Increasingly, childbirth experts endorse waiting a minute or two before clamping umbilical cords.

But other complications make that timing less clear in premature births.

Now, two meta-analyses of 60 studies and almost 10,000 births published in the Lancet find waiting at least two minutes before clamping umbilical cords reduces the risk of death in premature babies by two-thirds.

The first looked at randomized controlled trials from high-income and middle-income countries and compared immediate clamping to delays ranging from 30 seconds to more than 180 seconds.

The second split clamping delays into three groups to gauge the most beneficial delay length: short deferral (15–45 seconds), medium deferral (45–120 seconds) and long deferral (120 seconds or more).

The authors hypothesize the delay lets blood flow from the placenta to the baby while it begins breathing and lowers iron deficiency.

However, the newborn must be kept warm to avoid hypothermia.

More research is needed, and the results might not apply in low-income settings, or to babies who need resuscitation.

Data from the Arizona health department shows premature babies are more likely to need intensive care than those with low birth weight.