not to put on much weight at the start of your pregnancy (the first 3 months). Some women even lose weight because of morning sickness and its effect on appetite. This isn't a problem for baby, who will continue to grow by drawing on your reserves! Nature is well designed: baby is always fed first, and you next.
Heer's a basic guide to weight gain
The ideal amount of weight to put on between the first and ninth month of pregnancy varies between 9 and 12kg. But this average doesn't take your natural body shape into account! If you're tall and slim, you should ideally be putting on 14kg; if you're short and full-figured, 8kg is enough.
if you continue to stay at the same weight throughout your pregnancy, you could suffer deficiencies because your reserves will be exhausted. Eat enough, get a varied, balanced diet, and make sue you drink plenty of water regularly. Weigh yourself once a week, always at the same time of day. If your weight gain stays little but regular, don't be alarmed: you probably don't naturally store extra weight. On the other hand, if your weight stays the same after 4 months, speak to your doctor about it.
Find out more about weight gain during pregnancy.