William Blair Investment Management, LLC filed a Schedule 13G with the SEC on November 6, 2026, disclosing beneficial ownership of 1,560,247 shares of GeneDx Holdings Corp. common stock as of September 30, 2026.

Key Highlights

  • Aggregate beneficial ownership: William Blair Investment Management, LLC reported beneficial ownership of 1,560,247 shares of GeneDx Holdings Corp. common stock.
  • Percent of class: The reported holdings represent 5.2% of the outstanding class of common stock.
  • Sole voting power: William Blair reported sole voting power over 1,418,435 shares, with no shared voting power.
  • Sole dispositive power: William Blair reported sole dispositive power over all 1,560,247 shares, with no shared dispositive power.
  • Triggering date: The event requiring the filing occurred on September 30, 2026.
  • Filer classification: William Blair Investment Management, LLC is identified as an investment adviser (type "IA"), organized in Delaware.

William Blair Investment Management Reports 5.2% Position in GeneDx Holdings Common Stock

According to the Schedule 13G filed on November 6, 2026, William Blair Investment Management, LLC, an investment adviser organized in Delaware and headquartered at 150 North Riverside Plaza, Chicago, IL 60606, disclosed a beneficial ownership position in GeneDx Holdings Corp. (NASDAQ:WGS) common stock. The filing was triggered by an event dated September 30, 2026, and covers shares with CUSIP number 81663L200. GeneDx Holdings Corp. is listed with its principal executive offices at 333 Ludlow Street, North Tower, 6th Floor, Stamford, Connecticut, 06902.

The filing states that William Blair beneficially owns 1,560,247 shares in aggregate, representing 5.2% of the class. Of those shares, 1,418,435 are subject to sole voting power, while the remaining shares carry no voting power attributed to William Blair. All 1,560,247 shares are subject to sole dispositive power, with zero shares subject to shared dispositive power, according to the filing.

William Blair's certifying officer, Chief Compliance Officer Telmo Martins, signed the filing on November 6, 2026. The filing certifies that, to the best of William Blair's knowledge, the securities "were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities," as stated verbatim in the document.

What Was Disclosed

William Blair Investment Management, LLC filed a Schedule 13G disclosing beneficial ownership of 1,560,247 shares, or 5.2%, of GeneDx Holdings Corp. common stock, with the reporting date of September 30, 2026, and filing date of November 6, 2026.