There are many different reasons why someone may experience brown discharge after their period. It is not necessarily an indication of pregnancy. It could be caused by hormonal changes, stress, or irregularities in the menstrual cycle. Feeling tired all the time, nausea, or tenderness in your breasts can be signs and symptoms that suggest you might be pregnant. To be sure, take a home pregnancy test. 

This indicates that both of your fallopian tubes are open and functioning properly. This is a positive result as it suggests that there are no blockages or obstructions in your fallopian tubes that could interfere with fertility or conception. It increases the chances of successful natural conception and may be reassuring if you are trying to conceive.

In pregnancy, you may not experience regular periods cycle. It's possible for some individuals to experience bleeding or spotting during early pregnancy, which might be mistaken for a period. This bleeding is often lighter and shorter than a typical period and is known as "implantation bleeding."

The "risk for fetal aneuploidy is low" means that the probability of the fetus having an abnormal number of chromosomes is considered to be low which is a positive indication.

Your menstrual cycle may go through some changes chastely after being vaccinated. The vaccine is known to be able to modify the menstrual cycle at times, but it's no cause for anxiety. Over time, your periods will return to when they were on their own. Meanwhile, always be healthy, be hydrated, and get enough sleep.