BROWNSVILLE, Texas -- When we first met 23-year-old Rocio Morado of Brownsville, Texas, last month, she was 36 weeks pregnant and doctors were seeing problems with her baby on ultrasound.

Rocio Morado CBS News

Morado tested positive for Zika infection. The virus is carried by mosquitoes both in Brownsville and across the border in Mexico, where she visited family early in her pregnancy.

"I'm kind of sad, but I know everything is going to be OK," Morado said last month.

Since then, she's had her baby, Hugo.

"I feel so happy, I'm so in love with him," she said.

He was born almost three weeks ago with the small-head characteristic of microcephaly and faces an uncertain future in terms of his development.

Baby Hugo CBS News

"For right now he's doing OK but maybe like in four or three years, we don't know," Morado said.

Dr. John Visintine is Morado's doctor at Driscoll Children's Hospital. Of the 18 pregnant women who tested positive for Zika infection, one other baby, born last month, also has microcephaly. Seven babies appear normal, and nine pregnancies are ongoing.

Dr. John Visintine CBS News

"I don't know what to tell patients who live in Brownsville that want to have a family," Visintine said. "What do you tell those moms? They are definitely at risk of having babies who potentially can be damaged."

With so many people going back and forth between Mexico and the U.S. every day, it's hard to know, when somebody tests positive for Zika, exactly where they picked it up.

The virus can be spread both by mosquito bite and sexual relations. Health officials are focusing on prevention through mosquito control and patient education.

Once a pregnant woman is infected, there is no treatment to protect the baby.

"In the meantime we'll keep watching and screening," Visintine said.

Watching, screening and feeling helpless.