My mother-in-law always added a pinch of hing to rasam for digestion, but my doctor advised keeping it very minimal during the first trimester. A tiny amount in cooking is fine, but avoid medicinal doses.
I was so paranoid about hing in my dal when I was pregnant, but my boy is a toddler now and completely fine! A small pinch in daily food is absolutely safe, don't worry.
I had bleeding in my early weeks, so I completely avoided hing as it's considered 'warm' in Ayurveda. Please check with your doctor before adding it to your daily meals.