WATCH: 1st baby born using uterus transplanted from deceased donor

Now Playing: 1st baby born using uterus transplanted from deceased donor

Now Playing: More US beef being recalled over salmonella fears

Now Playing: The best toys for kids make use of their imaginations, not a screen

Now Playing: Two blood pressure medications pulled in heart-drug recall

Now Playing: Younger school entry linked to ADHD diagnosis: Study

Now Playing: Teen left in tears as her classmates reveal she’s cancer free

Now Playing: Studies show women who snore pose greater cardiac risk

Now Playing: US life expectancy drops for 3rd year in a row

Now Playing: Deborah Norville of ‘Inside Edition’ shares how she dropped 30 pounds

Now Playing: Doctor behind first genetically modified babies: ‘I feel proud’

Now Playing: Researcher in middle of gene controversy defends his work

Now Playing: Number of cases of AFM nearly doubled in the last month: CDC

Now Playing: Romaine lettuce from California linked to E. coli, FDA says

Now Playing: How to use fats and oils for healthy hair, skin

Now Playing: New cancer treatment credited for saving the life of 9-year-old boy

Now Playing: American professor investigated for involvement in genetically edited babies

Now Playing: What is ‘bloating’?

Now Playing: Chinese researcher claims to have made 1st genetically edited babies

Now Playing: Refocus on health after the indulgent Thanksgiving meal

Now Playing: ALS researcher living with the disease still fighting for a cure