Okay so you're pregnant and fat. This means you are also increasing in breast size. So you put Vala in a STUNNING colour, like a real colour not the colour of fricking toast and you play to the cleavage. Everything else is swathed in a way that makes the cleavage all the more rubenesque. Swathed, because the Goa'uld are so incredibly wealthy and glorious and a few extra yards of fabric make that all the more apparent. A long train would go down a treat.
It could have been fabulous. That dress needs shoulders so that the cleavage really catches the eye, instead we're just looking at bare shoulders. But the biggest crime is that disgusting colour, even if Claudia Black had said, "I WANT A MATERNITY FROCK" they could have done it in a real colour.