Hormones – it's all about hormones for a change and they radically affect your body's relationship with water. Your blood volume will double by seven months, amniotic fluid gets topped up by about 230ml EVERY hour. Your kidneys go into overdrive, keeping you and baby clean and fresh, so to speak, and as for the effort of carrying baby around; that results in increased water loss through your lungs.
Remember that if you feel thirsty you are probably already dehydrated so you need to get ahead of the game, water wise! Many women experience fatigue during pregnancy and proper and constant hydration will minimise, or perhaps even eradicate this completely. If you feel dehydrated increase your water intake for a few days and see if it resolves the problem.
Most women know of the need to remain hydrated but are unaware of the extent of additional requirements during pregnancy. During pregnancy mum should plan to be drinking between 8 and 12, 250 ml glasses of water a day. Don't forget that by month seven mums blood supply will have doubled to support her new needs as well as those of the baby.
It all sounds as though you need to be connected to a tap all day and every day but there are some simple things you can do to make dealing with this increased demand for water manageable.
Obviously drink as much as you can, good choices include water (mineral or tap), fruit juices, herbal teas, soft drinks, and of course decaffeinated tea and coffee. Your diet can help out with your hydration levels. You need to eat fresh fruits and vegetables for you and for baby's nutrition but you will also be helping your hydration at the same time.
Morning sickness can be a problem! Try not to avoid drinking water if you are suffering as this will increase your risk of dehydration and make things worse – nausea can also be a side effect of dehydration. Which means that a bout of morning sickness could stop you from hydrating which in turn could dehydrate, which could cause nausea, which could be taken for morning sickness, which could stop you hydrating...!
Fresh root ginger has a calming effect on queasy tummies. Try infusing some hot water or perhaps black tea with it.
Avoid coffee and tea wherever possible – don't forget that caffeine is a diuretic; it'll make you pee more and only increase the risk of dehydration. Be wary though; don't go from 8 cups to 0 cups overnight. Cut it out gradually over a period of weeks to avoid side effects.