Weight gain up to week 13 should be ideally no more than about 5lb (2.3kg). Mid to late pregnancy is when you really start to notice an increase, as your body lays down fat stores for breastfeeding, so it's best to avoid putting on too much, too soon.
Weight gain in the middle trimester (weeks 13-25) tends to be more marked. From about week 20 you'll put on around 1lb for each week of your pregnancy, but don't expect it necessarily to be steady: some women put on 3-4lb in a week after a growth spurt, then nothing for two or three weeks.
During the final trimester, your appetite will probably grow, but if you have heartburn or feel full after eating you may find it helpful to have small frequent meals. You should be aiming to gain about 8-11lb.
Food you eat now is crucial for labour so try to aim for energy food like meat, chicken and fish, and carbohydrates such as pasta, rice and cereal to help build your reserves of stamina and energy.
Where the weight comes from
By the end of your pregnancy, you may have put on 15-40lb (7-18kg), but, on average, just 28 per cent of that weight is baby.
Here's how it all adds up:
Baby 7lb 4oz
Fat 7lb 11oz
Blood 2lb 12oz
Fluid retention 3lb
Amniotic fluid 1lb 12oz
Uterus 1lb 12oz