When interviewing potential doulas (or midwives, OBs, or anyone involved in your birth) I think it's important to find out what their agenda is for your birth. As a doula when I meet with parents we discuss their birth history and what their hopes and goals are for their birth experience. When you are the expectant parent I think it's also beneficial to discuss what goals or hopes your doula (or care provider) may have for YOUR birth. Which sounds odd, but when interviewing birth professionals for my own deliveries I was surprised to discover how many clearly had an agenda for MY birth.
As a doula now I can tell you - there should be no agenda beyond supporting the parents' choices! When talking with other mothers about their births I discovered many of them also discovered people on their birth team had their own hopes for the birth, and were clearly conveying their opinion when things did not go as they expected! Whether the agenda came from the doula wanting the birth to go a certain way, a care provider that was trying to make things go the way they wanted, or a family member expressing disapproval about a choice - any of those things can interfere with the mother's birth environment. Sometimes there were comments clearly made, other times it was body language or non-verbal indicators that they were not happy with what was happening. This could be for things out of anyone's control (such as a necessary intervention) but other times it was simply because the mother made a choice the doula would not personally have made (such as asking for the epidural.)
When a woman is in labor she focuses internally, and the birth environment needs to support this and encourage the mother to let go of her external concerns so she can be focused on the work of birth. Everyone on the birth team ideally is respectful and reverent and encouraging, but sometimes they bring their own agenda into the room and this can be distracting and devastating for a woman in labor! Each mother has her own birth journey to make, and none of us can know in advance where that will take us! While we may make birth "plans" and discuss our goals and hopes for birth, ultimately we have to adapt to the surprises and try to gracefully handle the unanticipated. This is emotionally challenging enough for the parents, and no one should be intruding into this with their own agenda!
While doulas witness a huge range of births and we each have our own "ideals" for our personal birth experiences, our job is to come support YOUR birth. Wherever and however and with whomever YOU want to birth. I wish I could say that is universally true for doulas but I've learned that is not the case, and it is something to discuss as you interview doulas. Little comments made, such as, "OH, you have to birth like this..." indicated to me that some doulas have a clear idea of the kind of birth they think is best. When laboring I knew that I may have to change plans and I did NOT want to have to worry about anyone disapproving of my choices. If your birth "ideal" matches up with your doulas then great! But what if things change? I've interviewed mothers that felt a sense of disapproval when plans were altered, who felt emotionally neglected by doulas that clearly did not like the choices the laboring mother made. How sad to have a birth memory tainted by the lack of support!
So while I think every couple can benefit from having a doula present at their birth, I do think it's important that you realize not every doula is the same! It is good to interview several doulas so you can get a feel for the type of support you need and ensure you are on the same page. Explore your options! If you know you want to birth with x, y, and z then let the doula know that. But remember, birth will always have a surprise! Can your doula adapt to last second changes? What if you decide really you want to birth with a, b, and c? I think it's helpful to discuss these things even in your initial consultation because responses are telling - not just in the words they verbalize but in the body language they convey.
Birth is beautiful and challenging and consuming and hard. We may plan and hope and dream of how our birth will go, but in the end it's a story that we watch unfold. We make the best choices we can with the information we have at the moment. Your birth team will ideally help you gather that information but will then support you through whatever choice YOU feel is best. Only you can know what that decision is for you and your baby, and as a doula my job is to encourage you to learn to trust that intuition and inspiration. This is your birth journey, and it's an honor to help support you on your way.