The collection of cord blood at birth in the UK is to be closely regulated for the first time.
Under the rules announced by the Human Tissue Authority (HTA), collection can only be carried out by a trained specialist at an approved premises.
Samples must also be traceable from collection to any use in treatments.
The trend of collecting cord blood in public or private banks for potential medical applications has grown more popular in recent years.
Thousands of couples have already paid large sums to store samples which - because they are a rich source of stem cells - could potentially be used in the treatment of disease.
Stem cells have the potential to turn into many different types of tissue, and in theory could be used to repair or replace damaged tissue.
In particular it is hoped that they could help replenish lost blood cells, providing an alternative to bone marrow transplant for leukaemia patients.
However, a Royal College of Obstetricians and Gynaecologists report has warned that there was "insufficient evidence" to recommend the practice.
The HTA is keen to ensure that the practice is safe for those people who want to press ahead anyway.
To that end it will only grant a licence if the applicant can demonstrate procedures are in place which will help prevent any medical attention being drawn away from mother or child during collection.
Adrian McNeil, HTA chief executive, said: "We are introducing this regulation to make sure that the best quality samples are taken in the safest way.
"We have heard that fathers, who of course have no experience in collecting cord blood, may be involved in this procedure.
"The worry is that if inexperienced people are involved, this will not be done at the right time and in the right way.
"The result is that the best samples may not be collected. It is also important for the midwife to be allowed to concentrate on the welfare of the mother and child."
The new rules have been drawn up following widespread consultation of people working in the field.
Professor Peter Braude, chairman of the Royal College of Obstetricians and Gynaecologists' expert committee on Umbilical Stem Cell Banking, welcomed the new regulations.
He said: "There is clear evidence from the NHS Cord Blood Bank that collection conditions can influence the likelihood of stem cells being obtained from the umbilical cord blood samples collected."
Belinda Phipps, of the National Childbirth Trust, welcomed the new safeguards.
She said: "It is vital that the birth and immediate post birth period is not disrupted and that the midwife is not distracted from her primary role.
"Care must be taken not to deprive the baby of blood from the cord or placenta.
"It is also important that, if parents choose to have a sample taken in the hope that science will advance enough to make effective use of it, that the sample remains identifiable and in a viable condition."