Morning sickness starts usually within 1-2 weeks of implantation and around the time you miss your period.
You become dehydrated when your body is using fluids faster than they are being replenished. Even outside of your pregnancy, dehydration can come on quickly and have serious side effects.
Many women experience a form of gastrointestinal discomfort at some
point during their pregnancy such as nausea, vomiting, constipation or
diarrhea. There may be a nutritional solution worth trying.
Vomiting normally does not harm the fetus. If the pregnant mom is vomiting excessively, something called 'hyperemesis gravidarum' then the larger danger is the threat of dehydration.
This is an overview and recommendations for nausea and vomiting morning sickness in pregnancy
What can be done about nausea and vomiting during pregnancy?