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In this episode I answer several questions about natural labor induction:

Can eating pineapple help induce labor contractions? What about having sex? Is that really effective for starting labor!
Natural induction techniques continue to be among our most searched and requested topics at Evidence Based Birth. I’m excited to share with you the evidence on these common labor induction techniques!


Monji, F., Adaikan, P. G., Lau, L. C., et al. (2016). Investigation of uterotonic properties of Ananas comosus extracts. J Ethnopharmacol, 193, 21-29. Click here.

Monji, F., Adaikan, P. G., Lau, L. C., et al. (2018). Role of the serotonergic pathway in uterotonic activity of Ananas comosus (L.) Merr. – An in vitro and in vivo study. Phytomedicine. 48, 32‐42. Click here.
Nwankudo, N. O., Ijioma, S. N., and Nwosu, C. O. (2014). In Vitro Investigation Of Fresh Juices Of Ripe Ananas Comosus(Pineapple), Carica Papaya (Pawpaw) And Citrullus Vulgaris (Watermelon) For Uterine Contractile Properties In Non-Pregnant Rats. International Journal of Zoology and Research, 4(3), 79-84. Click here.
Nwankudu, N. O., Ndibe, N. U., and Ijioma, S. N. (2015). Oxytocic Effect of Ananas comosus Fruit Juice on Isolated Pregnant Rats Uteri. Nigerian Veterinary Journal, 36(4), 1318-1326. Click here.

Bendvold, E., Gottlieb, C., Svanborg, K., et al. (1987). Concentration of prostaglandins in seminal fluid of fertile men. Int J Androl, 10(2), 463-469. Click here.
Bovbjerg, M. L., Evenson, K. R., Bradley, C., & Thorp, J. M. (2014). What started your labor? Responses from mothers in the third pregnancy, infection, and nutrition study. J Perinat Educ, 23(3), 155-164. Click Click here.
Carbone, L., De Vivo, V., Saccone, G., et al. (2019). Sexual Intercourse for Induction of Spontaneous Onset of Labor: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. J Sex Med. 16(11), 1787-1795. Click here.
Castro, C., Afonso, M., Carvalho, R., et al. (2014). Effect of vaginal intercourse on spontaneous labor at term: A randomized controlled trial. Arch Gynecol Obstet; 290, 1121-1125. Click here.
Chayen, B., Tejani, N., Verma, U. L., et al. (1986). Fetal heart rate changes and uterine activity during coitus. Acta Obstet Gynecol Scand, 65(8), 853-855. Click here.
Declercq, E. R., Sakala, C., Corry, M. P., & Applebaum, S. (2007). Listening to Mothers II: Report of the Second National U.S. Survey of Women’s Childbearing Experiences: Conducted January-February 2006 for Childbirth Connection by Harris Interactive(R) in partnership with Lamaze International. J Perinat Educ, 16(4), 15-17. Click here.
Foumane, P., Mboudou, E. T., Sama, J. D., et al. (2014). Sexual activity during pregnancy and prognosis of labor in Cameroonian women: a cohort study. J Matern Fetal Neonatal Med, 27(13), 1305-1308. Click here.
Kafaei Atrian, M., Sadat, Z., Rasolzadeh Bidgoly, M., et al. (2014). The association of sexual intercourse during pregnancy with labor onset. Iran Red Crescent Med J. 17(1), e16465. Click here. Free full text!
Kavanagh, J., Kelly, A. J., & Thomas, J. (2001). Sexual intercourse for cervical ripening and induction of labour. Cochrane Database Syst Rev(2), CD003093. Click here.
Kavanagh, J., Kelly, A. J. and Thomas, J. (2005). Breast stimulation for cervical ripening and induction of labour. Cochrane Database Syst Rev 2005;3:CD003392. Click here.
Omar, N. S., Tan, P. C., Sabir, N., et al. (2013). Coitus to expedite the onset of labor: A randomized trial. BJOG;120, 338-345. Click here. Free full text!
Schaffir, J. (2006). Sexual intercourse at term and onset of labor. Obstet Gynecol, 107(6), 1310-1314. Click here.
Sekhavat, L & Akhavan Karbasi, S. (2010). Effect of coital activity on hastening onset of labor and prevention of postdate pregnancy. Iran J Obstet Gynecol Infertil. 13(2), 13–6. Click here.
Tan, P. C., Andi, A., Azmi, N., et al. (2006). Effect of coitus at term on length of gestation, induction of labor, and mode of delivery. Obstet Gynecol, 108(1), 134-140. Click here.
Tan, P. C., Yow, C. M., & Omar, S. Z. (2007). Effect of coital activity on onset of labor in women scheduled for labor induction: a randomized controlled trial. Obstet Gynecol, 110(4), 820-826. Click here.


Rebecca Dekker:

Hi, everyone. On today’s episode, we’re going to talk about eating pineapple or having sex for natural labor induction. 

Welcome to the Evidence Based Birt podcast. My name is Rebecca Dekker, and I’m a nurse with my PhD and the founder of Evidence Based Birth®. Join me each week as we work together to get evidence based information into the hands of families and professionals around the world. As a reminder, this information is not medical advice. See for more details.

Hi everyone, and welcome to today’s episode of the Evidence Based Birth® podcast. Today, we are continuing our series on the evidence on different natural labor induction methods. If you go to our archives at, you’ll see all of our past episodes, including episodes we’ve done on acupressure, breast stimulation, castor oil, evening primrose oil, and more. Today we’re getting towards the end of our series, and we’re going to talk about eating pineapple and also having sex to naturally induce labor.

Let’s start with pineapple. Eating pineapple is a popular suggestion I see on social media when people are looking for ways to get labor going naturally. Pineapple, or ananas comosus fruit, ripe or unripe, has been used as a traditional medicine to induce labor and terminate pregnancies in many part of the world. For example, traditional healers in Fiji prescribe unripe pineapple for the purpose of terminating early pregnancy. The use of unripe fruit juice, or aqueous, or watery extract of pineapple to induce abortion is also practiced in the Philippines, Indonesia, Malaysia, and Trinidad. In India, a hot aqueous extract from ripe pineapple is also used to terminate pregnancy. The enzyme bromelain is thought to be the active ingredient that contributes to cervical ripening, or the softening and thinning of the cervix that can help start labor.

Unfortunately, we do not have any clinical research studies on pineapple for natural labor induction. In other words, we don’t have any human subjects research. However, there are a few studies on rats and some Petri dish studies on isolated human uterine tissue. A 2014 study by Nwankudu demonstrated that pineapple juice from ripe fruit is capable of inducing strong uterine contractions in non-pregnant rat tissue in vitro. So when they looked at rat tissue from the uterus in non-pregnant rats in a Petri dish, pineapple juice could induce contractions. A followup study in 2015 by the same researchers randomized pregnant rats to normal saline or salt water or pineapple juice by mouth for 24 hours, 36 hours, or 48 hours, and then studied different doses of pineapple juice on pregnant rat uterine tissue in vitro. In the in vivo experiment with live rats, there were no abortions and all of the rats littered at full term. The authors think that this suggests that digestive enzymes could be causing the juice to lose its uterotonic properties when taken by mouth.

In the in vitro or Petri dish experiment, all doses of pineapple juice significantly induced contractions in the isolated rat uterine tissue. They think this could be due to the combined effects of bromelain and other components of the juice. They exposed the tissue to pineapple juice at different doses and to oxytocin, a hormone that can induce labor, and the contractions induced by pineapple juice were similar to those of oxytocin.

Another study published by Monji et al. in 2016 tested different pineapple extracts on isolated strips of uterine muscle from pregnant humans and from pregnant rats. The human tissue was obtained with informed consent from women who were having elective cesareans in Singapore. The researchers found that the pineapple extract induced strong uterine contractions in both the rat and the human tissue.

A 2018 followup study by the same researchers examined the uterotonic effect of pineapple extract in rats, both in vitro and in vivo. The researchers collected ripe and unripe pineapples from Malaysia and prepared extracts. They compared the stimulatory response to pineapple extracts in live rats and isolated rat uterine tissue. Ripe pineapple extract stimulated uterine activity, but not the unripe pineapple extract, which is contrary to customary beliefs. The contraction response increased in late pregnant rat uterine tissue, suggesting that it may help in inducing labor. This study identified the neurotransmitter serotonin as a major bioactive compound that contributed to the uterotonic activity of ripe pineapple extract in vitro and in vivo. Now, this study was limited to rats, so further studies are needed to clarify how pineapple extract could affect contractions throughout human pregnancy.

In summary, when we look at the research on pineapple for natural labor induction, there’s very little research on this topic. So far, there is no evidence that eating pineapple or drinking pineapple juice will cause miscarriage or induce labor at term. There is some evidence from studies on rats and human tissue samples that pineapple extract can cause contractions, but this hasn’t been observed when pineapple fruit is consumed normally by mouth. As a natural induction method, eating pineapple would not be considered to be evidence-based, but it is also not likely to be harmful, unless it gives you a sore mouth. Also, it might not be the best option for people who are limiting their carb intake, for example, if you have gestational diabetes. So that’s the research that we have on pineapple.

Now let’s talk about using sex for natural labor induction. The Listening to Mothers II survey by Declercq et al. in 2006 found that 22% of pregnant people tried to self-induce their labors, and that the most common methods were walking or physical activity, having sexual intercourse, and nipple stimulation.

Another study, by Bovbjerg et al in 2014, using data from the third Pregnancy Infection and Nutrition Cohort focused on 663 pregnant people who experienced spontaneous labor. Of those who reported a specific labor trigger, the majority, 32%, reported physical activity, usually walking; 14% reported some other physical trigger of labor, including sexual activity; and 12% reported ingesting something that triggered labor.

In 2019, Carbone et al. offered three explanations as to why sex might be an effective method for natural labor induction. First, we’ve known for a long time that human semen is the biological source that is presumed to contain the highest prostaglandin concentration, and prostaglandins are a hormone that are known to induce labor. Semen is rich in prostaglandins E and F2-alpha, and these prostaglandins are used in higher doses to induce labor. Researchers have taken samples of cervical mucus from pregnant people and found that the concentration of prostaglandins was 10 to 50 times higher than normal two to four hours after having sex.

Second, sex sometimes includes nipple stimulation, and nipple or breast stimulation has been found to increase the chance of going into labor in the next 72 hours among people at term with a favorable or ripened cervix. This is because nipple stimulation leads to higher levels of the hormone oxytocin in the body. The synthetic version of the same hormone, pitocin, is commonly used to induce labor. Researchers think that nipple stimulation only helps to induce labor in late pregnancy, once oxytocin receptors are fully present in the uterus. We talk more about the research evidence on nipple simulation for natural labor induction in EBB episode 125.

Third, sexual intercourse and female orgasm have been linked to an increase in uterine contractions. There may be mechanical effects, both possibly from penetration and from muscle contractions in the sexual organs. Researchers have monitored the fetal heart rate and uterine activity in three healthy pregnant women during sexual intercourse. This was a classic study published by Chayen et al. in 1986. They noticed increased uterine activity and fetal heart rate changes immediately following orgasm. So that’s some theory and background on why sex might work for natural labor induction.

Excitingly, we have the very first meta-analysis on this topic that just came out in 2019. In a meta-analysis, researchers combine the results from multiple studies on the same topic into one large or meta-study. Carbone et al. in 2019 evaluated the effectiveness of sex for starting labor at term in lowest pregnancies with a single, head-down baby. They included three randomized control trials with a total of nearly 1500 pregnant participants. The randomized trials included one by Tan published in 2007, one by Omar published in 2012, and one by Castro published in 2014. Two of the trials were from Malaysia, and one was from Portugal.

The number of participants in the trials range from 210 to 1,150. In all three of the trials, the intervention group was encouraged to have frequent vaginal sex. One trial specified, quote, “at least twice a week.” The control group was neither encouraged nor discouraged from having sex in two of the trials, and in one trial, they were asked to abstain from sex completely. Two of the trials asked participants to keep diary sheets to document their sexual activity. Spontaneous labor was defined as cervical dilation of three centimeters or more with regular contractions and/or premature rupture of membranes.

So what did they find? Well, the meta-analysis found that people who are randomly assigned to sex went into spontaneous labor at the same rate as those who were assigned to reduced sex or no sex. In other words, having sex did not improve someone’s chance of spontaneous labor. About 82% of people went into spontaneous labor in both groups. They also did not find a difference in pregnancy duration, premature rupture of membranes, induction of labor for post-term pregnancy, epidural use, oxytocin augmentation, cesareans, postpartum hemorrhage, newborn birth weight, or NICU admissions. These findings are not surprising because none of the three individual trials found evidence that sex increases the chance of spontaneous labor.

Interestingly, significantly fewer people who were assigned to the sex encouraged groups had an emergency cesarean due to abnormal fetal heart rate patterns compared to the control groups. Although this was not a very large clinical difference, 6% versus 9.4%, it was statistically significant. The authors were surprised by this finding and could not propose an explanation.

Our research editor at Evidence Based Birth®, Anna Bertone, mentioned when she was reviewing the research that there is a documented increase in fetal heart rate changes following orgasm. So we were wondering, is it possible if sex might prepare the fetus to cope with labor? Also, the percentage of people who reported that they had any sex during their term pregnancy was not significantly different between the sex encouraged and the sex neutral/discouraged groups. However, the two trials that asked participants to keep a diary of sexual activity found that those who were assigned to the sex encouraged groups reported significantly more sex during the third trimester.

Another important limitation is that the available research really does not assess many of the different features of sex that can vary. There are aspects such as condom use, orgasm or no orgasm, duration of nipple stimulation, sexual positions, duration of intercourse, volume of ejaculate with a male partner, concentration of prostaglandins in ejaculate, cervical exposure to the ejaculate, et cetera, and all of these factors could potentially impact the outcome. As you can imagine, it would be very difficult, and probably impossible, to conduct a randomized trial to assess all of these potential influencing factors.

So although we lack evidence that sex is an effective way to start labor, there’s no harm in trying. Sex is considered safe for most pregnancies, it has not been found to increase the risk of preterm birth, and penetration does not harm the baby. Sex is contraindicated in high-risk pregnancies, such as after a premature rupture of membranes with a low line bleeding placenta, and when there’s an increased risk of preterm labor, such as with a short cervix.

So that’s the information we have from randomized trials and a meta-analysis on having sex to naturally induce labor. There are some observational studies, though, that are worth mentioning. At least four observational studies have found benefits from sex in the third trimester. However, since these are not randomized studies, we don’t know if the act of sex itself is influencing these outcomes. It could be that the healthier people were more likely to have sex and more likely to have spontaneous labors. Researchers asked 200 healthy people with uncomplicated pregnancies and an established gestational age to keep a diary of sexual activity from 36 weeks until birth and to answer a questionnaire. This was a study done by Tan et al. in 2006. They found that reported sex at term was significantly associated with earlier onset of labor and reduced requirement for labor induction at 41 weeks.

In another study by Skhavat and Karbasi in 2010, researchers in Iran surveyed 215 low-risk pregnant people who were 36 weeks or greater about sexual activity each week. 105 women reported intercourse in the last weeks of pregnancy, and 110 reported no sexual activity. Sex at term was significantly associated with less post-date pregnancy and less need for induction. Spontaneous labor incurred in about 67% of the sex group and 48% of the control group, and birth after 40 weeks was about 8% in the sex group and 17% in the control group.

Another study from Iran included 120 pregnant people with signs of labor onset. This was published by Kafaei Atrian et al. in 2014. Participants were questioned in face-to-face interviews with a midwife about their history of sex in the last week of pregnancy. They found that gestational age at birth was significantly lower in the sex group based on last menstrual period and ultrasound results.

Finally, a study in Cameroon compared 72 pregnant people reporting unprotected vaginal sex after 37 weeks of pregnancy with 72 women reporting no sex after 37 weeks of pregnancy. The author’s name was Foumane et al. They found that the sexually active group had shorter first and second stages of labor, less need for pitocin augmentation, and a lower cesarean rate.

At least one observational study has found a negative association between sex at term and spontaneous labor. In 2006, Schaffir asked pregnant people at each term prenatal visit if they had engaged in sex during the previous week. About half of the 93 women reported having sexual intercourse. The people reporting sexual activity gave birth later than those reporting no sexual activity, 39.9 weeks versus 39.3 weeks. This finding could be explained by the fact that people experiencing signs and symptoms of imminent labor might avoid sex, while those who are still far from the start of labor might feel more comfortable and be more likely to have sex.

So in summary, when we look at the research on sex for natural labor induction, the highest quality evidence we have on this topic comes from a meta-analysis of three randomized control trials. These authors did not find that sex is an effective means of natural labor induction. Results from observational studies are mixed, but they’re subject to what we call a healthy user bias, with healthier people more likely to engage in sex and also experience better birth outcomes. On the other hand, an opposite effect could occur where people closer to the onset of labor may be less likely to have sex.

As I mentioned earlier, there are three possible ways that sexual activity could possibly affect labor induction. The prostaglandins in semen, if you’re having female to male sex and being exposed to semen. Second, the increase in oxytocin from sexual activity and close skin-to-skin contact and nipple stimulation. And third, sexual activity and orgasm stimulating uterine activity. So it’s possible that sex to induce labor is more effective if it involves all three components, nipple-breast stimulation, orgasm, and semen in close contact with the cervix.

More research is needed in this area before sex can be called an effective means of inducing labor. However, researchers agree that it is indeed safe to attempt unprotected vaginal sex as a means to induce labor, as long as your membranes are intact, your water hasn’t broken, the sexual partner has been tested for sexually transmitted infections and is found to be negative, and there are no other health concerns.

So I hope you found this information helpful, all about eating pineapple and having sex and whether or not these can help induce labor naturally. Just a reminder, you can go back to our past episodes, episode 125 about acupressure, acupuncture, and breast stimulation; episode 128 about castor oil and eating dates; episode 134 about evening primrose oil; and episode 139 about red raspberry leaf tea for labor preparation. We will likely have two more episodes in this series, so stay tuned for later in October, we will look at the evidence on some herbal methods for inducing labor naturally, and in November, we’ll wrap up the series.

Thank you for listening. I hope you have a great rest of your week, and I’ll see you next week. Bye!

This podcast episode was brought to you by the Evidence Based Birth® childbirth class. This is Rebecca speaking. When I walked into the hospital to have my first baby, I had no idea what I was getting myself into. Since then, I’ve met countless parents who felt that they, too, were unprepared for the birth process and navigating the healthcare system.

The next time I had a baby, I learned that in order to have the most empowering birth possible, I needed to learn the evidence on childbirth practices. We are now offering the Evidence Based Birth® childbirth class totally online. In your class, you will work with an instructor who will skillfully mentor you and your partner in evidence based care, comfort measures, and advocacy, so that you can both embrace your birth and parenting experiences with courage and competence. Get empowered with an interactive online childbirth class you and your partner will love. Visit to find your class now.

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