What Is SIDS?

Medically Reviewed by Renee A. Alli, MD on July 01, 2021
3 min read

New parents do everything they can to keep their babies healthy. But sometimes, a baby who seems perfectly fine passes away for no clear reason.

When this happens to an infant under the age of 1, doctors refer to it as sudden infant death syndrome, or SIDS. Because it often happens when a baby is asleep, you might also hear it called crib death or cot death.

The fact that it’s so hard to predict makes SIDS the leading cause of death for babies younger than 12 months in the U.S. It claims about 1,600 infants every year.

Doctors aren’t sure, but they have a few ideas. Some babies have a gene or a change to their genes that causes certain health problems that can lead to SIDS.

Other babies are born with problems in the part of their brain that controls breathing, heart rate, blood pressure, temperature, and waking from sleep.

Right now, there’s no way to test for these issues. But researchers found some things that, when put together, raise a little one’s risk:

  • A hidden health problem, like brain defects
  • Being in the first 6 months of life
  • Stress from something like a poor sleep position, secondhand smoke, or a respiratory infection

Remember, none of these by itself is enough to cause SIDS.

You can’t predict whether your family will be touched by SIDS, but there are a few things that make it more likely:

Age. It’s most common for babies between 2 and 4 months. But it can happen at any time during the first year of life.

Sex. It’s more likely to affect boys, but only slightly.

Race. It happens most often among African-Americans, Native Americans, and Alaska natives. Doctors aren’t sure why.

Birth weight. It’s more likely in preemies, especially those born very small, than full-term babies.

Familyhistory. A baby’s odds are high if a sibling or cousin passed away from SIDS.

Mom’s health. It’s more likely to happen to a baby whose mother:

  • Is younger than 20
  • Doesn’t get good prenatal care
  • Smokes, uses drugs, or drinks alcohol while pregnant or during baby’s first year


Yes. There are a few easy things you can do to prevent SIDS and keep your little one safe:

Put your baby on their back to sleep. Once they can roll over on their own, it’s safe for them to sleep on their tummy. Until then, remember this phrase: “back to sleep.” It’ll help keep your baby’s odds of having SIDS much lower.

Choose a firm, flat surface for their bed. Use tight-fitting sheets. Keep pillows, blankets, and other objects out of their sleep area until they are at least 1. You can swaddle them for warmth, but only until they learn how to roll over.

Sleep in the same room, but not in the same bed. Sharing a room with your baby can cut their chances in half. But sleeping in the same bed with them raises their odds. Try not to fall asleep while sitting up and holding your baby.

Use a pacifier, vaccinate, and breastfeed if you can. All three lower their risk.

Keep them cool while they are asleep. Don’t overdress them when you put them down. Their room should be cool and comfortable. You can use a special wearable blanket (called a sleep sack) that covers their body and leaves their face uncovered.

Don’t smoke, drink, or use drugs. It’s bad for your growing baby when you’re pregnant. Using drugs and alcohol might even make you a less alert or careful parent. Breathing in secondhand smoke can also raise the odds of SIDS.

Stay healthy during pregnancy. Avoid risky behaviors, eat healthy food, and see your doctor for regular checkups.