You can buy activated carbon filters from companies like Fileder,
www.fileder.co.uk that will remove lead. You would need to enquire as to how efficient they are. A plastic food grade 10" housing plus filter cartridges would not be very expensive, may be ~£100 including 12 catridges but that could be several years out of date.
To be honest, if the worry is only for the nine months or so that your daughter will be pregnant then buy 2 litre supermarket own brand bottled water at around 10p per litre, at least it is in the UK. As lead is a cumulative poison that may not be the most sensible option. Does your water supply company offer a water analysis service? At least you'd then know if you had a problem. If they don't it may cost you something up to £100 to pay for your own analysis by a food standards laboratory, we pay around £150 in the UK for testing whisky samples to check on half a dozen key chemicals that are controlled.
Hope that gives you options and is helpful.
Ooops, too many interuptions, Dane got there first
PPS I believe that if it is found that you have lead pipes they can now line them simply and cheaply by disconnecting the pipe art the supply and rolling in a membrane liner through the pipe work and then reconnecting,. May be something else to enquire about.