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.

Pregnancy detection can be accomplished using one or more various pregnancy tests, which detect hormones generated by the newly formed placenta, serving as biomarkers of pregnancy. Blood and urine tests can detect pregnancy 12 days after implantation. Blood pregnancy tests are more sensitive than urine tests (giving fewer false negatives). Home pregnancy tests are urine tests, and normally detect a pregnancy 12 to 15 days after fertilization. A quantitative blood test can determine approximately the date the embryo was conceived because HCG doubles every 36 to 48 hours. A single test of progesterone levels can also help determine how likely a fetus will survive in those with a threatened miscarriage (bleeding in early pregnancy).

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.

A staging system proposed by fetal surgeon Dr. Ruben Quintero is commonly used to classify the severity of TTTS.

Stage I: A small amount of amniotic fluid (oligohydramnios) is found around the donor twin and a large amount of amniotic fluid (polyhydramnios) is found around the recipient twin.

Stage II: In addition to the description above, the ultrasound is not able to identify the bladder in the donor twin.

Stage III: In addition to the characteristics of Stages I and II, there is abnormal blood flow in the umbilical cords of the twins.

Stage IV: In addition to all of the above findings, the recipient twin has swelling under the skin and appears to be experiencing heart failure (fetal hydrops).

Stage V: In addition to all of the above findings, one of the twins has died. This can happen to either twin. The risk to either the donor or the recipient is roughly equal & is quite high in Stage II or higher TTTS.

The Quintero staging does not provide information about prognosis, and other staging systems have been proposed.

DES (diethylstilbestrol) is a drug that mimics estrogen, a female hormone. From 1938 until 1971 doctors prescribed this drug to help some pregnant women who had had miscarriages or premature deliveries on the theory that miscarriages and premature births occurred because some pregnant women did not produce enough estrogen naturally to sustain the pregnancy for full term . An estimated 5-10 million pregnant women and the children born during this period were exposed to DES. Currently, DES is known to increase the risk of breast cancer, and cause a variety of birth-related adverse outcomes exposed female offsprings such as spontaneous abortion, second-trimester pregnancy loss, preterm delivery, stillbirth, neonatal death, sub/infertility and cancer of reproductive tissues . DES is an important developmental toxicant which links the fetal basis of adult disease.

Fetal alcohol spectrum disorders (FASD) is a term that constitutes the set of conditions that can occur in a person whose mother drank alcohol during the course of pregnancy. These effects can include physical and cognitive problems. FASD patient usually has a combination of these problems. Extent of effect depends on exposure frequency, dose and rate of ethanol elimination from amniotic fluid. FAS disrupts normal development of the fetus, which may cause certain developmental stages to be delayed, skipped, or immaturely developed. Since alcohol elimination is slow in a fetus than in an adult and the fact that they do not have a developed liver to metabolize the alcohol, alcohol levels tend to remain high and stay in the fetus longer. Birth defects associated with prenatal exposure to alcohol can occur in the first three to eight weeks of pregnancy before a woman even knows that she is pregnant.

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.

A laparoscopy or laparotomy can also be performed to visually confirm an ectopic pregnancy. This is generally reserved for women presenting with signs of an acute abdomen and/or hypovolemic shock. Often if a tubal abortion or tubal rupture has occurred, it is difficult to find the pregnancy tissue. A laparoscopy in very early ectopic pregnancy rarely shows a normal looking fallopian tube.

Culdocentesis, in which fluid is retrieved from the space separating the vagina and rectum, is a less commonly performed test that may be used to look for internal bleeding. In this test, a needle is inserted into the space at the very top of the vagina, behind the uterus and in front of the rectum. Any blood or fluid found may have been derived from a ruptured ectopic pregnancy.

Progesterone levels of less than 20 nmol/l have a high predictive value for failing pregnancies, whilst levels over 25 nmol/l are likely to predict viable pregnancies, and levels over 60 nmol/l are strongly so. This may help in identifying failing PULs that are at low risk and thereby needing less follow-up. Inhibin A may also be useful for predicting spontaneous resolution of PUL, but is not as good as progesterone for this purpose.

In addition, there are various mathematical models, such as logistic regression models and Bayesian networks, for the prediction of PUL outcome based on multiple parameters. Mathematical models also aim to identify PULs that are "low risk", that is, failing PULs and IUPs.

Dilation and curettage is sometimes used to diagnose pregnancy location with the aim of differentiating between an EP and a non-viable IUP in situations where a viable IUP can be ruled out. Specific indications for this procedure include either of the following:

- no visible IUP on transvaginal ultrasonography with a serum hCG of more than 2000 IU/ml

- an abnormal rise in hCG level. A rise of 35% over 48 hours is proposed as the minimal rise consistent with a viable intrauterine pregnancy.

- an abnormal fall in hCG level, such as defined as one of less than 20% in 2 days

The data presented is for comparative and illustrative purposes only, and may have been superseded by updated data.

Prenatal cocaine exposure is associated with, for example, premature birth, birth defects and attention deficit disorder.

A recent study on cocaine in Prenatal Drug Exposure(2008) explores how the differences between children who were exposed to drugs prenatal and those with non-drug prenatal exposure differ at the age of five.

Many of the side effects from the children who were exposed to the recreational drug being cocaine had side effects including the following; lack in school readiness, slower impulse control and lack in visual attention.

A number of studies have shown that tobacco use is a significant factor in miscarriages among pregnant smokers, and that it contributes to a number of other threats to the health of the fetus. Smoking and pregnancy, combined, cause twice the risk of premature rupture of membranes, placental abruption and placenta previa. Also, it causes 30% higher odds of the baby being born prematurely.

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.

There have been many assessments of tests aimed at predicting pre-eclampsia, though no single biomarker is likely to be sufficiently predictive of the disorder. Predictive tests that have been assessed include those related to placental perfusion, vascular resistance, kidney dysfunction, endothelial dysfunction, and oxidative stress. Examples of notable tests include:

- Doppler ultrasonography of the uterine arteries to investigate for signs of inadequate placental perfusion. This test has a high negative predictive value among those individuals with a history of prior pre-eclampsia.

- Elevations in serum uric acid (hyperuricemia) is used by some to "define" pre-eclampsia, though it has been found to be a poor predictor of the disorder. Elevated levels in the blood (hyperuricemia) are likely due to reduced uric acid clearance secondary to impaired kidney function.

- Angiogenic proteins such as vascular endothelial growth factor (VEGF) and placental growth factor (PIGF) and anti-angiogenic proteins such as soluble fms-like tyrosine kinase-1 (sFlt-1) have shown promise for potential clinical use in diagnosing pre-eclampsia, though evidence is sufficient to recommend a clinical use for these markers.

- Recent studies have shown that looking for podocytes (specialized cells of the kidney) in the urine has the potential to aid in the prediction of preeclampsia. Studies have demonstrated that finding podocytes in the urine may serve as an early marker of and diagnostic test for preeclampsia.

For many adopted or adults and children in foster care, records or other reliable sources may not be available for review. Reporting alcohol use during pregnancy can also be stigmatizing to birth mothers, especially if alcohol use is ongoing. In these cases, all diagnostic systems use an unknown prenatal alcohol exposure designation. A diagnosis of FAS is still possible with an unknown exposure level if other key features of FASD are present at clinical levels.

Confirmed absence of exposure would apply to planned pregnancies in which no alcohol was used or pregnancies of women who do not use alcohol or report no use during the pregnancy. This designation is relatively rare, as most people presenting for an FASD evaluation are at least "suspected" to have had a prenatal alcohol exposure due to presence of other key features of FASD.

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.

According to current recommendations by the WHO, US CDC and U.S. Department of Health and Human Services (DHHS), all individuals with HIV should begin ART. The recommendation is stronger under the following conditions:

- CD4 count below 350 cells/mm

- High viral load (>100,000 copies/ml)

- Progression of HIV to AIDS

- Development of HIV-related infections and illnesses

- Pregnancy

Women are encouraged to begin treatment as soon as they are diagnosed with HIV. If they are diagnosed prior to pregnancy, they should continue with ART during the pregnancy. If the diagnosis of HIV is made during the pregnancy, ART should be initiated immediately.

Day to day requirements of vitamin d are set around 800-1000IU to maintain healthy levels which in most cases can be provided by sun exposure. Increased amounts are required for individuals who are previously diagnosed as deficient. For those of moderate deficiencies,oral supplementation can be implemented into the diet at levels of 3000-5000 IU per day for a 6- to 12-week period continued by an ongoing reduced dose of 1000- 2000 IU per day to maintain stores in the body.

Severe deficiency is treated through megadose therapy where patients are given doses around 100 000 IU to assist in raising stores faster to ensure physical health in restored to prevent further illness or disease.

Vaccinating the majority of the population is effective at preventing congenital rubella syndrome.

Pregnancy also poses as another high risk factor for vitamin D deficiency. The status levels of vitamin D during the last stages of pregnancy directly impact the new borns first initial months of life. Babies who are exclusively breastfed with minimal exposure to sunlight or supplementation can be at greater risk of vitamin D deficiency,as human milk has minimal vitamin D present. Recommendations for infants of the age 0–12 months are set at 5 ug/day, to assist in preventing rickets in young babies. 80% of dark skinned and or veiled women in Melbourne were found to have serum levels lower than 22.5 nmol/L considering them to be within moderate ranges of vitamin D deficiency.

Congenital rubella syndrome (CRS) can occur in a developing fetus of a pregnant woman who has contracted rubella, usually in the first trimester. If infection occurs 0–28 days before conception, the infant has a 43% risk of being affected. If the infection occurs 0–12 weeks after conception, the risk increases to 51%. If the infection occurs 13–26 weeks after conception, the risk is 23% of the infant being affected by the disease. Infants are not generally affected if rubella is contracted during the third trimester, or 26–40 weeks after conception. Problems rarely occur when rubella is contracted by the mother after 20 weeks of gestation and continues to disseminate the virus after birth.

It was discovered in 1941 by Australian Norman McAlister Gregg.

Cannabis consumption in pregnancy might be associated with restrictions in growth of the fetus, miscarriage, and cognitive deficits. The American Congress of Obstetricians and Gynecologists recommended that cannabis use be stopped before and during pregnancy, Cannabis is the most commonly used illicit substance

among pregnant women.

Although it is difficult to draw firm conclusions, there is some evidence that prenatal exposure to marijuana may be associated with deficits in language, attention, cognitive performance, and delinquent behaviors. THC exposure in rats during the prenatal developmental phase may cause epigenetic changes in gene expression, but there is limited knowledge about the risk for psychiatric disorders because of ethical barriers to studying the developing human brain. While animal studies cannot take into account factors that could influence the effects of cannabis on human maternal exposure, such as environmental and social factors, a 2011 review of rodent studies by Campolongo "et al." said there was "... increasing evidence from animal studies showing that cannabinoid drugs ... induce enduring neurobehavioral abnormalities in the exposed offspring ..." Campolongo "et al." added that "clinical studies report hyperactivity, cognitive impairments and altered emotionality in humans exposed in utero to cannabis". Martin "et al." investigated recent trends in substance abuse treatment admissions for cannabis use in pregnancy in the US, based on Treatment Episodes Data Set (TEDS) from 1992 to 2012, and discovered that, while the proportion of treatment admissions for pregnant women was stable (about 4%), the admissions for women who were pregnant and reported any marijuana use grew from 29% to 43%. A 2015 review found that cannabis use by pregnant mothers impaired brain maturation in their children, and that it also predisposed their children to neurodevelopmental disorders.

There is a lack of good evidence to support the use of any particular intervention for morning sickness.

Australia has a slightly different pregnancy category system from the United Statesnotably the subdivision of Category B. (For drugs in B1, B2 and B3 categories, human data are lacking or inadequate. Subcategorisation is based on animal data, and allocation of a B category does not imply greater safety than C category). The system, as outlined below, was developed by medical and scientific experts based on available evidence of risks associated with taking particular medicines while pregnant. Being general in nature it is not presented as medical advice to health professionals or the public.

Some prescribing guides, such as the Australian Medicines Handbook, are shifting away from using pregnancy categories since, inherent in these categories, there is an implied assumption that the alphabetical code is one of safety when this is not always the case. Categorisation does not indicate which stages of fetal development might be affected and does not convey information about the balance between risks and benefits in a particular situation. Additionally, maintenance of categories is not necessarily maintained or updated with availability of new data.

Thalidomide was originally developed and prescribed as a cure for morning sickness in West Germany, but its use was discontinued when it was found to cause birth defects. The United States Food and Drug Administration never approved thalidomide for use as a cure for morning sickness.