Four out of five children below the age of five infected by Ebola are dying, with an even higher mortality rate among one-year-olds who require nursing and care.
Isolation from parents was causing great distress among the young patients, said WHO technical adviser Dr Margaret Harris.
Following a meeting of clinicians, there was a consensus that the strict "no touch" policy for Ebola patients could be lifted if good measures are in place to protect health workers from infection.
At least 21 pregnant women survived the haemorrhagic disease, but their babies or foetuses rarely did.
Survivors are displaying symptoms including severe muscle pain, headaches, mood swings, depression, loss of concentration and impaired vision, according to WHO.
Guinea sees new cases
Meanwhile, the number of people sick with Ebola fever has doubled in Guinea in the past week, said WHO.
Two dozen new suspected and confirmed Ebola cases were recorded in the past two weeks in remote regions where inhabitants had previously prevented health workers from entering.
The number of new Ebola cases rose in all three countries for the first time this year in the last week of January.
Sierra Leone registered 80 of the 124 new cases, Guinea 39 and Liberia the remaining five.
Only 21% of new cases in Sierra Leone were from known contacts, proving that health workers have no idea where the virus might be lurking.
Exhaustion among aid workers who have been on the front line of the battle means there is need for renewed international support to control the outbreak before the onset of rains. It is feared floods and muddy roads will hamper relief efforts.
Nearly 9,000 people have died out of 22,495 known cases in the epidemic that began in December 2013.