The problem was that if they were going to have a baby, they actually needed to do the act that would get them to have a baby. And for a while, ever since Tony'd been depressed, he didn't seem to want to have sex with her. This part was even worse, with him feeling bad about having the arc reactor not only in himself, but in her too. She knew deep down what had caused her to get the arc reactor, but she was faking innocent for the time being.
Pepper had tried lots of things to get him interested, but nothing seemed to work. So she thought she'd try something relatively old fashioned, she went to the store and bought herself lingerie. Arc reactor or no, she wasn't letting him get away with telling her no. Again. After she put on the lingerie, she covered herself with a housecoat that buttoned up in the front and was fairly easy to remove. She even had her high heels on, and went downstairs to the basement to find Tony.