The total amount of fluids in your body increase while you are pregnant,and lower protein levels can result in fluids spilling over from your blood vessels into other tissues. As your uterus grows, the pressure on your veins will go up, and fluid retention will get worse. The lower half of your body is most commonly affected ankles especially.
But fluid retention can also strike your hands and arms, and even your face. Swelling, which tends to go along with water retention, might be uncomfortable and even cause some pain. Putting your feet up and continuing to eat a good diet can help fight fluid retention. Standing up for long periods of time makes fluid retention and swelling worse, so try to avoid that if at all possible.
Accepting it as a normal part of pregnancy, that will go away totally as soon as you give birth, will probably make you fret less about this symptom. Extreme swelling of the hands and face, and asymmetrical swelling, is something you want to pay attention to because it can be a possible symptom of more serious medical conditions, including pre-eclampsia. If you notice this kind of swelling, everything may still be totally normal, but it is advisable to go to get checked out by your doctor or midwife, just to be on the safe side.