Yogi Honey Lavender Stress Relief Tea

My neuro suggested chamomile or lavender tea to help the magnesium for migraine treatment that's safe while TTC. I got Yogi Honey Lavender Stress Relief Tea on Amazon and there's a warning label on it that says pregnant and breastfeeding women should check with a doctor before drinking. Now I'm afraid to drink it. Why is there a warning label on the tea?