A high-risk pregnancy is a pregnancy where the mother or the fetus has an increased risk of adverse outcomes compared to uncomplicated pregnancies. No concrete guidelines currently exist for distinguishing “high-risk” pregnancies from “low-risk” pregnancies; however, there are certain studied conditions that have been shown to put the mother or fetus at a higher risk of poor outcomes.[1] These conditions can be classified into three main categories: health problems in the mother that occur before she becomes pregnant, health problems in the mother that occur during pregnancy, and certain health conditions with the fetus.[2]
In 2012, the CDC estimated that there are approximately 65,000 pregnancies deemed "high-risk" in the United States each year.[3]
Older age - Pregnancies in women over the age of 35 are considered "advanced age". First-time pregnant women in this age group may have normal pregnancies, but research indicates that these women are at increased risk of having: first trimester miscarriage, chromosomal abnormalities in the fetus, and fetal growth restriction (FGR).[5] Advanced age is associated with a higher risk for fetal chromosomal abnormalities such as Down Syndrome (Trisomy 21) and Trisomy 13.[5] Some of these chromosomal abnormalities are further associated with an increased risk of miscarriage in the first trimester.[5] It is not yet well-understood how older age leads to increased risk of FGR, but studies have suggested that it could be related to placenta dysfunction.[5][6]
Chronic high blood pressure - The CDC estimates the rate of chronic hypertension in the US as 166.9 per 100,000 hospital deliveries.[8] Hypertension is considered a risk factor for high-risk pregnancy because it leads to an increased risk of pre-eclampsia, restricted fetal growth, and preterm birth.[9][10] It is not yet well-understood how hypertension leads to increased risk of these outcomes. However, it is thought that hypertension leads to decreased blood flow to the placenta.[10] Decreased blood flow to the fetus could lead to restricted growth and trigger other changes that increase the risk of pre-eclampsia, restricted fetal growth, and pre-term birth.[11]
In some pregnancies, certain conditions that arise in the developing fetus or fetuses can put a pregnancy into a high-risk category. In these situations, special care must be taken during the pregnancy to address these factors while the fetus is still in the womb to reduce the chances of morbidity and mortality. Common fetal-related factors that can create a high-risk pregnancy include:
Other reasons a pregnancy may be classified as high-risk include if the mother develops a medical condition during pregnancy or if complications occur during pregnancy.
Conditions developed during pregnancy:
Pre-eclampsia: Pre-eclampsia is a syndrome marked by a sudden increase in the blood pressure of a pregnant woman after the 20th week of pregnancy. It can affect the mother's kidneys, liver, and brain. When left untreated, the condition can be fatal for the mother and/or the fetus and result in long-term health problems.[16]
Gestational diabetes: Gestational diabetes (GDM) is diabetes that first develops when a woman is pregnant. Many women can have healthy pregnancies if they manage their diabetes, following a diet and treatment plan from their health care provider. Uncontrolled gestational diabetes increases the risk for adverse perinatal outcomes such as preterm labor and delivery, preeclampsia, and other hypertension-related conditions in pregnancy. Additionally, some evidence suggests that GDM is associated with long-term outcomes such as development of type 2 diabetes in the mother and future obesity in the infant.[19][20][21]
Timing of pregnancy:
Preterm birth (infants born before 37 weeks of pregnancy)[22][23]
Placenta - The placenta is a structure within the uterus that facilitates exchange of nutrients, oxygen, and waste products between the mother and the fetus. When this connection between mother and fetus is abnormally positioned, the pregnancy is more complicated and requires careful delivery technique.
Infections - Different types of infections may be spread from mother to fetus, predisposing adverse pregnancy outcomes. An existing infection in the mother may be passed along to the fetus during pregnancy through the placenta. A newborn infant is also directly exposed to pathogens during delivery through the vaginal canal or breastfeeding. Fetal infections that develop during pregnancy may trigger spontaneous abortion or affect typical fetal growth and development.[31] Several infections that are notably associated with pregnancy include Group B streptococcus,[32]Bacterial vaginosis,[33]yeast infections,[34] and Zika virus.[35] Some of these infections may be rare but are associated with significant infant morbidity and mortality, particularly if the infection spreads throughout the fetal nervous system. Early evidence shows that COVID-19 maternal infection in pregnancy may increase adverse outcomes such as preeclampsia.[36][37]
Management of high-risk pregnancy is dependent on the specific etiology and situation of each particular pregnancy. Some examples of management for certain conditions include:
Chronic hypertension: Anti-hypertensive agents that are safe to use during pregnancy should be used to manage hypertension during pregnancy.[40] The American College of Obstetricians and Gynecologists (ACOG) also recommends low dose aspirin in pregnant women who have chronic hypertension and other pre-eclampsia risk factors.[41]
Congenital defects: The management of congenital defects in the fetus depends on the specific condition. For example, certain cardiac anomalies must be corrected to avoid irreversible damage during the gestational period, such as using fetal cardiac catheterization to correct pulmonary atresia with intact ventricular septum.[42]Spina Bifida is another common condition that can be repaired before birth.[43] Other anomalies, such as hypoplastic left heart syndrome, can be monitored throughout the pregnancy and treated with surgery soon after birth.[44]
Multiple gestations: Although conditions that are more common in multiple gestations, such as preterm birth, should be monitored properly during the pregnancy, there is currently limited evidence to evaluate the ability of specialized antenatal care on improving outcomes for the parent or infant.[45]
The concept of a high-risk pregnancy has been shown to elicit a strong emotional response in some pregnant women, including fear, anger, and guilt.[50] In addition, some studies show that a pregnancy labeled "high-risk" may lead to more unnecessary testing than without the label, increasing these fears and reducing the pregnant woman's sense of control over the situation.[51] Managing anxiety in pregnancies deemed high-risk has been deemed an important focus in research, although there is currently limited high-quality studies on the issue.[52]
^Jeha D, Usta I, Ghulmiyyah L, Nassar A (March 2015). "A review of the risks and consequences of adolescent pregnancy". Journal of Neonatal-Perinatal Medicine. 8 (1): 1–8. doi:10.3233/NPM-15814038. PMID25766198.
^ abKitzmiller JL, Buchanan TA, Kjos S, Combs CA, Ratner RE (May 1996). "Pre-conception care of diabetes, congenital malformations, and spontaneous abortions". Diabetes Care. 19 (5): 514–41. doi:10.2337/diacare.19.5.514. PMID8732721. S2CID11516620.
^Drenthen W, Pieper PG, Roos-Hesselink JW, van Lottum WA, Voors AA, Mulder BJ, et al. (June 2007). "Outcome of pregnancy in women with congenital heart disease: a literature review". Journal of the American College of Cardiology. 49 (24): 2303–11. doi:10.1016/j.jacc.2007.03.027. PMID17572244.
^Fortner KB, Nieuwoudt C, Reeder CF, Swamy GK (June 2018). "Infections in Pregnancy and the Role of Vaccines". Obstetrics and Gynecology Clinics of North America. 45 (2): 369–388. doi:10.1016/j.ogc.2018.01.006. PMID29747736. S2CID13682135.
^Fortner KB, Nieuwoudt C, Reeder CF, Swamy GK (June 2018). "Infections in Pregnancy and the Role of Vaccines". Obstetrics and Gynecology Clinics of North America. 45 (2): 369–388. doi:10.1016/j.ogc.2018.01.006. PMID29747736. S2CID13682135.