Pregnancy hormones. Those things definitely wreak havoc on you.
Meredith learns this first-hand in this scene from Thursday's Grey's Anatomy, and the impact is wide-ranging. It starts out positively, as Mer whisks Der away to satisfy her supercharged sexual urges.
Of course, the downside is that emotions can turn on a dime.
When Mer learns she has a consult and can't get it on with her man, it's like her world is crashing down ... and clueless Dr. Ross ends up in the crossfire when he shows up asking for a favor from Derek.
Check out the scene from "Walking on a Dream" below ...