Exhibit 3.1

AMENDMENT TO

FOURTH AMENDED AND RESTATED BY-LAWS OF HOLOGIC, INC.

Article I, Section 1.4(a)(2) of the Fourth Amended and Restated By-laws of Hologic, Inc. is hereby amended to add the following underlined text:

ARTICLE I.

Stockholders

Section 1.4 Notice of Stockholder Business and Nominations.

(a) Annual Meetings of Stockholders.

(2) For nominations or other business to be properly brought before an annual meeting of stockholders by a stockholder pursuant to clause (c) of paragraph (A)(1) of this Section 1.4, the stockholder must have given timely notice thereof in writing to the secretary of the corporation and any such proposed business other than the nominations of persons for election to the board of directors must constitute a proper matter for stockholder action. To be timely, a stockholder’s notice shall be delivered to the secretary at the principal executive offices of the corporation not later than the close of business on the ninetieth day nor earlier than the close of business on the one hundred twentieth day prior to the first anniversary of the preceding year’s annual meeting; provided, however, that with respect to the corporation’s annual meeting to be held during calendar year 2014, to be timely, a stockholder’s notice of nominations must be delivered to the secretary at the principal executive offices of the corporation not later than 5:00 p.m. EST on December 9, 2013 (provided further, however, that in the event that the date of the annual meeting is more than thirty (30) days before or more than seventy (70) days after such anniversary date, notice by the stockholder must be so delivered not earlier than the close of business on the one hundred twentieth day prior to such annual meeting and not later than the close of business on the later of the ninetieth day prior to such annual meeting or the tenth day following the day on which public announcement of the date of such meeting is first made by the corporation). In no event shall the public announcement of an adjournment or postponement of an annual meeting of stockholders commence a new time period (or extend any time period) for the giving of a stockholder’s notice as described above. Such stockholder’s notice shall set forth: (a) as to each person whom the stockholder proposes to nominate for election as a director (i) all information relating to such person that is required to be disclosed in solicitations of proxies for election of directors in an election contest, or is otherwise required, in each case pursuant to and in accordance with Section 14(a) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”) and the rules and regulations promulgated thereunder, and (ii) such person’s written consent to being named in the proxy statement as a nominee and to serving as a director if elected; (b) as to any other business that the stockholder proposes to bring before the meeting, a brief description of the business desired to be brought before the meeting, the text of the proposal or business (including the text of any resolutions proposed for consideration and in the event that such business includes a proposal to amend the by-laws of the corporation, the language of the proposed amendment), the reasons for conducting such business at the meeting and any material interest in such business of such stockholder and the beneficial owner, if any, on whose behalf the proposal is made; and (c) as to the stockholder giving the notice and the beneficial owner, if any, on whose behalf the nomination or proposal is made (i) the name and address of such stockholder, as they appear on the corporation’s books, and of such beneficial owner, (ii) the class or series and number of shares of capital stock of the corporation which are owned beneficially and of record by such stockholder and such beneficial owner, (iii) a description of any agreement, arrangement or understanding with respect to the nomination or proposal between or among such stockholder and/or such beneficial owner, any of their

respective affiliates or associates, and any others acting in concert with any of the foregoing, including in the case of a nomination, the nominee, (iv) a description of any agreement, arrangement or understanding (including any derivative or short positions, profit interests, options, warrants, convertible securities, stock appreciation or similar rights, hedging transactions, and borrowed or loaned shares) that has been entered into as of the date of the stockholder’s notice by, or on behalf of such stockholder and such beneficial owners, whether or not such instrument or right shall be subject to settlement in underlying shares of capital stock of the corporation, the effect or intent of which is to mitigate loss, to manage risk or benefit of share price changes for, or to increase or decrease the voting power of, such stockholder or such beneficial owner, with respect to the shares of stock of the corporation, (v) a representation that the stockholder is a holder of record of stock of the corporation entitled to vote at such meeting and intends to appear in person or by proxy at the meeting to propose such business or nomination, (vi) a representation whether the stockholder or the beneficial owner, if any, intends or is part of a group which intends (a) to deliver a proxy statement and/or form of proxy to holders of at least the percentage of the corporation’s outstanding capital stock required to approve or adopt the proposal or elect the nominee and/or (b) otherwise to solicit proxies or votes from stockholders in support of such proposal or nomination, and (vii) any other information relating to such stockholder and beneficial owner, if any, required to be disclosed in a proxy statement or other filings required to be made in connection with solicitations of proxies for, as applicable, the proposal and/or for the election of directors in an election contest pursuant to and in accordance with Section 14(a) of the Exchange Act and the rules and regulations promulgated thereunder. The foregoing notice requirements of this Section 1.4 shall be deemed satisfied by a stockholder with respect to business other than a nomination if the stockholder has notified the corporation of his, her or its intention to present proposal at an annual meeting in compliance with applicable rules and regulations promulgated under the Exchange Act and such stockholder’s proposal has been included in a proxy statement that has been prepared by the corporation to solicit proxies for such annual meeting. The corporation may require any proposed nominee to furnish such other information as it may reasonably require to determine the eligibility of such proposed nominee to serve as a director of the corporation.