Final answer:
Nifedipine is the calcium channel blocker most often used to delay labor due to its ability to relax the muscles of the uterus.
Step-by-step explanation:
The calcium channel blocker (CCB) most often used to delay labor is nifedipine. Nifedipine, which is also known as Adalat or Procardia, is a medication that works by relaxing the muscles of the uterus, which can help to postpone labor.
Nifedipine is a common choice for delaying labor because it is considered safe for both the mother and the baby. It is often used in cases where the mother is at risk of delivering prematurely.
Other calcium channel blockers, such as amlodipine, verapamil, and diltiazem, are not typically used to delay labor.