Our Physicians

A. Radford MacFarlane, MD
Dr. MacFarlane graduated from Jefferson Medical College in 1982 and completed his pediatric residency at Dartmouth Hitchcock Medical Center, NH in 1985.  He became board certified in 1987. After a brief period of service in Ohio, Dr. MacFarlane joined St. Francis pediatric center in 1991. He founded Millcreek Pediatrics in 1999 and has been the lead pediatrician for over 22 years.
Dr. MacFarlane has a life long interest in personal fitness and activity. He enjoys hiking and, at least yearly, has visited the mountains of Colorado, North Carolina, Scotland and Switzerland.  A naturalist, Dr. MacFarlane is interested in birds, wildlife and alpine plants.

He enjoys his spending time with his adult children and his grandchildren.

Jenna Seiff, MD 
Dr. Seiff attended medical school in her home state of New Jersey at UMDNJ, New Jersey medical school and graduated in 2002. Dr. Seiff completed her pediatric residency at Mount Sinai Medical Center, NYC and became board certified in 2005. Dr. Seiff worked in NYC for one year and then, with her husband, moved to San Francisco where she joined a private practice in the East Bay. Upon her husband’s completion of a facial plastic surgery fellowship, they relocated to Delaware in 2008. Both she and her husband initially worked in the downstate area and she later joined Mill Creek Pediatrics in May 2012. 
Dr. Seiff, her husband and children are happy to call Wilmington their home. Together they enjoy outdoor activities, beach going and traveling. 
Dr. Seiff speaks fluent Spanish.

Joanna Shaffer, DO
Dr. Shaffer joined our group practice in August of 2018. Dr. Shaffer graduated from UMDNJ School of Medicine and completed her residency at Cooper University Hospital in 2016. She became a staff Pediatrician at Advocare Pediatrics in 2016 and later worked for Laurel Pediatrics and Teen Medical Center through 2018. Dr. Shaffer is Board Certified by the American Academy of Pediatrics since 2013 as well as the American College of Osteopathic Pediatricians since 2009. Dr. Shaffer enjoys spending time with her family which includes her 3 dogs. Joanna is expecting her first child in February 2022.