If a small amount of bleeding is seen in early pregnancy a physician may request:

- A quantitative human chorionic gonadotropin (hCG) blood test to confirm the pregnancy or assist in diagnosing a potential miscarriage

- Transvaginal pelvic ultrasonography to confirm that the pregnancy is not outside of the uterus

- Blood type and Rh test to rule out hemolytic disease of the newborn

For bleeding seen in later pregnancy tests may include:

- Complete blood count (CBC) and blood type and screen

- Ultrasound to determine placental location

- Kleihauer-Betke (KB) test especially if there was maternal trauma

The following tests have been promoted as supposedly diagnosing placental insufficiency, but all have been unsuccessful at predicting stillbirth due to placental insufficiency:

- Placental grading

- Amniotic fluid index

- Fetal biophysical profile test scoring

- Doppler velocimetry

- Routine ultrasound scanning

- Detection and management of maternal diabetes mellitus

- Antenatal fetal heart rate monitoring using cardiotocography

- Vibroacoustic stimulation, fetal movement counting

- Home vs. hospital-based bed rest and monitoring in high-risk pregnancy

- In-hospital fetal surveillance unit

- Use of the partograph during labor

- Cardiotocography during labor with or without pulse oximetry

Pregnant patients may have bleeding from the reproductive tract due to trauma, including sexual trauma, neoplasm, most commonly cervical cancer, and hematologic disorders. Molar pregnancy (also called hydatiform mole) is a type of pregnancy where the sperm and the egg have joined within the uterus, but the result is a cyst resembling a grape-like cluster rather than an embryo. Bleeding can be an early sign of this tumor developing.

Foetal demise occurs if the circulating blood volume is decreased significantly. The critical factor deciding the prognosis is the site of the hematoma and not the volume. If discovered antinatally, serial USG and/or Doppler scans is indicated to monitor the size of the hematoma and well-being of the foetus.

Placental abruption is suspected when a pregnant mother has sudden localized abdominal pain with or without bleeding. The fundus may be monitored because a rising fundus can indicate bleeding. An ultrasound may be used to rule out placenta praevia but is not diagnostic for abruption. The diagnosis is one of exclusion, meaning other possible sources of vaginal bleeding or abdominal pain have to be ruled out in order to diagnose placental abruption. Of note, use of magnetic resonance imaging has been found to be highly sensitive in depicting placental abruption, and may be considered if no ultrasound evidence of placental abruption is present, especially if the diagnosis of placental abruption would change management.

History may reveal antepartum hemorrhage. Abdominal examination usually finds the uterus non-tender, soft and relaxed. Leopold's Maneuvers may find the fetus in an oblique or breech position or lying transverse as a result of the abnormal position of the placenta. Malpresentation is found in about 35% cases. Vaginal examination is avoided in known cases of placenta previa.

Although the risk of placental abruption cannot be eliminated, it can be reduced. Avoiding tobacco, alcohol and cocaine during pregnancy decreases the risk. Staying away from activities which have a high risk of physical trauma is also important. Women who have high blood pressure or who have had a previous placental abruption and want to conceive must be closely supervised by a doctor.

The risk of placental abruption can be reduced by maintaining a good diet including taking folic acid, regular sleep patterns and correction of pregnancy-induced hypertension.

It is crucial for women to be made aware of the signs of placental abruption, such as vaginal bleeding, and that if they experience such symptoms they must get into contact with their health care provider/the hospital "without any delay".

Previa can be confirmed with an ultrasound. Transvaginal ultrasound has superior accuracy as compared to transabdominal one, thus allowing measurement of distance between placenta and cervical os. This has rendered traditional classification of placenta previa obsolete.

False positives may be due to following reasons:

- Overfilled bladder compressing lower uterine segment

- Myometrial contraction simulating placental tissue in abnormally low location

- Early pregnancy low position, which in third trimester may be entirely normal due to differential growth of the uterus.

In such cases, repeat scanning is done after an interval of 15–30 minutes.

In parts of the world where ultrasound is unavailable, it is not uncommon to confirm the diagnosis with an examination in the surgical theatre. The proper timing of an examination in theatre is important. If the woman is not bleeding severely she can be managed non-operatively until the 36th week. By this time the baby's chance of survival is as good as at full term.

The exact incidence of maternal mortality related to placenta accreta and its complications is unknown, but has been reported to be as high as 6-7% in case series and surveys.

Clinically, Breus' mole may be asymptomatic, or may present with signs of decreased blood flow to the foetus such as growth restriction and foetal distress. Postnatally, Breus' mole is found in placental examination following live birth or spontaneous abortion. Breus' mole is diagnosed antinatally by ultrasound, where a thick multilobulated hematoma can be seen beneath the chorion. Occasionally, subchorial thrombohematoma may later become intraplacental, making its diagnosis difficult. The mole may be echogenic or hypoechoic depending upon the amount of fresh blood present in it. Breus' mole should be differentiated from vesicular mole and missed abortion in an ultrasound examination.

Pre-eclampsia can mimic and be confused with many other diseases, including chronic hypertension, chronic renal disease, primary seizure disorders, gallbladder and pancreatic disease, immune or thrombotic thrombocytopenic purpura, antiphospholipid syndrome and hemolytic-uremic syndrome. It must be considered a possibility in any pregnant woman beyond 20 weeks of gestation. It is particularly difficult to diagnose when preexisting disease such as hypertension is present. Women with acute fatty liver of pregnancy may also present with elevated blood pressure and protein in the urine, but differ by the extent of liver damage. Other disorders that can cause high blood pressure include thyrotoxicosis, pheochromocytoma, and drug misuse.

In low-risk pregnancies, the association between cigarette smoking and a reduced risk of pre-eclampsia has been consistent and reproducible across epidemiologic studies. High-risk pregnancies (those with pregestational diabetes, chronic hypertension, history of pre-eclampsia in a previous pregnancy, or multifetal gestation) showed no significant protective effect. The reason for this discrepancy is not definitively known; research supports speculation that the underlying pathology increases the risk of preeclampsia to such a degree that any measurable reduction of risk due to smoking is masked. However, the damaging effects of smoking on overall health and pregnancy outcomes outweighs the benefits in decreasing the incidence of preeclampsia. It is recommended that smoking be stopped prior to, during and after pregnancy.

Studies suggest that marijuana use in the months prior to or during the early stages of pregnancy may interfere with normal placental development and consequently increase the risk of preeclampsia.

Another core feature of pre-eclampsia is proteinuria, which is the presence of excess protein in the urine. To determine if proteinuria is present, the urine can be collected and tested for protein; if there is 0.3 grams of protein or more in the urine of a pregnant woman collected over 24 hours, this is one of the diagnostic criteria for pre-eclampsia and raises the suspicion that a seizure is due to eclampsia.

In cases of severe eclampsia or pre-eclampsia, the level of platelets in the blood can be low in a condition termed thrombocytopenia. A complete blood count, or CBC, is a test of the blood that can be performed to check platelet levels.

Other investigations include: renal function test (RFT), liver function tests (LFT), coagulation screen, 24-hour urine creatinine, and fetal/placental ultrasound.

Convulsions during pregnancy that are unrelated to pre-eclampsia need to be distinguished from eclampsia. Such disorders include seizure disorders as well as brain tumor, aneurysm of the brain, and medication- or drug-related seizures. Usually the presence of the signs of severe pre-eclampsia precede and accompany eclampsia, facilitating the diagnosis.

The Kleihauer–Betke test is a blood test used to measure the amount of foetal hemoglobin transferred from a foetus to its mother's bloodstream. It takes advantage of the differential resistance of foetal hemoglobin to acid. A standard blood smear is prepared from the mother's blood, and exposed to an acid bath. This removes adult hemoglobin, but not foetal hemoglobin, from the red blood cells. Subsequent staining, using Shepard's method, makes fetal cells (containing foetal hemoglobin) appear rose-pink in color, while adult red blood cells are only seen as "ghosts". 2000 cells are counted under the microscope and a percentage of foetal to maternal cells is calculated.

Foetal-maternal haemorrhage can also be diagnosed by flow cytometry, using anti-foetal hemoglobin antibodies (anti-HbF).

It is recommended that women with vasa previa should deliver through elective cesarean prior to rupture of the membranes. Given the timing of membrane rupture is difficult to predict, elective cesarean delivery at 35–36 weeks is recommended. This gestational age gives a reasonable balance between the risk of death and that of prematurity. Several authorities have recommended hospital admission about 32 weeks. This is to give the patient proximity to the operating room for emergency delivery should the membranes rupture. Because these patients are at risk for preterm delivery, it is recommended that steroids should be given to promote fetal lung maturation. When bleeding occurs, the patient goes into labor, or if the membranes rupture, immediate treatment with an emergency caesarean delivery is usually indicated.

Depending on gestational age the differential diagnoses for abdominal pregnancy include miscarriage, intrauterine fetal death, placental abruption, an acute abdomen with an intrauterine pregnancy and a fibroid uterus with an intrauterine pregnancy .

With treatment, maternal mortality is about 1 percent, although complications such as placental abruption, acute renal failure, subcapsular liver hematoma, permanent liver damage, and retinal detachment occur in about 25% of women. Perinatal mortality (stillbirths plus death in infancy) is between 73 and 119 per 1000 babies of woman with HELLP, while up to 40% are small for gestational age. In general, however, factors such as gestational age are more important than the severity of HELLP in determining the outcome in the baby.

It is diagnosed by a microscopic examination of the placenta.

Commonly used criteria from Altshuler are: "a minimum of 10 villi, each with 10 or more vascular channels, in 10 or more areas of 3 or more random, non-infarcted placental areas when using a ×10 ocular." The Altshuler criteria are not theoretically rigorous, as they do not define the area. Normal villi have up to five vascular channels.

Advanced abdominal pregnancy refers to situations where the pregnancy continues past 20 weeks of gestation (versus early abdominal pregnancy < 20 weeks). In those situations, live births have been reported in academic journals and also in the lay press where the babies are not uncommonly referred to as 'Miracle babies'. A patient may carry a dead fetus but will not go into labor. Over time, the fetus calcifies and becomes a lithopedion.

It is generally recommended to perform a laparotomy when the diagnosis of an abdominal pregnancy is made. However, if the baby is alive and medical support systems are in place, careful watching could be considered to bring the baby to viability. Women with an abdominal pregnancy will not go into labor. Delivery in a case of an advanced abdominal pregnancy will have to be via laparotomy. The survival of the baby is reduced and high perinatal mortality rates between 40–95% have been reported.

Babies of abdominal pregnancies are prone to birth defects due to compression in the absence of the uterine wall and the often reduced amount of amniotic fluid surrounding the unborn baby. The rate of malformations and deformations is estimated to be about 21%; typical deformations are facial and cranial asymmetries and joint abnormalities and the most common malformations are limb defects and central nervous malformations.

Once the baby has been delivered placental management becomes an issue. In normal deliveries the contraction of uterus provides a powerful mechanism to control blood loss, however, in an abdominal pregnancy the placenta is located over tissue that cannot contract and attempts of its removal may lead to life-threatening blood loss. Thus blood transfusion is frequent in the management of patients with this kind of pregnancy, with others even using tranexamic acid and recombinant factor VIIa, which both minimize blood loss.

Generally, unless the placenta can be easily tied off or removed, it may be preferable to leave it in place and allow for a natural regression. This process may take several months and can be monitored by clinical examination, checking human chorionic gonadotropin levels and by ultrasound scanning (in particular using doppler ultrasonography. Use of methotrexate to accelerate placental regression is controversial as the large amount of necrotic tissue is a potential site for infection, mifepristone has also be used to promote placental regression. Placental vessels have also been blocked by angiographic embolization. Complications of leaving the placenta can include residual bleeding, infection, bowel obstruction, pre-eclampsia (which may all necessitate further surgery) and failure to breast feed due to placental hormones.

Outcome with abdominal pregnancy can be good for the baby and mother, Lampe described an abdominal pregnancy baby and her mother who were well more than 22 years after surgery.

If ongoing and rapid haemorrhage is occurring then immediate delivery of the foetus may be indicated if the fetus is sufficiently developed. If the haemorrhage has already occurred and now stopped, an inutero transfusion of red cells to the foetus may be recommended.

HELLP syndrome can be difficult to diagnose due to the variability of symptoms among pregnant women (frequently a woman will have no symptoms other than general abdominal pain), and early diagnosis is key in reducing morbidity. If not treated in a timely manner, a woman can become critically ill or die due to liver rupture/hemorrhage or cerebral edema.

In a woman with possible HELLP syndrome, a batch of blood tests is performed: a full blood count, a coagulation panel, liver enzymes, electrolytes, and renal function studies. Often, fibrin degradation product levels are determined, which can be elevated. Lactate dehydrogenase is a marker of hemolysis and is elevated (>600 U/l). Proteinuria is present but can be mild.

In one 1995 study, a positive D-dimer test in the presence of pre-eclampsia was reported to be predictive of woman who will develop HELLP syndrome.

The diagnostic criteria for and subtypes of HELLP vary across studies, which "makes comparison of published data difficult." The classifications include:

- Criteria developed at the University of Tennessee:

- HELLP is characterized by hemolysis on peripheral blood smear with serum lactate dehydrogenase >600 IU/l; serum aspartate aminotransferase >70 IU/l; and platelet count <100,000/μl.

- Partial HELLP syndrome is characterized by one or two features of HELLP.

- Criteria developed at the University of Mississippi, as of 1999:

- "The diagnosis of HELLP syndrome required the presence of thrombocytopenia (perinatal platelet nadir ≤150,000 cells/μl), evidence of hepatic dysfunction (increased aspartate aminotransferase level of ≥40 IU/l, increased alanine aminotransferase level of ≥40 IU/l, or both, with increased lactate dehydrogenase (LDH) level of ≥600 IU/l), and evidence of hemolysis (increased LDH level, progressive anemia)..."

- "Class 1 HELLP syndrome featured severe thrombocytopenia with a platelet nadir of ≤50,000 cells/μl, class 2 HELLP syndrome featured moderate thrombocytopenia with a platelet nadir between >50,000 and ≤100,000 cells/μl, and class 3 HELLP syndrome featured mild thrombocytopenia with a platelet nadir between >100,000 and ≤150,000 cells/μl."

- Criteria developed at the University of Mississippi, as of 2006: "For a patient to merit a diagnosis of HELLP syndrome, class 1 requires severe thrombocytopenia (platelets ≤50,000/μl), evidence of hepatic dysfunction (AST [aspartate aminotransferase] and/or ALT [alanine aminotransferase] ≥70 IU/l), and evidence suggestive of hemolysis (total serum LDH ≥600 IU/l); class 2 requires similar criteria except thrombocytopenia is moderate (>50,000 to ≤100,000/μl); and class 3 includes patients with mild thrombocytopenia (platelets >100,000 but ≤150,000/μl), mild hepatic dysfunction (AST and/or ALT ≥40 IU/l), and hemolysis (total serum LDH ≥600 IU/L)."

"Maternal floor infarcts" are "not" considered to be true placental infarcts, as they result from deposition of fibrin around the chorionic villi, i.e. perivillous fibrin deposition.

There is no effective pharmacological treatment for retained placenta. It is useful ensuring the bladder is empty. However, ergometrine should not be given as it causes tonic uterine contractions which may delay placental expulsion. Controlled cord traction has been recommended as a second alternative after more than 30 minutes have passed after stimulation of uterine contractions, provided the uterus is contracted. Manual extraction may be required if cord traction also fails, or if heavy ongoing bleeding occurs. Very rarely a curettage is necessary to ensure that no remnants of the placenta remain (in rare conditions with very adherent placenta such as a placenta accreta).

However, in birth centers and attended home birth environments, it is common for licensed care providers to wait for the placenta's birth up to 2 hours in some instances.

A placental infarction results from the interruption of blood supply to a part of the placenta, causing its cells to die.

Small placental infarcts, especially at the edge of the placental disc, are considered to be normal at term. Large placental infarcts are associated with vascular abnormalities, e.g. hypertrophic decidual vasculopathy, as seen in hypertension. Very large infarcts lead to placental insufficiency and may result in fetal death.