In a secret valley full of leeches, spiders and angophoras two hours from Sydney, scientists are waiting like anxious parents to welcome the birth of a baby pinosaur or two.

Pinosaur is the nickname given by some scientists to the prehistoric and critically endangered Wollemi pine. It was thought to be extinct until 100 of these Jurassic era conifers were found in four groves in a dark canyon in the Wollemi National Park 150km from Sydney.

Now an "insurance population" of 191 trees planted six years ago in an undisclosed location – far enough away from the original trees that if fire or predators strikes one lot of trees the other will survive – is producing fertilised seeds for the first time.

"The good news is that the Wollemi pines are making babies. Just like me," said Dr Heidi Zimmer, a senior scientist with NSW Environment who is also seven months pregnant. She's tracked the trees' progress since they were planted as juveniles.