Predominantly: The word “Predominantly” makes DALL-E focus more what you want.
In 1st sample, you can see the first sentence “Predominantly the baby is lying on her back on a colorful play mat”, also repeating it end of prompt is make better.
Position of the elements: When DALL-E creates images, it thinks general thing, for example blankets; blankets are used to cover our body while sleeping or when sitting on the chair to cover our legs. We need to say where located this blanket otherwise it shows over the body or on the legs. In the sample prompts I said “her knees are pressing on a corner of the blanket, joyfully lifting the corner of a brightly patterned blanket in front of her.”. DALL-E knows if it is under the knee, it is not over the baby, also blanket should be “in front of baby.”
If you try several times and DALL-E does not give output what you want, use a different element instead of “blanket” that is not used to cover the baby, for example “long tablecloth” or “large towel”.
Please look at the image below, I remove only the word “blanket” and replaced “long tablecloth” or " large towel" in your prompt, not any other words changed. Exactly your prompt you provided above. And it works,
Sometimes we have problem also back, front, side angle, or vertical, widescreen images. You may visit these three topics for it: