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Our Team

Dr. Bryan Oshiro

Maternal Fetal Medicine Physician

Dr. Oshiro obtained his M.D. degree from Loma Linda University, where he also completed his residency in obstetrics and gynecology. He  subsequently completed a fellowship at the University of Texas in Houston. Dr. Oshiro is board certified in obstetrics and gynecology and  Maternal-Fetal Medicine. He has participated in numerous multi-center trials and has published numerous articles and book chapters in the areas of quality improvement, perinatal infectious diseases and high-risk pregnancy conditions. 

Dr. Ronald Johnson

Chair Department of Gynecology and Obstetrics

Ronald Johnson M.D. is a board-certified Ob/Gyn specialist who has worked with Riverside University Health System since early 2017. He is a graduate of Loma Linda University School of Medicine and trained in his residency at Loma Linda University Medical Center. He has been involved in resident education for the past 31 years and is currently an Assistant Professor at Loma Linda University School of Medicine. His specialty is gynecologic surgery including minimally invasive approach and gynecologic ultrasound. He is the current Department Chair at RUHS-MC. He is working with Dr. Bryan Oshiro with a $6.38 million grant from First 5 Riverside through the HeRCARe Foundation to improve high risk prenatal care in Riverside County.

Dr. Janet Horenstein

Maternal Fetal Medicine Physician

Dr. Janet Horenstein is board certified in Obstetrics / Gynecology and Maternal Fetal Medicine. She has been with RUHS since 2019. She completed her medical training at the Universidad Autonoma de Guadalajara. After she completed residency in Obstetrics and Gynecology at White Memorial Medical Center in Los Angeles, she completed fellowship in Maternal Fetal Medicine at LAC-USC. She remained on staff for a number of years teaching medical students, residents and fellows. Her interest is fetal evaluation and treatment. She had published many articles and has lectured nationally and internationally. She has been involved in outreach teaching ultrasound to midwives in Ghana. When not working, she spends time with her animals and travels.


Dr. Sarah Smithson

Maternal Fetal Medicine Physician

Sarah Smithson, DO, MS is the newest physician member of the MFM Department at RUHS. She obtained her medical degree at the University of New England College of Osteopathic Medicine in Biddeford, Maine followed by residency in Obstetrics and Gynecology at Monmouth Medical Center in Long Branch, New Jersey. During residency, she also completed a master’s degree in Medical Education and Leadership from the University of New England College of Osteopathic Medicine. After residency, she finally moved to the west coast to complete fellowship in Maternal Fetal Medicine at Cedars Sinai Medical Center in Los Angeles. Her research interests include hypertensive disorders of pregnancy and postpartum depression. She has conducted several research studies which have resulted in multiple recent publications. Clinical interests include prenatal ultrasound as well as resident education.

Sabreen White

Program Director, MBA

Sabreen has a master’s degree in business and healthcare management along with 16 years of experience in public health and government programs. She is a seasoned project manager with a demonstrated history of budget management and preparation, grant writing, community and government collaboration, IRB/Research Coordination, program evaluation and development.

Gloria Fajardo

Patient Services Coordinator, MPH

Gloria has 23 years of experience as a perinatal health specialist and care management. She is knowledgeable in community programs, education, nutrition, and risk of pregnant moms. In her free time, Gloria has provided education on Spanish radio on topics such as car seat safety, child safety, and community resources for low income moms.


Teresa Soto-Ordonez

Patient Services Coordinator

Teresa has 11 years of experience as an OB/GYN Medical Assistant and patient services coordinator. She handles the daily management of referrals which includes, input of data into manage care system, verify member eligibility, provider participation, tracking of pending referrals and follow up with office staff. She has vast experience and knowledge in the area of high-risk pregnancies, as well as patient education. During her spare time, she volunteers at community health fairs.

Amanda Koch

Diagnostic Medical Sonographer

Amanda has a bachelor’s degree in Kinesiology from Cal Poly Pomona and an associate’s in Diagnostic Medical Sonography from Cypress College. She holds credentials through the American Registry for Diagnostic Medical Sonography and has specialties in both OB/GYN and Abdominal sonography. Amanda is also certified through the Perinatal Quality Foundation to perform nuchal translucency ultrasounds.

Marissa Elizarraraz

Diagnostic Medical Sonographer

Marissa has an associate’s in Diagnostic Medical Sonography from Cypress College. She holds credentials through the American Registry for Diagnostic Medical Sonography and has specialties in both OB/GYN and Abdominal sonography. Marissa is currently pursuing a certification for nuchal translucency ultrasounds.

Gabriela Fajardo

Medical Assistant

Gabriela known as “Gabby’ has 5 years of experience as a Medical Assistant, she attended North West College in Riverside. Prior to working with Maternal Fetal Medicine she worked in Pediatrics where she completed her externship and continued working there for 3 years.

Natalie Whaples

Sweet Success Program Coordinator, RD

Natalie Padgett, RD, CDE has over 20 years’ experience as a Registered Dietitian, Certified Diabetes Educator. Natalie graduated From Charles R. Drew University with a Bachelor of Science in Cultural Diversity and Community Nutrition. Natalie enjoys being in nature and writing

Natacha Talbot

Sweet Success Associate, RN

Natacha has 21 years of experience in the medical field, 18 of those years as a LVN, and the last 3 years as a RN. She went to San Bernardino Valley College for her Associates degree and will obtain her BSN from CTU.

Gladys Holt


Gladys has 23 years of Medical experience. She has worked as an Emergency Room Technician, Admissions, Pre-Operative Nursing, Diagnostics as well as Medical Assisting. Gladys takes pride in her current position as a Comprehensive Perinatal Service Program Coordinator for Maternal Fetal Medicine. She enjoys providing great services for her patients. In her free time, she likes to give back to her community and spend time with her 3 beautiful grandchildren.


Jessica Veloz

Perinatal Care Manager, RN

Jessica Veloz has been an OB nurse for over 13 years. She has experience in Postpartum, Nursery, and Sweet Success. She received her Associates in Nursing from RCC and her Bachelors of Science Nursing from Grand Canyon University. She has taken the Lactation Education Counselor course at UC San Diego. She is Neonatal Resuscitation Program (NRP) and Sugar, Temperature, Airway, Blood pressure, Lab work, and Emotional support (S.T.A.B.L.E.) certified. Jessica plans on pursing her Masters in Nursing Education in the future.


Nereida Moreno

Patient Services Coordinator

Nereida has 13 years of experience as a Medical Assistant working in Primary Care, also worked in OB/GYN and specialty clinics Gynecologic Oncology.


Carla Meza


Carla has 28 years of experience as a medical assistant. She graduated from Edutek College in San Diego. She has worked in many specialties including Internal Medicine, Pediatrics and Cardiology but her favorite has always been OB-GYN.

"Itzel Hernandez-Soto"

Itzel Hernandez-Soto



Manika Vann

Diagnostic Medical Sonographer


Stephanie Calzadias