Have a look at these two sites

https://www.rcog.org.uk/en/news/rcog-release-timing-of-clamping-the-umbilical-cord-analysed-in-new-opinion-paper/    and 

 https://www.rcog.org.uk/globalassets/documents/guidelines/scientific-impact-papers/sip-14.pdf

Too many factor will affect the final Hct so I will say there is no perfect answer for your question. For most term infants I will say it makes limited efficacy for delayed clamping but for premature infants if makes big change. I have read 30 s to 3 min but you need to consider how the baby is delivered, your obstetricians' style of delivery, the operating room temperature. You do not want to wait too long and the baby ends up hypothermic. Milking the cord is commonly used in Japan and remains a new way in USA.

The cord stops pulsing between 1 and 3 minutes and so 3 minutes is the best time to cut it.  The only reason to cut it is to make delivering the placenta easier.

Judy's 3,4,5 protocol eliminates all PPH and includes cutting the cord  at exactly 3 minutes postpartum while the baby is in her mother’s arms, to allow for expedient delivery of the placenta by 5 minutes.

........The midwife keeps hands off the fundus and the cord. At 4 minutes: The midwife assists or directs the mother, as necessary, into a squatting position on the floor with both feet flat on the floor or on the floor of an empty bathtub. The mother hands the baby to someone or baby waits on the bed for one minute. The midwife encourages the woman to push out the placenta without a contraction.  It is helpful to say things like: pushing out the placenta prevents bleeding and that the placenta is right there, ready to deliver.  The woman is in a squatting position while she pushes out and births the placenta. The time of delivery is noted. Immediately after delivery of the placenta, the mother is dressed with a sanitary pad, assisted into the bed and immediately given the baby. The uterus is massaged once immediately to check for clots.

If bleeding is above average during the next 5 minutes, a shot of either 10 u Pitocin, 0.2 mg methergine intramuscularly, or both is given at 10 minutes postpartum.

I attached to you the NICE Guideline Intrapartum care (http://www.nice.org.uk/guidance/cg190/resources/intrapartum-care-for-healthy-women-and-babies-35109866447557)

Please, see the page number 68.

Take care. 

Please read this article:

J Matern Fetal Neonatal Med. 2010 Nov;23(11):1274-85. doi: 10.3109/14767050903551475.

Timing of umbilical cord clamping: new thoughts on an old discussion.

Arca G1, Botet F, Palacio M, Carbonell-Estrany X

According to the latest ACOG and NICE guidelines the optimal time to wait before cord clamping is 60 seconds, ACOG is not very clear if we can wait for 3-5 minutes.

It is good to formulate local protocols according to the data and labour protocols

In our institution we practice cord clamping after 60 minutes for all babies who are born vaginally and do not require immediate resuscitation. The benefits are more as compared to the slightly higher incidence of physiological jaundice.

This debate will never stop.