Your correct Curtis but it has also been seen in women of nomadic tribes during moves without the lower body fat and in women undergoing high levels of stress.

Since the human body doesn't differentiate wether a stress is physical or emotional the results are much the same. It is also why the sustained "fight or flight" response during emtional stress is so harmful over time. It is there for short term increased reactions to save us, but when it continues over time due to emotional stress it becomes very harmful to the body.

Based on what I know of women's reproduction and the bodies reactions to stressors I strongly doubt that a woman has an increased chance of becoming pregnant during a rape.