A doctor has dismissed trolls bizarrely accusing Anne Hathaway of faking her pregnancy – and revealed why her bump may be seen as 'prominent'.

On Monday the 43-year-old Oscar winner hit back at the cruel speculation that she's wearing a prosthetic bump, subtly addressing the claims.

She wrote in the caption of a behind-the-scenes video montage: 'Fake hair, real bump. Enjoy The End Of Oak Street Block Party chaos with me as my outfit literally melts in the heat!!'

The clip came after fans blasted her latest maternity outfit – a cropped blouse and a pair of low-rise jeans that revealed her bump – as 'ridiculous', while others bizarrely speculated she was faking the pregnancy.

But speaking to the Daily Mail, Dr Asiya Maula, private GP at The Health Suite, stressed there is no such thing as a bump that looks 'correct'.

She said: 'There are several entirely normal reasons why one pregnancy bump may look more defined, higher, lower, rounder or more pronounced than another.

'Its appearance can be influenced by the stage of pregnancy, the mother's height and torso length, her natural build, posture, the position of the uterus and baby, whether she has been pregnant before, and how the abdominal wall adapts as the uterus expands.'

For those who have strong abdominal muscles – and it wouldn't be surprising if Anne, who has in the past worked with a number of fitness instructors to get into shape for a myriad of roles, was among them – 'it may affect how the bump is carried and how sharply defined it appears'.

'But that cannot be confirmed simply by looking at a picture,' Dr Maula warned. 'The abdominal muscles and connective tissue naturally stretch during pregnancy to accommodate the growing uterus, and the degree and pattern of that stretching will differ between women.

'A leaner frame may make the outline of a bump appear more prominent because there is less surrounding tissue to soften its contours.

'However, it would be inappropriate to draw conclusions about Anne's body composition from photographs. Lighting, camera angle, posture and clothing can all dramatically change how a bump looks from one image to the next.'

She added Anne's low-rise jeans from the recent outing 'are also likely to make the lower curve of the abdomen much more visible'.

'The uterus begins within the pelvis and expands upwards as pregnancy progresses, so clothing that sits below the bump can expose the point at which the abdomen starts to project,' the expert continued. 'That can create a particularly rounded or pronounced appearance without indicating anything unusual.'

Pregnancy also 'increases blood volume and can cause changes to the skin and small blood vessels'. 

The doctor added: 'This may sometimes make areas of skin look warmer, pinker or more flushed. However, colour in a photograph can equally be affected by temperature, lighting, friction from clothing or image processing, so it would not be possible to attribute that redness to one cause.

'Previous pregnancies can also influence the way a bump presents. The muscles and connective tissues may respond differently after they have stretched before, meaning some women show earlier or carry differently in subsequent pregnancies. Again, that is normal variation rather than evidence that something is wrong.

'Most importantly, the outward size or shape of a bump is not a reliable way for members of the public to judge the health, stage or authenticity of a pregnancy. 

'Clinicians assess pregnancy through medical history, antenatal examinations, measurements and scans, not comparisons with how somebody believes a pregnant body should look.'

She also hit out at trolls accusing Anne of faking her bump. 

'Comments accusing a woman of faking a pregnancy because her bump does not conform to an imagined norm are medically baseless and potentially very hurtful,' she said.

'Women's bodies do not follow one visual template during pregnancy, and even the same woman can carry very differently from one pregnancy to another.

'From what can be seen publicly, there is nothing about a sharply defined or prominent bump that is inherently abnormal.

'The responsible conclusion is simply that pregnancy bumps vary enormously, while Anne's own maternity team are the only people able to comment meaningfully on her individual pregnancy.'

Anne attended the Los Angeles premiere of her latest film The End Of Oak Street over the weekend, where she bared her midriff in a cropped top and low-waisted jeans after announcing this summer she and husband Adam Shulman are expecting baby number three.

While some comments accused the star of wearing a prosthetic, many came to her defence, saying her stomach looks different to other pregnant women's because she's in great shape.

'It looks different because she was already fit and probably continues to work out, so she is all muscle and baby!' said one fan.

And someone else commented on the star's Instagram post, 'The fact that other women were questioning her literal pregnant belly because "mine didn't look like that" is so strange to me.' 

Anne shares sons Jonathan, ten, and Jack, six, with Shulman, whom she wed in 2012. 

While appearing on Late Night with Seth Meyers in July, she got candid about her pregnancy.

'I mean, we knew what we were doing, but we were so shocked it worked!' she said about finding out she was with child. 

'We were so shocked it went this way', the actress echoed about her and her husband's surprise at their baby news.

She described the pregnancy as a 'buzzer beater'.

And remarking on becoming pregnant in her 40s, she recently told Access Hollywood: 'There’s always hope until there’s not, but when you get to a certain age, that hope looks like 1 per cent to 2 per cent.

'So we just decided to see where life took us, with a very, very healthy, realistic expectation, which was very low.

'We’re overjoyed because we just know from personal experience that not everybody gets this, and certainly not when you want it – sometimes not ever.'