There is no one answer to this question as the growth of labia minora can be affected by a number of factors. These can include puberty, hormones, pregnancy and even certain types of exercise.
During puberty, the body starts to produce more estrogen, which can cause the labia minora to grow in size. This is perfectly normal and nothing to worry about.
Pregnancy can also cause the labia minora to grow due to an increase in blood flow and estrogen levels in the body. Again, this is perfectly normal and nothing to be concerned about.
Certain types of exercise (such as cycling or horse riding) can put pressure on the area between the legs which can lead to an increase in size of the labia minora over time. However, this usually isn't a problem unless it's causing discomfort.
If you're concerned about the size of your labia minora then it's best to speak to a doctor who will be able assess whether there is anything abnormal or if you just have naturally larger lips.