The aetiology of nausea and vomiting in early pregnancy is unknown, but is related to the rise in serum oestrogen and progesterone.
It is also associated with human chorionic gonadotrophin, and is more common in conditions where there is a larger trophoblastic tissue mass such as multiple pregnancy, diabetic pregnancy, and molar pregnancy. There are varying grades of severity and the most severe form (Hyperemesis Gravidarum) is associated with fluid and electrolyte disturbance and in progressive cases, with weight loss > 5% of initial body weight.
The main aim is to keep hydrated and get enough calories in during the first couple of months of the pregnancy. Frequent, small meals (The Tapas approach) combined with regular intake of small amounts of water and minerals (dilute Diorylate or sugar drinks without the fizz) are the best way of maintaining health during this time. A multivitamin is advised if you are not able to keep a well balanced diet during this time.