<PAGE>
                                                                    EXHIBIT 4.12

                             SUPPLEMENTAL INDENTURE

         THIS SUPPLEMENTAL INDENTURE (the "Supplemental Indenture") is executed
this 4th day of October, 2002, by the Additional Guarantor (as herein after
defined) and Wells Fargo Bank Minnesota, N. A., as Trustee (the "Trustee").

         WHEREAS, MATRIA HEALTHCARE, INC., a Delaware corporation, as issuer
(the "Issuer") and certain of its wholly-owned subsidiaries listed on Exhibit A
attached hereto (the "Existing Guarantors") have heretofore entered into an
Indenture, dated as of July 9, 2001 (the "Original Indenture"), with the Trustee
pursuant to which the Trustee acts as trustee for the Holders of the Issuer's
11% Senior Notes due 2008;

         WHEREAS, pursuant to the term of Article Ten of the Indenture, each
Guarantor, by executing the Indenture, jointly and severally, unconditionally
guarantees the Issuer's payment and performance obligations under the Indenture;

         WHEREAS, in accordance with Section 4.13 of the Original Indenture, the
Restricted Subsidiary listed on Exhibit B attached hereto (the "Additional
Guarantor") must execute supplements to the Original Indenture for the purpose
of joining the Existing Guarantors as a Guarantor;

         WHEREAS, Section 4.13 of the Original Indenture permits the Additional
Guarantor to execute supplements to the Original Indenture for the purpose of
adding Guarantors; and

         WHEREAS, Section 4.13 also requires the Additional Guarantor to execute
and deliver a notation of guarantee.

         NOW THEREFORE, in consideration of the agreements and obligations set
forth herein and for other good and valuable consideration, the sufficiency of
which is hereby acknowledged, the parties hereto agree as follows.

         Section 1.        Definitions. All capitalized terms used in this
Supplemental Indenture not defined herein shall have the meanings ascribed to
them in the Original Indenture.

         Section 2.        Additional Guarantors.

                  (a)      The Additional Guarantor is hereby added as a
Guarantor with all of the obligations of a Guarantor as set forth in the
Original Indenture, as amended and supplemented by this Supplemental Indenture.

                  (b)      As further evidence of the Additional Guarantor's
Note Guarantee, the Additional Guarantor shall execute and deliver along with
this Supplemental Indenture a notation of guarantee, the form of which is
attached hereto as Exhibit C, and shall have all of the obligations of a
Guarantor thereunder.


<PAGE>

         Section 3.        Counterparts. This Supplemental Indenture may be
executed in any number of counterparts, each of which shall be deemed an
original, but of all which together shall constitute one and the same document.

         Section 4.        Governing Law. This Supplemental Indenture shall be
governed by and construed in accordance with the laws of the State of New York,
without regard to the principles of conflicts of laws.

                            [signature pages follow]


<PAGE>

         IN WITNESS WHEREOF, Quality Oncology, Inc. has caused this Supplemental
Indenture to be duly executed all as of the date and year first above written.


                                      QUALITY ONCOLOGY, INC.



                                      By:
                                         --------------------------------------
                                         Name:  Parker H. Petit
                                         Title: Chairman of Board



                                      By:
                                         --------------------------------------
                                         Name:  Roberta L. McCaw
                                         Title: Vice President and Secretary


This Supplemental Indenture is hereby acknowledged
and accepted this _____ day of October, 2002 by
WELLS FARGO BANK MINNESOTA, N.A., as Trustee



By:
   -------------------------------------
   Name:
        --------------------------------
   Title:
         -------------------------------


<PAGE>

                                    EXHIBIT A

                               EXISTING GUARANTORS

A.R. Medical Supplies, Inc.

Clinical-Management Systems, Inc.

Diabetes Acquisition, Inc.

Diabetes Management Solutions, Inc.

Diabetes Self Care, Inc.

Facet Technologies, L.L.C.

Gainor Medical Acquisition Company

Gainor Medical International, L.L.C.

Gainor Medical Direct, L.L.C.

Matria of New York, Inc.

National Reproductive Medical Centers, Inc.

Infertility Management Services, Inc.

PFCC Liquidation Corp.

PFCF Liquidation Corp.

PFMG Liquidation Corp.

Q Liquidation Corp.

Shared Care, Inc.

Matria Laboratories, Inc.

MarketRing.com, Inc.


<PAGE>

                                    EXHIBIT B

                              ADDITIONAL GUARANTOR

Quality Oncology, Inc.


<PAGE>

                                    EXHIBIT C

                         [attach notation of guarantee]


<PAGE>

                              NOTATION OF GUARANTEE

         Each of the undersigned (the "Guarantor") hereby unconditionally
guarantees, to the extent set forth in the Indenture dated July 9, 2001 by and
among Matria Healthcare, Inc., as issuer, the Guarantors, as guarantors, and
Wells Fargo Bank Minnesota, N.A., as Trustee (as amended, restated or
supplemented from time to time, the (Indenture"), and subject to the provisions
of the Indenture, (a) the due and punctual payment of the principal of, and
premium, if any, and interest on the Notes, when and as the same shall become
due and payable, whether at maturity, by acceleration or otherwise, the due and
punctual payment of interest on overdue principal of, and premium and, to the
extent permitted by law, interest, and the due and punctual performance of all
other obligations of the Company to the Holders or the Trustee, all in
accordance with the terms set forth in Article Ten of the Indenture, and (b) in
case of any extension of time of payment or renewal of any Notes or any of such
other obligations, that the same will be promptly paid in full when due or
performed in accordance with the terms of the extension or renewal, whether at
stated maturity, by acceleration or otherwise.

         The obligations of the Guarantor to the Holders and to the Trustee
pursuant to this Guarantee and the Indenture are expressly set forth in Article
Ten of the Indenture, and reference is hereby made to the Indenture for the
precise terms and limitations of this Guarantee. Each Holder of the Note to
which this Guarantee is endorsed, by accepting such Note, agrees to and shall be
bound by such provisions.

         IN WITNESS WHEREOF, the Guarantor has caused this Guarantee to be duly
executed as of the 4th day of October, 2002.


                                     QUALITY ONCOLOGY, INC.



                                     By:
                                        ------------------------------------
                                        Name: Parker H. Petit
                                              Chairman of Board



                                     By:
                                        ------------------------------------
                                        Name: Roberta L. McCaw
                                              Vice President and Secretary