Hepatitis B doesn't cross the placenta, it is transmitted perinatally. Mothers with HBeAg in their blood have an extremely high risk of passing the infection to their child, whereas mothers with no HBeAg have a low rate of infectivity. The WHO says that transplacental trasmission doesn't occur as the virus is too large, however medscape says it can occur in a minority of cases.
Both HCV and HBV are trasmitted thru blood and can therefore effect IVDUs