Eden Hazard put Chelsea ahead after 25 minutes as the visitors capitalised on a lapse pass from Hammers captain Mark Noble as the league went in a goal-up at the interval.
And it was not long before the Blues extended their lead.
Five minutes after the restart and Chelsea’s top goalscorer Diego Costa added a second to put the West Londoners in control of the match, before Manuel Lanzini pulled one back for the Hammers late in the game.
Defeat for Slaven Bilic’s side leaves the Hammers in eleventh place.
EPL | The Premier League table after 27 matches
Second-placed Tottenham had closed the gap between themselves and Conte’s side to seven points with Sunday’s victory over Everton at White Hart Lane, after north London rivals Arsenal lost away to Liverpool.
That defeat at Anfield leaves Arsene Wenger’s side outside the top four in fifth place, behind Liverpool and Manchester City – who won away at Sunderland on Sunday – on 52 and 55 points respectively.
Jose Mourinho’s Manchester United find themselves in sixth spot, with 49 points, though they, the Gunners, and Pep Guardiola’s City all have a game in hand on their rivals.
Down the bottom of the table, Crystal Palace’s 2-0 win at West Brom saw them pick up back-to-back league victories for the first time since September, to move themselves three-points clear of the drop zone.