Bristol Palin's plans to marry fiancee Levi Johnston have been rocked by rumours that his ex-girlfriend may be pregnant with his child.

Just weeks after announcing their surprise reunion, Sarah Palin's 19-year-old daughter was said to be reconsidering her future with beau Johnston after a report emerged in the National Enquirer, reports News.com.au.

The US tabloid claimed that Lanesia Garcia became pregnant after a brief reunion with Johnston, 20, during his break-up from Bristol Palin last year.

Garcia, who is about to give birth to the child, reportedly told a source that Johnston was one of a number of possible fathers to be determined using a paternity test.

A spokesman for the Palin family told celebrity website RadarOnline that "no official decision has been made," about whether Bristol would stay with Johnston, but added that the couple were currently in contact "by text message" only. (ANI)