Thanks for the query.
The possible causes are:
There will be increased blood supply to external genital organs during pregnancy
, so mild friction can cause spotting that may be responsible for your brown discharge.
During pregnancy when uterus
grows there will be stretching of round ligament which can cause pain when sudden change of posture occurs.
As these are normal symptoms no need to worry.
If the spotting or pain increases better to consult the doctor once.