Straight answer: No, fasting is not recommended when you are growing a human. Your baby needs constant nutrition and you need hydration to keep amniotic fluid levels up. Skip the fast and just do a simple puja instead.
Yaar, actually modern docs strictly say no to fasting during pregnancy. It's super risky for your sugar levels and can make you dizzy. Why take a chance, just eat light fruits and keep sipping water throughout the day.
When I wanted to fast, my mother and grandmother strictly told me that a pregnant woman is already doing a 'tapasya' by carrying a child. They made me delicious kheer and fruits and told me to focus on keeping the baby well-fed. Listen to your body and avoid starving yourself.
I remember feeling so guilty for skipping Karwa Chauth during my pregnancy, but looking at my healthy active toddler now, I know I made the right choice. Doctors strictly advise against long fasts. Your health and your baby's health come first, rituals can wait!
As someone who has been through this, I highly recommend avoiding fasting, especially without water. Dehydration can trigger early contractions or make you extremely weak. If you must, do a 'falahari' fast where you eat fruits and drink milk/juice every 2 hours.
After waiting so long for my miracle baby, I didn't want to take even a 1% risk, so I didn't fast at all. If your heart still wants to, please consult your doctor first because every pregnancy is unique and delicate. Your baby's safety is the biggest blessing.
Oh please don't fast, I would be way too terrified of the baby getting dehydrated or sugar levels dropping! What if the baby stops moving or gets distressed? Honestly, it's better to skip it this year, God understands our situation.