Jenni 'jwoww' Farley feared she had harmed her unborn child early in her pregnancy after a doctor informed her the baby had a cyst on its brain.

The former Jersey Shore star's physician found an irregularity in her ultrasound and subsequently discovered it was a rare cyst, and now the mum-to-be has opened up about the drama on her website.

She writes, "(I was) literally hysterical to the point where I was hyperventilating thinking... 'I did something so horrible to my daughter'.

"(But), they tell me this happens to about 1-2 (per cent) of pregnancies. It's called choroid plexus cyst and over time the cyst should go away. Honestly I was happy, but still my heart felt heavy. And even though I know I did nothing to cause it I felt guilty and so helpless. Such a horrible feeling."

But there was another complication to come - after her doctor discovered Farley had a low-lying placenta.

She recalls, "He said... we need to be cautious until the next visit, so no bleeding occurs...' (I say), 'What do you mean by cautious?' (He says), 'Well no sex.' I literally burst out laughing hysterically."

She adds, "Fast forward to this checkup which brings me to... six months (pregnant). My daughters cyst went away! Also my placenta is higher so I'm no longer at risk..."

The child will be the reality star's first with fiance Roger Mathews.