Inclusion Criteria:
1. Age 18 through 45 years (inclusive) at screening
2. Able and willing to provide written informed consent and take part in the study procedures
3. Able and willing to provide adequate locator information, defined as at least two other alternate contacts
4. HCV antibody seropositivity with detectable HCV RNA viral load at screening
5. Chronic HCV infection of at least 6 months by laboratory report or participant reported medical history as determined by the site PI, or if duration of HCV cannot be determined then the participant can be enrolled if there is no clinical evidence of acute hepatitis C infection (defined by CDC as presence of jaundice or total bilirubin \>/= 3.0 mg/dL or ALT \>200IU/L)
6. Singleton pregnancy at 20 + 0 to 30 + 0 weeks' gestation at enrollment with gestational dating confirmed by ultrasound
7. Having a comprehensive anatomy scan with no evidence of major structural abnormalities as defined by the CDC birth surveillance toolkit (https://www.cdc.gov/ncbddd/birthdefects/surveillancemanual/chapters/chapter-4/chapter4-1.html) or an anomaly that would significantly impact delivery timing or neonatal outcomes as determined by the Protocol Safety Review Team (PSRT) prior to enrollment
8. Documented negative Hepatitis B testing for current infection (negative HBsAg test) prior to enrollment
9. If living with HIV, must be on antiretroviral therapy with HIV viral load \<50 copies/mL on the most recent HIV viral load test within 30 days before enrollment and agree to continue antiretroviral therapy throughout study participation
10. If taking acid-suppressant medication(s), willing and able to either discontinue administration during the 12-week period of study treatment or to follow specific dosing instructions for concomitant use with SOF/VEL
11. Per participant report at screening and enrollment, agrees not to participate in other research studies involving investigational medications or investigational medical devices for the duration of study participation (does not include duration of infant participation). Note: maternal participants can participate in research studies that include standard of care medications.
Exclusion Criteria:
1. Participant report of any of the following at screening or enrollment:
1. Previous DAA treatment for HCV (prior interferon-based treatment is acceptable) without documentation of SVR12 (HCV RNA below the lower limit of quantification at least 24 weeks after DAA initiation)
2. Use of any medications contraindicated with concurrent use of velpatasvir or sofosbuvir according to the most current EPCLUSA® package insert30
3. Plans to relocate away from the study site area in the next 16 months and unable/unwilling to return for study visits
4. History of cirrhosis documented or reported by previous liver biopsy, imaging tests or on at least 2 noninvasive laboratory tests of fibrosis, including compensated cirrhosis
2. Reports participating in any other research study involving investigational medications or investigational medical devices within 60 days or less prior to enrollment (does not include research studies involving standard of care medications)
3. Known fetal chromosomal abnormality prior to enrollment (confirmed by chorionic villus sampling or amniocentesis)
4. Clinically significant and habitual non-therapeutic drug use, not including marijuana, as determined by site PI at screening and enrollment
5. At screening and enrollment, as determined by site PI, any significant, uncontrolled, active or chronic cardiovascular, renal, liver, hematologic, neurologic, gastrointestinal, psychiatric, endocrine, respiratory, immunologic disorder or infectious disease other than HCV (or HIV as outlined in eligibility criteria)
6. Any of the following laboratory abnormalities at screening:
1. Aspartate aminotransferase (AST) or alanine transaminase (ALT) greater than 10 times the upper limit of normal
2. Hemoglobin less than 9 g/dL
3. Platelet count less than 90,000 per mm3
4. International normalized ratio (INR) \> 1.5
5. Creatinine greater than 1.4
7. If living with HIV, CD4 count less than 200 cells/mm3 within 6 months of enrollment.
8. Any other condition that, in the opinion of the site PI/designee, would preclude appropriate informed consent, make study participation unsafe, complicate interpretation of study outcome data, or otherwise interfere with achieving study objectives.
