How far back does a drug test go using the baby's umbilical cord?

Depends: Depends on the drugs you are looking for many metabolize and get out of the system with in 24-48 hrs but some like marijuana/ thc can take up to a month.

It depends...: It depends on the drug taken, the dosage, and the length of time taken (a couple of doses or maintenance medication). More details are required to answer the question accurately.

About 1 month: Usually newborn urine or meconium is tested not the umbilical cord. Different drugs stay in the system for different amounts of time and detection will vary. Remember that it is crucial you tell your doctor about any drug use. This is about keeping your baby safe not avoiding getting caught. The doctors can best care for your baby is they know the truth. Be open and honest and keep your baby safe.

Many variables : Detection of drugs depends on the extent of maternal drug use, drug stability, deposition of the drug analytes in umbilical cord tissue, and the analytic method used. The actual time window for detecting exposure is unknown but is thought to represent at least the last trimester.