In September 2017, there was a change to the Foreign Affairs Manual that affects the entry rules into the United States. According to Boundless, the change created a new rule which states that people who come to the United States within the first 90 days are presumed to be immigrants if they do certain things. 

We are focusing now on the intent of the person entering the United States to change status. This is important for adjustment of status, especially when you specifically marry a citizen or you file for an adjustment based on a family member. 

So what does the 90-day intent rule do? Initially, before this change, U.S. embassies and consulates were looking at a 30 to 60-day rule. If somebody entered the United States on a non dual intent visa like a tourist visa or an investor visa and they change their status within the first 30 or 60 days, the presumption is that they were intending to immigrate or a change of status. 

Under the new 90 day rule, if you do any of those things, such as change your status, marry a U.S. citizen or file for an adjustment within the first three months, the presumption is that you planned this all along and it could be considered fraud or misrepresentation. Therefore, when you enter the U.S. in the first three months, do not marry a U.S citizen, do not file for an adjustment of status and do not do any of these things. If you do, when you come to the USCIS interview, there could be some issues with your intent.