Lots of mums swear their pregnancies were different when they carried girls versus boys.
Take Mim, for example.
The 38 year-old mother of two from NSW had a daughter first, then a son.
While her pregnancies began identically, Mim developed eczema in her second pregnancy - for the first time in her life.
Consequently, Mim believes that having skin issues in pregnancy "must be a boy thing".
Now new research, published in the journal Brain, Behavior and Immunity in February this year, shows that pregnant women's bodies respond differently when they're carrying daughters as opposed to sons.
The researchers found that mums with girls on board had a heightened inflammatory response (a greater response to infection when exposed to bacteria) than those carrying boys.
This heightened inflammation could account for why women experience exacerbated symptoms of some medical conditions (including asthma) when carrying a girl.
There are lots of other 'clues' people use to try to work out whether a mum is having a boy or girl, says Midwife Amanda Bude from Groovy Babies.
The way you 'carry'
If you carry just "out front" (with a 'pointy' bump), that's often said to mean you're having a boy, says Amanda.
Meanwhile, a "tree trunk waist" (round all over) is more likely to signal a girl.
But is there any truth to this?
Obstetrician and Gynaecologist Dr Alex Polyakov says there isn't.
He says the way you look is mostly determined by muscle tone, body shape, weight gained and the position of the baby – not what gender you're carrying.
Amanda says mums of girls often discuss craving sugary treats, while mums of boys prefer to dig into savoury snacks.
"[This one's] certainly not true," says Dr Polyakov.
He says cravings can relate to particular dietary deficiencies, such as iron or calcium.
But, more commonly, he says cravings probably have to do with a heightened sense of smell. This happens during pregnancy because you get increased blood flow through your nose during this time.
Amanda says mums of girls tend to complain of morning sickness more often.
"There is some truth to this one," says Dr Polyakov.
He explains that when mums are carrying a girl, they have higher levels of the pregnancy hormone hCG, which may worsen morning sickness.
However, because mums of boys can also have pretty severe morning sickness, Dr Polyakov says the distinction is "quite unreliable".
Baby's heart rate
A common old wives' tales says that if your baby's heart rate is over 140 beats per minutes, you're having a girl.
Dr Polyakov understands where this one comes from.
He says research has shown that, just before delivery, female babies have slightly higher heart rates than male babies.
Mind you, that difference is "marginal" and can't be used to determine a baby's gender.
Increased hair growth on mum
If you develop a hairy tummy, some say that means you're carrying a boy, as the male hormones are said to be responsible for that growth.
However, Dr Polyakov says the amount of male hormone made by a baby boy is "quite small".
Plus, "Placental traffic is mostly one-way: from mother to baby".
He says hair growth in mum relates more to the increased amount of hormones produced by the mother herself.
So how can you find out your baby's gender?
If you want to know your baby's gender, an ultrasound can help, with the 20-week scan being more accurate than the 12 week one.
Or, you can have an NIPT (Non-Invasive Prenatal Test), which examines fragments of the baby's DNA in the mother's blood stream.
This test is a highly accurate way to find out your baby's gender and has no risks for your baby, Dr Polyakov reassures.
But if you don't want to find out your baby's gender while you're expecting, Amanda says there's only one sure-fire method to tell what you're having:
Wait till you give birth, "Then check that bundle of joy in your arms!"
Did you notice any differences in your pregnancies when you were pregnant with a girl versus a boy? Were any of the old wives' tales right?