Vertical transmission of the hepatitis C virus: Current knowledge and issues

Question 1

What is the rate of vertical transmission of HCV, and what factors may increase this rate?

Answer 1

Vertical transmission rate = 5%, with the rate being lower if the mother is HCV RNA-negative.

Incr with:
Higher maternal viral titre
Incr ALT in the year before pregnancy
Maternal cirrhosis 
HIV coinfection is clearly a risk factor for HCV vertical transmission, with rates of approximately 25% being described in early studies (Rx ART may eliminate this extra risk)
Maybe maternal IVDU

Question 2

What is the role of mode of delivery and breast milk in HCV transmission?

Answer 2

Both intrauterine and intrapartum transmission of HCV.
No specific interventions to decr transmission.
PROM has inconsistently been demonstrated to be a risk factor for HCV transmission. Pending RCTs, the mode of delivery should not be determined by maternal HCV status.
Procedures that promote mixing of fetal and maternal blood, such as the use of scalp electrodes or amniocentesis, should be avoided because there is some evidence of risk.
HCV RNA has been detected in breast milk, but transmission very unlikely. The benefits of breastfeeding outweigh the theoretical, but unproven, risk of HCV transmission to the infant.

Question 3

How do you manage the child born to an HCV-infected mother?

Answer 3

HCV serology is not reliable during infancy because passively transferred maternal antibody may persist for up to 18 months.
Serology at 12-18 months of age is the primary diagnostic test (repeat at 18 months of age, if still positive). Earlier Dx is unlikely to alter management, but there may be significant parental anxiety or concern that an infant will be lost to follow-up. In these situations only, do HCV RNA at 2mos of age (very sensitive and specific), keeping in mind the fact that clearance of the virus can be expected to occur in ~25% of viremic infants. If the HCV RNA test is positive, then the infant will require testing for HCV RNA and AST/ALT q6mos to determine whether chronic infection (=active viral replication >6mos, risk HCC) or spontaneous clearance will ensue.

Question 4

What are the main risk factors for HCV infection?

Answer 4

~1-3% of Canadians

The major risk factors for seropositivity in pregnant women are previous or current IVDU, being the sexual partner of an IVDU and blood transfusion before 1990. Before adolescence, the infection is now transmitted almost exclusively by perinatal exposure.

(sexual contact in a small proportion)
(higher rates in Aboriginals)