The short answer is no. You can meditate in a dress with nylon stockings and high heels on, and it will work just fine.
The longer answer is if you have a choice, it’s nice to feel comfortable. Many women enjoy meditating in yoga clothes or sweatpants at home. But no need to get hung up on what you’re wearing. If you’re at the office and your only chance to meditate before meeting your date at the theatre, that little black business dress that doubles for a night out won’t stop you from transcending. You sit down, start your meditation, and your mind automatically settles down while your breath slows and your heartbeat normalizes. It’s an automatic transcending experience. All the stress of the day leaves you like a giant sigh. That’s what Transcendental Meditation is all about—and it all happens on the inside, regardless of what you’re wearing.