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

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.

The most rapidly effective treatment in infants with severe hemorrhage and/or severe thrombocytopenia (30,000 μL) an infusion of (1 g/kg/day for two days) in the infant has been shown to rapidly increase platelet count and reduce the risk of related injury.

After a first affected pregnancy, if a mother has plans for a subsequent pregnancy, then the mother and father should be typed for platelet antigens and the mother screened for alloantibodies. Testing is available through reference laboratories (such as ). testing of the father can be used to determine zygosiity of the involved antigen and therefore risk to future pregnancies (if homozygous for the antigen, all subsequent pregnancies will be affected, if heterozygous, there is an approximate 50% risk to each subsequent pregnancy). During subsequent pregnancies, the genotype of the fetus can also be determined using amniotic fluid analysis or maternal blood as early as 18 weeks gestation to definitively determine the risk to the fetus.

Maternal and paternal platelet antigen phenotyping and screening of the maternal serum for anti-platelet antibodies can be performed.

Additionally, platelet antigen genotyping can be performed on the maternal and paternal blood to determine the exact nature of the incompatibility.

Neonatal platelet counts on laboratory testing are typically under 20,000 μL. Higher counts may suggest a different diagnosis, such as maternal immune thrombocytopenic purpura.

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.

Most women with a PUL are followed up with serum hCG measurements and repeat TVS examinations until a final diagnosis is confirmed. Low-risk cases of PUL that appear to be failing pregnancies may be followed up with a urinary pregnancy test after 2 weeks and get subsequent telephone advice. Low-risk cases of PUL that are likely intrauterine pregnancies may have another TVS in 2 weeks to access viability. High-risk cases of PUL require further assessment, either with a TVS within 48 h or additional hCG measurement.

Where no intrauterine pregnancy is seen on ultrasound, measuring β-human chorionic gonadotropin (β-hCG) levels may aid in the diagnosis. The rationale is that a low β-hCG level may indicate that the pregnancy is intrauterine but yet too small to be visible on ultrasonography. While some physicians consider that the threshold where an intrauterine pregnancy should be visible on transvaginal ultrasound is around 1500 IU/ml of β-hCG, a review in the JAMA Rational Clinical Examination Series showed that there is no single threshold for the β-human chorionic gonadotropin that confirms an ectopic pregnancy. Instead, the best test in a pregnant woman is a high resolution transvaginal ultrasound. The presence of an adnexal mass in the absence of an intrauterine pregnancy on transvaginal sonography increases the likelihood of an ectopic pregnancy 100-fold (LR+ 111). When there are no adnexal abnormalities on transvaginal sonography, the likelihood of an ectopic pregnancy decreases (LR- 0.12). An empty uterus with levels higher than 1500 IU/ml may be evidence of an ectopic pregnancy, but may also be consistent with an intrauterine pregnancy which is simply too small to be seen on ultrasound. If the diagnosis is uncertain, it may be necessary to wait a few days and repeat the blood work. This can be done by measuring the β-hCG level approximately 48 hours later and repeating the ultrasound. The serum hCG ratios and logistic regression models appear to be better than absolute single serum hCG level. If the β-hCG falls on repeat examination, this strongly suggests a spontaneous abortion or rupture. The fall in serum hCG over 48 hours may be measured as the hCG ratio, which is calculated as:

formula_1

An hCG ratio of 0.87, that is, a decrease in hCG of 13% over 48 hours, has a sensitivity of 93% and specificity of 97% for predicting a failing PUL. The majority of cases of ectopic pregnancy will have serial serum hCG levels that increase more slowly than would be expected with an IUP (that is, a "suboptimal rise"), or decrease more slowly than would be expected with a failing PUL. However, up to 20% of cases of ectopic pregnancy have serum hCG doubling times similar to that of an IUP, and around 10% of EP cases have hCG patterns similar to a failing PUL.

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.

Obstetric ultrasonography can detect fetal abnormalities, detect multiple pregnancies, and improve gestational dating at 24 weeks. The resultant estimated gestational age and due date of the fetus are slightly more accurate than methods based on last menstrual period. Ultrasound is used to measure the nuchal fold in order to screen for Downs syndrome.

Amniocentesis and chorionic villus sampling are procedures conducted to assess the fetus. A sample of amniotic fluid is obtained by the insertion of a needle through the abdomen and into the uterus. Chorionic villus sampling is a similar procedure with a sample of tissue removed rather than fluid. These procedures are not associated with pregnancy loss during the second trimester but they are associated with miscarriages and birth defects in the first trimester. Miscarriage caused by invasive prenatal diagnosis (chorionic villus sampling (CVS) and amniocentesis) is rare (about 1%).

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".

Medical imaging may be indicated in pregnancy because of pregnancy complications, intercurrent diseases or routine prenatal care. Magnetic resonance imaging (MRI) without MRI contrast agents as well as obstetric ultrasonography are not associated with any risk for the mother or the fetus, and are the imaging techniques of choice for pregnant women. Projectional radiography, X-ray computed tomography and nuclear medicine imaging result in some degree of ionizing radiation exposure, but in most cases the absorbed doses are not associated with harm to the baby. At higher dosages, effects can include miscarriage, birth defects and intellectual disability.

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.

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.

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.

A review article in The New England Journal of Medicine based on a consensus meeting of the Society of Radiologists in Ultrasound in America (SRU) has suggested that miscarriage should be diagnosed only if any of the following criteria are met upon ultrasonography visualization:

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.

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)."

Pregnancy does not have an adverse effect on the course of Behçet's disease and may possibly ameliorate its course. Still, there is a substantial variability in clinical course between patients and even for different pregnancies in the same patient. Also, the other way around, Behçet's disease confers an increased risk of pregnancy complications, miscarriage and Cesarean section.

Thyroid disease in pregnancy can, if uncorrected, cause adverse effects on fetal and maternal well-being. The deleterious effects of thyroid dysfunction can also extend beyond pregnancy and delivery to affect neurointellectual development in the early life of the child. Demand for thyroid hormones is increased during pregnancy which may cause a previously unnoticed thyroid disorder to worsen. The most effective way of screening for thyroid dysfunction is not known. A review found that more women were diagnosed with thyroid dysfunction when all pregnant women were tested instead of just testing those at ‘high-risk’ of thyroid problems (those with family history, signs or symptoms). Finding more women with thyroid dysfunction meant that the women could have treatment and management through their pregnancies. However the outcomes of the pregnancies were surprisingly similar so more research is needed to look at the effects of screening all women for thyroid problems.

Generally gynecologic hemorrhage does not arise out of nowhere. Regular gynecologic examinations, cancer screening, and contraceptive measures go a long way in preventing and forestalling unsuspected acute bleeding events.

A history will establish if the condition is acute or chronic, and if external circumstances are involved. A gynecologic examination is usually complemented by a gynecologic ultrasonography. A blood count determines the degree of anemia and may point out bleeding problems. The pregnancy test is important, particularly as bleeding in early pregnancy presents as gynecological hemorrhage and ectopic pregnancy can be fatal.

Diagnosis is broadly classified into supportive and definitive investigations:

In 2011, the International Federation of Gynaecology and Obstetrics (FIGO) recognized two systems designed to aid research, education, and clinical care of women with abnormal uterine bleeding (AUB) in the reproductive years.

A possible pregnancy must be considered in any woman who has abdominal pain or abnormal vaginal bleeding. A heterotopic pregnancy may have similar signs and symptoms as a normal intrauterine pregnancy, a normal intrauterine pregnancy and a ruptured ovarian cyst, a corpus luteum, or appendicitis. Blood tests and ultrasound can be used to differentiate these conditions.

The Centers for Disease Control and Prevention (CDC) recommends HIV testing for all pregnant women as a part of routine prenatal care. The test is usually performed in the first trimester of pregnancy with other routine laboratory tests. HIV testing is recommended because HIV-infected women who do not receive testing are more likely to transmit the infection to their children.

HIV testing may be offered to pregnant women on an "opt-in" or an "opt-out" basis. In the "opt-in" model, women are counseled on HIV testing and elect to receive the test by signing a consent form. In the "opt-out" model, the HIV test is automatically performed with other routine prenatal tests. If a woman does not want to be tested for HIV, she must specifically refuse the test and sign a form declining testing. The CDC recommends "opt-out" testing for all pregnant women because it improves disease detection and treatment and helps reduce transmission to children.

If a woman chooses to decline testing, she will not receive the test. However, she will continue to receive HIV counseling throughout the pregnancy so that she may be as informed as possible about the disease and its impact. She will be offered HIV testing at all stages of her pregnancy in case she changes her mind.

HIV testing begins with a screening test. The most common screening test is the rapid HIV antibody test which tests for HIV antibodies in blood, urine, or oral fluid. HIV antibodies are only produced if an individual is infected with the disease. Therefore, presence of the antibodies is indicative of an HIV infection. Sometimes, however, a person may be infected with HIV but the body has not produced enough antibodies to be detected by the test. If a woman has risk factors for HIV infection but tests negative on the initial screening test, she should be retested in 3 months to confirm that she does not have HIV. Another screening test that is more specific is the HIV antigen/antibody test. This is a newer blood test that can detect HIV infection quicker than the antibody test because it detects both virus particles and antibodies in the blood.

Any woman who has a positive HIV screening test must receive follow-up testing to confirm the diagnosis. The follow-up test can differentiate HIV-1 from HIV-2 and is a more specific antibody test. It may also detect the virus directly in the bloodstream.