How can I make an imprint on a pregnant stomach in photoshop?

First, get picture of a fist pushing through some elastic material. Make sure the lighting you use will be the same as that used on the pregnancy shot.

Now get your picture of a pregnant woman. Mind the lighting, that will be one of the biggest factors in determining how well your pictures blend together.

The photoshop operations will be mildly advanced.
1. Open both pictures.
2. Use the lasso with feathering to select the fist and surrounding texture.
3. Copy the selection and paste it as a new layer into the pregnancy shot.
4. Use a free transformation on the fist to get it into the position and scale you want.
5. Create a layer mask on the fist layer, and use a soft black brush to fade the edges.
6. Set the fist layer’s blending mode to Multiply, and tinker with opacity.
7. Use filters and/or adjustment layers to tweak.

I *think* that will help you reach your goal.

Do this with a displacement map.

• Get a picture of a fist and size it to your needs
• Desaturate and save it
The more contrast you have in the fist image, the better this will work
• Select the portion of the target image where you want the fist
• Filter > Distort > Displace

See your dentist… for real. See if you can get a sheet of dental dam elastic. This rubber material can be stretched without breaking. This is what you can use to get the stretched skin effect with the fist with one hand or more. Throw in a foot if you like. The photo shop can be used to change the color of the rubber to match the skin. Light the rubber to get the best definition and details of the hand so it shows through texture mapping techniques. You can change the size of the the hand to get the effect you need.