Get yer freak on. Doula's orders.

The first thing people do when they find out you're a doula (other than asking what the hell that is) is tell you their birth stories.  Which I love, but they very often end with, "So then I had a c-section, and did I really need one?"  Um, I dunno.  I wasn't there, and if I was, I wouldn't exactly have the authority to say.

The second thing people do is ask about some old wives' tales surrounding birth.  The favorite of mine is always, "Is it true that having sex can bring on labor?"  And let me tell you, the answer is yes.

But why?

Oxytocin, the so-called "love hormone," is at least partly responsible for three distinct physiological events in a woman's reproductive cycle: orgasm, labor, and breastfeeding.  As a sex-positive doula and lactation educator, you might say that oxytocin is my homegirl.

The female orgasm was once thought of as relatively inconsequential to the reproductive process.  In fact, some fertility specialists have even suggested that orgasm "dilutes" a woman's chance of becoming pregnant.  (I call bullshit.  Also sexism.  But that's another post.)  Au contraire, says a bulk of new-ish research that essentially reaffirms what lay-health workers have been saying for years: orgasm increases your chances of conception.  See, when a woman orgasms, her body releases even more vaginal secretion than she does when simply "aroused," helping to lubricate the sperm's path to the egg.  Additionally, the oxytocin released via orgasm contracts the uterus, lowering the cervix (the "neck" of the uterus) and making the uterus more accepting of a fertilized egg (ever wonder what that tight feeling in your lower abdomen was?).

Sidebar: Oxytocin is also associated
with trust, which helps explain why
women who have good relationships
with their care providers tend to have
smoother labors.

So oxytocin contracts the uterus.  Hence labor.  But the wonder-hormone's job isn't over when the placenta is delivered.  Oxytocin is also responsible for the milk "letting down" during breastfeeding.  See, when a woman first lays eyes on her baby, she's essentially OD'ing on oxytocin, as is baby.  That's the love hormone doing its job.  Baby will hopefully find her/his way to a nipple and begin suckling.  When the nipples are stimulated, oxytocin is released from the posterior pituitary gland, contracting the tiny myoepithelial cells inside the milk ducts, forcing milk out of the breast and into baby's mouth.  That oxytocin release is still doing it's job "down there," helping mama's uterus to clamp down post-delivery, thus reducing risk of excessive postpartum bleeding. 

I mention the connection to breastfeeding because oxytocin is also released with nipple stimulation.  Women who are into nipple stimulation during sex may enjoy it for a number of reasons, but physiologically it's because that burst of oxytocin contracts the uterus (which essentially puts interior pressure on the clitoris and, well, you get it).  In other words, if you're into nip-stim, include that in your labor-inducing sex practice.  Otherwise you can just turn on your breast pump when you're finished doin' the deed, and you will probably get a lot of the same benefits.

If a woman is having sex with a man, his stuff may play a labor-inducing role as well.  Semen contains prostaglandins, autocrine hormones that help to soften ("ripen") the cervix.  A softer cervix makes the fertilization/implantation process more likely, but these hormones work the same when a woman is already pregnant.  The low dose of prostaglandins in semen alone aren't likely to induce labor in a woman who's not yet term (which is why care providers don't warn against sex during pregnancy unless a woman is at risk for preterm labor), but the mild softening in a term mama might just be enough to tip her into labor mode.  As an added bonus, if he's, let's say, "gifted," his penis hitting against the cervix may indeed induce some mild (but not earth-shattering) uterine contractions.

Captain Obvious moment: I generally don't recommend the prostaglandin method if a mama is in a relationship where she's at risk for a sexually transmitted infection.  The last thing she needs is to be infected with an STI right before a baby comes squeezing through her vagina!  If infection is an issue, sex with a condom still contains the benefits of oxytocin and cervical pressure.  Masturbation is a safe and effective alternative for women who don't have a partner (or just simply don't want to engage in partner sex).  Again, oxytocin is stronger than prostaglandins... go team vag!

So yes, good sex can in fact induce labor.  In other words, if you're trying to get labor started, just get yer freak on.  Doula's orders.