  Production of deuterons and antideuterons was studied by the NA49 experiment
in the 23.5% most central Pb+Pb collisions at the top SPS energy of
$\sqrt{s_{NN}}$=17.3 GeV. Invariant yields for $\bar{d}$ and $d$ were measured
as a function of centrality in the center-of-mass rapidity range $-1.2<y<-0.6$.
Results for $\bar{d}(d)$ together with previously published $\bar{p}(p)$
measurements are discussed in the context of the coalescence model. The
coalescence parameters $B_2$ were deduced as a function of transverse momentum
$p_t$ and collision centrality.
