even distribution of weight. A pillow under the knees helps. After the first trimester, back sleeping is not recommended due to pressure on the vena cava and reduced fetal circulation.

Stomach sleeping (early first trimester only): Personal preference from before pregnancy applies. It becomes uncomfortable before it becomes harmful, so you will know when to stop.

Body type and firmness

Firmness recommendations are approximations. Your body type significantly affects how a given firmness performs.

If you have wider hips, your hip creates a larger contact zone with the mattress, which distributes pressure more broadly. You may be able to use a slightly firmer surface than someone with narrower hips.

If you carry pregnancy weight concentrated in the abdomen and have relatively narrow hips, the hip pressure point can be sharper. Medium-soft or adding a latex topper may help.

If you are petite (under 130 pounds pre-pregnancy), be cautious about medium-soft ratings. Many mattresses rated "medium" by manufacturers are calibrated for average-weight adults. A petite person may not compress the surface enough to engage the support layers, and the mattress effectively feels firmer than rated.

What if your current mattress is the wrong firmness?

If you are mid-pregnancy and your mattress is too firm, a latex or responsive foam topper can adjust it without a full replacement. A 2-inch medium latex topper adds meaningful hip cushioning while keeping the support structure of the mattress underneath intact. Memory foam toppers work but have the same slow-response issue as memory foam mattresses. Latex toppers respond immediately, which is better for the frequent position changes of late pregnancy.

If your mattress is too soft and you are sinking through, a topper will not help. The problem is the support core, and a topper adds more softness rather than firmness. In this case, the practical option is either a new mattress or placing a piece of plywood under the mattress to firm up the base temporarily.

Specific recommendations

Available in three firmness options, which makes it unusually practical for pregnancy: the Plush Soft works for most second and third trimester side sleepers, and the Luxury Firm works for those with a firmer preference or who are earlier in pregnancy. Lumbar enhancement bar prevents center sag, which matters for back support when sleeping on your side.

Available with and without a pillow top, effectively giving you two firmness profiles. The standard version is a medium-firm that works well for first and early second trimester. The pillow top version adds hip cushioning that becomes valuable in the third trimester. Natural latex responds immediately and does not develop the body impression that memory foam does over months of use.

Designed for side sleepers with pressure relief at the hip and shoulder as the primary goal. The medium feel is calibrated for side sleeping rather than back sleeping, which aligns with what is recommended during pregnancy. For women whose primary complaint is hip and shoulder soreness from side sleeping, this is a strong option.

How firmness interacts with circulation

The left side sleeping recommendation exists because of the inferior vena cava. The IVC runs along the right side of the spine and carries venous blood from the lower body to the heart. After roughly 20 weeks, the uterus is large enough to compress it when lying on the back. Left side sleeping shifts the uterus off the IVC, restoring venous return and improving cardiac output by 8 to 18 percent compared to supine.

Firmness does not directly control circulation, but it affects how easy it is to maintain the position that does. A mattress with the right firmness under the hip makes sustained left side sleeping comfortable. A too-firm surface creates enough hip pressure that women unconsciously roll toward their back during sleep. A too-soft surface creates the asymmetric sinking that makes staying on one side through the night harder.

There is a secondary mechanism worth knowing. When the hip sinks very deeply into a soft surface, the leg is sometimes positioned in a way that partially impairs venous drainage from the lower leg on the downward side. This is less significant than the IVC question, but it is part of why avoiding a mattress that is too soft is not just about lumbar alignment.

Research: Sustained left lateral decubitus positioning in late pregnancy is associated with higher uteroplacental perfusion and fetal heart rate variability compared to supine and right lateral. Positional comfort, which is partly determined by sleep surface properties, is a significant predictor of sustained side sleeping through the night. (Warland J, Midwifery, 2018)

The practical implication is that getting firmness right serves two goals at once: it reduces hip pressure (the structural angle) and it makes the recommended position more sustainable (the circulatory angle). A mattress that is comfortable enough to stay on does more good than one you roll off of in your sleep.

The one adjustment that costs nothing

Before adjusting firmness, add a pillow between your knees. It keeps the pelvis level, takes torque off the SI joint, and reduces the compression at the hip that firmness is trying to solve. Many women find that the right pillow placement makes their current mattress workable even if it is not ideal. It is the highest-leverage free adjustment available.

---