[5] The death of her younger sister Elisa, who had made known her desire to become a doctor for the poor, inspired del Mundo to choose a career in medicine.

Her exposure while in medical school to various health conditions afflicting children in the provinces, particularly in Marinduque, led her to choose pediatrics as her specialization.

[7] After del Mundo graduated from UPM, President Manuel Quezon offered to pay for her further training, in a medical field of her choice, at any school in the United States.

Further suggesting that she was a graduate student and not a medical student, in her autobiographical statement in Women Physicians of the World (1977), Dr. Del Mundo explains "I spent three years of my postgraduate studies at the Children's Hospital in Boston and at Harvard Medical School, one year at the University of Chicago, six months at Johns Hopkins Hospital, and short terms in various pediatric institutions, all to round out my training.

[16] After the Japanese authorities shut down the hospice in 1943, del Mundo was asked by Manila mayor León Guinto to head a children's hospital under the auspices of the city government.

[17] Towards that end, she sold her home and most of her personal effects,[16][17] and obtained a sizable loan from the GSIS (the Government Service Insurance System) in order to finance the construction of her own hospital.

[16] Dr. Fe del Mundo lived on the second floor of the Children's Medical Center in Quezon City and continued making early morning rounds until she was 99 years old.

This foundation saved thousands of children by establishing family planning clinics and treating preventable health issues such as poor nutrition and dehydration.

She died of cardiac arrest on August 6, 2011 three months before her 100th birthday, and was buried at the Libingan ng mga Bayani.

She made numerous breakthroughs in the field of pediatrics from immunization, treatment of jaundice, and providing accessible health care to countless families living in poverty.

[citation needed] Del Mundo was noted for her pioneering work on infectious diseases in Philippine communities.

Undeterred by the lack of well-equipped laboratories in post-war Philippines, she unhesitatingly sent specimens or blood samples for analysis abroad.

[15] She authored over a hundred articles, reviews, and reports in medical journals[15] on such diseases as dengue, polio and measles.

[30] On April 22, 2010, President Gloria Macapagal-Arroyo awarded del Mundo the Order of Lakandula with the rank of Bayani at the Malacañan Palace.