People who are taller are at greater risk of developing cancer. The World Cancer Research Fund reports there is strong evidence taller people have a higher chance of of developing cancer of the:

• pancreas
• large bowel
• uterus (endometrium)
• ovary
• prostate
• kidney
• skin (melanoma) and
• breast (pre- and post-menopausal).

But why? Here’s what we know, don’t know and suspect.

A well established pattern

The UK Million Women Study found that for 15 of the 17 cancers they investigated, the taller you are the more likely you are to have them.

It found that overall, each ten-centimetre increase in height increased the risk of developing a cancer by about 16%. A similar increase has been found in men.

Let’s put that in perspective. If about 45 in every 10,000 women of average height (about 165 centimetres) develop cancer each year, then about 52 in each 10,000 women who are 175 centimetres tall would get cancer. That’s only an extra seven cancers.

So, it’s actually a pretty small increase in risk.

Another study found 22 of 23 cancers occurred more commonly in taller than in shorter people.

Why?

The relationship between height and cancer risk occurs across ethnicities and income levels, as well as in studies that have looked at genes that predict height.

These results suggest there is a biological reason for the link between cancer and height.

While it is not completely clear why, there are a couple of strong theories.

The first is linked to the fact a taller person will have more cells. For example, a tall person probably has a longer large bowel with more cells and thus more entries in the large bowel cancer lottery than a shorter person.

Scientists think cancer develops through an accumulation of damage to genes that can occur in a cell when it divides to create new cells.

The more times a cell divides, the more likely it is that genetic damage will occur and be passed onto the new cells.

The more damage that accumulates, the more likely it is that a cancer will develop.

A person with more cells in their body will have more cell divisions and thus potentially more chance that a cancer will develop in one of them.

Some research supports the idea having more cells is the reason tall people develop cancer more and may explain to some extent why men are more likely to get cancer than women (because they are, on average, taller than women).

However, it’s not clear height is related to the size of all organs (for example, do taller women have bigger breasts or bigger ovaries?).

One study tried to assess this. It found that while organ mass explained the height-cancer relationship in eight of 15 cancers assessed, there were seven others where organ mass did not explain the relationship with height.

It is worth noting this study was quite limited by the amount of data they had on organ mass.

Another theory is that there is a common factor that makes people taller as well as increasing their cancer risk.

One possibility is a hormone called insulin-like growth factor 1 (IGF-1). This hormone helps children grow and then continues to have an important role in driving cell growth and cell division in adults.

This is an important function. Our bodies need to produce new cells when old ones are damaged or get old. Think of all the skin cells that come off when you use a good body scrub. Those cells need to be replaced so our skin doesn’t wear out.

However, we can get too much of a good thing. Some studies have found people who have higher IGF-1 levels than average have a higher risk of developing breast or prostate cancer.

But again, this has not been a consistent finding for all cancer types.

It is likely that both explanations (more cells and more IGF-1) play a role.

But more research is needed to really understand why taller people get cancer and whether this information could be used to prevent or even treat cancers.

I’m tall. What should I do?

If you are more LeBron James than Lionel Messi when it comes to height, what can you do?

Firstly, remember height only increases cancer risk by a very small amount.

Secondly, there are many things all of us can do to reduce our cancer risk, and those things have a much, much greater effect on cancer risk than height.

We can take a look at our lifestyle. Try to:

• eat a healthy diet
• exercise regularly
• maintain a healthy weight
• be careful in the sun
• limit alcohol consumption.

And, most importantly, don’t smoke!

If we all did these things we could vastly reduce the amount of cancer.

You can also take part in cancer screening programs that help pick up cancers of the breast, cervix and bowel early so they can be treated successfully.

Finally, take heart! Research also tells us that being taller might just reduce your chance of having a heart attack or stroke.

Susan Jordan, Associate Professor of Epidemiology, The University of Queensland and Karen Tuesley, Postdoctoral Research Fellow, School of Public Health, The University of Queensland

This article is republished from The Conversation under a Creative Commons license. Read the original article.

A vaginal birth after caesarean (known as a VBAC) is when a woman who has had a caesarean has a vaginal birth down the track.

In Australia, about 12% of women have a vaginal birth for a subsequent baby after a caesarean. A VBAC is much more common in some other countries, including in several Scandinavian ones, where 45-55% of women have one.

So what’s involved? What are the risks? And who’s most likely to give birth vaginally the next time round?

What happens? What are the risks?

When a woman chooses a VBAC she is cared for much like she would during a planned vaginal birth.

However, an induction of labour is avoided as much as possible, due to the slightly increased risk of the caesarean scar opening up (known as uterine rupture). This is because the medication used in inductions can stimulate strong contractions that put a greater strain on the scar.

In fact, one of the main reasons women may be recommended to have a repeat caesarean over a vaginal birth is due to an increased chance of her caesarean scar rupturing.

This is when layers of the uterus (womb) separate and an emergency caesarean is needed to deliver the baby and repair the uterus.

Uterine rupture is rare. It occurs in about 0.2-0.7% of women with a history of a previous caesarean. A uterine rupture can also happen without a previous caesarean, but this is even rarer.

However, uterine rupture is a medical emergency. A large European study found 13% of babies died after a uterine rupture and 10% of women needed to have their uterus removed.

The risk of uterine rupture increases if women have what’s known as complicated or classical caesarean scars, and for women who have had more than two previous caesareans.

Most care providers recommend you avoid getting pregnant again for around 12 months after a caesarean, to allow full healing of the scar and to reduce the risk of the scar rupturing.

National guidelines recommend women attempt a VBAC in hospital in case emergency care is needed after uterine rupture.

During a VBAC, recommendations are for closer monitoring of the baby’s heart rate and vigilance for abnormal pain that could indicate a rupture is happening.

If labour is not progressing, a caesarean would then usually be advised.

Why avoid multiple caesareans?

There are also risks with repeat caesareans. These include slower recovery, increased risks of the placenta growing abnormally in subsequent pregnancies (placenta accreta), or low in front of the cervix (placenta praevia), and being readmitted to hospital for infection.

Women reported birth trauma and post-traumatic stress more commonly after a caesarean than a vaginal birth, especially if the caesarean was not planned.

Women who had a traumatic caesarean or disrespectful care in their previous birth may choose a VBAC to prevent re-traumatisation and to try to regain control over their birth.

We looked at what happened to women

The most common reason for a caesarean section in Australia is a repeat caesarean. Our new research looked at what this means for VBAC.

We analysed data about 172,000 low-risk women who gave birth for the first time in New South Wales between 2001 and 2016.

We found women who had an initial spontaneous vaginal birth had a 91.3% chance of having subsequent vaginal births. However, if they had a caesarean, their probability of having a VBAC was 4.6% after an elective caesarean and 9% after an emergency one.

We also confirmed what national data and previous studies have shown – there are lower VBAC rates (meaning higher rates of repeat caesareans) in private hospitals compared to public hospitals.

We found the probability of subsequent elective caesarean births was higher in private hospitals (84.9%) compared to public hospitals (76.9%).

Our study did not specifically address why this might be the case. However, we know that in private hospitals women access private obstetric care and experience higher caesarean rates overall.

What increases the chance of success?

When women plan a VBAC there is a 60-80% chance of having a vaginal birth in the next birth.

The success rates are higher for women who are younger, have a lower body mass index, have had a previous vaginal birth, give birth in a home-like environment or with midwife-led care.

For instance, an Australian study found women who accessed continuity of care with a midwife were more likely to have a successful VBAC compared to having no continuity of care and seeing different care providers each time.

An Australian national survey we conducted found having continuity of care with a midwife when planning a VBAC can increase women’s sense of control and confidence, increase their chance to be upright and active in labour and result in a better relationship with their health-care provider.

Why is this important?

With the rise of caesareans globally, including in Australia, it is more important than ever to value vaginal birth and support women to have a VBAC if this is what they choose.

Our research is also a reminder that how a woman gives birth the first time greatly influences how she gives birth after that. For too many women, this can lead to multiple caesareans, not all of them needed.

Hannah Dahlen, Professor of Midwifery, Associate Dean Research and HDR, Midwifery Discipline Leader, Western Sydney University; Hazel Keedle, Senior Lecturer of Midwifery, Western Sydney University, and Lilian Peters, Adjunct Research Fellow, Western Sydney University

This article is republished from The Conversation under a Creative Commons license. Read the original article.