Three infants in U.S. states have been born with Zika-related birth defects, according to a new report by the U.S. Centers for Disease Control and Prevention.

Three other pregnancies ended in miscarriage, with the fetuses showing signs of birth defects associated with the mosquito-borne virus, the CDC reported on Thursday. Officials are now reporting on these births weekly as the Zika virus continues to spread across the globe.

"The pattern that we are seeing here among travel-associated cases are consistent with the pattern that we are seeing elsewhere," said Dr. Denise Jamieson, a co-leader of the pregnancy and birth defects task force on the CDC's Zika virus response team.

At least 234 pregnant women in the 50 states and the District of Columbia are infected with the Zika virus, and an additional 198 pregnant women in the U.S. territories have tested positive for Zika, according to the CDC.

"Most of those pregnancies are still ongoing," said Jamieson. The CDC is not releasing further details or numbers out of respect for patient privacy.

All the cases were travel-associated, meaning either the pregnant woman or a sexual partner had visited a country with active Zika transmission, she said.

Zika-related birth defects include microcephaly (a rare disorder in which a baby is born with an abnormally small head and possibly underdeveloped brain), calcium deposits in the brain, excess fluid in the brain cavities, abnormal eye development and damage to nerves, muscles and bones, according to the CDC.

"The period with the greatest risk for microcephaly and other brain abnormalities is in the first trimester," said Jamieson.

"I think it reinforces our guidance … to avoid mosquito bites and avoid the risk of sexual transmission," she said. The CDC continues to advise pregnant women to avoid travel to areas with the Zika virus.

Dr. Akshay Ganju is a resident in emergency medicine at Emory University in Atlanta. He is currently a resident in the ABC News Medical Unit.