Pregnancy comes with plenty of excitement ─ and plenty of advice from others! From predictions based on bump shape to old sayings about heartburn and hair, you’ll probably hear it all. We spoke to Breda Crotty, Vhi Midwife Support Service Manager, about some of the most common pregnancy myths, and if any have some truth to them. 

FAQs can be found at the end of the page. 

Can the shape of your bump predict your baby’s sex?

It’s one of the oldest pregnancy myths, but the science is simple: no, your bump can’t tell you if you’re having a boy or a girl! The only reliable ways to determine your baby’s sex are:

• An ultrasound.

• A blood test that identifies foetal sex chromosomes. 

People often guess based on whether you’re “carrying high” or “carrying low”, but there’s no clinical link between bump shape and a baby’s sex.

So why can baby bumps look so different?

• Everyone’s body shape and muscle tone varies.

• The baby’s position changes the appearance of your bump. 

• Pelvic and uterine shape also play a role.

But none of these factors relate to your baby’s sex, they simply reflect how your body carries a pregnancy.

Is your bump smaller with your first baby and bigger with your second?

There’s some truth here. Let’s break it down: 

During a first pregnancy

• Your abdominal muscles are tighter because they haven’t stretched in this way before.

In subsequent pregnancies:

• Your muscles have stretched before so they might not hold your baby as tightly or as high as the first time. This can also lead to needing to urinate more frequently, as the lower position of the baby puts increased pressure on your bladder! 

Aside from multiple pregnancies, other factors like genetics, nutrition, anaemia, and the amount of amniotic fluid present can also influence bump size. 

Does heartburn mean your baby will have lots of hair?

Surprisingly, there’s a small connection, but not in the way people think! A small 2006 study1 found a mild association between maternal heartburn and babies born with a lot of hair. But association is very different to causation. 

Here’s what’s actually happening: 

• Certain pregnancy hormones can increase both foetal hair growth and your risk for heartburn.

• It’s a shared hormonal effect, not a cause-and-effect relationship.

So, your baby might have lots of hair if you’re getting regular heartburn, but it’s far from being the cause or the rule.

Is it safe to fly during pregnancy? 

Yes, but it depends on when you’re travelling and how you’re feeling.

First trimester

You can fly, but doing so in this trimester can bring challenges:

• Nausea and fatigue 

• Higher risk of fainting

• Increased risk of blood clots

If you’re flying, stay hydrated, move regularly, wear compression socks, and make sure your travel insurance has you covered. 

Second trimester 

This is often considered the safest and most comfortable time to fly. Still, always check your airline’s policy because cutoff points for flying when you’re pregnant can vary for different airlines.

Third trimester

Many airlines restrict travel after:

• 28 weeks for long-haul flights. 

• 32 weeks for short-haul flights and long-haul flights.

This is mainly because labour could start suddenly. There’s an increased risk of blood clots when flying, so this is a consideration, too. My rules of thumb are to always check with your healthcare provider, confirm the airline’s rules, if both are okay and you do take a flight; move regularly throughout, and make sure you have reliable insurance. It’s a good idea to travel with the clinical details of your pregnancy – due date, latest ultrasound details, etc. – in case you need them while you’re abroad. 

Do you need to “eat for two” when pregnant?

This is one of the most persistent myths, but medically, it’s not entirely accurate. 

This is what the evidence tells us:

• You certainly don’t need to double your food intake.

• Your calorie needs increase only slightly, depending on the trimester.

• A balanced, nutritious diet is what matters most. 

Your healthcare provider will be able to guide you on how many extra calories you need each trimester. They’ll also remind you that some foods should be limited for safety reasons:

• Avoid unpasteurised foods like soft cheeses.

• Stay clear of undercooked or runny eggs. 

• Limit high mercury fish. 

• Keep caffeine within recommended limits. 

• Don’t eat sushi or any raw food. 

• Ensure you wash all fruits and vegetables 

• Don’t consume alcohol. 

Is it safe to exercise during pregnancy?

Yes, it’s safe to exercise during pregnancy ─ unless advised otherwise by your healthcare provider ─ and staying active is encouraged for most pregnant women. Activities like prenatal Pilates, yoga and swimming are generally safe when supervised or taught by a qualified professional. Be sure to let the instructor know that you’re pregnant. 

Even in the third trimester, many women comfortably continue exercising if they feel well and up to it. Just be careful to avoid:

• Overexertion. 

• High-risk or high-impact activities such as team sports.

• Anything that feels unstable or painful.

Listening to your body is key because it will let you know as soon as something feels too much. If there’s anything you’re unsure of, have a check-in with your healthcare provider to be sure. 

Can you dye your hair during pregnancy?

This is a concern I often hear from expectant mums, and there are a few things to consider:

• It’s generally advised waiting until the second trimester to dye your hair.

• Techniques like highlights or balayage are preferable because they reduce direct scalp exposure to the chemicals. 

• Current evidence doesn’t show strong risks, but a cautious approach is sensible.

Most women safely colour their hair during pregnancy with small adjustments.

Are hot tubs, saunas, and Jacuzzis unsafe for pregnant women?

Heat is the issue here – not because it harms the baby directly, but because it can make you unwell. Higher temperatures can cause: 

• Drops in blood pressure.

• Dizziness or feeling faint. 

• An increased risk of falling.

Hot tubs also carry a slight infection risk, so they’re best avoided during pregnancy. 

Top tip: Always pause and assess the potential risk before doing an activity that involves hot temperatures, speed, height, or sudden motion.

Can spicy food induce labour?

There’s no clinical evidence to support the idea that spicy food induces labour. The myth most likely stems from the fact that spicy foods can irritate your digestive system, which could in turn irritate your cervix. But this isn’t the same as causing contractions. Spicy foods won’t cause any harm to your baby, but if you’re already dealing with heartburn or indigestion, it might be best to avoid!

Pregnancy myths FAQs  

Q. Can the shape or height of your baby bump predict the baby’s gender?

A. No. Bump shape, size, or height cannot predict whether you’re having a boy or a girl. The only accurate ways to determine sex are an ultrasound performed by a trained professional or a blood test that identifies foetal chromosomes. Bump appearance varies due to body shape, muscle tone, pelvic structure, and the baby’s position.

Q. Is it true you’re smaller on your first pregnancy and bigger on your second?

A. Often, yes. During a first pregnancy, abdominal muscles are tighter and haven’t been stretched before. In later pregnancies, muscle tone is naturally reduced, so bumps tend to appear earlier and may look larger or lower. Other factors like genetics, nutrition, anaemia, and amniotic fluid levels also influence bump size. 

Q. Does heartburn during pregnancy mean the baby will have lots of hair?

A. Not exactly. A small study found a mild correlation between heartburn and babies born with more hair, but heartburn doesn’t cause hair growth. Pregnancy hormones that relax the oesophageal sphincter (causing heartburn) also contribute to foetal hair growth – it’s a shared hormonal effect, not a direct cause.

Q. Is it safe to fly while pregnant?

A. Yes – with precautions and depending on the trimester. 

• First trimester: You can fly, but nausea, faintness, and clot risk are higher.

• Second trimester: Usually the safest and most comfortable time to fly.

• Third trimester: Many airlines restrict travel from 28–32 weeks due to the risk of early labour and blood clots. 

Always check with your doctor or midwife, confirm airline rules, stay hydrated, move often, and ensure your travel insurance covers pregnancy.

Q. Do you need to 'eat for two' during pregnancy?

A. No. Calorie requirements rise only slightly depending on the trimester. What matters is a balanced, nutritious diet and avoiding or limiting certain foods for safety reasons – such as unpasteurised soft cheeses, high mercury fish, and excessive caffeine.

Q. Can spicy food induce labour? 

A. No, there’s no clinical evidence to support the idea that spicy food induces labour. 

This content is for information purposes only and is not intended or implied to be a substitute for professional medical advice, diagnosis, or treatment. Always seek advice from your GP or an appropriate medical professional if you have concerns about your health or before commencing a new healthcare regime. If you believe that you are experiencing a medical emergency call 999 / 112 or seek emergency assistance immediately.