Your Goldfish is not pregnant it has a deadly disease called 'Dropsy'. So the prognosis is very bad. This disease is usually caused by the fish being kept in poor water conditions. There is no known, reliable cure for this disease the fish will die.
Goldfish are egg laying fish, so they do not get pregnant. If your fish is female and appears fat, it's possible that she is full of eggs, but she will either release them on her own, or reabsorb them.
Goldfish don't get pregnant. When a Goldie is in spawning condition a female will get fat with eggs, then "lay" them and the male will fertilise them externally. It's only when a Goldie is a couple of years old and in spawning condition that they get like this.
Goldfish don't get pregnant. They lay eggs (ova). If it is springtime in your part of the world then female goldfish could well have their ovaries full of eggs and be ready to spawn. If they do not spawn, the eggs will be reabsorbed by the body.
Their are many varieties of goldfish, however goldfish with fat or potbellied stomachs are classified into the "Egg Bodied" goldfish category. Egg Bodied goldfish are their own distinct group of fancy goldfish which all have an unusually large abdomen. The most popular goldfish in this group are the Orandas, Ranchus, lionheads, and the pearl scale/Hama Nishiki.
If it looks fat because its scales are sticking out like a rasp or file the fish is dying and has a disease called Dropsy. If it is not swimming right that is usually caused by the same kind of things but the problem this time is with its swim bladder. These problems are usually caused by bad water conditions (Insufficent water changes, overcrowding, too small a tank, poorly set up filter etc). MY advice is do a water change ASAP.
They will be really fat.
No
Don't get your hopes, high, because goldfishes DO NOT, umm... become pregnant. Most probably, it might have a case of dropsy. Quarantine it immediately (I don't know if dropsy is infectious, but don't risk it.) and examine it closely. If its scales are protruding, the fish is doomed. If there is no signs of anything like that, relax. It is most probably ... carrying eggs? and there is no disease infecting it.
Online Body Fat calcuator or fat calipers.
Tanita does indeed sell body fat scales. They sell many different types of scales as well. I am including a link to a body fat scale sold on the Tanita website, http://www.tanita.com/en/bf683w-scale/
if your goldfish id going to get fat if not fatter regardles of how fancyscmansy it is als don't forget you need a guy goldfish to fertilize them
You can get your body fat measured at a gym, health clinic, or with at-home body fat scales.