You are supposed to become "wet" and slippery with natural lubrication in the vagina during sex. This means that you are stimulated and ready for sex. This is natural and normal. Some women become "wetter" than others but there is nothing you can do to stop this nor should you want to. It is normal natural healthy response and it is to make penetration easier.
When you get pregnant, having sex may or may not be on your to-do list. For some women, first trimester symptoms like nausea and exhaustion make sex pretty much a non-starter. For others, however, there's a boost in sex drive once you become pregnant. Whether you're having sex during your pregnancy or not, you might notice that your vagina goes through some changes over the course of those nine months.
Vaginal lubrication is often closely tied to levels of the hormone estrogen, which changes at various life stages. Medications including hormonal birth control may cause vaginal dryness. Vaginal dryness is common but treatable, and can happen at any age. Symptoms may include a burning sensation, vaginal discomfort or itching, abnormal vaginal discharge , or pain during sex or masturbation.
Sexual responses are different in older men and women than younger people. Just getting older is one cause of the change in response, but things other than age can also have an effect. For example, some medicines can affect how you respond to sexual activity. Some diseases such as diabetes or heart disease can make it harder to have or keep an erection.