Leaking, Cramps, & Crying: Thanks, Oxytocin
How my uterus stumped my post-partum nurse
“I’m getting cramps whenever my baby cries. Is that common?” I asked one of my post-partum nurses a day or two after giving birth.
“No one has ever asked me that!” She exclaimed, which was not something you really hope to hear while recovering from childbirth. She said she would ask other doctors during medical rounds later that day and get back to me. I wasn’t too concerned, because the scientist in me already had a guess about the connection between my baby crying and my uterus pain: Oxytocin.
One of the main jobs of the hormone oxytocin is to stimulate uterine contractions during labor. This is why many laboring people are provided exogeneous oxytocin (aka Pitocin) to help induce labor and/or help the uterus contract after childbirth. Oxytocin is also responsible for milk release. During breastfeeding, infant suckling sends a signal to make more oxytocin to your brain, which then releases the hormone to your breast tissue to make more milk (the “letdown” response). Oxytocin has been referred to as the “love” hormone1 because, in addition to these functions, it is associated with mother-infant bonding and is also released during sex. Additionally, it has been suggested as a possible treatment for mental health concerns associated with social difficulties, including autism and schizophrenia2.
So what does this have to do with my cramps in the hospital? Well, wouldn’t you know it, baby cries are associated with a release of oxytocin in mammals. This makes sense: a baby’s cry is the only way they can signal to mom that they’re hungry, and if oxytocin is needed to release milk, then baby’s crying should signal to mom’s brain to release oxytocin to start making food for them. Any mom that has leaked milk when their baby cried knows this relationship all too well3. As a side effect of this oxytocin production/release, one’s uterus might also contract, especially immediately following labor and delivery when the uterus needs to shrink back to its original size4. Indeed, some women have increased uterine pain during breastfeeding, most likely because of oxytocin release.
I couldn’t find a study that explicitly examined the relationship between uterine cramps and infant crying. However, because we understand the general mechanisms of action for oxytocin, I think it’s a safe bet to say that it was responsible for the discomfort I experienced. My nurse did get back to me after rounds and confirmed my suspicions that yes, according to the other practitioners, this is a thing that can happen. In fact, for a few weeks after birth, my baby’s cry caused me to both leak milk AND experience uncomfortable cramps. Thanks, oxytocin!
Side Note: Great Minds Think Alike!
Emily Oster, Ph.D. (professor, economist, author, and personal fave) recently discussed the relationship between sleep training and mental health in her newsletter, including a shout out to the article on cortisol and infant stress I also wrote about a few weeks ago. I highly recommend her parenting newsletter and all of her books - they have been and continue to be incredibly helpful and reassuring during my journey as a first time parent. Also, perhaps obviously, she was a big inspiration for me to start this project because she’s so good at disseminating the science behind many pregnancy and parenting concerns.
Quick Housekeeping Note
Moving forward, I’m going to try to make this a weekly newsletter, to be delivered to you by Sunday/Monday. We’ll see if that happens. Thanks for your patience, and please share with others!
With very mixed results, just FYI.
Anecdotally, some women also leak milk during orgasm. Angela Garbes shares a funny instance of this (along with other cool pregnancy-related science) in her book, Like A Mother.
Uterus shrinkage is known as “involution” and it generally takes six weeks for your uterus to go from the size of a watermelon back to the size of your fist, which parenting websites love to say is 500 times its original size. I don’t know how many times I Google’d this information when I was pregnant, because I just didn’t believe it.