For an answer in terms of Bergman kernels associated with line bundles (a little bit of functional analysis is involved), see Theorem 4.2.3 in: 

Berndtsson, Bo An introduction to things $\overline\partial$∂−.  Analytic and algebraic geometry,  7–76, IAS/Park City Math. Ser., 17, Amer. Math. Soc., Providence, RI, 2010