There is no evidence sex is harmful for healthy pregnant women with uncomplicated pregnancies and no underlying health conditions, regardless of trimester.
It is currently assessed that any contraction-type activity as a result of sexual activity is not sustained nor strong enough to lead to adverse outcomes. However, sex during pregnancy, and its changes in blood flow, oxygen, hormones, and uterine activity has not been adequately studied in humans – especially in high-risk pregnancies.
Due to a lack of information, there is no significant guidance offered to HCPs regarding contraindications of sex during pregnancy, although risk of preterm labor, placenta previa, and placenta abruption continue to remain primary reasons HCPs recommend its avoidance.
Additionally, women need to engage in safe sex practices, as sexually transmitted infections (STI) can cause serious complications during pregnancy, some of which may present with no initial symptoms. Most HCPs will screen for STIs during the first prenatal visit. If a woman suspects she may have contracted an STI, she needs to tell her HCP immediately.
Women need to ask their HCPs any questions they have regarding sexual activity during pregnancy, especially in relation to their own individual health risks.
Background
Physical changes of pregnancy both increase and decrease sex drive at the same time, although the factors that decrease it appear to be much stronger. Increased blood flow and hormone production can make orgasms easier to achieve; however, increased weight gain, enlarged abdomen, sore breasts, swelling, and other symptoms can also make sex uncomfortable and less enjoyable depending on stage of pregnancy.
In general, sex drive appears to be the highest in the second trimester but decreases significantly by the third trimester. It has been documented in numerous studies the frequency of sex for most couples diminishes during pregnancy – sometimes even right away – usually due to a fear of bleeding, miscarriage, preterm delivery, or concerns of pain and discomfort, as well as general misinformation related to safety.
Safety – Overview
Overall, there is no evidence that sex is harmful at any stage of gestation in healthy, uncomplicated pregnancies.
However, there is very little information regarding how sex can affect “high risk” pregnancies, in which women may have cardiovascular, bleeding, or placental concerns, or are considered at risk for preterm labor. Sex is usually contraindicated in these scenarios by HCPs, but overall, there is very little guidance toward any specific recommendation.
Some studies have even found the reverse, in that sexual activity during pregnancy may be associated with a higher chance of having a full‐term pregnancy, which only leads to further confusion.
It is evident that more research is needed regarding the avoidance of sex during pregnancy, and until then, HCPs are likely to err on the side of caution and ask women who may have certain risk factors during pregnancy to avoid sex until the postpartum period.
Blood Flow
Blood volume increases dramatically within the first few weeks of pregnancy, almost one full liter of which progressively goes to the pelvic region by term. Uterine blood flow can increase more than 3.5 to 40-fold during pregnancy (depends on measurement technique, read Uterus).
It is well known that in non-pregnant individuals, an increase in blood flow is a key component to positive sexual satisfaction; during sexual stimulation, blood flow to the vagina and clitoris can increase up to 3-fold and 11-fold, respectively. However, after orgasm, blood flow is estimated to return to baseline within 20 to 30 minutes.
This extra blood flow can make achieving an orgasm much easier. However, the effects of blood flow changes during pregnancy on the pregnant uterus or in an embryo/fetus after sex/orgasm has not been studied in humans.
Contractions
In contrast to the above, contractions have been monitored on the pregnant human uterus immediately after sex/orgasm, which has shown an increase in uterine activity. Breast stimulation and prostaglandins in semen can also cause uterine contractions during pregnancy.
Note: While uterine contractions do occur after sex, studies showing actual longevity and continual strengthening of contractions are lacking, and therefore sex as a positive tool to initiate labor is not backed by strong evidence. Similar to blood flow changes, these contractions may be too short-lived and temporary to have any beneficial or adverse effect.
Fetal heart rate changes have also been reported immediately following orgasm, but these too were noted to be temporary.
Later in pregnancy, an orgasm/sex may initiate Braxton Hicks contractions, but these are also temporary and do not lead to sustained contractions over time; that only occurs when true labor starts.
Regarding the first trimester specifically, hormones – especially progesterone – are significantly increased, and progesterone acts as an inhibitor to contractions. However, it is unclear if progesterone can minimize or regulate uterine contractions after orgasms in the first trimester as a protective factor, as this has not been studied.
Bleeding
Whether sex causes bleeding during pregnancy is controversial, as some studies indicate this is very unlikely, and may be due to other causes. However, several studies have documented bleeding immediately following intercourse; it was not noted how much bleeding occurred, when it stopped, how sex could have caused the bleeding, or if those women suffered any negative pregnancy outcomes.
Increased blood flow to the pelvic region and cervix could cause bleeding after sex, but this is mostly hypothetical as there is a lack of research regarding sex and bleeding during pregnancy.
It is possible that bleeding during sex is more common in the first trimester, but bleeding early in pregnancy is already common, regardless of sexual activity. Bleeding can occur in up to 25% of women in early pregnancy; of these women, an estimated three-quarters go on to have healthy, viable pregnancies (read Bleeding).
If bleeding occurs after the first trimester, some HCPs may recommend – as a cautionary step – stopping all sexual activity for the remainder of pregnancy.
Miscarriage
Fear of miscarriage is a common reason some couples avoid sex completely during the first trimester. Although there is a lack of research on the subject, there is no current evidence that sex during pregnancy can lead to miscarriage, especially in women who otherwise have no health concerns.
Further, at least one studied concluded that sexual intercourse was associated with reduced odds of miscarriage, unless bleeding was already present.
It is common practice, as caution, to recommend the avoidance of sex in women who are bleeding or have been diagnosed with threatened miscarriage (bleeding, closed cervix).
In the 1980s, sex was listed as a cause of early pregnancy loss in a popular medical textbook in the United Kingdom. In 1990, an updated edition indicated that sex “has no effect in a normal pregnancy”, and a more recent update did not mention sex in the context of pregnancy loss at all. This is also a common occurrence in the scientific literature in general.
Current U.S. textbooks indicate there are no restrictions regarding sexual intercourse during pregnancy except in the case of placenta previa, ruptured membranes, or preterm labor.
Infection and Preterm Labor
Frequency of sex is not likely to increase the risk for infection during pregnancy. The cervical mucus plug forms a physical and immunological barrier against bacteria present in the vagina, as any bacteria present must go through the cervix before infecting the uterus and/or amniotic cavity. Therefore, the plug plays a critical role in blocking harmful bacteria that can be introduced from sex.
However, the mucus plus is not 100% effective at blocking all bacteria (researchers are still learning why), and it is possible for infection from any source to get passed through the cervix and into the fetal membranes. This is usually a major cause of preterm labor.
At least two studies found that in women with colonized bacteria or symptoms of genital tract infection and engaged in sex had a higher incidence of preterm labor compared to those without these symptoms.
It is possible that in women with with a present infection, sex could increase the risk of the infection ascending into the fetal membranes. One studied assessed that in low-risk pregnancies with no sign of lower genital tract infection, sex was not considered to increase the risk of preterm delivery.
Women should always be aware of the signs of vaginal infection during pregnancy and call their HCP for assessment (read Vaginal Infection).
Evidence regarding sex and the initiation of preterm labor is conflicting, as not all studies have reached this conclusion. It is possible the conflict arises from study design, reporting bias, low-risk women, and the rarity of preterm labor (smaller study sizes).
However, the avoidance of sex to prevent preterm labor is often recommended in those who may be considered high-risk; but overall, very little information is known regarding any type of high-risk pregnancy and sex.
Women carrying twins or more are also often advised to avoid sex due to the higher incidence of preterm delivery among multiple gestations. However, at least one study of 126 women with a multiple pregnancy did not find this association.
Placental Concerns/Complications
Several issues regarding the placenta can arise during pregnancy that may be affected by sex – placenta previa and placental abruption. However, there is very little evidence-based guidance to help HCPs make recommendations, and some researchers advocate there is no clear benefit to sex avoidance, even in these cases.
Placenta previa occurs when the placenta partially or totally covers the cervix and can cause severe bleeding during pregnancy or delivery. The exact cause of placenta previa is unknown but it occurs in about 1 in 200 pregnancies. The most common symptom of placenta previa is painless bleeding. Read more.
It is possible, but only reported via case study, that sex/orgasm in women highly predisposed to, or currently experiencing placental problems, could trigger possible abruption or severe bleeding.
HCPs are often advised that if a woman is suspected of having placenta previa after presentation to a clinic with bleeding, that a vaginal exam via speculum or fingers is not recommended, as any contact to the cervix could cause catastrophic bleeding. This advice is often extrapolated to sex via cervical contact with fingers or a penis.
Some researchers indicate that simple contact with the cervix likely will not cause bleeding; it is more likely the fingers would have to go through the cervix to make contact with the placenta. However, even in this review, the researchers indicated that until more research is completed, continued practice of sex avoidance in the case of placenta previa may be the safest option.
Sexually Transmitted Infections
STIs are considered common in pregnancy, but true prevalence is hard to determine. Although cases of most STIs are reported to the U.S. Centers for Disease Control and Prevention (CDC), pregnancy status is not usually included. However, as of July 2020, CDC has indicated a significant increase in congenital syphilis infections since 2013, which can be life-threatening to a newborn.
All pregnant women should get screened for STIs by their HCP during their first prenatal visit. It is estimated that up to 90% of chlamydial infections, 85% of trichomonal infections, and up to 80% of gonorrhea infections cause minimal to no symptoms. Additionally, herpes infections can lie dormant for years after the original infection, which may also show no initial symptoms.
Condoms do offer protection against STIs, but not complete protection; however, they must be used correctly every single time (see Resources section).
The only two ways to ensure complete protection is to either abstain from sex during pregnancy, or have a sex with a long-term monogamous partner who is free of STIs.
Venous Air Embolism
Venous Air Embolism (VAE) is a common concern of pregnant women, but is very, very rare, with an occurrence rate estimated at 1 in 1 million pregnancies. One study highlighted this infrequency, reporting 18 deaths caused by VAE out of 20 million pregnancies.
Venous Air Embolism: blockage of a vein to the heart by gas (i.e. air bubbles); when air is introduced into the circulatory system.
In an analysis of 22 incidences of VAE that occurred during pregnancy, 14 occurred due to “air insufflation of the vagina” (oral sex) and five occurred during sex (four were rear entry); rear entry has been documented to be a risk factor in other studies as well.
During pregnancy, the vagina can be a direct pathway to the vasculature of the uterus and placenta. Air can be forced into the cervical canal through blowing during oral sex or deep penetration and intense thrusting during sex; however, this is still incredibly rare.
VAE is rare because in order for it to occur – especially during vaginal or oral sex – direct communication between the source of air and vasculature must occur, as well as a pressure gradient that helps the air get into the circulation; it also has to be a large volume of air, estimated to be at least 150 ml.
Action
Sex is safe in all trimesters for healthy women with no underlying medical conditions and uncomplicated pregnancies.
For more comfort, women should try to manage their current symptoms and find positions that work for both partners. Women should also consider avoiding any sexual position in which they lie on their abdomens or flat on their backs (the latter should be avoided after 20 weeks).
Women need to engage in safe sex practices, as STIs can cause serious complications during pregnancy, some of which may present with no initial symptoms. If a woman suspects she may have contracted an STI, she needs to tell her HCP immediately.
Women need to ask their HCPs any questions they have regarding sexual activity during pregnancy, especially in relation to their own individual health risks. They should also see/call their HCP if they experience pain during sex, or bleeding after sex. Although both of these symptoms could be caused by sex, it is good practice to rule out other possibilities, especially during pregnancy.
Partners/Support
Sex is safe for healthy women with no underlying medical conditions and uncomplicated pregnancies. However, women may feel very insecure due to their changing bodies and feel more cautious due to anxiety regarding safety. Women may also feel less comfortable as pregnancy progress due to a myriad of physical symptoms.
The sexual partner of a pregnant woman should:
Get tested for STIs
Use a condom (if necessary/not monogamous), and use it correctly, every time.
Avoid blowing forcefully during oral sex
Avoid missionary position when the woman is on her back after 20 weeks of pregnancy
Change positions often to make sure she is comfortable
Offer reassuring and positive emotional support
Resources
Sexual Health (American College of Obstetricians and Gynecologists; July 2017)
How to Prevent Sexually Transmitted Infections (STIs) (American College of Obstetricians and Gynecologists; June 2017)
Male Condom Use (U.S. Centers for Disease Control and Prevention)