Bleeding During Pregnancy: Prevalence, Risks, and Research 2


If you’ve found this page looking for information on bleeding during pregnancy, there’s no question I have no need to express what a scary situation early pregnancy bleeding can be. Why bleeding occurs in pregnancy and just how common it is are questions you do likely have though. Right after, of course, whether or not your baby is going to be OK.

how common is bleeding during pregnancy

We’ve already covered the why of bleeding during pregnancy in these in-depth pages below including:

Reasons for Bleeding in very Early pregnancy
Reasons for Bleeding in the First Trimester
Reasons for Bleeding in the Second and Third trimesters

Now we’ll look at research into how common bleeding in pregnancy is, when it’s most likely to occur, and statistics as far as the outcome of pregnancies where bleeding occurs.

We also have a page set up here for stories from women who have had bleeding in pregnancy as well as an interactive user poll on bleeding during pregnancy.

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 on the subject 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 for the prevalence of early pregnancy bleeding by most sources.

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.bleeding during pregnancy by week

Bleeding in pregnancy is sporadic, without a timely occurrence like a period, 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 women who are:

-Older than 35.
-Carrying multiples.
-Have had previous miscarriages.
-Have hormonal conditions or symptoms of hormonal imbalance, such as PCOS, fibroids, very long/short cycles, etc.
-Have uterine abnormalities.
-Have diabetes.
-Vaginal infections.

I certainly hope this page has answered all your questions, but if there’s something I’ve missed, feel free to comment. I do my best to respond within 48 hours. Please note, however, that I am not a doctor nor adequate replacement for medical care. Any bleeding during pregnancy should be reported to your health care provider.

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.

 


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2 thoughts on “Bleeding During Pregnancy: Prevalence, Risks, and Research

  • Anonymous

    Hi! So I recently ended my last cycle 6 days ago and I also took plan b 5 days ago. Today, I started bleeding (heavy) but it wouldn’t make sense for me to have another period. I am not sure if this bleeding could be a sign of pregnancy or not. I took a pregnancy test today as well and it was negative. Has anyone ever heard of this?

    • Life with Gremlins admin

      Plan B is a large dose of hormones used to trick the body, so to speak, into thinking it’s already pregnant so you don’t ovulate. When that large dose dissipates, there is often bleeding (because its also simulating the hormone drop that triggers a period). That’s likely the cause of your bleed. Pregnancy from sex during a period is already exceptionally low, it’s highly unlikely you’ll become pregnant.