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                                                                    Exhibit 10.5

March 12, 2007

Dear Mary,

You have made an outstanding contribution to ViaCell, Inc. (the "Company" or
"ViaCell") since joining us, and we feel confident that you will continue to be
a valuable contributor to our success. On behalf of the Company, I am pleased to
offer you continued employment on the terms described below.

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POSITION                      Senior Vice President, Business Development,
                              ViaCell Reproductive Health, reporting to Jim
                              Corbett, President, ViaCell Reproductive Health.

COMPENSATION                  The base salary for this position will continue to
                              be $237,952 per year, payable in substantially
                              equal bi-weekly installments or in accordance with
                              the Company's regular payroll practices as in
                              effect from time to time, subject to adjustment
                              pursuant to the Company's standard annual salary
                              review process. Currently, our standard annual
                              salary review process occurs each January for
                              senior management.

                              In addition, you will continue to be eligible to
                              participate in the Management Bonus Plan at an
                              annual target of 25% of base salary. This bonus is
                              payable annually based on agreed-to Company and
                              individual performance objectives. Your bonus
                              payout is determined based on achievement of both
                              corporate and individual goals.

ADDITIONAL EMPLOYMENT TERMS   ViaCell will provide for twelve (12) months'
                              severance pay in the event of involuntary
                              termination without Cause or voluntary termination
                              for Good Reason. If the Company terminates your
                              employment without Cause or if you terminate your
                              employment for Good Reason then ViaCell will
                              continue paying your base salary and medical and
                              dental benefit contributions for a period of
                              twelve (12) months in accordance with its regular
                              payroll practices at such time (the "Severance
                              Payments").

                              The term "Cause" as used herein means (i) your
                              continued failure to substantially perform your
                              duties, provided you are reasonably notified of
                              such failure and given reasonable time to correct
                              such failure, (ii) any misappropriation of funds,
                              properties or assets of the Company by you, (iii)
                              any damage or destruction of any property or
                              assets of the Company caused by you, whether
                              resulting from your willful actions or willful
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Mary Thistle
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                              omissions or gross negligence; (iv) your being
                              convicted of a felony; or (v) any material breach
                              of your employment obligations or of the
                              Intellectual Property and Confidential Information
                              Agreement.

                              The term "Good Reason" as used herein means any
                              action by the Company without your prior consent
                              which results in (i) any material diminution in
                              your title, position, duties, responsibilities or
                              authority; or (ii) any breach by the Company of
                              any material provision contained herein; provided
                              that a Good Reason shall not be deemed to exist
                              for purposes of this severance provision until you
                              have provided the Company with written notice of
                              same and the Company has not cured it for 30 days
                              following the receipt of such notice.

CHANGE OF CONTROL             Upon a Change of Control of the Company, all
                              options held by you at the time of such Change of
                              Control scheduled to vest in the subsequent
                              twelve-month period only as a result of the
                              passage of time shall vest immediately with
                              respect to that portion of such options so
                              scheduled to vest. Such options will otherwise
                              continue to be subject to other applicable grant
                              provisions.

                              If the Company terminates your employment without
                              Cause or you voluntarily resign for Good Reason
                              within twelve months of a Change of Control, all
                              options held by you at the time of such Change of
                              Control that, by their terms, become exercisable
                              only as a result of the passage of time shall
                              become fully vested and exercisable. Such options
                              will otherwise continue to be subject to other
                              applicable grant provisions. Further, ViaCell
                              will, upon such a termination following a Change
                              of Control and in addition to the severance
                              payment described above, pay you your bonus
                              pursuant to the Management Bonus Plan for the
                              bonus year in which such termination occurs, with
                              the bonus for such period determined by assuming
                              achievement of Company and individual performance
                              objectives (the "Change of Control Bonus").

                              A "Change in Control" shall mean: (i) a merger,
                              consolidation or similar combination after which
                              50% or more of the voting stock of the surviving
                              corporation is held by persons who were not
                              stockholders of the Company immediately prior to
                              such merger or combination; (ii) the sale,
                              transfer or other disposition of all or
                              substantially all of the Company's assets to one
                              or more persons (other than any wholly owned
                              subsidiary of the Company) in a single transaction
                              or series of related transactions; or (iii) any
                              person or related group of persons (other than the
                              Company or a person who directly or indirectly
                              controls, is controlled by, or is under common
                              control with the Company) directly or indirectly
                              acquires beneficial ownership (determined pursuant
                              to Rule 13d-3 promulgated under the Securities
                              Exchange Act of 1934, as amended) of securities
                              comprising more than 50% of the total combined
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Mary Thistle
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                              voting power of the Company's outstanding
                              securities pursuant to a tender or exchange offer
                              made directly to the Company 's stockholders.

RELEASE OF CLAIMS             Any obligation of the Company to pay you the
                              Severance Payments or the Change of Control Bonus
                              described above is conditioned on your signing and
                              returning to the Company a timely and effective
                              release of claims in the form provided by the
                              Company (the "Release of Claims"). Such Release of
                              Claims creates legally binding obligations on your
                              part, and the Company therefore advises you to
                              seek the advice of an attorney before signing it.
                              Any Severance Payment or Change of Control Bonus
                              to which you are entitled shall be payable in
                              accordance with the normal payroll practices of
                              the Company, and will begin at the Company's next
                              regular payroll period which is at least five
                              business days following the later of the effective
                              date of the Release of Claims or the date the
                              Release of Claims, signed by you, is received by
                              the Company; but the first payment shall be
                              retroactive to the date of termination.

BENEFITS                      Because we care about the well being of our
                              employees, we are pleased to continue to provide
                              you with a comprehensive offering of benefits. Our
                              benefits currently include medical, dental, life
                              insurance, 401k, three weeks vacation (accrued
                              monthly and pro-rated during your first calendar
                              year of employment), balance benefit, educational
                              assistance and flexible-spending accounts.

EMPLOYMENT RELATIONSHIP       While we look forward to a long and mutually
                              beneficial relationship, you acknowledge that this
                              letter does not constitute a contract of
                              employment for any particular period of time and
                              does not affect the at-will nature of your
                              employment relationship with the Company. Either
                              you or ViaCell have the right to terminate your
                              employment at any time.
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We are very excited about the future of ViaCell and believe that the
opportunities presented will allow you significant personal and professional
growth. If you have any questions or concerns, please do not hesitate to contact
me anytime. We look forward to having you continue on our team!

Sincerely,


/s/ Marc D. Beer
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Marc D. Beer
Chief Executive Officer


/s/ Mary Thistle
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Signature