"Some People Should Be Careful With Intermittent Fasting (or Avoid It Altogether)" from Healthline's "Intermittent Fasting 101 - The Ultimate Beginner's Guide":
There are plenty of anecdotal reports from women whose menstrual periods stopped when they started doing IF, then went back to normal when they stopped doing it. For these reasons, women should definitely be careful with intermittent fasting. Ease into it, and if you have any problems like this then stop doing it immediately. If you have problems with fertility and/or are trying to conceive, then consider holding off on intermittent fasting for now. Intermittent fasting is probably a bad idea when pregnant or breastfeeding.