Hi Ian,
Hmmm, a tricky one.
I've just realized that I have a copy of J.E. Neale's Pioneer Passengers: To Nelson by sailing ship, March 1842-June 1843, which includes the passenger list of the Martha Ridgway although any that died are not indicated. This mentions twenty-one deaths and seven births (page 13).
The full passenger list on page 148 of this title was taken from the Examiner, 9 April 1842, page 19 but this title isn't available on Papers Past.
Spades