There are countless myths surrounding fertility and pregnancy, some of them repeated so often that many people believe they’re true.

Here, two top experts in fertility and pregnancy – Professor Adam Balen, a consultant in reproductive medicine at Leeds Teaching Hospitals NHS Trust, and spokesperson for the  Royal College of Obstetricians and Gynaecologists  (rcog.org.uk),  and  Carmel Lloyd, head of education at the Royal College of Midwives (rcm.org.uk), outline which common fertility and pregnancy statements are truths – and which are not.

The truth or myth answer is at the end of each section. So how many do you know?

1.  Stress causes infertility

Balen says: “Being stressed raises certain chemicals in the blood, like cortisol, which can have an effect on fertility. So it’s a bit of a vicious circle – if you’re stressed it can have an impact on your natural chances of conceiving, but the longer it takes you to get pregnant, the more stressed couples become, and that has an additional impact on their wellbeing.

“So, for example, it’s well-known that couples trying to get pregnant have intercourse less frequently the longer they’re trying because they get anxious about being sure they’re having intercourse at the right time in the cycle, and making love to order causes additional stress and anxiety. So there are all sorts of components that play into stress and fertility – infertility itself is extremely stressful, and stress, in turn, can then have an impact on ovulation and the chances of getting pregnant.

“It can cause infertility in some people – it can stop some women who lose weight when they’re stressed from ovulating. Rarely it causes such an extreme problem, but there’s certainly a close interaction between stress and fertility.”Answer: Truth

2. Diet affects fertility

“Diet definitely has a major impact on fertility,” says Balen. “It’s not only whether someone is overweight or underweight, it’s also the nutritional content in their diet – vitamin and mineral levels can have a major impact on the health of eggs and sperm. Probably one of the best known is vitamin D – there’s a lot of vitamin D deficiency in the UK. Taking supplements certainly improves the health of eggs and sperm.

“It’s important to have a balanced diet, and there’s absolutely no doubt that diet does have a significant bearing on both men and women’s fertility. Fertility is a couples’ thing and both parties are important. Reproductive health is giving you a snapshot of your overall health, and many people who have fertility problems have other health problems as well, and if you can address someone’s overall health it will have a positive benefit on their fertility too.”Answer: Truth

3. Smoking doesn’t affect fertility

“Smoking does affect fertility, for men and women,” stresses Balen. “It significantly damages the ovaries and brings forward the age of the menopause. To put it bluntly, it kills the eggs in the ovaries and also affects the genetic profile of sperm so there’s less sperm as well.”Answer: Myth

4. Men’s fertility doesn’t decline

“Male fertility declines with age, but at an older age and slower rate than it does for women,” explains Balen.

“So whereas girls are born with a fixed number of eggs, and when they become menopausal there aren’t any fertile eggs left, men can continue to make sperm until they die, but the quality of the sperm, its fertility potential and genetic health, does decline.

“Older men also have an increased risk of children with certain genetic abnormalities as well. Autism, for example, increases in the children of older men.”

Answer: Myth

5. You need to have sex on the day the woman ovulates to get pregnant

“Sperm survive in the fallopian tubes of a woman for up to five days after intercourse, and you need to have sperm there when the egg is released, but the egg only survives for a day, so the fertile window is potentially six days,” says Balen,

Answer: Myth

6. Lying flat after sex increases your chances of getting pregnant

Balen says: “You don’t need to lie flat after sex to get pregnant – that’s a myth. Soon after ejaculation the sperm that’s going to fertilise the egg will already be up in the womb and fallopian tubes, and any fluid that’s left in the vagina isn’t going to travel up anyway. It’s natural for women to feel they want to stay lying down for a bit, but it doesn’t affect fertility.”

Answer: Myth

7.  Pregnant women should eat for two

Lloyd says: “Eating for two is a myth. In the last three months of your pregnancy, the advice is to have about 200 extra calories a day, equivalent to about two slices of wholemeal toast and margarine. There’s good advice on eating in pregnancy on  NHS Start4life (nhs.uk/start4life/pregnancy/healthy-eating-pregnancy).”

Answer: Myth

8. Eating spicy food can induce labour

“There’s no strong evidence to suggest this, though some women say this has helped,” says Lloyd. “Some may find they have problems such as heartburn in pregnancy and spicy food could exacerbate this, particularly towards the end of the pregnancy as the growing baby causes a backflow of acids from the stomach.”

Answer: Myth

9.  You’ll have pregnancy cravings

“Not all women have pregnancy cravings, but many do,” says Lloyd. “This is often for specific foods such as chips or odd combinations of food, or even things we don’t think of as food such as coal.

“If you get cravings, they often start early in pregnancy and tend to fade away towards the end. If you find yourself craving things that aren’t food, speak to your midwife or doctor, as this could be a sign of a vitamin or mineral deficiency.”

Answer: Sometimes True

10. You shouldn’t have a hot bath when you’re pregnant

“You should avoid hot baths while pregnant as this may cause you to overheat which can cause problems for you and your baby,” explains Lloyd. “But there’s no reason why you can’t have a warm bath when you’re pregnant. To check your bath’s a safe temperature, test the water first with your elbow or forearm.”

Answer: Truth

11. You shouldn’t dye your hair when pregnant

Lloyd says: “The limited research available shows it’s safe to dye your hair and the chemicals in hair dyes aren’t highly toxic. While the risk is small throughout pregnancy, some women wait until after the first 12 weeks before dyeing their hair, when the risk of any chemicals harming the baby is much lower.

“There’s good advice on this from the NHS here (nhs.uk/common-health-questions/pregnancy/is-it-safe-to-use-hair-dye-when-i-am-pregnant-or-breastfeeding).”

Answer: Myth

12. You can tell if it’s a boy or a girl by the pregnancy bump

“There’s no way of telling by the shape or size of your bump whether you’re having a boy or girl,” says Lloyd. “If you want to know your baby’s gender, ask the sonographer doing your 20-week scan. They can’t be 100% sure, especially if your baby’s lying in a position that makes it difficult to tell, but it’s a better indication than by the size or shape of your bump.”

Answer: Myth

For advice on pregnancy, talk to your midwife or GP, and visit the NHS website (nhs.uk/common-health-questions/pregnancy/).