Nikolaos Zacharias, MD, FACOG

Dr. Nikolaos Marios Zacharias, MD, FACOG, is a distinguished maternal-fetal medicine specialist and educator with over two decades of experience in high-risk obstetrics and prenatal care. Currently, he serves as Director of Medical Education at Obstetrix MFM Specialists of Houston and holds clinical professorships at both the University of Houston Tilman J. Fertitta Family College of Medicine and Texas A&M University Veshisht School of Medicine. He also contributes as a subspecialty faculty educator at Houston Methodist Hospital and as Chairman of the Obstetrics & Gynecology Department at Saint Joseph Medical Center. Dr. Zacharias combines clinical excellence with academic leadership, shaping the next generation of obstetricians and maternal-fetal medicine specialists.

Born in Greece in 1971, Dr. Zacharias completed his medical degree at the National and Kapodistrian University of Athens, graduating at the top of his class. After serving in the Greek National Health Service, he moved to the United States to pursue advanced training in obstetrics and gynecology, completing his residency at Baylor College of Medicine and a fellowship in maternal-fetal medicine at the University of Texas Medical Branch in Galveston. He is board-certified in both general obstetrics and gynecology and maternal-fetal medicine and became a Fellow of the American College of Obstetricians and Gynecologists in 2010.

Throughout his career, Dr. Zacharias has been actively involved in research and clinical innovation. He has authored numerous peer-reviewed publications and book chapters on topics ranging from prenatal ultrasound and fetal growth restriction to placenta accreta and perinatal outcomes. He has mentored dozens of physicians and researchers, contributing to high-impact studies presented at national and international conferences. His work has helped advance evidence-based practices in maternal-fetal medicine and improve outcomes for mothers and babies in diverse populations.

In addition to his clinical and academic achievements, Dr. Zacharias is recognized for his dedication to teaching and professional development. He has taught courses and lectures across multiple institutions, including Baylor College of Medicine, UTHEALTH McGovern Medical School, and Saint Joseph Medical Center, covering topics such as prenatal ultrasound, high-risk pregnancy management, and operative obstetrics. His teaching has earned him numerous awards, including recognition from medical students and faculty for excellence in education.

Dr. Zacharias is fluent in English, Greek, French, and Spanish, reflecting his international background and commitment to serving diverse communities. He resides in Bellaire, Texas, with his wife, Dr. Ioanna Athanassaki, a pediatric endocrinologist, and their two daughters. Outside of medicine, he continues to engage with professional societies, including the Society for Maternal-Fetal Medicine and the American Institute of Ultrasound in Medicine, contributing to the advancement of obstetric care both nationally and internationally.

• M.D., National and Kapodistrian University of Athens School of Medicine, Greece, 1995
• Masters in Medical Science (MMSc), University of Texas Medical Branch, Galveston, TX, 2005
• Advanced Cardiac Life Support (ACLS) Certification, American Heart Association
• Board Certified, American Board of Obstetrics & Gynecology (General Ob/Gyn, 2008; Maternal-Fetal Medicine, 2011)
• Fellow, American College of Obstetricians & Gynecologists (ACOG), 2010

• Biomedical Investigators
• GCP for Clinical Trials with Investigational Drugs and Medical Devices (U.S. FDA Focus)
• Pediatrix Clinical Research Policies (To be completed by Pediatrix employees only)
• Board Certified Subspecialist in Maternal-Fetal Medicine
• Board certified maternal-fetal medicine expert
• Board Certified Obstetrician Gynecologist

• Graduated first in class, Papagos Lyceum, Athens, Greece
• Ranked 13th of 10,000+ applicants in Pan-Hellenic University Examinations; awarded National Scholarship Foundation scholarship
• Top 3% of class at National and Kapodistrian University of Athens School of Medicine
• Top 5% on all USMLE Steps; top 5% of Ob/Gyn residents on CREOG exams (1999–2002)
• Baylor College of Medicine Faculty Teaching Award, 2010–2011
• UTHealth McGovern Medical School Dean’s Teaching Excellence Award, 2015–2018
• Named in America’s Top Obstetricians & Gynecologists, 2012–present
• Elected Chairman, OB/GYN Department, Saint Joseph Medical Center, 2025
• Listed in Americas Best in Medicine, 2025–2026

• American College of Obstetricians and Gynecologists
• Texas Medical Association
• Society for Maternal-Fetal Medicine
• American Institute of Ultrasound in Medicine
• International Society of Ultrasound in Obstetrics and Gynecology

• Provided medical care as a General Practitioner at Vassiliki Health Center, Lefkas Hospital, Greece, including an honorary extension for outstanding service (1996–1997)
• Active in community health education through lectures, prenatal care workshops, and patient counseling
• Participates in online patient education, answering questions on HealthTap since 2012, supporting thousands of patients with accessible, evidence-based advice
• Engaged in mentorship of medical students, residents, and fellows, fostering the next generation of maternal-fetal medicine specialists
• Contributed to multidisciplinary hospital committees promoting patient safety, quality care, and perinatal health initiatives in Houston-area hospitals

Peer-reviewed journal articles on prenatal ultrasound, maternal-fetal medicine, placenta accreta, fetal growth, and high-risk pregnancy management. Notable publications include:

• High false-positive rate of HIV screening in a predominantly Hispanic population – J Perinatol, 2004
• Prospective trial on obstructive sleep apnea in pregnancy and fetal heart monitoring – Am J Obstet Gynecol, 2010
• Maternal morbidity in patients with morbidly adherent placenta treated with/without multidisciplinary approach – Am J Obstet Gynecol, 2015
• Cyclone sign: prenatal ultrasound diagnosis of a true umbilical cord knot – Am J Obstet Gynecol, 2023

Book chapters in Copel’s Obstetric Imaging, Shnider & Levinson’s Anesthesia for Obstetrics, and Case Files in Obstetrics & Gynecology

Conference abstracts and posters presented at Society for Maternal-Fetal Medicine (SMFM) and ACOG Annual Meetings (2009–2014)

Author of the Perinatal Mortality chapter on UpToDate.

For a complete list of publications, visit his Doximity profile: Dr. Nikolaos Zacharias, MD – Houston, TX | Obstetrics & Gynecology