Infrastructure investment group International Public Partnerships Limited expects its net asset value to have increased in the first quarter.The group said it based the forecast on the assumption that the decline in government bond yields in the markets in which it invest will offset the strengthening pound."The decrease in these rates could, other things being equal, be expected to have a positive effect on the company's net asset value," the group said in a statement on Wednesday.FTSE-250 listed International PPL added the strengthening of the sterling had weighed on its net asset value, which amounted to 127p per share at the end of last year."The pound sterling forward curve has strengthened against the three currencies to which the company has exposure, particularly the euro," the group said."The strengthened foreign exchange position of the pound sterling could be expected to have a negative effect on the company's net asset value."However, the company added it was positive about its prospects for the year and was confident to add "high quality investments" to its portfolio during 2015.International PPL shares were down 0.07% to 138.00p at 09:51 on Wednesday.