Nairobi, Feb. 9 -- Grace Wamuhua's heart jumps every time her toddler calls "Mama!" as she sells second-hand clothes on the bustling Tom Mboya Street of downtown Nairobi.

It could mean he's wandered too far in the crowds or is in distress. Grace must stop her work and swiftly grab him before he disappears or gets hurt.

It happens all day long as the single mother balances her trade with protecting her rambunctious child. She can't afford childcare, so he stays by her side.

The baby keeps calling his mother while pointing at honking vehicles and touts directing passengers to matatus, thus interrupting our interview.

Getting the luggage to the city centre is not a walk in the park, she says. It involves manoeuvring within the market, th...