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.

The data presented is for comparative and illustrative purposes only, and may have been superseded by updated data.

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%).

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.

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:

According to American Congress of Obstetricians and Gynecologists, the main methods to calculate gestational age are:

- Directly calculating the days since the beginning of the last menstrual period.

- Early obstetric ultrasound, comparing the size of an embryo or fetus to that of a reference group of pregnancies of known gestational age (such as calculated from last menstrual periods), and using the mean gestational age of other embryos or fetuses of the same size. If the gestational age as calculated from an early ultrasound is contradictory to the one calculated directly from the last menstrual period, it is still the one from the early ultrasound that is used for the rest of the pregnancy.

- In case of in vitro fertilization, calculating days since oocyte retrieval or co-incubation and adding 14 days.

The apprehension is not necessarily data driven and is a cautionary response to the lack of clinical studies in pregnant women. The indication is a trade-off between the adverse effects of the drug, the risks associated with intercurrent diseases and pregnancy complications, and the efficiency of the drug to prevent or ameliorate such risks. In some cases, the use of drugs in pregnancy carries benefits that outweigh the risks. For example, high fever is harmful for the fetus in the early months, thus the use of paracetamol (acetaminophen) is generally associated with lower risk than the fever itself. Similarly, diabetes mellitus during pregnancy may need intensive therapy with insulin to prevent complications to mother and baby. Pain management for the mother is another important area where an evaluation of the benefits and risks is needed. NSAIDs such as Ibuprofen and Naproxen are probably safe for use for a short period of time, 48–72 hours, once the mother has reached the second trimester. If taking aspirin for pain management the mother should never take a dose higher than 100 mg.

A woman's risk of having a baby with chromosomal abnormalities increases with her age. Down syndrome is the most common chromosomal birth defect, and a woman's risk of having a baby with Down syndrome is:

- At age 20, 1 in 1,441

- At age 25, 1 in 1,383

- At age 30, 1 in 959

- At age 35, 1 in 338

- At age 40, 1 in 84

- At age 45, 1 in 32

- At age 50, 1 in 44

U.S. Code of Federal Regulations requires that certain drugs and biological products must be labelled very specifically with respect to their effects on pregnant populations, including a definition of a "pregnancy category." These rules are enforced by the Food and Drug Administration (FDA). The FDA does not regulate labelling for all hazardous and non-hazardous substances and some potentially hazardous substances are not assigned a pregnancy category.

Australia’s categorisations system takes into account the birth defects, the effects around the birth or when the mother gives birth, and problems that will arise later in the child's life caused from the drug taken. The system places them into a category of their severity that the drug could cause to the infant when it crosses the placenta(Australian Government, 2014).

People infected with CMV develop antibodies to it, initially IgM later IgG indicating current infection and immunity respectively. If the virus is detected in the blood, saliva, urine or other body tissues, it means that the person has an active infection.

When infected with CMV, most women have no symptoms, but some may have symptoms resembling mononucleosis. Women who develop a mononucleosis-like illness during pregnancy should consult their medical provider.

The Centers for Disease Control and Prevention (CDC) does not recommend routine maternal screening for CMV infection during pregnancy because there is no test that can definitively rule out primary CMV infection during pregnancy. Women who are concerned about CMV infection during pregnancy should practice CMV prevention measures.Considering that the CMV virus is present in saliva, urine, tears, blood, mucus, and other bodily fluids, frequent hand washing with soap and water is important after contact with diapers or oral secretions, especially with a child who is in daycare or interacting with other young children on a regular basis.

A diagnosis of congenital CMV infection can be made if the virus is found in an infant's urine, saliva, blood, or other body tissues during the first week after birth. Antibody tests cannot be used to diagnose congenital CMV; a diagnosis can only be made if the virus is detected during the first week of life. Congenital CMV cannot be diagnosed if the infant is tested more than one week after birth.

Visually healthy infants are not routinely tested for CMV infection although only 10–20% will show signs of infection at birth though up to 80% may go onto show signs of prenatal infection in later life. If a pregnant woman finds out that she has become infected with CMV for the first time during her pregnancy, she should have her infant tested for CMV as soon as possible after birth.

A woman's fertility peaks lasts during the twenties and first half of thirties, after which it starts to decline, with advanced maternal age causing an increased risk of female infertility.

According to Henri Leridon, PhD, an epidemiologist with the French Institute of Health and Medical Research, of women trying to get pregnant, without using fertility drugs or in vitro fertilization:

- At age 30

- 75% will have a conception ending in a live birth within one year

- 91% will have a conception ending in a live birth within four years.

- At age 35

- 66% will have a conception ending in a live birth within one year

- 84% will have a conception ending in a live birth within four years.

- At age 40

- 44% will have a conception ending in a live birth within one year

- 64% will have a conception ending in a live birth within four years.

There are 3 possible ways to test the fetal antigen status. Free Cell DNA, Amniocentesis, and Chorionic Villus Sampling. Of the three, CVS is no longer used due to risk of worsening the maternal antibody response. Once antigen status has been determined, assessment may be done with MCA scans.

- Free Cell DNA can be run on certain antigens. Blood is taken from the mother, and using PCR, can detect the K, C, c, D, and E alleles of fetal DNA. This blood test is non-invasive to the fetus and is an easy way of checking antigen status and risk of HDN. Testing has proven very accurate and is routinely done in the UK at the International Blood Group Reference Laboratory in Bristol. Sanequin laboratory in Amsterdam, Netherlands also performs this test. For US patients, blood may be sent to either of the labs. In the US, Sensigene is done by Sequenome to determine fetal D status. Sequenome does not accept insurance in the US, but US and Canadian patients have had insurance cover the testing done overseas.

- Amniocentesis is another recommended method for testing antigen status and risk for HDN. Fetal antigen status can be tested as early as 15 weeks by PCR of fetal cells.

- CVS is possible as well to test fetal antigen status but is not recommended. CVS carries a higher risk of fetal maternal hemorrhage and can raise antibody titers, potentially worsening the antibody effect.

MCA scans Middle cerebral artery - peak systolic velocity is changing the way sensitized pregnancies are managed. This test is done noninvasively with ultrasound. By measuring the peak velocity of blood flow in the middle cerebral artery, a MoM (multiple of the median) score can be calculated. MoM of 1.5 or greater indicates severe anemia and should be treated with IUT.

Blood is generally drawn from the father to help determine fetal antigen status. If he is homozygous for the antigen, there is a 100% chance of all offspring in the pairing to be positive for the antigen and at risk for HDN. If he is heterozygous, there is a 50% chance of offspring to be positive for the antigen. This test can help with knowledge for the current baby, as well as aid in the decision about future pregnancies. With RhD, the test is called the RhD genotype. With RhCE, and Kell antigen it is called an antigen phenotype.

Most healthy people working with infants and children face no special risk from CMV infection. However, for women of child-bearing age who previously have not been infected with CMV, there is a potential risk to the developing unborn child (the risk is described above in the Pregnancy section). Contact with children who are in day care, where CMV infection is commonly transmitted among young children (particularly toddlers), may be a source of exposure to CMV. Since CMV is transmitted through contact with infected body fluids, including urine and saliva, child care providers (meaning day care workers, special education teachers, as well as mothers) should be educated about the risks of CMV infection and the precautions they can take. Day care workers appear to be at a greater risk than hospital and other health care providers, and this may be due in part to the increased emphasis on personal hygiene in the health care setting.

Recommendations for individuals providing care for infants and children:

- Employees should be educated concerning CMV, its transmission, and hygienic practices, such as handwashing, which minimize the risk of infection.

- Susceptible nonpregnant women working with infants and children should not routinely be transferred to other work situations.

- Pregnant women working with infants and children should be informed of the risk of acquiring CMV infection and the possible effects on the unborn child.

- Routine laboratory testing for CMV antibody in female workers is not specifically recommended due to its high occurrence, but can be performed to determine their immune status.

Blood is generally drawn from the father to help determine fetal antigen status. If he is homozygous for the antigen, there is a 100% chance of all offspring in the pairing to be positive for the antigen and at risk for HDN. If he is heterozygous, there is a 50% chance of offspring to be positive for the antigen. This test can help with knowledge for the current baby, as well as aid in the decision about future pregnancies. With RhD, the test is called the RhD genotype. With RhCE, and Kell antigen it is called an antigen phenotype.

In some cases, the direct coombs will be negative but severe, even fatal HDN can occur. An indirect coombs needs to be run in cases of anti-C, anti-c, and anti-M. Anti-M also recommends antigen testing to rule out the presence of HDN.

- Hgb - the infant’s hemoglobin should be tested from cord blood.

- Reticulocyte count - Reticulocytes are elevated when the infant is producing more blood to combat anemia. A rise in the retic count can mean that an infant may not need additional transfusions. Low retic is observed in infants treated with IUT and in those with HDN from anti-Kell

- Neutrophils - as Neutropenia is one of the complications of HDN, the neutrophil count should be checked.

- Thrombocytes - as thrombocytopenia is one of the complications of HDN, the thrombocyte count should be checked.

- Bilirubin should be tested from cord blood.

- Ferritin - because most infants affected by HDN have iron overload, a ferritin must be run before giving the infant any additional iron.

- Newborn Screening Tests - Transfusion with donor blood during pregnancy or shortly after birth can affect the results of the Newborn Screening Tests. It is recommended to wait and retest 10–12 months after last transfusion. In some cases, DNA testing from saliva can be used to rule out certain conditions.

Most Rh disease can be prevented by treating the mother during pregnancy or promptly (within 72 hours) after childbirth. The mother has an intramuscular injection of anti-Rh antibodies (Rho(D) immune globulin). This is done so that the fetal rhesus D positive erythrocytes are destroyed before the immune system of the mother can discover them and become sensitized. This is passive immunity and the effect of the immunity will wear off after about 4 to 6 weeks (or longer depending on injected dose) as the anti-Rh antibodies gradually decline to zero in the maternal blood.

It is part of modern antenatal care to give all rhesus D negative pregnant women an anti-RhD IgG immunoglobulin injection at about 28 weeks gestation (with or without a booster at 34 weeks gestation). This reduces the effect of the vast majority of sensitizing events which mostly occur after 28 weeks gestation. Giving Anti-D to all Rhesus negative pregnant women can mean giving it to mothers who do not need it (because her baby is Rhesus negative or their blood did not mix). Many countries routinely give Anti-D to Rhesus D negative women in pregnancy. In other countries, stocks of Anti-D can run short or even run out. Before Anti-D is made routine in these countries, stocks should be readily available so that it is available for women who need Anti-D in an emergency situation.

A recent review found research into giving Anti-D to all Rhesus D negative pregnant women is of low quality. However the research did suggest that the risk of the mother producing antibodies to attack Rhesus D positive fetal cells was lower in mothers who had the Anti-D in pregnancy. There were also fewer mothers with a positive kleihauer test (which shows if the mother’s and unborn baby’s blood has mixed).

Anti-RhD immunoglobulin is also given to non-sensitized rhesus negative women immediately (within 72 hours—the sooner the better) after potentially sensitizing events that occur earlier in pregnancy.

The discovery of cell-free DNA in the maternal plasma has allowed for the non-invasive determination of the fetal RHD genotype. In May 2017, the Society for Obstetrics and Gynecology of Canada is now recommending that the optimal management of the D-negative pregnant woman is based on the prediction of the fetal D-blood group by cell-free DNA in maternal plasma with targeted antenatal anti-D prophylaxis. This provides the optimal care for D-negative pregnant women and has been adopted as the standard approach in a growing number of countries around the world. It is no longer considered appropriate to treat all D-negative pregnant women with human plasma derivatives when there are no benefits to her or to the fetus in a substantial percentage of cases.

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.

The risk of pregnancy complications increases as the mother's age increases. Risks associated with childbearing over the age of 50 include an increased incidence of gestational diabetes, hypertension, delivery by caesarean section, miscarriage, preeclampsia, and placenta previa. In comparison to mothers between 20 and 29 years of age, mothers over 50 are at almost three times the risk of low birth weight, premature birth, and extremely premature birth; their risk of extremely low birth weight, small size for gestational age, and fetal mortality was almost double.

The pregnancy category of a medication is an assessment of the risk of fetal injury due to the pharmaceutical, if it is used as directed by the mother during pregnancy. It does "not" include any risks conferred by pharmaceutical agents or their metabolites in breast milk.

Every drug has specific information listed in its product literature. The British National Formulary used to provide a table of drugs to be avoided or used with caution in pregnancy, and did so using a limited number of key phrases, but now Appendix 4 (which was the Pregnancy table) has been removed. Appendix 4 is now titled "Intravenous Additives". However, information that was previously available in the former Appendix 4 (pregnancy) and Appendix 5 (breast feeding) is now available in the individual drug monographs.

Opinions differ about optimal screening and diagnostic measures, in part due to differences in population risks, cost-effectiveness considerations, and lack of an evidence base to support large national screening programs. The most elaborate regimen entails a random blood glucose test during a booking visit, a screening glucose challenge test around 24–28 weeks' gestation, followed by an OGTT if the tests are outside normal limits. If there is a high suspicion, a woman may be tested earlier.

In the United States, most obstetricians prefer universal screening with a screening glucose challenge test. In the United Kingdom, obstetric units often rely on risk factors and a random blood glucose test. The American Diabetes Association and the Society of Obstetricians and Gynaecologists of Canada recommend routine screening unless the woman is low risk (this means the woman must be younger than 25 years and have a body mass index less than 27, with no personal, ethnic or family risk factors) The Canadian Diabetes Association and the American College of Obstetricians and Gynecologists recommend universal screening. The U.S. Preventive Services Task Force found there is insufficient evidence to recommend for or against routine screening.

Some pregnant women and careproviders choose to forgo routine screening due to the absence of risk factors, however this is not advised due to the large proportion of women who develop gestational diabetes despite having no risk factors present and the dangers to the mother and baby if gestational diabetes remains untreated.

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.

Pregnancy over age 50 has, over recent years, become more possible for women, due to recent advances in assisted reproductive technology, in particular egg donation. Typically, a woman's fecundity ends with menopause, which by definition is 12 consecutive months without having had any menstrual flow at all. During perimenopause, the menstrual cycle and the periods become irregular and eventually stop altogether, but even when periods are still regular, the egg quality of women in their forties is lower than in younger women, making the likelihood of conceiving a healthy baby also reduced, particularly after age 42. It is important to note, that the female biological clock can vary greatly from woman to woman. A woman's individual level of fertility can be tested through a variety of methods.

Men also experience a decline in fertility as they age, for example, the average time to pregnancy if a man is under 25 is just over 4.5 months but nearly two years if a man is over 40 (if the woman is under 25). The risk of genetic defects is greatly increased due to the paternal age effect. Children with fathers aged 40 or older are more than five times as likely to have an autism spectrum disorder than children fathered by men aged under 30. Researchers estimate that compared to a male fathering a child in his early 20's - there is double the chance of the child getting schizophrenia when the father is age 40, and triple the risk of schizophrenia when the father is age 50 (though, for most people this means the risk goes from approximately 1 in 121 when a man is 29, to 1 in 47 when a man is age 50 to 54). Men's fertility declines throughout the lifespan, with the volume of a man’s semen and sperm motility (the ability of sperm to move towards an egg) decrease continually between the ages of 20 and 80. The risk of dwarfism and miscarriage also increases as men age

In the United States, between 1997 and 1999, 539 births were reported among mothers over age 50 (four per 100,000 births), with 194 being over 55.

The oldest mother to date to conceive, was 71 years, and the youngest mother, 5 years old. According to statistics from the Human Fertilisation and Embryology Authority, in the UK more than 20 babies are born to women over age 50 per year through in-vitro fertilization with the use of donor oocytes (eggs).

Maria del Carmen Bousada de Lara is the oldest verified mother; she was aged 66 years 358 days when she gave birth to twins; she was 130 days older than Adriana Iliescu, who gave birth in 2005 to a baby girl. In both cases the children were conceived through IVF with donor eggs. The oldest verified mother to conceive naturally (listed currently in the Guinness Records) is Dawn Brooke (UK); she conceived a son at the age of 59 years in 1997 while taking oestrogen.

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.