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Beyonce broke the internet last week when she announced that she's expecting not one but two siblings for daughter Blue Ivy, joining celebrity mothers of twins, including fellow divas Jennifer Lopez, Celine Dion and Mariah Carey.

Having multiple births, especially in the late 30s and early 40s, indicates that fertility treatment may be involved, given that one in six IVF births is twins as opposed to one in 80 among the general population.

Now experts are warning that celebrities may be giving women the false impression that it's easy to fall pregnant over the age of 35 without fertility treatment.

Fertility Consultant Dr Irfana Koita, Director of IVF Matters has called on high profile figures to be open about help they may have had to conceive, telling Femail they may encourage women to delay motherhood. Many then realise they have left it too late and they are unable to afford the expensive treatment celebrities easily can. 

She said: 'One can't Botox the ovaries. Knowledge is power. Celebrities conceiving at the top end of their reproductive age may offer false reassurance.

'Most of these women may have had fertility treatment using their own eggs or donated eggs.'

Beyonce announced last week that she's pregnant with twins, meaning she will join the long list of celebrity mothers who've had multiple births 

Jennifer Lopez, pictured in 2008, after falling pregnant with twins at the age of 39 while married to her third husband Marc Anthony 

'Let's be honest and spread the word so that our women are well informed of their options and can take steps that best suit them.'

Julia Roberts had twins at 37, Jennifer Lopez at 39, actress Rebecca Romijn at 36 and Mariah Carey at 41.

Of course, it can't be said for certain that any of these famous women did undergo fertility treatment. 

But if they have, choosing to keep it quiet may give women the wrong impression that it's easy to fall pregnant naturally over the age of 35.

Desperate Housewives star Marcia Cross (left) in 2006, while expecting her twins who she conceived with a donor egg. Singer Mariah Carey (right) fell pregnant with her son and daughter in 2010 while married to her second husband Nick Cannon

Ugly Betty and X-Men star Rebecca Romijn announced that she was expecting twins with her husband Jerry O'Connell in 2008, aged 36

'Celebrities conceiving at the top end of their reproductive age may offer false reassurance,' Dr Koita said. 

'Most of these women may have had fertility treatment using their own eggs or donated eggs.'

Desperate Housewives star Marcia Cross has been open about having fertility treatment after giving birth to twins aged 45 using donor eggs. 

Mariah Carey with her twins Moroccan and Monroe, now five-years-old 

Jennifer Lopez takes her twins Max and Emme, now eight years old, to the premiere of Home in LA 

Julia Roberts with her twins Hazel and Phinnaeus in 2007. The actress conceived when she was 37-years-old 

Marcia Cross with Eden and Savannah: The Desperate Housewives star is one of the few famous mothers of twins to admit she had fertility struggles 

And singer Celine Dion has spoken openly about using IVF to conceive her eldest son René-Charles before having six rounds to get pregnant with her twins Eddy and Nelson at the age of 42. 

Although those in the public eye may understandably wish to keep their fertility struggles private, Dr Koita added that those to who speak out like Marcia and Celine can help women to understand reality.

'One in six couples has difficulty getting pregnant. A woman’s age is the biggest predictor of a successful outcome whether one conceives spontaneous or following fertility treatment,' she said.  

'It is unfortunate that we have failed to convey this message effectively. We need to work together to educate our young women.

'Those in a stable relationship should aim to complete their child bearing by 35 years of age. 

'Ovarian aging is irreversible! However, if you are not ready to have children get your egg reserves assessed and consider freezing your eggs.'