CARACAS (Reuters) - Carolina, who lives on the vertiginous hills of a Caracas slum, says she fell pregnant with her third child last year because birth control pills went scarce.

When the mosquito-borne virus Zika - linked to severe birth defects in thousands of babies in Brazil - started to spread through the Americas the homemaker, now seven months pregnant, set out to protect herself.

But repellent is also running short in crisis-hit Venezuela. And as water cuts are frequent in the slums, people keep reserve jars in store at home, a potential breeding ground for mosquitoes.

"I keep the doors closed. I can't do much more," said Carolina, 30, as she waited in line for a check-up at a state-run maternity centre in southern Caracas.

Zika is the latest worry for pregnant Venezuelans, who already search high and low for scarce folic acids, medical equipment and medicines, and even diapers to have in stock for when they give birth.

Around 4,700 cases of potential Zika infection have been reported in the country, Venezuela's Health Minister Luisana Melo told state television on Thursday in the first official estimate, vowing fumigation efforts and training for medical personnel.

It was unclear how many pregnant women have been infected with the virus.

Many doctors and health activists worry that the country will be ill-equipped to fight the virus as it grapples with economic crisis and constant shortages of consumer goods and medicines. With no vaccine or cure for the virus, much of the fight against the outbreak is going to depend on protecting people from mosquito bites and reducing the mosquito population.

"We're exposed like no other country in Latin America for this to be a pandemic," said Huniades Urbina, president of the Venezuelan Paediatrics Society, who is critical of the leftist government of Nicolas Maduro.

Drawing a full picture of the state of health in Venezuela is difficult as the government over a year ago stopped issuing weekly health bulletins, which included data on infant mortality and mosquito-born diseases.

"EXPLOSIVE" SPREAD OF ZIKA

At the clinic, where late leader Hugo Chavez's quote "pregnant women are sacred" emblazons a colourful mural of breast-feeding mothers, many of the dozen of pregnant women Reuters spoke to had partial or no information about Zika.

A pregnant teenager who thought she might have the virus flashed her bite-filled left hand and complained of itches, but said she had not heard Zika could hinder brain development in unborn babies.

The Paediatrics Society says it has received reports of pregnant women likely suffering Zika in each of Venezuela's states. One obstetrician in the sweltering border city of Maracaibo said she had already seen 20 pregnant patients with what appeared to be Zika.

There have been no reports of the deformation known as microcephaly, in which infants are born with abnormally small heads and brains.

But as the virus spreads from Brazil, other countries in the Americas are likely to see Zika-linked birth defects, the World Health Organization (WHO) said on Thursday. The virus is spreading "explosively" and could affect as many as four million people in the Americas, according to the WHO.

"I'm very worried. There's no medicine and the government isn't taking measures," said George Mendoza, 21, as he accompanied his 11-weeks pregnant girlfriend, who said she fell pregnant due to lack of condoms, to a check-up.

(Editing by Frances Kerry)