When should I notice results?

That all depends on your personal definition of "Results" Progress can be measured in a hundred different ways.

For example...when you did your leg lifts....how many did you do and how difficult were they? Next week when your body has adapted to the movement patterns and you're able to do double with ease...is that not a measured result you can see?

I find most people focus on just one thing (scale weight) as a "result" without looking at the big picture, most often leading to frustration and dissappointment.

A body compositoin change is a process of several smaller factors that work together in order to produce the end results. It's a lifestyle change for a lifetime.

I am in my 5th week of working out, and I saw results in about 2.5-3 weeks. My workout at the time consisted of about 45 minutes on the elliptical (w/resistance) 3-4 days per week.

Ok. That's a good response. So that then would be your long term and final goal, the result of which comes from several smaller goals along the way.

Building up your strength and endurance in your core will help you posturally which will make a difference in your core.

Leg lifts and Crunches will only go so far, since they're isolation movements of a single muscle.

Try adding in some stability exercises that cover your entire body. Those force your core to activate throughout making you stronger down the middle.

Front and Side planks are great and can be done from your knees to start if you don't have the strength to go from your feet.

As well, there are several simple movements you can do with a stability ball that'll help strengthen the entire mid-region.

Keep in mind, none of the above will specifically target any body fat stores in and around the midsection, but by being more posturally strong through the middle, you'll begin to feel some results more reminicent of your pre-pregnancy shape.