According to Snopes the answer is NO:
Barbara Mikkelson (who has contacted several airlines to get to the bottom of this) speculates:
... the origin of the "lifetime pass" legend came about as a fanciful explanation for why some airlines refuse passage to expectant women.
And there are indeed special regulations for pregnant women, e.g.
Whilst pregnancy is not a “medical condition”, flying whilst pregnant
is a frequently raised topic.
Normally pregnancy is a happy event for
all concerned but delivery in flight it is not without risks to the
mother and baby. For this reason British Airways, along with many
airlines, refuses to carry women in the latter stages of pregnancy,
typically after 36 weeks for single pregnancies, 32 weeks for
Civil Aviation Authority
Delivery in flight, or diversion in flight to a location that may not
have high quality obstetric services, is undesirable.
For this reason,
most airlines do not allow travel after 36 weeks for a single
pregnancy and after 32 weeks for a multiple pregnancy.
IATA (International Air Transport Association), which represents some 240 airlines, has a 398 pages thick Standard's Manual (from December 2011), but there is no mention of free flights for new-borns.
IATA Medical Guidelines for pregnancy:
I also browsed through several airline's webpages and while they all do mention special rules for pregnant women, neither says anything about a "bonus" when you deliver in-flight.
On the contrary some airlines even refuse to carry "highly" pregnant women (see above).
But, as the link in the question shows, reported cases do exist:
A baby boy who made a surprise arrival on board an AirAsia flight this
week will be given free flights for life with the budget carrier, as
will his mother.
"To celebrate this momentous occasion, we
decided to present both mother and child with free flights for life,"
said AirAsia's director of operations Moses Devanayagam.