Background:  Successful mother-to-child transmission (MTCT) prophylaxis is based on reduction of maternal viral load to undetectable levels. Late presenters, pre-treated patients with multi-drug resistant virus, and pregnancy complications require special short-term antiretroviral intervention in late pregnancy. Enfuvirtide (ENF) is characterized by rapid activity and might therefore be an option to intensify ART close to delivery.

Methods:  We observed the effectiveness and safety of ENF, administered during the third trimester of pregnancy in 12 pregnant women. Indication for ENF were :  In 6 women viral load had not been successfully suppressed antenatal; 3 women were late presenters (>32 week of pregnancy); 3 cases of pregnancy complications resulting in premature birth. ENF was combined with at least 3 other antiretroviral drugs. Viral load changes, adverse events, and the outcome of the newborns were investigated. At time of delivery maternal plasma levels of ENF were compared to levels in the umbilical cord blood. All children were born by caesarean section.

Results:  The mean duration of treatment for ENF was 17 days before delivery (range, 1 to 57). Mean viral load before the onset of ENF was 87,600 copies/mL (range, 70 to 1,000,000) Mean viral load by the time of delivery was 236 copies/mL (range, <40 to 1780). Average time of delivery was 37 weeks of pregnancy (range 34 to 41) Mean weight of the 12 newborns was 2710 g (range, 1580 to 4.270). In 8 of 12 cases, we collected samples for pharmacokinetic analysis. Mean maternal plasma concentration of ENF was 1.460 ng/mL (range, 412 to 2.980). In all 8 newborns the ENF concentration was <200 ng/mL, which means a lack of transplacental distribution. No ENF-related adverse events were observed in all mothers and children. There has been no case of vertical HIV-transmission in the 12 children.

Conclusions:  In this investigation ENF in combination with other antiretroviral drugs has been a successful and safe MTCT prophylaxis in late pregnancy. The use of ENF in pregnant women might be a useful option, particularly with regard to late presenters, multi-drug-resistant virus and premature delivery.