You can also use the practice of ujjayi breath for deeper focus, and to generate a bit of heat. (mindbodygreen.com)
Use the common yoga practice of ujjayi breathing, in which you sit with spine straight and inhale and exhale while slightly constricting your throat (and sounding more than a bit like Darth Vader). (health.com)
Yoga classes will generally begin by teaching you to rejuvenate your pregnant body through the core inhalation and exhalation method called ujjayi pranayama (ooh - jah - yee prah - nah - yah - mah). (lovingmomentsbras.com)