This is the one of the first signs you are pregnant with twins that the majority of women will experience, and the one that will probably push them into suspecting that they might be carrying twins. After all, it is an incredibly noticeable sign!
If you're experiencing bloating that makes you look further along than you are, parents or friends have commented along those same sort of lines, or you just feel like you're getting bigger faster than you'd have expected, then it's possible you're carrying twins.
Doctors and midwives will also normally measure your fundal height (the distance between the top of your pubic bone and your uterus) when you go for check ups. If this distance is further than expected, it's a possible sign of a multiple pregnancy.
There are multiple reasons why this might happen, though, so don't get excited if you're a little larger than you have been with past pregnancies or than you expected to be. It's not a sure fire sign of twins.