Bleeding during the second and third trimester has special clinical significance, encompassing problems that are quite serious and those that are normal or expected. It’s important to be able to distinguish between them.

One normal occurrence of bleeding is called Bloody show

As the cervix thins and begins to dilate in preparation for labor, the patient may notice the passage of some bloody mucous. This is a normal event during the days leading up to the onset of labor at term. If this is the only symptom, the patient can be reassured of its normalcy. If the patient is also having significant contractions, she should be evaluated for the possible onset of labor.

If this bloody mucous show appears prior to full term, then it may signal the imminent onset of preterm labor. These patients are evaluated for possible pre-term labor.

Bleeding that is more than bloody mucous (bright red, no mucous, passage of clots) requires further evaluation.

Cervicitis and cervical trauma ARE relatively innocent causes for bleeding.

During pregnancy, the cervix becomes softer, more fragile, and more vulnerable to the effects of trauma and microbes.

Cervical ectropion, in which the soft, mucous- producing endocervical mucosa grows out onto the exocervix is common among pregnant women. This friable endocervical epithelium bleeds easily when touched. This situation can lead to spotting after intercourse, a vaginal examination, or placement of a vaginal speculum.

Cervical ectropion also can lead to cervicitis. The normal squamous cell cervical epithelium is relatively resistant to bacterial attack. The endocervical mucosa is less resistant. If infected, the cervical ectropion is even more likely to bleed if touched.

These changes are usually easily seen during a vaginal speculum exam.

Placental abruption can be a very serious cause for bleeding at this time.

Placental abruption is also known as a premature separation of the placenta. All placentas normally detach from the uterus shortly after delivery of the baby. If any portion of the placenta detaches prior to birth of the baby, this is called a placental abruption. Placental abruption occurs in about 1% of all pregnancies.

A placental abruption may be partial or complete.

A complete abruption is a disastrous event. The fetus will die within 15-20 minutes. The mother will die soon afterward, from either blood loss or the coagulation disorder which often Women with complete placental abruptions are generally desperately ill with severe abdominal pain, shock, hemorrhage, a rigid and unrelaxing uterus.
Partial placental abruptions may range from insignificant to the striking abnormalities seen in complete abruptions.

Clinically, an abruption presents after 20 weeks gestation with abdominal cramping, uterine tenderness, contractions, and usually some vaginal bleeding. Occasionally, the blood loss is trapped inside the uterus. These cases are called “concealed abruptions.”

A number of factors are associated with an increased risk of placental abruption.

Prior placental abruption roughly doubles the risk of abruption in a subsequent pregnancy.

Abdominal trauma, including motor vehicle accidents are associated with placental abruption.

Many previous babies, Low socio-economic status , and Poor nutrition have an association.

Use of cocaine or its derivatives and Cigarette smoking , as well as Maternal hypertension, including pre-eclampsia and eclampsia are all associated with abruption.

Abnormalities in amniotic fluid volume, including Polyhydramnios and Oligohydramnios have the association.

Finally, Multiple gestations are associated with abruption.

Abruptions are often diagnosed clinically, based on the symptoms of bright red vaginal bleeding, frequent contractions and uterine tenderness.

There are no laboratory findings that are specific for placental abruption. In mild cases, laboratory tests are usually normal. In more advanced cases, the Hgb and Hct go down, as do the platelets and fibrinogen (due to the massive bleeding and consumption of coagulation factors) while fibrin split products go up. Fetal RBCs may be identified in the maternal blood.

In the case of large abruptions, ultrasound may identify a retroplacental blood clot. In milder cases, ultrasound scans are frequently normal.

Mild abruptions may resolve with bedrest and observation, but the moderate to severe abruptions generally result in rapid labor and delivery of the baby. If fetal distress is present (and it sometime is), an emergency cesarean section may be needed.

Because so many coagulation factors are consumed with the internal hemorrhage, coagulopathy is common. This means that even after delivery, the patient may continue to bleed because she can no longer effectively clot. In a hospital setting, this can be treated with infusions of platelets, fresh frozen plasma and cryoprecipitate. If these products are unavailable, fresh whole blood transfusion can give good results.

Placenta previa is another potentially disastrous cause of bleeding during the second and third trimester.

Normally, the placenta is attached to the uterus in an area remote from the cervix. Sometimes, the placenta is located in such a way that it covers the cervix. This is called a placenta previa.

There are degrees of placenta previa:

A complete placenta previa means the entire cervix is This positioning makes it impossible for the fetus to pass through the birth canal without causing maternal hemorrhage. This situation can only be resolved through cesarean section.
A marginal placenta previa means that only the margin or edge of the placenta is covering the In this condition, it may be possible to achieve a vaginal delivery if the maternal bleeding is not too great and the fetal head exerts enough pressure on the placenta to push it out of the way and tamponade bleeding which may occur.
Clinically, these patients present after 20 weeks with painless vaginal bleeding, usually mild. This is in contrast to patients with placental abruption, who usually experience significant pain and contractions. An old rule of thumb is that the first bleed from a placenta previa is not very heavy. For this reason, the first bleed is sometimes called a “sentinel bleed.”

Later episodes of bleeding can be very substantial and very dangerous. This can lead to hypovolemic shock and maternal death. Because a pelvic exam may provoke further bleeding it is important to avoid a vaginal or rectal examination in pregnant women during the second half of their pregnancy unless you are certain there is no placenta previa.

Factors associated with an increased risk of placenta previa include:

High maternal parity, Increased maternal age, Previous cesarean section, Previous uterine surgery, and Uterine malformations.
It may also be associated with the use of cocaine or its derivatives, Cigarette smoking, scherman’s syndrome, and Large numbers of D&Cs.
The location of the placenta is best established by ultrasound. If ultrasound is not available, one reliable clinical method of ruling out placenta previa is to check for fetal head engagement just above the pubic symphysis.

Using a thumb and forefinger and pressing into the maternal abdomen, the fetal head can be palpated. If it is deeply engaged in the pelvis, it is basically impossible for a placenta previa to be present because there is not enough room in the birth canal for both the fetal head and a placenta previa. An x-ray of the pelvis (pelvimetry) can likewise rule out a placenta previa, but only if the fetal head is deeply engaged. Otherwise, an x-ray will usually not show the location of the placenta.

Clinical approach to third trimester bleeding

The clinical approach depends on the clinical situation. For example:

A 3rd trimester patient who is actively hemorrhaging bright red blood should go directly to the operating room for a cesarean section to deliver her from the placental abruption or placenta previa. While en route to the OR, call for blood transfusions and labs to determine coagulopathy.
A patient at term with regular contractions and a small amount of bloody mucous can be examined vaginally after confirming (through ultrasound or clinical exam of the abdomen) that there is no placenta previa.
Patients with bright red vaginal bleeding that is less than hemorrhage should be carefully evaluated prior to performing a pelvic Ultrasound can be helpful in locating the placenta and looking for retroplacental blood clot. Laboratory tests for coagulopathy can be helpful. Hgb is useful, not to determine whether to transfuse or not (that is a clinical, not laboratory decision), but to indicate the margin of safety available to the clinician in caring for this patient.
Continuous electronic fetal monitoring is important to determine the degree of tolerance the fetus has for this bleeding and the extent to which uteroplacental circulation has been disrupted. After ruling out a placenta previa, examine the patient with a speculum to determine the source of the bleeding (from the cervical os? from the surface of the cervix? from a laceration of the vaginal wall? etc.)