Labor and birth are incredibly vulnerable times. My general advice: only allow people in your space who you feel safe letting anything fly out either end of your body (vomit, swearing, angry words, a harsh tone, poop).
So, if birth is so vulnerable, why would you invite a total stranger to participate? How can you trust them to fully support you in the ways you need support?
There are three steps I recommend:
Research
Interview any potential doulas before hiring them
Attend prenatal meetings with your doula
Number one: Research
This one may seem obvious, but it is super important. Research your potential doula's certifying organization. What does it say is within their standards of practice and code of ethics? Does their organization have any (specific or general) philosophies or attitudes about birth? Follow a few posts on the potential doula's blog and/or social media pages. Does what they're posting resonate with you? Do they have any philosophies or attitudes about birth? Do you share those philosophies? Does this person have conditions in which they will or will not support a certain type of birth?
Number Two: The Interview
This is the time to really dig in. Remember all those questions about philosophies a doula might have about how birth should be, or conditions in which they won't support certain types of births? Now is the time to find out how they plan to respond if your original plan changes. For example, if a potential doula only supports birth center births, what will they do if you end up needing to transfer to a hospital during labor? Do they instill a sense of confidence and trust in your medical provider? This is the time to ask really deep questions about the doula and their certifying organization. Ask them how they provide information to their clients (do they give information to you as soon as an intervention is proposed, or do they wait to see how much information you're ready for?). Does that correspond with how you prefer to receive information?
Number Three: Prenatal Meetings
Most doulas will host two or three prenatal meetings with their clients, although that number can usually be tailored as needed. These meetings are the greatest opportunity for you and your doula to forge a trusting relationship. They usually last anywhere from one to two hours, and they are yet another opportunity to dig in to your birth preferences and make sure your doula is on board with those preferences. Find out how your doula will respond in certain situations (i.e. the doctor proposes an intervention you had previously expressed concerns about). Ask them for specific examples of phrases they might use if they see you are beginning to truly suffer during labor. Ask them how they will respond if you poop, vomit or swear if that is something you're worried about.
A doula's presence at your birth can provide solid, reassuring, constant support, but only if you fully trust them. So make sure your doula fits.