Generally, your period arriving is a pretty solid indication you aren’t pregnant, but generally is not always. Bleeding during pregnancy or spotting during pregnancy which can be mistaken for a period while pregnant is possible– most especially during the first month of pregnancy. Bleeding can also occur later in pregnancy, even if there was not bleeding early on. No matter the when, bleeding in pregnancy is always a scary experience, we do our best below to detail the possible causes of bleeding in pregnancy at each stage as well as cover how common it is to have bleeding in pregnancy.
Note: The probable causes of bleeding in pregnancy vary by when in your pregnancy the bleeding occurs. This article covers three major time periods as well as the prevalence and risk factors of bleeding in pregnancy:
-Period while pregnant: very early pregnancy, typically before pregnancy is confirmed.
-In the first trimester (month 1 – 3)
-In the second and third trimester
-How rare is it to be pregnant and have your period? What are the risk factors?
Spotting during pregnancy in the first month: Can you have a period while pregnant?
Conception that occurs close to menstruation or low progesterone levels may cause what looks like a period while pregnant.
Conception may not occur until mere days before your period is due if you have a short menstrual cycle or don’t ovulate mid-cycle.
For example, let’s say you’re regularly maintaining a 26-day cycle. Chances are you’ll ovulate around day 13. Even if you had unprotected sex on that day and sperm found egg later that day, it would still take the fertilized egg six to twelve days to reach and implant in your uterine lining.
By this timeline, your body wouldn’t know to continue producing the hormone progesterone that ceases menstruation until somewhere between day 20 to 25 of your cycle. This could leave as little as one day between conception and projected menstruation.
If those hormone levels are insufficient, such as in a situation of low progesterone from luteal phase defect or had already begun to fall, you could have what seems like a lighter than usual period while pregnant or even one that seems entirely normal and wouldn’t think you missed a period until you were already around eight weeks pregnant.
This type of bleeding is often referred to as “break through bleeding,” and is the most common type of bleeding mistaken for a period while pregnant. Break through bleeding is usually seen during the first month of pregnancy, but may continue in the first trimester if hormone levels stay low.
It’s important to note in this case that any bleeding following the first bleed would not occur in a timely, predictable manner like a period. It would be sporadic bleeding that will vary in flow. Multiple timely periods of bleeding like a period, whether irregular/light for you or not, are very unlikely to be pregnancy bleeding.
As this can be indicative of low progesterone, it should be evaluated by a doctor. In fact, any bleeding during pregnancy should. It should also be noted that even if there is bleeding when your period is due, if you are pregnant, ovulation will not occur again. This type of bleeding is not a true period while pregnant. You cannot have what is technically referred to as a period while pregnant, because your uterine lining is not entirely shed along with an egg.
Basal body temping can be a great way to catch such a situation, because a rise in temperature confirms ovulation and prolonged high temps for 16 days can be a way to confirm you’re pregnant, period-like bleeding or not.
Implantation bleeding may be mistaken for a period while pregnant.
Many women also mistake implantation bleeding for a period while pregnant. If you followed the same example above, usually had a light period, and had spotting on day 23, you may think that spotting was your period simply a day or two early. Bleeding varies from woman to woman, but a heavy flow is almost never implantation bleeding. You can read a full article on telling the difference between implantation and your period here.
Some of causes of spotting during pregnancy or bleeding during pregnancy in the first trimester covered below may also apply to very early pregnancy and be mistaken for a period while pregnant. If your bleeding is later than 14 days after intercourse, and you don’t have a short cycle, you might explore those causes as well.
Bleeding during pregnancy in the first trimester (First month to about month 3):
Possible pregnancy bleeding cause: Cervical changes
During pregnancy your cervix becomes soft and blood flow is increased. This can make it more prone to minor damage. Things such as sex, dilation or position checks, PAP smears, and even excessive physical activity which may have triggered small contractions can cause spotting during pregnancy. You should always mention any bleeding to your care provider, though short-term spotting is not often a cause for concern, especially if it was just once and after an activity that may have affected your cervix.
Possible pregnancy bleeding cause: Progesterone dip
Around week 6 the placenta begins to take over production of progesterone. Sometimes during this time there is a slight and temporary progesterone dip that can cause light bleeding in pregnancy. This is the most common time for spotting during pregnancy to occur.
Possible pregnancy bleeding cause: Infection
Infections that may cause inflammation to the cervix or vaginal canal can also cause spotting during pregnancy. These may include common infections such as yeast infections and bacterial vaginosis as well as sexually transmitted diseases such as herpes, gonorrhea, and chlamydia. Spotting accompanied by foul smelling discharge, itching, skin rashes or warts may be a good tip off this is what you’re dealing with, though not all infections present with symptoms.
Possible pregnancy bleeding cause: Subchronic hematoma
A subchronic hematoma is a pocket of blood or blood clot within the uterine wall. This cause of spotting or bleeding during pregnancy might sound a bit scary, but in most cases subchronic hematomas are minor and resolve on their own. Bleeding from a hematoma may be as light as spotting or heavy with clots depending on severity. Ultrasound is often used to confirm and determine that severity. Hematomas are another type of bleeding sometimes mistaken for a period while pregnant, because they can cause heavier and repeated bleeds.
Possible pregnancy bleeding cause: Ectopic pregnancy
Sadly, there are a few causes of spotting during pregnancy or bleeding that are bad news. Ectopic pregnancy, where the baby has implanted somewhere outside of the uterus such as the fallopian tube, is one of those causes. Ectopic pregnancy can cause long-term fertility issues and even be life threatening, so the earlier it’s discovered the better. Symptoms of ectopic pregnancy in addition to bleeding or spotting may include severe cramping, abdominal pain, light headedness, and a pregnancy test that is positive, then negative.
Possible pregnancy bleeding cause: Molar Pregnancy
Keeping up with those bad news causes of spotting during pregnancy, molar pregnancy occurs when tissue (a tumor) begins to grow within the uterine wall causing a positive pregnancy test. Molar pregnancies are rare and caused by chromosomal abnormalities within the fertilized egg. In addition to spotting, symptoms may include severe nausea or vomiting, high blood pressure, measuring large (rapid uterine growth), passing of cysts, and occasionally pelvic pain or pressure.
Possible pregnancy bleeding cause: Miscarriage
Finally, spotting during pregnancy can indeed be caused by miscarriage, whether missed or impending. Keep in mind that in almost all cases, nothing was done to cause or can be done to prevent early miscarriage. The most common cause is chromosomal abnormality.
Bleeding during pregnancy in the second or third trimester
While bleeding during pregnancy during the first month of pregnancy, and throughout the first trimester even, is quite common and usually not cause for concern, most of the cases later in pregnancy are far more rare, but also often less benign unfortunately.
Possible pregnancy bleeding cause: Placenta abruption
Placenta abruption occurs when the placenta partially or completely separates from your uterine wall before birth. This can deprive your baby of nutrients and oxygen. Minor abruptions can be managed with rest.
Possible pregnancy bleeding cause: Uterine rupture
Uterine rupture is most common in women who have previously had a c-section and is rare even in that case. Usually during early labor contractions, the uterine wall ruptures. Uterine rupture is life threatening to both mother and child and requires emergency c-section.
Possible pregnancy bleeding cause: Placenta Previa
Placenta previa occurs when the placenta partially or completely covers your cervix (the opening from your womb to the vaginal canal.) Depending on the severity of placenta previa, treatment may range from bed rest at home without physical exertion or sex to emergency c-section.
Possible pregnancy bleeding cause: Vasa previa
Note that this condition is quite rare occurring in 1 in every 2000 pregnancies, but is seen more in those who also have placenta previa. Vasa previa occurs when the blood vessels in the umbilical cord block your cervix. It is harmless during pregnancy but can prove fatal to your child during delivery as the rupture of these vessels will cause blood loss from the baby.
Possible pregnancy bleeding cause: Incompetent cervix:
Incompetent cervix occurs when your cervix is weak and attempts to open or does open before the end of your pregnancy. This condition is present throughout pregnancy but isn’t typically symptomatic causing bleeding during pregnancy until your baby becomes large enough to begin placing weight on your cervix. It is one of the most common causes of second trimester losses. You may notice increased pressure, as if your baby has dropped into your pelvis, a change in discharge prior to spotting or bleeding, back pain, or contractions. An incompetent cervix can be treated by stitching your cervix closed if caught before preterm labor has occurred.
Possible pregnancy bleeding cause: Miscarriage or Premature labor
Before 20 weeks, an attempted loss or loss is still referred to as a threatened miscarriage or miscarriage. After 20 weeks, it’s referred to as premature labor. All of the above-mentioned causes of bleeding during pregnancy can also be a cause of miscarriage or preterm labor. Certain infections, abdominal trauma, and chromosomal abnormalities can also be to blame, but in other cases no cause is known. Take heart, however, in knowing the current rate of miscarriage after a heart beat is seen at 8 weeks is a mere 1 percent.
As mentioned earlier on this page bleeding during pregnancy, any bleeding, no matter how slight, should be reported to your doctor right away. Light bleeding during pregnancy is very likely no cause for concern, heavy bleeding can be more serious, but either way, better safe than sorry.
How common is bleeding during pregnancy?
Surprisingly, I wouldn’t say there are a wealth of studies on this subject. From 1983 to 2017, 18 studies could be found (a full list of studies used in this piece including summaries and links can be found at the end of this page).
The observed rate of bleeding during pregnancy varied from 7 to 27 percent. As a result, 1 in 4 pregnant women is considered an accurate estimate by most sources for the prevalence of early pregnancy bleeding often mistaken for a period while pregnant.
What type of bleeding is most common in pregnancy, and when it is most likely to occur?
Bleeding described as spotting or light accounts for roughly 90 percent of all pregnancy bleeding. Bleeding is most common in the first trimester, occurs only once, lasts one to two days, and is most frequently seen between weeks 5 and 8. This is suggested to be because around that time progesterone production is taken over by the placenta and a slight, temporary progesterone dip may result. It’s likely this common flow, duration, and timing is why so many women suspect they are having or have had a light period while pregnant.
Bleeding in pregnancy is sporadic, without a timely occurrence like a period while pregnant, though episodes in the first trimester are also frequently seen around the time the next period after conception would have occurred.
What are the likely outcomes of bleeding during pregnancy?
Unfortunately, in studies that examined the outcome of pregnancy bleeding, a similar pregnancy loss rate of around 50 percent was found. The rate of miscarriage in all pregnant women is estimated at between 10 and 25 percent, so it’s important to note that no studies found bleeding in pregnancy to cause miscarriage, rather, it’s the other way around. Miscarriage is one possible cause of bleeding in pregnancy. Rates of loss were higher in those who experienced heavy bleeding and/or bleeding that exceeded 4 days.
In second trimester bleeding, the chances of preterm labor, C-section, and low birth weight also increase.
What are the risk factors for bleeding during pregnancy?
Rates of bleeding in pregnancy are higher:
-In those older than 35.
-When carrying multiples.
-If you have had previous miscarriages.
-When you have hormonal conditions or symptoms of hormonal imbalance, such as PCOS, fibroids, very long/short cycles, etc.
-If you have uterine abnormalities.
-In those with diabetes.
-With vaginal infections.
Studies on Bleeding During Pregnancy: A Chronological List
Below is a list of studies done on bleeding during pregnancy with quick summaries of the rate of bleeding in pregnancy that was found and any other note-worthy points, such as when the bleeding occurred, whether it was light or heavy, how long it lasted, risk factors, etc.
Note: Many of these studies were read using a University Library login and may not offer full free access without login. I only included studies here I was able to read. If you find others, and would like them included, please contact me.
1983: Study of 16,305 women found a rate of bleeding of 14.6 percent. 91 percent experienced spotting only and 8 percent heavy bleeding.
Berkowitz GS, Harlap S, Beck GJ, Freeman DH, Baras M. Early gestational bleeding and pregnancy outcome: a multivariable analysis. Int J Epidemiol. 1983;12:165–73
1984: Retroactive study of 7,486 women. Rate of pregnancy bleeding: 7 percent.
Batzofin JH, Fielding WL, Friedman EA. Effect of vaginal bleeding in early pregnancy on outcome. Obstet Gynecol. 1984;63:515–8.
1991: Study of 14,458 women. Rate of pregnancy bleeding: 17.6 percent. 55 percent of bleeding occurred in the first trimester. 6.82 percent light bleeding only.
Williams MA, Mittendorf R, Lieberman E, Monson RR. Adverse infant outcomes associated with first-trimester vaginal bleeding. Obstet Gynecol. 1991;78:14–8.
1992: Study of 8,718 women. Rate of pregnancy bleeding: 9.3 percent. 6.89 percent in the first trimester.
Sipila P, Hartikainen-Sorri AL, Oja H, Von Wendt L. Perinatal outcome of pregnancies complicated by vaginal bleeding. Br J Obstet Gynaecol. 1992;99:959–63.
1994: Meta-analysis of 28 studies from 1950-1992. Rate of pregnancy bleeding: 12.9 percent.
Ananth CV, Savitz DA. Vaginal bleeding and adverse reproductive outcomes: a meta-analysis. Paediatr Perinat Epidemiol. 1994;8:62–78.
1995: Study of 5,868 women. Rate of pregnancy bleeding: 19 percent. Bleeding was most common at 8 weeks, lasted no more than 2 days, and was a single occurrence.
Axelsen SM, Henriksen TB, Hedegaard M, Secher NJ. Characteristics of vaginal bleeding during pregnancy. Eur J Obstet Gynecol Reprod Biol. 1995;63:131–4.
1997: Study of 550 women. Rate of pregnancy bleeding: 21 percent.
Everett C. Incidence and outcome of bleeding before the 20th week of pregnancy: prospective study from general practice. BMJ. 1997;315:32–4.
1999: Study of 1,100 women. Rate of pregnancy bleeding: 11 percent. Vaginal infection found to be a risk factor.
French JI, McGregor JA, Draper D, Parker R, McFee J. Gestational bleeding, bacterial vaginosis, and common reproductive tract infections: risk for preterm birth and benefit of treatment. Obstet Gynecol. 1999;93:715–24.
2001: Study of 7,658 women. Rate of pregnancy bleeding 14.4 percent. Preterm birth was more common in those with early pregnancy bleeding.
Yang J, Savitz D. The effect of vaginal bleeding during pregnancy on preterm and small-for-gestational-age births: US National Maternal and Infant Health Survey, 1988. Paediatr Perinat Epidemiol. 2001;15:34–9
2003: Study of 221 women before pregnancy. 68.3 percent (151) became pregnant. 9 percent had bleeding before 8 weeks. Data was not continued beyond 8 weeks.
Harville EW, Wilcox AJ, Baird DD, Weinberg CR. Vaginal bleeding in very early pregnancy. Hum Reprod. 2003;18:1944–7.
2004: Screening of 16,506 women. Rate of pregnancy bleeding: 14.38 percent. Light bleeding accounted for 12.86 percent, heavy bleeding 1.52 percent.
Weiss JL, Malone FD, Vidaver J, et al. Threatened abortion: A risk factor for poor pregnancy outcome, a population-based screening study. Am J Obstet Gynecol. 2004;190:745–50.
2005: Study of 2,806 women. Rate of pregnancy bleeding: 24.48 percent. 77.4 percent occurred in the first trimester. 69.9 percent had only one episode of bleeding. 79.3 percent light bleeding only. Risk factors including older maternal age and previous miscarriage.
Yang J, Savitz DA, Dole N, et al. Predictors of vaginal bleeding during the first two trimesters of pregnancy. Paediatr Perinat Epidemiol. 2005;19:276–83.
2007: Study of 2,678 women. Rate of pregnancy bleeding: 26 percent. 83.6 percent of which occurred in the first trimester.
Hossain R, Harris T, Lohsoonthorn V, Williams MA. Risk of preterm delivery in relation to vaginal bleeding in early pregnancy. Eur J Obstet Gynecol Reprod Biol. 2007;135:158–63.
2009: Study of 4,510 women. Rate of pregnancy bleeding: 27 percent. 42.9 percent of those with bleeding miscarried. Heavy bleeding was only seen in 8 percent. Episodes of heavy bleeding correlated with a three times higher chance of miscarriage, while episodes of light spotting showed no difference in comparison to those who experienced no bleeding.
Hasan R, Baird DD, Herring AH, Olshan AF, Jonsson Funk ML, Hartmann KE. Association between first-trimester vaginal bleeding and miscarriage. Obstet Gynecol. 2009;114:860–7
2010: Study of 4,539 women. 12 percent ended in miscarriage with about 2 in 3 experiencing bleeding prior to their loss. These losses were excluded from the rate of bleeding in pregnancy given, which was 25 percent. 75.6 percent of bleeding was light. 71 percent of bleeding occurred only once. Risk factors included prior miscarriage, advanced maternal age, fibroids, blood sugar issues, and signs of hormonal imbalance. The rate of loss was higher in those with heavy bleeding.
Hasan R, Baird DD, Herring AH, Olshan AF, Jonsson Funk ML, Hartmann KE. Patterns and predictors of vaginal bleeding in the first trimester of pregnancy. Annals of epidemiology. 2010;20(7):524-531.
2010: Study of 2,054 women. Rate of pregnancy bleeding: 23.9 percent. Most episodes were light bleeding in the first 20 weeks.
Skorokhod, Veronika. Vaginal Bleeding during the First 20 Weeks of Pregnancy and the Risk of Preterm Delivery, Michigan State University, Ann Arbor, 2010, ProQuest Dissertations & Theses Global.
2011: Study of 3,431 women. Rate of pregnancy bleeding: 23 percent. 72 percent of bleeding occurred in the first trimester with week 6 being most common. 73 percent occurred only once. 90 percent of bleeding was light.
Smits LJM, North RA, Kenny LC, Myers J, Dekker GA, Mccowan LME. Patterns of vaginal bleeding during the first 20 weeks of pregnancy and risk of pre-eclampsia in nulliparous women: results from the SCOPE study. Acta Obstet Gynecol Scand 2012.
2017: Study of 11,835 women. Rate of pregnancy bleeding: 8.5 percent. 84 percent of those later miscarried. Bleeding prior to 6 weeks was more likely to lead to loss. Bleeding was also most common prior to 6 weeks. 83.2 percent experienced only spotting, 16.8 percent heavy bleeding, and the miscarriage rate was higher in those with heavy bleeding.
Kamble PD, Bava A, Shukla M, Nandanvar YS. First trimester bleeding and pregnancy outcome. Int J Reprod Contracept Obstet Gynecol 2017;6:1 48-7.
The extensive comment base on this page led to the writing of its sister articles, “Missed Period Negative Pregnancy Test Explanation” , “Late period, missed period, irregular period, Oh, Why!?,” “When to Take a Pregnancy Test,” and “Am I Pregnant? Calculating Your Chances of Pregnancy or the quiz version” which offer other explanations for irregular bleeding or missed periods in-depth and may help you assess whether or not you could be pregnant.
I do my best to respond to comments within 48 hours. All comments are moderated. Please remember though, I am not a doctor nor a replacement for medical care. I can’t tell you if you are pregnant over the Internet or tell you what’s causing your spotting or bleeding during pregnancy. I do have a medical background (medical assisting) and am a mother of four who struggled with infertility as well as multiple miscarriages. However, I am not a doctor nor claim to be one.
If you enjoyed, “Period While Pregnant? Spotting or Bleeding in Pregnancy? Causes and Prevalence,” you may also find helpful:
Early Signs of Pregnancy Quiz
When Do Pregnancy Symptoms Start?
Period Blood Colors and Textures Explained
Brown Discharge Before a Period Explained