When cats become pregnant, they will go into heat again approximately 8 weeks after pregnancy. This can take 1 to 21 weeks and generally coincides with the period when kittens are weaned. It's worth noting that cats don't have to become pregnant when they mate. They can show all signs of pregnancy, such as gaining weight and appetite but won't have kittens. This is referred to as false or pseudo-pregnancy. It takes cats 4 to 6 weeks to go back into heat after a false pregnancy. If a cat that goes into heat fails to mate, she will go back into heat 1 to 14 days later. This cycle can repeatedly continue until she mates or when the breeding period comes to an end. Generally, cats go into heat 2-3 weeks from spring to early fall.