LIMITED POWER OF ATTORNEY

The undersigned hereby constitutes and appoints each of Jason F.
Cole, Kory Wentworth, and Helen Fu, and each of them individually,
and with full power of substitution, the undersigned's true and
lawful attorney-in-fact to:

	(1)	Complete and execute for and on behalf of the undersigned,
in the undersigned's capacity as an officer, director and/or ten
percent (10%) shareholder of bluebird bio, Inc., a Delaware
corporation (the "Company") any and all instruments, certificates and
documents required to be executed on behalf of the undersigned as an
individual or on behalf of the undersigned's company or partnership,
as the case may be, pursuant to Section 13 and Section 16 of the
Securities Exchange Act of 1934, as amended (the "Exchange Act") or
the rules and regulations thereunder;

	(2)	Do and perform any and all acts for and on behalf of the
undersigned which may be necessary or desirable to complete and
execute any such instruments, certificates or documents required to
be filed pursuant to Sections 13 and 16 of the Exchange Act or the
rules or regulations thereunder and timely file such forms with the
United States Securities and Exchange Commission and any stock
exchange or similar authority; and

	(3)	Take any other action of any type whatsoever in connection
with the foregoing which, in the opinion of such attorney-in-fact,
may be of benefit to, in the best interest of, or legally required
by, the undersigned, it being understood that the documents executed
by any such attorney-in-fact on behalf of the undersigned pursuant to
this Power of Attorney shall be in such form and shall contain such
terms and conditions as such attorney-in-fact may approve in such
attorney-in-fact's discretion.

	The undersigned hereby grants to each such attorney-in-fact,
acting singly, full power and authority to do and perform any and
every act which is necessary, proper or desirable to be done in the
exercise of any of the rights and powers herein granted, as fully to
all intents and purposes as the undersigned might or could do if
personally present, with full power of substitution or revocation,
hereby ratifying and confirming all that any such attorney-in-fact,
or any such attorney-in-fact's substitute or substitutes, shall
lawfully do or cause to be done by virtue of this Power of Attorney
and the rights and powers herein granted.

      The undersigned acknowledges that each of the foregoing
attorneys-in-fact, in serving in such capacity at the request of the
undersigned, are not assuming, nor is the Company assuming, any of
the undersigned's responsibilities to comply with Section 13 or
Section 16 of the Exchange Act or the rules or regulations
thereunder.  The undersigned hereby agrees to indemnify each
attorney-in-fact and the Company from and against any demand, damage,
loss, cost or expense arising from any false or misleading
information provided by the undersigned to such attorney-in fact.

	This Power of Attorney shall remain in full force and effect
until the undersigned is no longer required to file any instruments,
certificates and documents pursuant to Section 13 and 16 of the
Exchange Act or the rules or regulations thereunder with respect to
the undersigned's holdings of and transactions in securities issued
by the Company, unless earlier revoked by the undersigned in a signed
writing delivered to the foregoing attorneys-in-fact.

	IN WITNESS WHEREOF, the undersigned has caused this Power of
Attorney to be executed as of January 6, 2020.

/s/ Joanne Smith-Farrell
Joanne Smith-Farrell