Vaginal Bleeding in the First Trimester of Pregnancy

Vaginal Bleeding in the First Trimester of Pregnancy

Brittany Hannon

Karen J. Jubanyik


Background and Importance

Vaginal bleeding is a common complaint among women seeking care in the emergency department. The first step in evaluating patients of reproductive age with vaginal bleeding is to determine whether they are pregnant. The patient’s history may be unreliable as to whether or not they are pregnant. A study demonstrated only 63% of patients that reported being pregnant were correct. In addition, 7% of patients that reported there was absolutely no chance they could be pregnant were found to be pregnant, with 10% of this subset of patients reporting a normal last menstrual period (LMP).1 Therefore, a pregnancy test should be obtained in all patients of reproductive potential with vaginal bleeding, regardless of the patients’ self-reported pregnancy status or LMP.

Once pregnancy is confirmed in a patient with vaginal bleeding, there are only a limited number of possible diagnoses to consider. Ectopic pregnancy is the most serious and life-threatening diagnosis; however, spontaneous abortion is the most common. An estimated 25% of first trimester pregnancies are complicated by vaginal bleeding, and 50% of these pregnancies will end in a spontaneous abortion.2 A correlation has been found between length of bleeding, heaviness of bleeding, presence of painful bleeding, and the risk of spontaneous abortion. Patients who experience painful heavy bleeding that lasts longer than 2 days are more likely to have pregnancies that spontaneously abort compared to patients who have painless spotting that lasts only a day or two.3


Differential Diagnoses

The differential diagnoses for vaginal bleeding in the first trimester range from benign to life-threatening etiologies. Knowing the hallmark signs of each possible diagnosis will ensure that the more dangerous etiologies are not missed.

Implantation Bleeding

Bleeding that begins close to or just after a patient’s scheduled menses is often implantation bleeding. This is a common and benign cause of vaginal bleeding in early pregnancy. As the embryo develops and implants into the endometrial tissue, irritation and inflammation can lead to bleeding within the uterine cavity, which then passes through the cervical os. This process generally occurs around the fifth or sixth week of gestation. The bleeding can range in severity from a light pink vaginal discharge to bleeding similar to a menstrual period. However, the duration of implantation bleeding should typically not exceed 1 to 2 days before self-resolving. Because implantation bleeding has the potential to become heavy, patients may mistake this as their menses and not realize they are pregnant.

Subchorionic Hematoma

The placenta may detach from its original site of implantation, creating a space between the uterine wall and the chorionic membrane. Blood will collect and clot in this space forming what is known as a subchorionic hematoma. This process is common, being the most frequent abnormality seen on ultrasonography of a live embryo in the first trimester. The body usually reabsorbs smaller hematomas, but larger hematomas may pass through the cervix, resulting in vaginal bleeding. The outcome of the pregnancy depends on the size of the hematoma and the gestational age of the fetus.4 Subchorionic hematomas may push the placenta further away from its attachment site on the endometrium. Therefore, rates of spontaneous abortion increase as hematoma size increases. Subchorionic hematomas are found to have a worse prognosis in early gestational ages.5 Figure 12.1 demonstrates a subchorionic hematoma in the presence of a live embryo.

Spontaneous Abortion

Spontaneous abortion is a general term that is used to refer to any spontaneous loss of pregnancy before the 20th week of gestation. Table 12.1 outlines the risk factors associated with spontaneous abortion. The clinician should differentiate among the various types of spontaneous abortion when evaluating pregnant patients with vaginal bleeding. A threatened abortion refers to any vaginal bleeding during the first trimester, but without passage of tissue or cervical dilation. These pregnancies continue in the majority of patients. Once cervical dilation occurs in the setting of first trimester bleeding, it is known as an inevitable abortion. Even if a fetal heart rate is identified, these pregnancies will fail. An incomplete abortion occurs when the patient has cervical dilation and has begun to pass some, but not all, of the products of conception. During this time, the patient may have heavy bleeding and severe abdominal cramping as the body attempts to expel the pregnancy.
These patients can hemorrhage severely and may require resuscitation. The patient is diagnosed with a complete abortion once all of the products of conception have passed and the cervix has closed. The patient will have a decrease in abdominal cramping and vaginal bleeding will begin to taper. The clinician should distinguish between an incomplete and complete abortion, as the former may require a dilation and curettage (D&C) if the patient is unable to spontaneously pass the remainder of the products of conception. Complete abortions can be medically managed and do not require surgical intervention. Figure 12.2 shows a spontaneous abortion in progress, with the products of conception located at the cervix.

Figure 12.1: Subchorionic hematoma in the presence of a live embryo. The hematoma tracks along the outside of the gestational sac between the gestational sac and the uterine wall. (Image courtesy of Yale Department of Emergency Medicine, Emergency Ultrasound Section, and Yale New Haven Hospital.)

TABLE 12.1 Risk Factors Associated with Spontaneous Abortion

Risk Factor


Advanced maternal age

Age >35 years

Prior poor obstetric history

Prior spontaneous abortions

Prior pregnancy-related complications

Concurrent comorbidities

Diabetes mellitus

Cystic fibrosis

Systemic lupus erythematous

Chemical exposures



Illicit drugs (i.e., cocaine, heroin)

Anesthetic gases






Infectious exposures


Varicella zoster

Treponema pallidum


Chlamydia trachomatis





In rare cases, patients can experience a missed abortion, in which there is fetal death in the first trimester, but no passage of tissue. The abortion is considered a missed abortion if the patient has not spontaneously begun to pass tissue within 4 weeks of fetal demise. Missed abortions are rare in modern medicine due to the accessibility of home pregnancy tests and ultrasonography. Another rare diagnosis is a septic abortion, which occurs when the fetus or placenta becomes infected. The etiology of the infection is usually a sexually transmitted infection (STI), but can originate from any bacteria that enters the uterine cavity. Symptoms are generally those of spontaneous abortion (abdominal cramping and vaginal bleeding), combined with those of pelvic inflammatory disease such as fevers, leukocytosis, and purulent vaginal discharge. The infection can quickly become life-threatening for the mother due to sepsis and disseminated intravascular coagulation (DIC). Prompt diagnosis, early initiation of broad-spectrum intravenous (IV) antibiotics, and timely evacuation of the products of conception are vital in decreasing maternal mortality.

Gestational Trophoblastic Disease

Gestational trophoblastic disease (GTD), also known as a molar pregnancy, is an abnormal proliferation of trophoblastic cells. GTD is a rare and unusual presentation, with increased prevalence in patients of Asian descent. Additional risk factors include history of a prior molar pregnancy and patients who are of early (less than 15 years) or late (greater than 35 years) child-bearing age.
There are two forms of presentation: a complete mole and a partial mole. A complete mole is the result of duplicated paternal chromosomes (both sets of chromosomes originate from the sperm), and no fetal tissue is present. The tissue that is present is entirely placental. A partial mole is the result of triploidy, with at least one set of chromosomes from maternal and paternal origin. Thus, fetal tissue is present and occasionally the fetus can be viable. Patients will typically present with vaginal bleeding mimicking an abortion, but rather than passing normal tissue, they may describe passing hydropic villi tissue, with a “grape-like” appearance. Hallmarks to making the diagnosis involve ultrasound imaging and quantitative beta human chorionic gonadotropin (β-hCG) testing. Ultrasonography will reveal enlarged cystic ovaries as a result of an abundance of theca lutein cysts and may reveal a mass within the uterine cavity that resembles a “snowstorm appearance.” This term refers to an image of frequent lucent areas scattered among many brighter areas, as shown in Figure 12.3. The patient’s β-hCG level will be much higher than expected for gestational
age, generally greater than 100,000 mIU/mL. Rarely, the presentation can be complicated by preeclampsia and hyperthyroidism. A formal diagnosis of GTD is made through histologic evaluation of the tissue after uterine evacuation. Most cases are benign, but in rare cases, a malignancy, choriocarcinoma, can develop. Malignant cases will cause β-hCG levels to remain high or continue rising after uterine evacuation. Therefore, β-hCG levels should be followed to ensure they are decreasing, in order to prevent missing persistent or metastatic disease. It may take several months for β-hCG levels to drop to an undetectable level after a molar pregnancy.

Figure 12.2: Spontaneous abortion in progress. The gestational sac is visualized outside the uterine cavity at the cervix, with impending complete abortion. (Image courtesy of Yale Department of Emergency Medicine, Emergency Ultrasound Section, and Yale New Haven Hospital.)

Figure 12.3: Molar pregnancy. There is no visualized fetal pole, but instead a “snowstorm appearance” with frequent lucent areas scattered among brighter areas. (Image courtesy of Yale Department of Emergency Medicine, Emergency Ultrasound Section, and Yale New Haven Hospital.)

Ectopic Pregnancy

An ectopic pregnancy occurs in 1% to 2% of all pregnancies and refers to implantation of a pregnancy anywhere outside of the uterus, most commonly in the fallopian tube. Patients generally present with lower abdominal pain localized to one side and vaginal bleeding. Delayed diagnosis can become life-threatening if the fallopian tube ruptures. Therefore, prompt diagnosis is important. Ectopic pregnancies are covered in detail in Chapter 13.

Nonobstetric-Related Bleeding

When evaluating pregnant patients with vaginal bleeding, the clinician should consider nonpregnancy-related etiologies for bleeding such as cervical polyps, cervical ectropion, cervical cancer, vaginal cancer, or vaginal lacerations. Therefore, it is recommended that the provider perform a pelvic examination to evaluate not just the cervical os, but the cervix itself, as well as the vaginal walls and labia. Cervical polyps/lesions should not be removed or sent for biopsy in pregnant patients in the emergency department setting due to increased risk of bleeding in these patients. Pregnant patients have an increased blood supply to support the developing fetus and, therefore, have a higher risk of uncontrolled bleeding. Cervicitis resulting from gonorrhea, chlamydia, or other bacteria can lead to friable cervical tissue, resulting in vaginal bleeding. Therefore, the clinician should consider cervicitis in the differential , as it can often be otherwise asymptomatic. In addition, what patients report as vaginal bleeding may not be vaginal bleeding; rather, it may be bleeding from the urinary or gastrointestinal (GI) tract. Hematuria may result from cystitis, pyelonephritis, and ureterolithiasis. Ureteral stones are more common in pregnant patients than in nonpregnant patients. Urine should be sent for evaluation, and cases of asymptomatic bacteriuria should be treated. There is an association between increased risk of preterm delivery and untreated urinary tract infections.5 GI bleeding can result from external or internal hemorrhoids or anal fissures, which are common problems in pregnant patients due to constipation. Doing an external and, if indicated, internal rectal examination may assist in establishing a diagnosis or ruling out concurrent etiologies for the bleeding.

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Dec 30, 2020 | Posted by in EMERGENCY MEDICINE | Comments Off on Vaginal Bleeding in the First Trimester of Pregnancy

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