  A subpopulation of neutron stars (NSs), known as central compact objects
(CCOs) in supernova remnants, are suspected to be low-field objects basing on
$P$-$\dot P$ measurements for three of them. The birth rate of low-field NSs is
probably comparable with the birth rate of normal radio pulsars. However, among
compact objects in High-Mass X-ray Binaries (HMXBs) we do not see robust
candidates for low-field NSs. We propose that this contradiction can be solved
if magnetic fields of CCOs was buried due to strong fall-back, and then the
field emerges on the time scale $10^4$-$10^5$ yrs.
