While I was pregnant with my first, I happened to have been reading a book,
Swimming with Scapulars. In it, the author recalls sitting with his wife during early labor and mentioning the intentions for which she was offering up this labor. Prior to that, the thought of a natural labor
for a purpose hadn't occurred to me. I figured, "if it's easy enough, do it naturally, otherwise, lean on modern medicine to get the job done with minimal difficulty."
So, I had that pregnancy to acclimate myself with the idea that labor
is inherently natural, we're called to suffer during labor (both emotionally and physically), and this suffering can be offered up for ourselves, our baby, or others. I also read
Your Labor of Love which although I don't recall it touching much on labor itself, is a series of meditations putting the sufferings of pregnancy into a Catholic perspective. So, in preparing for labor, my husband and I put together a list of small intentions to pray for during contractions.
I wasn't and am still by no means opposed to medical interventions--there are times when such is necessary--but, I do believe every woman should be equipped with the understanding that childbirth was created by God, it shouldn't be a source of fear (but rather an opportunity to trust God), and they are capable of it. As with all of our duties in life, accepting childbirth as God's will and following His will to the best of your ability is meritorious.
However, I also know now that childbirth doesn't always "just happen". I thought with my first that as long as I was able to effectively deal with the physical pain and let my body do its thing, the rest was mostly outside my control. But, I know now that there is an art to childbirth -- positions, techniques, remedies -- that is largely lost in the Western world, especially among doctors. Failure to either equip yourself with this knowledge or seek birth help from someone who knows it (midwife, doula, etc) often leads to "necessary" medical interventions which would have otherwise been unnecessary.
So, yes, you should trust that God has given all you need to successfully labor and birth a child. But, you should also know that part of what He has given you is the accuмulated experience of centuries of women before you and failure to access that information might hinder your ability to bring a child into the world naturally.