Issues of infant feeding for postnatal prevention of HTLV-1 mother-to-child transmission.

BACKGROUND A nationwide antenatal HTLV-1 antibody screening has been conducted in Japan. Our study purpose is to clarify the issues related to feeding options for prevention of postnatal mother-to-child transmission. METHODS Of the pregnant carriers at 92 facilities in Japan between 2012 and 2015, 735 were followed prospectively. Among the children born to them, 313 (42.6%) children were followed up to the age of 3 and tested for HTLV-1 antibody. The mother-to-child transmission rates on feeding options were calculated based on antenatal selection. RESULTS Among the 313 pregnant carriers, 55.0, 35.1, 6.1, and 3.8% selected short-term breastfeeding (≤3 months), exclusive formula feeding, frozen-thawed breastmilk feeding, and longer-term breastfeeding, respectively. Despite short-term breastfeeding was selected before labor, 8-18% of the mothers continued breastfeeding for 4-6 months. The mother-to-child transmission rate on the short-term breastfeeding was 2.3% (4/172) and its risk ratio compared to that on exclusive formula feeding was not significantly different (0.365; 95% CI 0.116-1.145). Because of small number of the children fed by frozen-thawed breastmilk, their mother-to-child transmission rate was not statistically reliable. CONCLUSION Pregnant HTLV-1 carriers tended to select short-term breastfeeding in Japan. While short-term breastfeeding was not always easy to wean within three months, it may be a viable option for preventing postnatal mother-to-child transmission because vertical transmission rate on short-term breastfeeding was not significantly higher than that on exclusive formula feeding. To increase follow-up rates for children born to pregnant carriers may provide clearer evidence of preventative effects by short-term breastfeeding and frozen-thawed breastmilk feeding. (250 words).