"Having a child now means making him suffer," said Milagros Martinez, waiting on a park bench on a recent morning ahead of her sterilisation at a nearby Caracas municipal health center.

The 28-year-old butcher from the poor outskirts of Caracas decided on the operation after having an unplanned second child because she could not find birth control pills.

Her daily life revolves around finding food: she gets up in the middle of the night to stand in long lines outside supermarkets, sometimes with no choice but to bring along her baby son, who has been sunburnt during hours-long waits.

"I'm a little scared about being sterilised but I prefer that to having more children," said Martinez, who with dozens of other women took a bus from the slums at 4 a.m. to attend a special "sterilisation day" in this wealthy area of Caracas.