Objective: Although HTLV-1 is associated with severe diseases, there is ongoing vertical transmission since prenatal HTLV screening is not implemented in countries where the virus is present. We performed a cross-sectional analysis to verify the impact of counseling pregnant HTLV-1 seropositive women, who participate in the GIPH cohort study in Brazil, on this vertical transmission. Methods: GIPH study started in 1997 as an open prevalent cohort of HTLV-positive individuals. Children born from

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... TLV-1 seropositive women were divided into: (1) born before and (2) after the participation of mothers in the GIPH cohort ("GIPH babies"). The pregnant women participating in the study were counseled in order to prevent viral transmission, with recommendations of avoiding breastfeeding, giving infant formula, and preferably having the delivery by cesarean section. Results: We identified 54 children born of HTLV seropositive mothers. 3/21 (14.3%) of the children born from mothers who received no counseling were found positive for HTLV-1, in contrast to 1/18 (5.6%) of the "GIPH babies", whose mothers received counseling. 15 children were not tested, either due to the family's refusal or impossibility to locate them. Discussion: We found that it was worthwhile to counsel the mothers, since, as previously reported in the literature, we could observe a decline in the vertical transmission, which demonstrates the importance of prenatal screening of the virus. These actions should be widespread in countries where HTLV is present, in order to avoid the silent transmission of HTLV and future diseases in children born from positive mothers.