In my opinion, you will have to file a change of status application from J-1 to B-2.
This is not legal advice and a client attorney relationship is not created. For a free consultation call (718)234-5588.
Talk to your J visa program sponsor (the one who signed your DS-2019).
You can try for a B .. .but your reasons aren't all that 'good'.
I'll be direct ... wanting to have a baby in the US will not be looked upon favorably by the US government. You should consider going home before March.
PROFESSOR OF IMMIGRATION LAW for over 10 years -- This blog posting is offered for informational purposes only. It does not constitute an attorney-client relationship.