Now Playing: Study shows rear-facing car seats perform well in rear-end crashes
Now Playing: Consumer Reports finds frozen veggies are just as healthy as fresh veggies
Now Playing: Mothers of babies with heart defects may have their own heart health risks
Now Playing: Moms whose babies have heart defects may have long-term heart health risks
Now Playing: Inside promising new colon cancer treatments
Now Playing: Coffee companies in Calif. to add cancer warnings
Now Playing: Coffee shops now must include cancer warning in California
Now Playing: Drug overdose deaths continue to rise in the US, especially in blacks and Hispanics
Now Playing: Did scientists uncover a new human organ?
Now Playing: After weight loss surgery, relationships might change as much as weight: Study
Now Playing: Drug trend ‘wasping’ mixes insecticide with meth
Now Playing: MLB star breaks silence on his eating disorder struggle
Now Playing: Harvard researchers suggest they’ve reversed sign of aging in mice
Now Playing: What is a ‘Stop The Bleed’ kit?
Now Playing: Teen boys are less likely to get the HPV vaccination, study finds
Now Playing: Majority of people with dangerously high cholesterol not taking medication
Now Playing: What does it mean to become a bone marrow donor?
Now Playing: Scheduling exercise time based on fitness goals
Now Playing: Obesity epidemic grows in adults; perhaps levels off in youth
Now Playing: ‘GMA’ Hot List: Study reveals how many minutes of exercise you need