i heared that anti strech marks lotions and creams are carcinoginic is it true?

There's no known clinical evidence says that anti-strech marks preparations are carcinogenic..

The majority of these preparations are designed to re-hydrate the skin while helping to maintain its natural elasticity as it is stretched during pregnancy.

Daily moisturisation of the skin both during and after pregnancy not only helps to keep the skin supple by reducing the dryness and itchiness often associated with stretch marks, but additionally, stimulates the skin on a deeper level, encouraging better circulation to the affected areas which in turn helps to further minimise the appearance of stretch marks.

Moisturisers which include concentrated amounts of vitamins E and A are popular, as are those which include some form of cocoa as this has also been found to help.

Anti-stretch mark creams which contain elastin and/or collagen are designed to penetrate the skin and increase elasticity at a deeper level ,many women find that creams containing these ingredients significantly help to reduce stretch marks.

TIPS
As a general rule, look for anti-stretch mark creams which are not too greasy and are easily absorbed into the skin, contain natural ingredients, including those listed above and always follow the manufacturers' directions for application of the cream.
By massaging anti-stretch mark cream into the skin daily throughout pregnancy and supplementing this with:

a balanced diet

lots of water

regular exercise,

the appearance of stretch marks should be minimised.