Dehydration during pregnancy can be caused by many things. For example, by diarrhea during a period of flu. The most common cause of dehydration during pregnancy is morning sickness (emesis gravidarum) or extreme morning sickness (hyperemesis gravidarum). Pregnant women can dehydrate very quickly when they vomit a lot, but even women who feel nauseous without vomiting can dehydrate if they are no longer able to absorb fluid.
Dehydration can be recognized by the following things (you may not have all the symptoms):
If you notice that you have these symptoms, it is wise to contact your healthcare provider. Do not feel embarrassed. Dehydration is a serious condition during pregnancy.
To prevent dehydration, it is important to drink enough. If you suffer from morning sickness or hyperemesis gravidarum, this is often very difficult. Experiment with different types of drinks (from water to milkshakes and from vegetable juice to tea) and different temperatures. Very cold drinks are sometimes better tolerated because they have less taste. It can also help to drink small amounts throughout the day.
Are you concerned that you can not get / keep enough, keep a hydration diary. Here you indicate what you have drunk and consumed in what amount, and what 'comes out' in what form (vomiting, urine, feces) and in what volume. After 24 hours, you can start using pluses and minuses and see if you get more fluid than goes out or vice versa. You can also take the diary to your care provider.
From angelababy In Q&A