That's about 19 years before viability ends, or about 228 months. You'd still get about 23 kids by the end of it.
BUT HEY let's do something fun and add in some random factors because that's assuming it'll just be one kid, and almost 2 decades of broodmothering is definitely gonna do something to the body.
So let's add the following factors: Every 2 years after the first pregnancy, there's a chance for twins, and every 5 years after the first pregnancy there's a chance for triplets (or more, but let's use triplets to make it easier).
Assuming every 2nd year and 5th year ends up producing twins and triplets respectively, you could end up with 38 kids by the time you're 35.