formsc13da.htm

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 13)

NATUS MEDICAL INCORPORATED (BABY)

(Name of Issuer)

Common Stock

(Title of Class of Securities)

639050103

(CUSIP Number)

David Nierenberg

The D3 Family Funds

19605 NE 8th Street

Camas, WA 98607

(360) 604-8600

With a copy to:

Henry Lesser, Esq.

DLA Piper LLP (US)

2000 University Avenue

East Palo Alto, CA 94303

(650) 833-2000

(Name, Address and Telephone Number of Person

Authorized to Receive Notices and Communications)

January 19, 2010

(Date of Event which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box Ô.

1	NAME OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (entities only) The D3 Family Fund, L.P.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (See Instructions) (a) x (b) o
3	SEC USE ONLY
4	SOURCE OF FUNDS (See Instructions) WC
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e) o
6	CITIZENSHIP OR PLACE OF ORGANIZATION Washington

NUMBER OF SHARES BENEFICIALLY	7	SOLE VOTING POWER 0
OWNED BY EACH REPORTING	8	SHARED VOTING POWER 532,291 Common shares (1.9%)
PERSON WITH	9	SOLE DISPOSITIVE POWER 0
	10	SHARED DISPOSITIVE POWER 532,291

11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON For the reporting person listed on this page, 532,291; for all reporting persons as a group, 3,252,044 shares (11.5%)
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (See Instructions)
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 11.5%
14	TYPE OF REPORTING PERSON (See Instructions) PN

1	NAME OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (entities only) The D3 Family Bulldog Fund, L.P.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (See Instructions) (a) x (b) o
3	SEC USE ONLY
4	SOURCE OF FUNDS (See Instructions) WC
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e) o
6	CITIZENSHIP OR PLACE OF ORGANIZATION Washington

NUMBER OF SHARES BENEFICIALLY	7	SOLE VOTING POWER 0
OWNED BY EACH REPORTING	8	SHARED VOTING POWER 2,143,766 common shares (7.6%)
PERSON WITH	9	SOLE DISPOSITIVE POWER 0
	10	SHARED DISPOSITIVE POWER 2,143,766

11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON For the reporting person listed on this page, 2,143,766; for all reporting persons as a group, 3,252,044 shares (11.5%)
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (See Instructions)
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 11.5%
14	TYPE OF REPORTING PERSON PN

1	NAME OF REPORTING PERSONS The D3 Family Canadian Fund, L.P.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (See Instructions) (c) x (d) o
3	SEC USE ONLY
4	SOURCE OF FUNDS (See Instructions) WC
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e) o
6	CITIZENSHIP OR PLACE OF ORGANIZATION Washington

NUMBER OF SHARES BENEFICIALLY	7	SOLE VOTING POWER 0
OWNED BY EACH REPORTING	8	SHARED VOTING POWER 129,931 common shares (0.5%)
PERSON WITH	9	SOLE DISPOSITIVE POWER 0
	10	SHARED DISPOSITIVE POWER 129,931

11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON For the reporting person listed on this page, 129,931; for all reporting persons as a group, 3,252,044 shares (11.5%)
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (See Instructions)
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 11.5%
14	TYPE OF REPORTING PERSON PN

1	NAME OF REPORTING PERSONS The DIII Offshore Fund, L.P.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (See Instructions) (a) x (b) o
3	SEC USE ONLY
4	SOURCE OF FUNDS (See Instructions) WC
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e) o
6	CITIZENSHIP OR PLACE OF ORGANIZATION Bahamas

NUMBER OF SHARES BENEFICIALLY	7	SOLE VOTING POWER 0
OWNED BY EACH REPORTING	8	SHARED VOTING POWER 446,056 common shares (1.6%)
PERSON WITH	9	SOLE DISPOSITIVE POWER 0
	10	SHARED DISPOSITIVE POWER 446,056

11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON For the reporting person listed on this page, 446,056; for all reporting persons as a group, 3,252,044 shares (11.5%)
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (See Instructions)
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 11.5%
14	TYPE OF REPORTING PERSON PN

1	NAME OF REPORTING PERSONS Nierenberg Investment Management Company, Inc.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (See Instructions) (a) x (b) o
3	SEC USE ONLY
4	SOURCE OF FUNDS (See Instructions) AF
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e) o
6	CITIZENSHIP OR PLACE OF ORGANIZATION Washington

NUMBER OF SHARES BENEFICIALLY	7	SOLE VOTING POWER 0
OWNED BY EACH REPORTING	8	SHARED VOTING POWER 3,252,044 shares (11.5%)
PERSON WITH	9	SOLE DISPOSITIVE POWER 0
	10	SHARED DISPOSITIVE POWER 3,252,044 shares

11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON For the reporting person listed on this page, 3,252,044; for all reporting persons as a group, 3,252,044 shares (11.5%)
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (See Instructions)
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 11.5%
14	TYPE OF REPORTING PERSON CO

1	NAME OF REPORTING PERSONS Nierenberg Investment Management Offshore, Inc.
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (See Instructions) (a) x (b) o
3	SEC USE ONLY
4	SOURCE OF FUNDS (See Instructions) AF
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e) o
6	CITIZENSHIP OR PLACE OF ORGANIZATION Bahamas

NUMBER OF SHARES BENEFICIALLY	7	SOLE VOTING POWER 0
OWNED BY EACH REPORTING	8	SHARED VOTING POWER 446,056 common shares (1.6%)
PERSON WITH	9	SOLE DISPOSITIVE POWER 0
	10	SHARED DISPOSITIVE POWER 446,056 common shares

11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON For the reporting person listed on this page, 446,056; for all reporting persons as a group, 3,252,044 shares (11.5%)
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (See Instructions)
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 11.5%
14	TYPE OF REPORTING PERSON CO

1	NAME OF REPORTING PERSONS David Nierenberg
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (See Instructions) (a) x (b) o
3	SEC USE ONLY
4	SOURCE OF FUNDS (See Instructions) AF
5	CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e) o
6	CITIZENSHIP OR PLACE OF ORGANIZATION United States of America

NUMBER OF SHARES BENEFICIALLY	7	SOLE VOTING POWER 0
OWNED BY EACH REPORTING	8	SHARED VOTING POWER 3,252,044 common shares (11.5%)
PERSON WITH	9	SOLE DISPOSITIVE POWER 0
	10	SHARED DISPOSITIVE POWER 3,252,044

11	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON For the reporting person listed on this page, 3,252,044; for all reporting persons as a group, 3,252,044 shares (11.5%)
12	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (See Instructions)
13	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 11.5%
14	TYPE OF REPORTING PERSON IN

This Amendment No. 13 to Schedule 13D amends the below-indicated Item from the Schedule 13D, as amended, previously filed by or on behalf of the undersigned parties (the “Reporting Persons”) by supplementing such Item with the information below:

Item 5. Interest in Securities of the Issuer.

(a, b) The Reporting Persons, in the aggregate, beneficially own 3,252,044 Shares, constituting approximately 11.5% of the outstanding Shares.

(c) During the past 60 days the following sales of Shares were made by the Reporting Persons named below in open market transactions:

Fund	Transaction Date	Shares Sold		Price
DIII Offshore Fund, LP	01/04/2010		26,270		15.01
D3 Family Bulldog Fund, LP	01/05/2010		3,000		14.96
DIII Offshore Fund, LP	01/05/2010		9,501		14.96
DIII Offshore Fund, LP	01/13/2010		100,000		14.36
D3 Family Bulldog Fund, LP	01/14/2010		45,400		14.56
D3 Family Bulldog Fund, LP	01/15/2010		38,340		14.50
D3 Family Fund, LP	01/19/2010		7,500		14.58
D3 Family Bulldog Fund, LP	01/19/2010		70,031		14.58
D3 Family Fund, LP	01/20/2010		10,500		14.61
D3 Family Bulldog Fund, LP	01/20/2010		39,458		14.61

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, each of the undersigned certifies that the information set forth in the Statement is true, complete and correct.

	D3 Family Fund, L.P., D3 Bulldog Fund, L.P., and D3 Family Canadian Fund, L.P.

	By:	Nierenberg Investment Management Company, Inc.

	Its:	General Partner

January 21, 2010	By:	/s/ David Nierenberg
		David Nierenberg, President

	DIII Offshore Fund, L.P.

	By:	Nierenberg Investment Management
		Offshore, Inc.

	Its:	General Partner

January 21, 2010	By:	/s/ David Nierenberg
		David Nierenberg, President

	Nierenberg Investment Management Company, Inc.

January 21, 2010	By:	/s/ David Nierenberg
		David Nierenberg, President

	Nierenberg Investment Management Offshore, Inc.

January 21, 2010	By:	/s/ David Nierenberg
		David Nierenberg, President

January 21, 2010	/s/ David Nierenberg
		David Nierenberg