With advances in prenatal testing it’s now possible to find out whether a pregnancy will result in a male or female baby as early as eight weeks’ gestation.

A quick check of web pregnancy forums would indicate that wait is too long for many parents-to-be who are excited to predict the sex of their baby by interpreting symptoms of pregnancy that might be related specifically to boys or girls.

The old wives’ tales and myths abound when it comes to predicting gender in pregnancy. For example, girls will steal your beauty, a boy will make your hair grow faster, girls will make you emotional, and boys will make you aggressive.

Did these myths grow from some kernel of truth that might be backed up by scientific evidence?

Hormone differences for baby boys and girls

There is evidence hormone concentrations in pregnancy can differ according to the sex of the fetus as early as three weeks after fertilisation. Studies have shown hCG (human chorionic gonadotropin, the hormone responsible for the second line appearing on a home pregnancy test) is higher for female fetuses compared with males, and remains higher throughout pregnancy. Some studies only report this later in pregnancy.

The surge of hCG early in pregnancy is one explanation for the less desirable symptoms of pregnancy, such as nausea and sickness. Researchers have found that severe morning sickness (called hyperemesis gravidarum) is slightly more common in pregnancies where the baby is a girl, which could reflect the differences in hCG.

There are plenty of other hormones at work in pregnancy, whatever the sex of the fetus. There’s a lay belief that when pregnant with a girl, maternal oestrogen levels are higher, but this is not backed up by most studies. Actually, maternal blood oestrogen levels rise steadily throughout pregnancy whatever the sex of the fetus, although female fetuses do show a higher oestrogen concentration in the amniotic fluid early in the second trimester.

Testosterone in the maternal bloodstream follows a similar pattern, increasing slowly throughout pregnancy with no fetal gender-related differences. Once again, within the amniotic fluid there are differing concentrations of testosterone though, higher for males than females.

Differences in maternal oestrogen levels in maternal blood have been reported though. In one Scandinavian study, oestrogen levels in the first half of pregnancy were around 9% higher for pregnancies where the baby was female, and progesterone levels were lower in the second trimester.

But the extent to which the maternal hormone levels matches up to the fetal hormones is difficult to predict. The fetus is influenced by its own internal hormones in addition to being exposed to circulating maternal hormones. Getting samples of fetal blood is complicated and risky, so there is much we don’t know about this relationship.

There is great interest in this type of research beyond parents who’d like to get the nursery painted early. The field of the developmental origins of health and disease focuses on how the environment in the uterus, including the hormonal environment, might affect later health, behaviour and well-being.

Hormonal imbalances in the uterus have been linked with heart disease, cancer, polycystic ovary syndrome and autistic behaviours in the offspring.

Are pregnancies with girls and boys different?

If there was an oestrogen surge in mothers who are expecting a female baby, could this explain some of the old wives’ tales of extra moodiness or teariness in girl pregnancies?

There are significant individual differences in how vulnerable women are to fluctuations in hormones. In some cases, higher oestrogen levels have been reported as “psycho-protective”. This means they moderate mood, while other authors report oestrogen fluctuations triggering mood disorders and even depression in women.

What about aversions or nausea that women report to be different in male and female pregnancies?

A fascinating 2015 study looked at the emotion of disgust and how it differs according to the sex of the baby. The researchers posited that disgust is a protective mechanism that helps the mother avoid risks and harms during pregnancy – for example, aversions to certain foods or situations.

They found that disgust was high in the first trimester for pregnancies bearing boys and girls, but it decreased for girl pregnancies after the first trimester and remained high for boy pregnancies into the second trimester.

The reasoning for this is that male fetuses are considered more vulnerable to their environment, and the aversions reflect a natural predisposition to maintain protective behaviours longer for male pregnancies than female pregnancies.

So it appears there’s not enough evidence to back up claims male or female pregnancies differ significantly in terms of the maternal hormonal environment. This makes it unlikely that anecdotes of moodier, angrier or uglier pregnancies are due to the sex of the fetus.

Our interactive body map of how a lack of physical activity makes you sick may have got you thinking, but it can be difficult to know how to get started if you don’t regularly exercise.

Here we review the best science about how to start an exercise habit, and how to keep it going.

What type of exercise, and how much?

The government tells us we should get at least 150 minutes of moderate to vigorous physical activity per week, and preferably 300 minutes. Moderate physical activity is generally described as exercise at least as intense as brisk walking – things like swimming, household chores and mowing the lawn all count.

For instance, in Nazi Germany, the women’s organisation Frauenschaft sponsored a “Health through Housework” movement which combined household chores with Swedish gymnastics. Picture making the bed standing on one leg and you’ve pretty much got the idea.

Vigorous physical activities are those that cause you to feel puffed, and include jogging, hiking and shovelling. Vigorous physical activity counts double: just 75-150 minutes per week is enough to make sizeable health gains.

Moderate and vigorous physical activities have important benefits for health by stressing the heart system, and therefore stimulating it to adapt. In addition, they contribute to weight control through burning calories, improve mood through release of endorphins, and benefit metabolic health (warding off diseases such as diabetes and cancer) by altering hormonal, inflammatory and immune responses.

In addition to moderate and vigorous physical activity, the guidelines recommend that physical activity should include muscle strengthening activities at least twice a week. Such activities include lifting weights or heavy chores that involve carrying loads. In particular, strengthening activities have important benefits for bone health.

Getting started

We used to think of physical activity in terms of leisure-time activities, like sports and fitness activities. However, health scientists now recognise that most forms of physical activity have beneficial effects. Physical activity from daily chores, or walking or cycling to get from place to place, are all helpful and offer realistic ways for people to squeeze more physical activity into their busy lifestyles.

It’s surprising how much difference a little effort can make. Imagine you decide to get off the bus a stop early, and walk the extra 500 metres to work, and then do the same on the way home. That’s an extra kilometre every day, or about 60 minutes of exercise a week.

That much exercise will reduce your risk of dying at any given age by about 10%. In theory, over a year you would lose 3kg of body fat. However research has found that people tend to crank up their eating and wind down their other exercise habits when they do these added extras, so your actual weight loss might be more like 500g.

It’s thought that physical activity accrued in sustained “bouts” (continuous periods of physical activity lasting 10 minutes or more) may have extra health benefits, although shorter spurts of activity also have a cumulative benefit.

Aim to gradually build up your physical activity, building on your base level of physical activity until you eventually meet the guidelines. The relationship between physical activity dosage and health effects is on a curve. It’s a bit like money: an extra 10 minutes a day means large health gains for someone who gets no exercise, whereas the same increase for someone already exercising for an hour a day will deliver diminishing returns.

If you’re starting from a low base, choose moderate, rather than vigorous, activities. This minimises your chance of getting an injury, and maximises your prospects of keeping your new habit going.

Research clearly shows that people who go hard early are more likely to drop out. If you have a pre-existing health condition such as high blood pressure, diabetes or arthritis, consider consulting your doctor first (though if your doctor is worth her salt, she will already have recommended physical activity, as it is a key component of managing these conditions).

Maximising your success

Unfortunately, it is common for people to fall off the physical activity wagon, and an estimated 50% of people who start a new exercise program will have given it up within 6 months. However, science has identified numerous factors that increase your chances of sticking with it.

1. Make a commitment to others. Exercise with a friend, or sign up to a team or group fitness program. Being around others who exercise is proven to increase people’s motivation to continue with their own exercise plans.
2. Choose a form of exercise you feel competent doing and enjoy. If there is a new form of exercise that interests you, but you don’t feel confident about it, find an exercise professional who can teach you.
3. Give your lifestyle a spring clean. Evidence suggests that healthy behaviours reinforce each other. For example, changing your diet can be a catalyst for continuing a new exercise program.
4. Set goals for your exercise. Goals that are specific, measurable and timely can significantly increase your chances of success.
5. Be aware of barriers you face (such as time and energy for exercise) and proactively plan strategies for addressing these. For example, having an exercise schedule can help people with lack of time, while planning exercise earlier in the day can help if energy or weakness are barriers.

Some of you may be thinking of other, more “intimate” and socially interactive methods of getting exercise. There’s bad news on this front. A bout of sexual activity uses about 90kJ, about the same as a gentle six-minute walk. You get more bang for your buck, so to speak, from the walk to work.

It is a common belief that herbal medicines are safe and research suggests that they are used by at least a third of people in some countries, such as the UK.

To better understand the relative risks involved, it is helpful to put herbal medicines and pharmaceutical drugs into context. It is generally accepted that pharmaceuticals cause side effects. But, as part of licensing requirements, a risk-benefit analysis is undertaken to determine whether the benefits outweigh the potential harms. In other words, is the possible harm caused by the drug acceptable? If it is, the drug may be granted a marketing authorisation (product licence) by a regulatory authority, such as the Food and Drug Administration in the US or the European Medicines Agency in Europe.

Undeniably, pharmaceutical drugs kill people. In the US, it is estimated that pharmaceuticals kill around 100,000 people every year. For certain conditions, however, there may be no alternative to drug therapy and certain medicines can prolong life, such as drugs used to treat diabetes, heart disease and cancer.

By contrast, herbal medicines are considered by many to be a safer alternative and are preferred by a sizeable section of the public for treating non-life-threatening conditions. And there is some evidence to support the idea that herbal medicines are safer for minor ailments. For example, drugs to treat mild to moderate pain, such as paracetamol and aspirin, are known to cause side effects, including some that – although rare – can be serious, such as gastric bleeds. Whereas with herbal equivalents, such as devil’s claw, the risks of side effects are reportedly lower.

A tricky comparison

Adverse events associated with herbal remedies are reported far less often than those associated with pharmaceuticals. For example, in the UK, between 2006 and 2008, there were only 284 such reports for herbal medicines compared with 26,129 for pharmaceuticals in a similar two-year period.

The reasons for this vast difference are complex, and it has been suggested that adverse events of herbal medicines are unrecognised or underreported. Also, there are many more drugs consumed than herbal remedies so it is to be expected that the figures for pharmaceuticals are higher. However, the enormous difference does suggest that adverse events are far more common with pharmaceuticals than herbal remedies.

When serious side effects are triggered by herbal remedies it is often due to poor quality products, products containing newly discovered plant ingredients, or products that have been adulterated – including with pharmaceutical drugs.

For the public, buying herbal products that are regulated offers some assurance that the medicines are both safe and of acceptable quality. For instance, in the UK, traditional herbal remedies are manufactured to a high standard and include a patient information leaflet, which lists known side effects and, importantly, warns of possible interactions with pharmaceuticals, another cause of adverse reactions.

For example, St John’s wort – a herbal remedy used to treat mild depression – is known to have side effects when taken alongside fluoxetine (Prozac). The makers of these products also have a legal obligation to monitor any adverse reactions and report them to the regulators.

Voluntary regulation

Another way to help avoid adverse reactions, especially when dealing with conditions that are not always suitable for self-treatment with over-the-counter drugs, is to visit a qualified herbalist. The training and regulation of herbalists varies widely from country to country and without government regulation of these practitioners, it is difficult for the public to assess who is legitimate.

However, voluntary regulation by professional associations does exist and is effective in many countries, including the US, Canada, the UK and Australia. This regulation helps to ensure that practitioners are appropriately educated and safe.

Herbal medicines are relatively safe compared with pharmaceuticals provided that they are regulated products or that they are prescribed by herbal practitioners who are registered with an appropriate governing body. But consumers need to be better informed about the dangers of obtaining herbs from unregulated sources if further cases of serious side effects are to be avoided.

The majority of women experience some cramping for one to two days during their period, and this is normal. Teenage girls are also more likely to suffer from painful periods compared to adult women, particularly adult women who’ve had children. But painful periods in adolescence usually improve over time.

However, some women have period pain that isn’t easily managed and that requires them to take time off school or work. Pain to this extent is not normal, and needs to be investigated.

Why periods cause pain

A period is the shedding of the endometrium – the lining of the womb (uterus). Every month, the uterus prepares itself for pregnancy by growing a thick lining that has a rich blood supply, awaiting implanting of an embryo.

When pregnancy does not ensue, the body produces a period, the by-product of the endometrium. During this time the blood vessels open, the lining sheds off the uterine wall, and the uterine muscle contracts to expel the blood and tissue.

During these mild contractions, it’s common for women to feel a lower abdominal cramping sensation as blood products are expelled through the uterine body and out of the cervix before it makes it way out the vagina.

The contractions are triggered by hormone-like compounds produced by the body called prostaglandins, which are the main source of pelvic pain associated with menstruation. Higher levels of prostaglandins have been associated with more severe menstrual cramps.

Cramping is usually strongest in the first one to two days of the period, then settles for the remaining four to five days.

Pain during periods is called dysmenorrhoea, and there are two types: primary and secondary.

Primary dysmenorrhoea refers to pain with periods, that begins soon after girls start menstruating. This tends to get better as the teenager gets older. The cause of this pain is not known, but hormonal fluctuations are thought to be implicated.

The main medications used to treat this pain are non steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen (Nurofen) or naproxen (Naprogesic). They work by blocking the action of prostaglandins.

Secondary dysmenorrhoea generally refers to period pain resulting from a medical disorder in the reproductive system. Instead of period pain improving over time, it worsens. This can be due to several conditions, the most common of which is endometriosis.

What is endometriosis?

Endometriosis is a condition in which tissue similar to the lining the endometrium (womb), grows outside of the womb. It can grow on the ovaries, bowel, and in some rare cases has even been found outside of the pelvis such as the lungs. The hormones that trigger a period cause bleeding at these sites of implanted endometrial tissue, and this causes pain.

Endometriosis usually causes period pain to start earlier and last longer than what is commonly experienced with menstruation. Sometimes the pain doesn’t go away when the period ends. Women with endometriosis can describe pain at the the time of ovulation, or pain with sex. Another problem associated with endometriosis is infertility.

It is a common condition affecting 16% to 61% of women of reproductive age experiencing symptoms. An estimated 100 million women worldwide suffer from endometriosis.

Women themselves may be unaware of endometriosis, or think their pain is normal. Many tend to tolerate the pain, which is can also occur in teenagers and young adults.

Although the exact cause of endometriosis is unknown, there are a number of theories such as retrograde (opposite to the intended direction) flow of endometrial tissue out of the womb through the fallopian tubes, and this tissue can implant in the pelvic cavity in locations outside of the womb.

The way nerves interpret pain in the pelvis also plays a role. It is an unusual disease in that some women can have a lot of endometriosis and have very few symptoms, whereas others can have only a small amount of disease and suffer from quite severe symptoms.

Affected girls and women often face negative impacts on their education or careers. There may be reduced productiveness at work or study as a result of the pain and discomfort caused by endometriosis.

Further reading: Women with endometriosis need support, not judgement

Treatment includes hormonal tablets such as the oral contraceptive pill. The progestogen implant or intrauterine device, are also helpful for some in reduction of pain with periods. But these treatments don’t work for everyone.

How will I know if I have endometriosis?

Diagnosis of endometriosis can only be made via keyhole surgery. If it is seen surgically, and removed, women often have an improvement in their symptoms. But symptoms can return. Although it is not a deadly disease, the disruption it causes to women and society can be distressing – and as it is chronic, persisting throughout the woman’s menstrual life.

One study found an average delay of nearly four years before women with endometriosis sought medical help for their symptoms, and this delay brings about much anxiety and distress over the uncertainty of their own condition and how it can be resolved.

Many women are told their period pain is normal, but at keyhole surgery a number of these women with pelvic pain actually have endometriosis. However, making a decision to pursue surgery is a difficult one, as this carries minor risks such as bladder, bowel and vessel injury as well as anaesthetic risks. Care for women needs to be individualised in terms of whether the risks of surgery outweigh the symptoms experienced.

There are a number of different conditions which contribute to period pain. These include pain from the intestines, bladder and kidney, muscles and bones (including hip and back pain). There are also conditions that cause pain from the nerves in the pelvis and back.

Psychological conditions can also be responsible for or contribute to pelvic and period pain.

If you have severe period pain affecting your school, work, or quality of life then you should seek help, by first consulting your GP.

Everyone loves a study that turns one of our favourite vices into a health benefit. This week, the news headlines tell us “eating chocolate improves brain function” and that it “could help protect against normal age-related decline”.

The study, published this month in the peer-reviewed journal, Appetite, found that memory and abstract thinking improved in those reporting more chocolate consumption. These effects were reported not to be influenced by factors such as age, weight and general health measures.

Before you reach for a Mars bar or a Dairy Milk, let’s take a step back.

This is a correlational study. That means it shows an association between people who reported regularly eating chocolate and better scores on brain function tests. It doesn’t show that chocolate consumption directly improves brain function.

Other factors are also at play. The people who consumed more chocolate also had better diets and drank less alcohol. And both groups relied on their memory to report their chocolate consumption levels.

Sorry folks, but you won’t be able to rely on this study to justify your 3pm chocolate binge.

How was the study conducted?

The 968 participants were from the Maine-Syracuse Longitudinal Study, which has followed the same group of New Yorkers for more than 35 years. The participants undertake questionnaires and physical examinations at various intervals so researchers can determine changes associated with ageing, the development of heart disease and also cognitive performance.

In 2006, the participants reported how often during the week they ate a variety of foods, including chocolate, meat, eggs, breads, rice, fruit, vegetables, dairy, chocolate, nuts and beverages such as tea, coffee, water, fruit juice and alcohol. Chocolate was not differentiated according to whether it was dark, milk or white chocolate.

The researchers compared those who never or rarely ate chocolate (337 people) and those who ate chocolate at least once a week (631 people).

Participants were given various brain function tests – including remembering where things were (spatial memory), abstract reasoning, working memory and attention. The relationships between chocolate intake and performance on the cognitive tasks were then analysed.

The results from people who had dementia were excluded, as this is a serious cognitive impairment, as were people who had experienced a stroke, as this would skew the results.

What were the results?

The participants reporting that they ate chocolate more than once a week performed better in most of the cognitive tests, particularly on their “visual-spatial memory and organisation” score. There was no relationship with working memory.

More women were self-reported chocolate eaters, so this could bias the results. Women often perform better than men in certain tests of cognitive function, particularly in the elderly.

The chocolate-eating group was less likely to have high blood pressure or diabetes and had lower fasting blood glucose levels (indicative of pre-diabetes) than non-chocolate-eating participants.

However, chocolate eaters had higher cholesterol, including low-density lipoprotein (bad) cholesterol, which is associated with poorer cardiovascular health.

So what does it all mean?

Chocolate is often demonised due to the high sugar and fat content in chocolate bars and its association with “guilty pleasure”. But cocoa (or chocolate in its raw form) actually contains lots of compounds that act in the brain.

In particular, cocoa contains flavanoids, which are found in fruits such as grapes and apples. Cocoa also contains caffeine and theobromine, which are the stimulants found in coffee and tea. These natural compounds are thought to improve alertness and so can improve brain function.

But the amounts of these chemicals depend on the cocoa concentration of chocolate – and milk chocolate contains much less of these active ingredients than dark chocolate. The study points out that the type of chocolate consumed wasn’t assessed, so we don’t know whether this had an impact on the results.

It’s important to remember that this is a correlational study. So it doesn’t examine whether chocolate consumption directly improves brain function. To test this, an experiment would ask people to eat a chocolate-rich diet or a no-chocolate diet for a reasonable amount of time, and then carry out the brain function tests. This would be a way of establishing whether chocolate can enhance cognitive performance.

What else do we need to take into account?

The participants who consumed chocolate also reported eating more serves of vegetables, meats and dairy foods, and more food overall, as well as drinking less alcohol. This indicates they may have had better diets overall, regardless of their reports of eating more chocolate.

Alcohol intake is known to diminish brain function, so could have impacted on the non-chocolate-eating group. The authors followed up this observation by examining alcohol intake separately and found no association between alcohol intake and the tests of brain function. This suggests that alcohol didn’t have an impact on brain functions measured. However, it could indicate differences in general health and well-being.

More people in the non-chocolate-eating group had diabetes, so they may have been avoiding chocolate because of the high sugar content. Diabetes has been linked with cognitive impairments, particularly in memory performance, so this could affect the results.

Another issue is that the participants were retrospectively self-reporting their food intake in response to a questionnaire. People can easily misreport or underestimate their consumption.

(In fact, the lower scores on the brain function tests by people who consumed less chocolate could reflect a group that was less able to accurately report their food consumption. Asking someone to recall their food for the week is a test of memory in itself!)

Portion sizes weren’t reported either, only the frequency of foods eaten over days. So the research didn’t differentiate between whether you eat a family-sized bar of chocolate, or just a single square.

This type of cross-sectional study is great for showing the relationship between diet and health at a snapshot in time. But correlation does not equal causation. To really get to the bottom of this issue, we need carefully designed experimental studies to examine the association between chocolate and cognitive health, and the mechanisms linking them. – Amy Reichelt

Peer review

This review of the article is a sound interpretation of the results.

The important point is that although the participants were in a longitudinal study that recruited people in waves between 1975 and 2000, the measurement of dietary intake and the cognitive function testing was only done on a sub-group who came in for testing during the sixth wave of follow-up, between 2001 and 2006. So the main analysis could only look at cross-sectional associations.

The participants were divided into three groups based on usual chocolate consumption: never, once a week, or more than once a week. But it’s not clear whether usual intake was over the past year, or just for the past week, which could affect the results.

The review clearly highlights some other potential explanations for the findings, including that those who ate chocolate also reported some healthier eating patterns. It’s very likely that those with diabetes would have been advised to eat less chocolate.

The observation of a lower proportion of chocolate eaters having high blood pressure is consistent with a systematic review showing that regular chocolate consumption can have a small blood-pressure-lowering effect.

However, as much as we would all love the results of the cross-sectional analysis to be true, a 2013 systematic review found that in trials lasting between five days to six weeks, chocolate did not improve cognitive function.

I agree with the conclusion that better quality trials, including mechanistic studies, are needed. – Clare Collins