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.

Doppler flow study is a type of ultrasound that measures the amount of blood flowing in and out of the placenta.

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.

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 .

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

A biophysical profile checks for the baby's heart rate, muscle tone, movement, breathing, and the amount of amniotic fluid surrounding the baby.

To diagnose the rare primary abdominal pregnancy, Studdiford's criteria need to be fulfilled: tubes and ovaries should be normal, there is no abnormal connection (fistula) between the uterus and the abdominal cavity, and the pregnancy is related solely to the peritoneal surface without signs that there was a tubal pregnancy first. Studdiford's criteria were refined in 1968 by Friedrich and Rankin to include microscopic findings.

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.

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.

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".

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

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.

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.

Miscarriage is the loss of a pregnancy prior to 20 weeks. In the UK miscarriage is defined as the loss of a pregnancy during the first 23 weeks.

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.

Oxytocin is typically used right after the delivery of the baby to prevent PPH. Misoprostol may be used in areas where oxytocin is not available. Early clamping of the umbilical cord does not decrease risks and may cause anemia in the baby, thus is usually not recommended.

Active management of the third stage is a method of shortening the stage between when the baby is born and when the placenta is delivered. This stage is when the mother is at risk of having a PPH. Active management involves giving a drug which helps the uterus contract before delivering the placenta by a gentle but sustained pull on the umbilical cord whilst exerting upward pressure on the lower abdomen to support the uterus.

Another method of active management which is not recommended now is fundal pressure. A review into this method found no research and advises controlled cord traction because fundal pressure can cause the mother unnecessary pain. Allowing the cord to drain appears to shorten the third stage and reduce blood loss but evidence around this subject is not strong enough to draw solid conclusions.

Nipple stimulation and breastfeeding triggers the release of natural oxytocin in the body, therefore it is thought that encouraging the baby to suckle soon after birth may reduce the risk of PPH for the mother. A review looking into this did not find enough good research to say whether or not nipple stimulation did reduce PPH. More research is needed to answer this question.

Some disorders and conditions can mean that pregnancy is considered high-risk (about 6-8% of pregnancies in the USA) and in extreme cases may be contraindicated. High-risk pregnancies are the main focus of doctors specialising in maternal-fetal medicine.

Serious pre-existing disorders which can reduce a woman's physical ability to survive pregnancy include a range of congenital defects (that is, conditions with which the woman herself was born, for example, those of the heart or , some of which are listed above) and diseases acquired at any time during the woman's life.

Vasa previa is seen more commonly with velamentous insertion of the umbilical cord, accessory placental lobes (succenturiate or bilobate placenta), multiple gestation, IVF pregnancy. In IVF pregnancies incidences as high as one in 300 have been reported. The reasons for this association are not clear, but disturbed orientation of the blastocyst at implantation, vanishing embryos and the increased frequency of placental morphological variations in in vitro fertilisation pregnancies have all been postulated.

When the antepartum diagnosis of placenta accreta is made, it is usually based on ultrasound findings in the second or third trimester. Sonographic findings that may be suggestive of placenta accreta include:

1. Loss of normal hypoechoic retroplacental zone

2. Multiple vascular lacunae (irregular vascular spaces) within placenta, giving "Swiss cheese" appearance

3. Blood vessels or placental tissue bridging uterine-placental margin, myometrial-bladder interface, or crossing the uterine serosa

4. Retroplacental myometrial thickness of <1 mm

5. Numerous coherent vessels visualized with 3-dimensional power Doppler in basal view

Although there are isolated case reports of placenta accreta being diagnosed in the first trimester or at the time of abortion <20 weeks' gestational age, the predictive value of first-trimester ultrasound for this diagnosis remains unknown. Women with a placenta previa or "low-lying placenta" overlying a uterine scar early in pregnancy should undergo follow-up imaging in the third trimester with attention to the potential presence of placenta accreta.

The World Health Organization recommends the use of a device called the non-pneumatic anti-shock garment (NASG) for use in delivery activities outside of a hospital setting, the aim being to improve shock in a mother with obstetrical bleeding long enough to reach a hospital.

The presence of subchorionic bleeding around the gestational sac does not have a significant association with miscarriage overall. However, the case of intrauterine hematoma observed before 9 weeks of gestational age has been associated with an increased risk of miscarriage. In one study women who complied with instructions for bed rest for the duration of bleeding had a lower rate of miscarriage and a higher rate of term pregnancy than non-compliant women. The study had several limitations; results were severely confounded by inherent differences between compliant and non-compliant women.

The diagnosis is strongly suggested by ultrasound (sonogram), but definitive diagnosis requires histopathological examination. On ultrasound, the mole resembles a bunch of grapes ("cluster of grapes" or "honeycombed uterus" or "snow-storm"). There is increased trophoblast proliferation and enlarging of the chorionic villi. Angiogenesis in the trophoblasts is impaired as well.

Sometimes symptoms of hyperthyroidism are seen, due to the extremely high levels of hCG, which can mimic the normal Thyroid-stimulating hormone (TSH).

In humans, retained placenta is generally defined as a placenta that has not undergone placental expulsion within 30 minutes of the baby’s birth where the third stage of labor has been managed actively.

Risks of retained placenta include hemorrhage and infection. After the placenta is delivered, the uterus should contract down to close off all the blood vessels inside the uterus. If the placenta only partially separates, the uterus cannot contract properly, so the blood vessels inside will continue to bleed. A retained placenta thereby leads to hemorrhage.

The diagnosis is made in asymptomatic pregnant women either by inspection seeing a bluish discolored cervix or, more commonly, by obstetric ultrasonography. A typical non-specific symptom is vaginal bleeding during pregnancy. Ultrasound will show the location of the gestational sac in the cervix, while the uterine cavity is "empty". Cervical pregnancy can be confused with a miscarriage when pregnancy tissue is passing through the cervix.

Histologically the diagnosis has been made by Rubin’s criteria on the surgical specimen: cervical glands are opposite the trophoblastic tissue, the trophoblastic attachment is below the entrance of the uterine vessels to the uterus or the anterior peritoneal reflection, and fetal elements are absent from the uterine corpus. As many pregnancies today are diagnosed early and no hysterectomy is performed, Rubin's criteria can often not be applied.

This is equivalent of zero intervention. It has been associated with almost 100% mortality rate of one or all fetuses. Exceptions to this include patients that are still in Stage 1 TTTS and are past 22 weeks gestation.