Here’s a (non-exhaustive) run-down of some basic principles and guidelines that you can look to in order to make a general (i.e., non-prenatal) asana class pregnancy-friendly:

1. Make Space for Baby

As pregnancy progresses, many asanas (in their classical forms, anyway) can start to feel restrictive and uncomfortable. Solution? Think “make space for baby” when you offer pose variations and alternatives. Avoid or modify poses that compress the belly. This might mean that you offer a prop or two (like blocks under hands in a standing forward bend or lunge), present spinal extensions as forward-bend alternatives (such as dandasana, or staff pose, in place of a seated forward bend), or suggest a wider stance.

2. Avoid or modify poses that compress the belly

It also means that pregnant students should avoid lying on their bellies (especially after the first trimester). In place of belly backbends like bhujangasana (cobra) or shalabhasana (locust), offer similar-ish poses that can be done on all fours, like cow or opposite arm/leg extensions.

3. Avoid Compressive “closed” twists—i.e., twisting toward the front leg side (in an asymmetrical standing twist like a lunge), or the bent leg side (in a seated twist like ardha matsyendrasana)—should be avoided for the same reason. Do “open twists” instead. This basically means “twist in the direction opposite to that of everyone else.” Pregnant students should also focus on opening up through the chest as they twist, not twisting from the belly.

4. Avoid Overstretching

During pregnancy, the hormone relaxin increases flexibility (the name itself is a bit of a giveaway!) and helps to prepare the body for birth. Because this influx of relaxin causes the ligaments to become more lax, pregnant students should take extra care not to overstretch. This can lead to pelvic and joint instability and/or pulled ligaments (which take a really long time to heal). To avoid overstretching, students should focus on strength and stability more than flexibility during pregnancy. This is especially important to keep in mind when it comes to hands-on adjustments. To avoid overstretching, students should focus on strength and stability more than flexibility during pregnancy.

5.. What’s the Deal with Inversions, Anyway?

In general, if inversions feel good, students can continue to practice them, but it is a good idea to avoid inverting near the end of the first and beginning of the second trimester (weeks 10-13), when the placenta is attaching to the uterine wall. Pregnant students should also avoid inverting for long periods of time (stick with 30 seconds or less). If you’re teaching long holds in inversions, a supported bridge pose (with a yoga block under the sacrum) with feet on the floor or legs in the air, is a great pregnancy-friendly alternative for most students.

6. Cut Out Kumbhaka

Pranayama practices involving breath retention (kumbhaka) should be avoided during pregnancy (as should powerful practices like bhastrika and kapalabhati). Remind pregnant students to breathe smoothly, evenly, and continuously, and suggest nadi shodhanam (alternate nostril breathing) or bhramari (bumble bee breath)—which are both wonderful to practice all through pregnancy—as alternatives to pranayamas that are contraindicated.

7. Avoid Lying on the Back If It’s No Longer Comfortable (or If You’re Not Sure)

Look at any “one-size-fits-all” list of pregnancy modifications for yoga, and you’ll likely see “avoid lying flat on the back.” This can be perplexing for students if lying supine still feels quite lovely.

8. Is it really dangerous for pregnant students to practice a traditional shavasana (corpse pose), or supine stretch?

The answer (of course!) is “it depends.” The reason why this caution is often given is that as baby continues to grow, lying flat on the back for an extended period of time can compress the inferior vena cava (an important vein which returns deoxygenated blood from the lower body back to the heart). When this happens, it tends to be pretty uncomfortable, and its likely that you will not want to remain on her back (which you shouldn’t).

9. Bottom line Listen to your body. Adjust your body and change positions if you start to feel nauseous, dizzy, or uncomfortable.

If a student is no longer comfortable lying flat on her back, she can practice a side-lying shavasana or a propped “incline” shavasana instead. For the side-lying variation, students should lie on their left sides (since the vena cava is on the right side of the body). A block, bolster, blanket, or pillow between the knees may help make this position more comfortable, and resting the head on a pillow or folded blanket, hugging a pillow bolster, or covering up with a blanket are other ways that you can make side-lying shavasana extra cozy and supportive.

For the incline variation, elevate the far end of a bolster with a yoga block or two, so that when a student lies over the bolster (with her bottom on the floor and her back on the bolster) her head is above her heart). A second bolster or rolled blanket under the knees can feel especially nice here, and may help to relieve lower back discomfort.