Where did you get that from? I could not find anything about that in the game files. The only thing that affects the baby's race is the father's race and lona's race. To be sure I've done some testing and I was even able to get a deepone baby three times in a row, so it doesn't look like this is the case. However, thanks to this I found out that the amount of semen also affects pregnancy chance. So to truly guarantee pregnancy Lona's hole must be filled to the brim before going to sleep.
By the way Womb Seedbed only affects new pregnancies, changing the amount of stacks won't speed up or slow down lona's current pregnancy. And lastly, the deduction in food is affected not only by pregnancy but also by difficulty, personality, parasites, bowel/bladder seedbed and breastfeeding if I didn't miss anything. None of these involve randomness so if you know all the values then you can even derive the stage of pregnancy from the deduction in food, but to me OP looks like a new player so it's probably better for him to just go to Elise for now