About Us

Get to Know the Office

sign At Pediatrics, P.C. we realize the importance of parent and patient participation in healthcare. That is why you will always be treated with dignity and respect by all members of our staff. We may be the medical experts, but you are the expert in what is normal for your child! From the moment you choose us as your child’s pediatrician we will begin to build a trusting relationship that will form the basis of our future interactions with both parent and patient.

We continue to strive to make our office environment welcoming for children of all ages. Because of the important role reading plays in academic achievement, we have chosen to decorate our exam rooms based on authors or genres in literature.

Subjects in the rooms range from the alphabet and picture books to classic early reading and teenage novels.

Our reception area has separate space for well and sick children which is divided by the ever popular fish tank.
Next to the cookie or sticker the kids can choose after the visit, "seeing the fishies" gets the most requests,
especially from those under five years of age.

Our Providers


Mark A. Blazek, M.D.

• St. Louis University - B.S. -1972
• Ohio State University - M.D. - 1976
Butterworth Hospital, Grand Rapids, Michigan
Joined Pediatrics, P.C. - 1982
American Board of Pediatrics - Certified 1984
Bio: Dr. Blazek believes that his interest in pediatrics can be traced to his being the oldest of nine siblings, growing up in the city of Cleveland, Ohio. After attending medical school at The Ohio State University, he began his career assisting an older family practitioner in Grant, Michigan. This gentleman's reluctance to care for his younger patients acted as a further nudge toward caring for children. Dr. Blazek has been with our practice since 1982, raising his our four children in the area. When not caring directly for patients, he has been active in scouting as well as community theater, contra dancing, kayaking and supporting his wife's endeavors as a teacher in the Montessori Program.


Kathleen L. Lemmen, M.D.

• Hope College - B.S. - 1973
• University of Michigan - M.D. - 1977
• Children's Hospital of Michigan
Children's Hospital of Michigan
Joined Pediatrics, P.C. - 1983
American Board of Pediatrics - Certified 1981
Bio: Growing up in a prominent West Michigan medical family, Dr. Lemmen pretty much knew that she would want to do something in the medical field. Following graduation from Hope College and the University of Michigan Medical School, she initially had to decide between her interest in neurology and a career in pediatrics. In the end, the choice seemed easy, as who wouldn't want to have the joy of seeing children grow and develop into competent young adults.To that end, Dr, Lemmen gets her greatest satisfaction from guiding parents through their child's infancy and young childhood years. When not in the office, Dr. Lemmen enjoys music, cooking, traveling and needle crafts.


David L. Ohmart, M.D.

• Miami University (Ohio) - B.S. - 1964
• Temple University School of Medicine - M.D. - 1968
• Germantown Hospital, Philadelphia, Pennsylvania
• Madigan Army Medical Center, Tacoma, Washington
Private Practice:
Allegan, Michigan
Joined Pediatrics, P.C. - July 1991
American Board of Pediatrics - Certified 1975
Bio: After attending Temple University school of Medicine on a military scholarship, Dr. Ohmart wasn't sure how he wanted to practice medicine until he did volunteer work on the pediatric unit of a provincial hospital while serving as a medical officer in a combat engineer unit in Viet Nam. After completing his pediatric training at Madigan Army Medical Center, Dr. Ohmart served at other military medical facilities at home and overseas as well as participating in the invasion of Panama in 1989 and Desert Storm in 1991. He has also taken part in medical missions to Ghana and Cameroon. When not working in our Portage office, Dr. Ohmart serves as Director of Medical Services at the Allegan County Juvenile Detention and Treatment Facilities and as an associate clinical professor of pediatrics at the Western Michigan University Homer Stryker School of Medicine.


Ann P. Sheehan, DNP, CPNP

• University of Iowa, Iowa City, IA - Doctor of Nursing Practice - 2010
• University of Iowa, Iowa, IA - Master of Arts, Pediatric Nurse Practitioner - 1992
• Nazareth College, Kalamazoo, MI - Bachelor of Science in Nursing - 1987
• Bronson Hospital School of Nursing, Kalamazoo, MI - Diploma in Nursing - 1986
Previous Employment:
Grand Valley State University College of Nursing, Grand Rapids, MI - Pediatric Nurse Practitioner,
Assistant Dean, Director of Family Health Center,
Doctoral Pediatric Nurse Practitioner Track Coordinator - 2012 - 2014
Shoreline Pediatrics, Holland, MI - Pediatric Nurse Practitioner - 1994-2012
Grand Valley State University College of Nursing, Grand Rapids, MI - Visiting Professor - 2010-2012
Detroit Health Department - Pediatric Nurse Practitioner - 1992-1994
Joined Pediatrics, P.C. - 2015
Bio: Dr. Sheehan traces her interest in pediatrics to when she was four years old and her mother told her she was going to grow up to be a "baby nurse", and indeed, she did. Finding the field of nursing not sufficiently challenging, she decided to pursue more advanced degrees, acquiring a PhD in Nursing Practice, as well as a Pediatric Nurse Practitioner degree from the University of Iowa. Dr. Sheehan has been a welcome addition to our practice since 2015, and although she enjoys caring for all children, her particular interest is helping adolescent girls navigate that challenging period in their lives. when not in the office, Dr. Sheehan keeps busy with her husband, Mike and daughter, Sophia, in addition to involving herself in legislative issues involving the care of children on the local, state and national levels.


Sandra D. Wiederhold, M.D.

• Hope College, Holland, MI - A.B. Biology - 1978
• State University of NY, Upstate Medical Center, Syracuse, NY - M.D. - 1983
• University of Wisconsin Hospitals and Clinics, Department of Pediatrics,
Madison, WI - 1983-1986
• University of Wisconsin Hospitals and Clinics, Department of Pediatrics,
Madison, WI - Chief Resident - 1986-1987
Previous Employment:
ProMed Physicians, Kalamazoo, MI - Pediatrician - 1987-2013
Joined Pediatrics, P.C. - 2015
Bio: Dr. Wiederhold roots in West Michigan go back to her days at Hope College, from where she graduated after growing up in Westchester County, New York. Returning to New York for medical school, she completed her training at the State University of New York at Syracuse. Although always interested in scientific research, she dates her interest in medicine from when she did volunteer work in the emergency room of Holland Hospital. She believes her desire to become a pediatrician stems from her interest in preventing disease rather than treating its consequences. She settled permanently in West Michigan after completing her pediatric training at the University of Wisconsin at Madison. In her off-time, Dr. Wiederhold serves as a scholar advisor at the Homer Stryker School of Medicine in Kalamazoo and enjoys supporting her children's activities in high school and college.

Our Clinical Staff



Our Administrative Staff

laura carol

Our Front Desk

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