GeneDx Holdings Corp.

1. The reported transaction represents the certification of achievement of a performance-based restricted stock unit award granted to the Reporting Person by the Issuer's compensation committee on March 15, 2025 (the "2025 PRSU Award"). Vesting of the 2025 PRSU Award is based on achievement of corporate performance metrics tied to revenue and adjusted net income, and subject to the Reporting Person's continued service through the certification date of achievement thereof.

2. The sales reported on this Form 4 represent shares sold by the Reporting Person to cover tax withholding obligations in connection with the vesting and settlement of the 2025 PRSU Award. The sales were effected to satisfy tax withholding obligations to be funded by a "sell to cover" transaction.

3. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $77.00 to $77.92 per share, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote and in footnotes 4 and 5 of this Form 4.

4. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $78.00 to $78.93 per share, inclusive.

5. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $79.00 to $79.64 per share, inclusive.

6. Following the reported sale undertaken to satisfy tax withholding liabilities and as of the date of filing of this Form 4, in addition to the 38,683 shares of Class A Common Stock beneficially owned by the Reporting Person, the Reporting Person beneficially owned RSUs representing contingent rights to receive up to an aggregate 451,912 shares of Class A Common Stock and options to purchase up to an aggregate 107,610 shares of Class A Common Stock, which RSUs and options vest according to their respective terms.

7. Each restricted stock unit ("RSU") reflected in this row represents a contingent right to receive 1 share of the Issuer's Class A Common Stock upon settlement for no consideration, subject to continued service as described in footnote 8 below.

8. 25% of the award shall vest annually on the anniversary of the grant date, with the first tranche vesting on April 1, 2027, subject to the Reporting Person's continued service to the Issuer on each vesting date. These RSUs do not have an expiration date; they either vest or are cancelled prior to the vesting date.