You have a new baby, and your friends and relatives are chock-full of advice. But some long-held assumptions about babies’ well-being don’t hold up under scientific scrutiny.

Find out what experts say when it comes to nine popular baby safety myths.

Myth #1: It’s safe to sleep with your baby in your bed.

The science: Research shows it’s dangerous by putting infants at an increased risk of suffocation, strangulation and sudden infant death syndrome (SIDS). In fact, a recent study found that bed sharing is the biggest risk factor for sleep-related infant deaths. Room sharing, perhaps using a co-sleeper bassinet, is a safer idea.

Related: Is Co-Sleeping With Your Baby Safe?

Myth #2: Crib bumpers protect your baby from injury while sleeping.

The science: There is no evidence that crib bumpers prevent injury in infants — but babies can get trapped and suffocate or strangle himself in them, according to the American Academy of Pediatrics (AAP). That group recommends using a firm sleep surface covered by a fitted sheet and removing soft objects such as sheepskins, wedges, bumper pads, quilts and pillows or pillow-like toys. If it sounds like you won’t be able to keep your little one warm on winter nights, sleepwear will solve the problem. The AAP recommends using sleep clothing designed to keep your baby warm without covering her head.

Related: 5 Dangerous Baby Products to Avoid

Myth #3: Giving more than one vaccine at a time can overload your baby’s immune system.

The science: Every day your baby is exposed to — and fights off — millions of antigens, the foreign particles that cause the immune system to respond. Since vaccines contain only a tiny amount of antigens (from either weakened or killed germs), they can’t cause serious or harmful illnesses even when combined or given several at a time, according to the Centers for Disease Control and Prevention.

Myth #4: Pediatric cough and cold medicines are safe for your baby.

The science: When your little one is stuffed up or coughing, you may be tempted to give him a pediatric cold or cough remedy. But resist that impulse, says the Food and Drug Administration. It urges parents not to use over-the-counter cough and cold products for infants and children under age 2 because they are neither safe nor effective for them. Side effects can be serious and even life threatening. Try alternative methods such as saline nasal sprays instead.

Myth #5: Walkers are a good way to help your baby learn to walk.

The science: You may remember seeing a baby propelling himself around the floor on wheels in a walker with a food tray. This device was popular for generations, but it’s now considered off limits. In fact, if the AAP had its way, walkers would be banned entirely. Even though modern walkers come equipped with safety features (such as brakes that kick in as soon as one wheel leaves the floor), Consumer Reports does not consider any walker to be safe. Babies in walkers have fallen down stairs, drowned in pools and toilets and suffocated when their necks were compressed against the food tray.

Related: Oh, Baby! Protect Your Wee One from These 5 Household Hazards

Myth #6: You should use sunscreen to protect your baby from the sun.

The science: Rather than use sunscreen, keep babies under 6 months out of the direct sun, say experts at the American Academy of Dermatology. Dress your baby in a hat and loose, long-sleeved and leg-covering clothing if you’re outside on sunny days. For babies over 6 months, you can use sunscreen, but look for one made especially for babies so their sensitive skin won’t break out in a rash.

Myth #7: Adding rice cereal to the night bottle will make your baby sleep better.

The science: It depends how old your baby is. The AAP recommends breastfeeding as the sole source of nutrition for about the first 6 months of life, and there’s good reason for it. It’s not just that breast milk provides all the nutritional requirements for your baby, it’s that your baby’s tongue, throat muscles and digestive system are not developed enough for solids before around 4 months — perhaps not even before 6 months, according to the AAP. Researchers have also found a link between early solids and obesity, as well as early solids and asthma triggered by grass pollen.

Related: Solving the Sleepless Baby Nightmare

Myth #8: Hard-soled shoes protect your baby's feet.

The science: Hard-soled shoes were the norm in our parents’ babyhood, but not anymore. Babies grasp the floor with their toes, and going barefoot allows them to develop their foot muscles, according to the American Podiatric Medical Association (APMA). Your baby’s first shoes should be lightweight and flexible with nonskid soles. They should also be made out of natural materials, according to the APMA, since those fat little feet sweat a lot.

Myth #9: Your baby needs water when it's hot outside.

The science: Healthy babies younger than 6 months do not need extra water when it’s hot outside — breast milk and formula provide everything your baby needs. But once you introduce solid foods, it’s OK to add water to your baby’s diet, according to the AAP.

Related: The Quantified Baby: How Safe Are Wearable Devices?

Ana Manley-Black, J.D., is a former immigration attorney and a freelance health and medical writer whose stories have appeared in Healthday, Consumer Health Interactive, and other media.