President Obama urged Congress to pass the full $1.9 billion funding requested to fight the Zika virus hours after federal health officials reported a dramatic increase in the number of pregnant women being monitored for possible complications related to the virus.

Obama said the funding request was a "pretty modest investment" in the attempt to curb the spread of the virus in the U.S.

"This is not something where we can build a wall to prevent it, mosquitoes don’t go through customs," Obama told reporters today. "To the extent that we are not handling this thing on the front end, we are going to have bigger problems on the back end."

Current proposed funds in the House of Representatives ($622 million) and the Senate ($1.1 billion) are woefully inadequate to fight the virus, the president said.

"We didn't just choose $1.9 billion from the top of our heads," Obama said. "This was based on public health assessments of all the work that needs to be done and to the extent that we want to be able to feel safe and secure."

"This is a pretty modest investment for us to get those assurances," he added.

The call for funding comes as a dramatic increase in the number of pregnant women with Zika infection being monitored for possible complications was reported by officials from the U.S. Centers for Disease Control and Prevention. The change was made after recent evidence about the virus' impact on pregnant patients who do not outwardly show symptoms of the infection.

The number of pregnant women being monitored after having a suspected Zika infection has more than doubled, from 112 to 279, in the U.S. and U.S. territories after changes made in reporting by officials from the U.S. Centers of Disease Control and Prevention.

CDC officials clarified today they were being more transparent after recent findings showed that even pregnant women who were infected with Zika virus but did not show symptoms had still given birth to children with birth defects.

Previously, only pregnant women with a laboratory-confirmed diagnosis and symptoms were being reported to the public, according to the CDC.

"We’ve learned a lot in the past four months and now we know of reports of asymptomatic Zika infection linked to microcephaly, miscarriage," said Dr. Margaret Honein, Chief of Birth Defects Branch at the National Center for Birth Defects and Developmental Disabilities.

Microcephaly is a birth defect in which the infant is born with an abnormally small head and brain, leading to significant developmental issues.

The CDC had been monitoring all of these women already, but decided to expand the number made public after seeing evidence that even an asymptomatic infection in a pregnant woman can affect the fetus. Officials said they are still monitoring a majority of these pregnancies and that they are "aware of less than a dozen adverse outcomes."

"These adverse outcomes include miscarriages and birth defects," Honein said. "It’s not possible to appropriately estimate the risks as most of these pregnancies are ongoing."

Officials highlighted that's crucial for pregnant women who may have been exposed to the virus to seek testing from their doctor or health center to monitor the pregnancy.

"It’s critical for pregnant women to have information on whether or not they’ve been infected," Honein said.

Since current data is limited, officials said they could not estimate the chance that a Zika infection could result in serious complications, such as miscarriage or birth defects, during pregnancy.