Taking aspirin is associated with a 1% to 5% reduction in pre-eclampsia and a 1% to 5% reduction in premature births in women at high risk. The World Health Organization recommends low-dose aspirin for the prevention of pre-eclampsia in women at high risk and recommends it be started before 20 weeks of pregnancy. The United States Preventive Services Task Force recommends a low-dose regimen for women at high risk beginning in the 12th week. Benefits are less if started after 16 weeks.

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.

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.

A Dutch 2010 research showed that "low-risk" pregnancy in the Netherlands may actually carry a higher risk of perinatal death than a "high-risk" pregnancy.

If the likely cause of recurrent pregnancy loss can be determined treatment is to be directed accordingly. In pregnant women with a history of recurrent miscarriage, anticoagulants seem to increase the live birth rate among those with antiphospholipid syndrome and perhaps those with congenital thrombophilia but not in those with unexplained recurrent miscarriage. One study found that in many women with chronic endometritis, "fertility was restored after appropriate antibiotic treatment."

There are currently no treatments for women with unexplained recurrent pregnancy loss. The majority of patients are counseled to try to conceive again, and chances are about 60% that the next pregnancy is successful without treatment. However, each additional loss worsens the prognostic for a successful pregnancy and increases the psychological and physical risks to the mother. Aspirin has no effect in preventing recurrent miscarriage in women with unexplained recurrent pregnancy loss. Immunotherapy has not been found to help. There is currently one drug in development, NT100, which is in clinical trials for the treatment of unexplained recurrent miscarriage. The study investigates the role of NT100 in improving maternal-fetal tolerance for women with unexplained recurrent miscarriage

In certain chromosomal situations, while treatment may not be available, in vitro fertilization with preimplantation genetic diagnosis may be able to identify embryos with a reduced risk of another pregnancy loss which then would be transferred. However, in vitro fertilization does not improve maternal-fetal tolerance imbalances.

Close surveillance during pregnancy is generally recommended for pregnant patients with a history of recurrent pregnancy loss. Even with appropriate and correct treatment another pregnancy loss may occur as each pregnancy develops its own risks and problems.

There is significant, and often unrecognized, psychological and psychiatric trauma for the mother – for many, miscarriage represents the loss of a future child, of motherhood, and engenders doubts regarding her ability to procreate.

"There is tremendous psychological impact of recurrent miscarriage. Psychological support in the form of frequent discussions and sympathetic counseling are crucial to the successful evaluation and treatment of the anxious couple. When no etiologic factor is identified, no treatment started at 60% to 80% fetal salvage rate still may be expected. Therefore, couples with unexplained recurrent miscarriage should be offered appropriate emotional support and reassurance."

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.

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).

An initial assessment to determine the status of the mother and fetus is required. Although mothers used to be treated in the hospital from the first bleeding episode until birth, it is now considered safe to treat placenta previa on an outpatient basis if the fetus is at less than 30 weeks of gestation, and neither the mother nor the fetus are in distress. Immediate delivery of the fetus may be indicated if the fetus is mature or if the fetus or mother are in distress. Blood volume replacement (to maintain blood pressure) and blood plasma replacement (to maintain fibrinogen levels) may be necessary.

Corticosteroids are indicated at 24–34 weeks gestation, given the higher risk of premature birth.

The method of delivery is determined by clinical state of the mother, fetus and ultrasound findings. In minor degrees (traditional grade I and II), vaginal delivery is possible. RCOG recommends that the placenta should be at least 2 cm away from internal os for an attempted vaginal delivery. When a vaginal delivery is attempted, consultant obstetrician and anesthetists are present in delivery suite. In cases of fetal distress and major degrees (traditional grade III and IV) a caesarean section is indicated. Caesarian section is contraindicated in cases of disseminated intravascular coagulation. An obstetrician may need to divide the anterior lying placenta. In such cases, blood loss is expected to be high and thus blood and blood products are always kept ready. In rare cases, hysterectomy may be required.

A grandmother who smoked during the pregnancy of her daughter transmits an increased risk of asthma to her grandchildren, even if the second-generation mother did not smoke. The multigenerational epigenetic effect of nicotine on lung function has already been demonstrated.

If one does continue to smoke after giving birth, however, it is still more beneficial to breastfeed than to completely avoid this practice altogether. There is evidence that breastfeeding offers protection against many infectious diseases, especially diarrhea. Even in babies exposed to the harmful effects of nicotine through breast milk, the likelihood of acute respiratory illness is significantly diminished when compared to infants whose mothers smoked but were formula fed. Regardless, the benefits of breastfeeding outweigh the risks of nicotine exposure.

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

Antepartum bleeding, also known as antepartum haemorrhage or prepartum hemorrhage, is genital bleeding during pregnancy from the 28th week (sometimes defined as from the 20th week) gestational age to term.

It can be associated with reduced fetal birth weight.

In regard to treatment, it should be considered a medical emergency (regardless of whether there is pain) and medical attention should be sought immediately, as if it is left untreated it can lead to death of the mother and/or fetus.

Treatment may be delivery by caesarean section and abdominal hysterectomy if placenta accreta is diagnosed before birth. Oxytocin and antibiotics are used for post-surgical management. When there is partially separated placenta with focal accreta, best option is removal of placenta. If it is important to save the woman's uterus (for future pregnancies) then resection around the placenta may be successful. Conservative treatment can also be uterus sparing but may not be as successful and has a higher risk of complications.

Techniques include:

- Leaving the placenta in the uterus and curettage of uterus. Methotrexate has been used in this case.

- Intrauterine balloon catheterisation to compress blood vessels

- Embolisation of pelvic vessels

- Internal iliac artery ligation

- Bilateral uterine artery ligation

In cases where there is invasion of placental tissue and blood vessels into the bladder, it is treated in similar manner to abdominal pregnancy and manual placental removal is avoided. However, this may eventually need hysterectomy and/or partial cystectomy.

If the patient decides to proceed with a vaginal delivery, blood products for transfusion and an anesthesiologist are kept ready at delivery.

In rare cases, inherited bleeding disorders, like hemophilia, von Willebrand disease (vWD), or factor IX or XI deficiency, may cause severe postpartum hemorrhage, with an increased risk of death particularly in the postpartum period. The risk of postpartum hemorrhage in patients with vWD and carriers of hemophilia has been found to be 18.5% and 22% respectively. This pathology occurs due to the normal physiological drop in maternal clotting factors after delivery which greatly increases the risk of secondary postpartum hemorrhage.

Another bleeding risk factor is thrombocytopenia, or decreased platelet levels, which is the most common hematological change associated with pregnancy induced hypertension. If platelet counts drop less than 100,000 per microliter the patient will be at a severe risk for inability to clot during and after delivery.

Early neonatal mortality refers to a death of a live-born baby within the first seven days of life, while late neonatal mortality covers the time after 7 days until before 28 days. The sum of these two represents the neonatal mortality. Some definitions of the PNM include only the early neonatal mortality. Neonatal mortality is affected by the quality of in-hospital care for the neonate. Neonatal mortality and postneonatal mortality (covering the remaining 11 months of the first year of life) are reflected in the Infant Mortality Rate.

Antepartum bleeding (APH), also prepartum hemorrhage, is bleeding during pregnancy from the 24th week (sometimes defined as from the 20th week) gestational age to full term (40th week). The primary consideration is the presence of a placenta previa which is a low lying placenta at or very near to the internal cervical os. This condition occurs in roughly 4 out of 1000 pregnancies and usually needs to be resolved by delivering the baby via cesarean section. Also a placental abruption (in which there is premature separation of the placenta) can lead to obstetrical hemorrhage, sometimes concealed. This pathology is of important consideration after maternal trauma such as a motor vehicle accident or fall.

Other considerations to include when assessing antepartum bleeding are: sterile vaginal exams that are performed in order to assess dilation of the patient when the 40th week is approaching. As well as cervical insufficiency defined as a midtrimester (14th-26th week) dilation of the cervix which may need medical intervention to assist in keeping the pregnancy sustainable.

Fetal mortality refers to stillbirths or fetal death. It encompasses any death of a fetus after 20 weeks of gestation or 500 gm. In some definitions of the PNM early fetal mortality (week 20-27 gestation) is not included, and the PNM may only include late fetal death and neonatal death. Fetal death can also be divided into death prior to labor, antenatal (antepartum) death, and death during labor, intranatal (intrapartum) death.

The reported incidence of placenta accreta has increased from approximately 0.8 per 1000 deliveries in the 1980s to 3 per 1000 deliveries in the past decade.

Incidence has been increasing with increased rates of Caesarean deliveries, with rates of 1 in 4,027 pregnancies in the 1970s, 1 in 2,510 in the 1980s, and 1 in 533 for 1982–2002. In 2002, ACOG estimated that incidence has increased 10-fold over the past 50 years. The risk of placenta accreta in future deliveries after Caesarian section is 0.4-0.8%. For patients with placenta previa, risk increases with number of previous Caesarean sections, with rates of 3%, 11%, 40%, 61%, and 67% for the first, second, third, fourth, and fifth or greater number of Caesarean sections.

The four goals of the treatment of eclampsia are to stop and prevent further convulsions, to control the elevated blood pressure, to deliver the baby as promptly as possible, and to monitor closely for the onset of multi-organ failure.

Detection and management of pre-eclampsia is critical to reduce the risk of eclampsia. The USPSTF recommends regular checking of blood pressure through pregnancy in order to detect preeclampsia. Appropriate management of women with pre-eclampsia generally involves the use of magnesium sulphate to prevent convulsions.

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.

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.

Methylmercury and inorganic mercury is excreted in human breast milk and infants are particularly susceptible to toxicity due to this compound. The fetus and infant are especially vulnerable to mercury exposures with special interest in the development of the CNS since it can easily cross across the placental barrier, accumulate within the placenta and fetus as the fetus cannot eliminate mercury and have a negative effect on the fetus even if the mother does not show symptoms. Mercury causes damage to the nervous system resulting from prenatal or early postnatal exposure and is very likely to be permanent.