Tradition and history — not medical advice
Daily practice, diet and moderation in the Haṭha Yoga Pradīpikā — and what's changed for a pregnant body
The Haṭha Yoga Pradīpikā names ten personal disciplines (niyama) for a practitioner, including a "sparing diet." It was written for a general adult practitioner, with no separate rule for a pregnant one.
What the texts say
Haṭha Yoga Pradīpikā — Chapter 1, verse 17
ahiṃsā satyamasteyaṃ brahmacharyaṃ kṣhamā dhṝtiḥ | dayārjavaṃ mitāhāraḥ śauchaṃ chaiva yamā daśa || 17 ||
The ten rules of conduct are: ahiṃsâ (non-injuring), truth, non-stealing, continence, forgiveness, endurance, compassion, meekness, sparing diet and cleanliness.
Pancham Sinh, The Hatha Yoga Pradipika (1914). Public domain.
Yoga Sūtra of Patañjali — Samādhi-pāda 1.14
This practice becomes well-grounded when continued with reverent devotion and without interruption over a long period of time.
BonGiovanni, The Yoga Sutras of Patanjali: The Threads of Union. Public domain.
Both texts describe practice, diet and moderation for a practitioner in general. Neither the Haṭha Yoga Pradīpikā's ten niyamas nor the Yoga Sūtra's teaching on practice names pregnancy, a trimester, or any change of routine for a pregnant body.
What modern guidance says
ACOG's exercise FAQ says that if you're healthy and your pregnancy is normal, it's safe to continue or start regular physical activity, and recommends working up gradually if you're new to exercise — see ACOG's own FAQ for the full guidance, including how much activity it suggests per week.
Keep up your normal daily physical activity or exercise (sport, running, yoga, dancing, or even walking to the shops and back)
NHS (reviewed 2023-03-15)
Speak to your doctor or midwife
Ask your doctor or midwife before starting or changing any exercise or diet routine in pregnancy, prenatal yoga included — this page is a history of two old texts, not a fitness or nutrition plan.