[7] Maddox's career has focused on healthcare equity for minorities, women, and children, in both the United States and abroad.

[13] From 1995 to 2014, Maddox was the deputy director of the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD).

[14] As deputy director, she led many federal and international efforts to improve maternal and child health, including the NICHD Safe to Sleep (formerly the Back to Sleep campaign), the NIH Down Syndrome Consortium,[15] and the Global Network for Women's and Children's Health Research.

[18] Maddox was inducted into the Historically Black Colleges and Universities Hall of Fame in recognition for her contributions in the field of medicine.

She has also received several honorary degrees, served on public service and academic boards, and delivered national and international keynote scientific lectures.