She was pregnant. Noah's brain simply couldn't seem to process the information. His mother - or, at least, this younger version of her - was pregnant. Which definitely wasn't a bad thing. He wouldn't exist if it were, but it was certainly... unexpected.
Still, Noah had grown up in a place where surprises were all well and good but you could only stay shocked for so long before it became dangerous. So he bounced back quickly enough mainly by forcing himself to breathe while keeping a close eye on Sylar's reaction to the news. Yes he looked happy, albeit shocked, but Noah wasn't willing to take any chances.
He kept his mouth shut about such things though and slid his gaze from Sylar to Elle, his smile sincere if a bit frayed at the edges. "Congratulations," he stated.
The word didn't seem to be enough, not even close, but it was all he could manage on such short notice.