Is a pregnant wife's insistence on fasting considered a mistake, especially after the doctor's advice that fasting may affect the water supply to the fetus?

A pregnant woman must break her fast if the lack of sufficient water reaching the fetus would harm it, especially if a Muslim doctor, who is an expert, instructs her to do so. Her insistence on fasting in this situation is a mistake and an extremism, as it entails hardship and harm, based on the words of Allah Almighty: "And He has not placed upon you in religion any difficulty."