Weight gain during pregnancy isnt linear. In the first trimester, most women gain only 1 to 4 pounds total. Some gain nothing. Some actually lose weight, particularly if morning sickness is severe.
However, a cats pregnancy bump will begin to show about 35-45 days in, and she will gain about 1-2 kilos. Apart from that, you may notice that when she lies down, her stomach juts out on the side- sometimes you might even be able to see the kittens moving and stretching about inside.

Pregnancy weight gain guidelines depend on your pre-pregnancy BMI not a single universal number. Here is how to find your target range and what the extra weight is actually made of.

Gaining weight is more important during the second and third trimesters. From weeks 13 and beyond, you can expect to gain about a pound a week until you give birth. This usually comes out to around 340 extra calories a day in the second trimester and then 450 extra calories in the third.
Weight gain is a common phenomenon during pregnancy, but excessive gain may be a sign of adverse health issues for mothers.The recommended amount of weight gain during pregnancy for each BMI category prepregnancy are as follows