Overview of High-Risk Pregnancy
There is no formal or universally accepted definition of a high-risk pregnancy. Generally, however, a high-risk pregnancy involves at least one of the following:
Maternal mortality
Maternal mortality refers to the death of women when death is caused by complications of pregnancy and childbirth.
In the United States, 14 women died for every 100,000 deliveries in 2015. In the United States, almost half of pregnancy-related deaths occur in black women. The maternal mortality rate is higher in the United States than in other Western countries, such as the following:
However, almost all maternal deaths occur in developing countries. More than half occur in sub-Saharan Africa (including Nigeria), and almost one third occur in South Asia (including India).
Comparing Mortality Ratios for Mothers in Different Countries
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In this graph, the maternal mortality ratios in different countries are compared. Maternal mortality refers to the number of women who die because of problems related to pregnancy and who die during pregnancy or soon after delivery. The maternal mortality ratio is the number of such deaths for every 100,000 live births (delivery of a living baby). In 2015, ratios ranged from 3 (Finland) to 1,360 (Sierra Leone) deaths per 100,000 live births (these countries are not shown below). The maternal mortality ratio is higher in the United States (14 per 100,000 live births) than in most other Western countries. Data from WHO, UNICEF, UNFPA, World Bank Group, and the United Nations Population Division. Trends in Maternal Mortality: 1990 to 2015. Geneva, World Health Organization, 2015. 
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The most common causes of death in mothers are
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Bleeding (hemorrhage), which accounts for over one fourth of deaths
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Preeclampsia (a type of high blood pressure that develops during pregnancy)
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Sepsis (a serious bodywide response to an infection)
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An abnormally located pregnancy (ectopic pregnancy)—that is, one not in its usual location in the uterus
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Complications and disorders that women had before they became pregnant (such as HIV infection)
Nearly half of maternal deaths could be prevented.
Perinatal mortality
Perinatal mortality refers to the death of fetuses and newborns that occur around the time of delivery. In the United States, the perinatal mortality rate is 6 to 7 deaths per 1,000 deliveries.
The most common causes of death in fetuses and newborns are
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Disorders in the mother, such as high blood pressure, diabetes, obesity, or an autoimmune disorder
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Infections
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Abnormalities in the placenta—one that detaches too soon (placental abruption) or is mislocated (placenta previa)
Risk Assessment During Pregnancy
Certain conditions or characteristics, called risk factors, make a pregnancy high risk. As part of routine care during pregnancy, doctors check for these factors to determine the degree of risk for a particular woman and baby and thus to provide better medical care.
Factors that can affect risk in women include
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Physical characteristics (such as age and weight)
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Social characteristics (such as marital status)
High-risk pregnancies must be closely monitored, and sometimes women are referred to a center that specializes in managing these pregnancies.
The most common reasons for referral before delivery are
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Preterm labor (often due to premature rupture of the membranes)
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Vaginal bleeding
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Disorders that were present before or that develop during the pregnancy, such as diabetes, high blood pressure, and severe (morbid) obesity
