Are pregnant women harming their babies by trying to stay so thin? We ask a doctor.

American model Sarah Stage, has been posting pictures of her baby bump – but those same photos have people very concerned about her health and the health of her child.

For many pregnant women, their body changes and the development of their child is something very private. For others, it is something to be shared. Model Sarah Stage, 31, falls into the latter category, documenting her pregnancy regularly via Instagram.

Read more:Carrie Bickmore brings the honesty to pregnancy. You know what? Sometimes, it sucks.

But her most recent photos have raised some eyebrows. According to Sarah, she is eight and a half months pregnant, but the photos reveal that her bump is barely showing.

Of course, all women are different, and no pregnancy is the same. But many of Sarah’s Instagram followers have expressed complete disbelief that she could possibly be so thin at this stage of her pregnancy (one asking “Where can a baby even fit in there?”).

For more:Men experience what pregnancy is really like. Spoiler alert: They cannot deal.

Other are a worried about the health of Sarah’s baby one stating “I really pray her baby is healthy. If she’s 8 months that baby is very much looking undersized.”

Mamamia asked Brisbane Obstetrician and Gynaecologist, Brad Robinson for his view on the issue.

Dr Robinson says that a mother’s weight isn’t always an indicator of the size of her baby:

Pregnancy is highly individual and appropriate weight gain during it is dependent upon the woman’s weight – more accurately her body mass index (BMI) – when she initially falls pregnant.

Women starting out in the healthy BMI range of 18.5 to 25 should gain between 11.5 and 16 kilograms across the pregnancy.  However, it is possible Sarah’s starting BMI was less than 18.5, meaning her recommended weight gain would be 12.5 to 18 kilograms.

While Sarah does look on the small side for a woman who is eight months pregnant (and I am going by one photo so it can be very hard to tell without seeing a patient in person) the fact is a mother’s weight isn’t necessarily an indicator of the size of her baby.

Sarah has talked about maintaining her fitness with “light prenatal training” and has joked that she “can’t really do abs these days”.

Dr Robinson says that you can exercise safely while pregnant – but he has an important proviso:

I encourage my patients to exercise throughout their pregnancies and it’s often possible to continue doing whatever exercise regime you were doing pre-pregnancy – albeit modified as necessary.

That said, I would also encourage my patients to focus on the wellbeing of themselves and their baby and not feel pressured by any societal expectation to look a certain way.

And that’s Dr Robinson’s main concern – women feeling pressured to maintain a particular body shape while they are pregnant:

As an obstetrician what I would say is that we need to stop judging pregnant women altogether.

I am getting tired of, and frustrated by, the pressure I see women put under to look a certain way not only within weeks of delivery, but increasingly during their pregnancy as well.

As for Sarah Stage, she’s prepared to shake off the criticism, saying, “these days it’s seems like everyone has something to say, especially on social media. Most are very positive and I try to ignore any negative comments.

“My doctor says the baby is healthy and that’s all that matters to us.”

It appears that pregnant bodies are as diverse as the women who own them.

Click through this gallery of women celebrating their baby bumps – in their various forms.

What do you think about Sarah Stage’s photos?