You can observe how long your contractions last (this is the duration) and how they are spaced that is how close they are (this is the interval or frequency).
In early labour, these may be 20 to 30 seconds at most with around a 20 minutes interval. As labour progresses, the duration may increase to over 60 seconds and the interval may decrease to about 3 minutes.
Remember: Rhythm is everything during labour. So, it would be prudent to wait and watch how this rhythm changes and evolves. Sometimes those early contractions can just stop and we could say in retrospect that this was pre-labor or practice contractions!
Using a stopwatch to monitor contractions
You may need a time-telling device to observe the rhythm of contractions. This may be a wall clock or a stopwatch. However, because birth is a primal function of the body where you need to focus on the work of labor rather than managing things on the outside; we suggest your partner to keep a track on time. Note: many women find timekeeping a distraction that slows the labor or gets in the way of her surrendering to the process.
When the birth companion/partner times the contraction, he can look for cues that tell the contraction has begun. This could be her breathing in a certain way or some movement. While keeping a watch on the clock, also notice how she automatically copes with the sensation of labor.
Labor will progress differently for different women. You will see this change in rhythm in many different ways, for example a woman who was gently breathing through a contraction may now get up and move her pelvis.