High-risk pregnancy

A high-risk pregnancy is a pregnancy in which the mother, fetus, or newborn may be at increased risk of complications during pregnancy or increased mortality before or after delivery.

In the United States, the maternal mortality rate is 6 per 100,000 births; the rate is 3-4 times higher among women of color. The leading causes of death are hemorrhage, pregnancy-related hypertension,pulmonary embolism, and infection. The perinatal mortality rate in the offspring is 11.5 per 1,000 births: 6.7 per 1,000 for the fetus and 4.8 per 1,000 for the neonate (<28 days). The most common causes of death are congenital malformations and preterm birth.

Risk factor assessment is a routine part of prenatal diagnosis. Risk factors are assessed throughout pregnancy or shortly after delivery and at any time when risk factors change. Risk factors are systematized; each factor increases the overall risk. High-risk pregnant women require careful monitoring and referral to a specialist in a perinatal center. Referral to a specialist before delivery reduces complications and mortality in newborns.

The main indications for referral to a specialist before delivery are the threat of premature birth (often due to premature rupture of membranes), pregnancy-related hypertension, and bleeding.

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Risk factors for high risk pregnancy

Risk factors include maternal health conditions, physical and social characteristics, age, complications of previous pregnancies (eg, spontaneous abortions), complications of the current pregnancy, labor, and delivery.

Arterial hypertension. Pregnant women suffer from chronic arterial hypertension (CAH) if they had arterial hypertension before pregnancy or it developed before the 20th week of pregnancy. CAH should be differentiated from pregnancy-induced arterial hypertension that developed after the 20th week of gestation. Arterial hypertension is defined as systolic with BP over 140 mm Hg and diastolic with BP over 90 mm Hg for over 24 hours. Arterial hypertension increases the risk of intrauterine growth retardation and reduces uteroplacental blood flow. CAH increases the risk of preeclampsia by up to 50%. Poorly controlled arterial hypertension increases the risk of placental abruption from 2 to 10%.

When planning a pregnancy, women with hypertension should undergo counseling taking into account all risk factors. If pregnant, it is recommended that such women begin prenatal preparation as early as possible. It is necessary to examine kidney function (measure creatinine and urea in the blood serum), ophthalmoscopic examination, and examination of the cardiovascular system (auscultation, ECG, echocardiography). In each trimester of pregnancy, protein in daily urine, uric acid, creatinine in the blood serum and hematocrit are determined. To monitor fetal growth, ultrasonography is used at 28 weeks and then every few weeks. Fetal growth retardation is diagnosed using Doppler ultrasound by a prenatal diagnostics specialist (to manage hypertension during pregnancy).

Assessment of risk factors during pregnancy

Category

Risk factors

Points 1

Previously existing

Cardiovascular and renal disorders	Moderate and severe preeclampsia	10
	Chronic arterial hypertension	10
	Moderate to severe renal impairment	10
	Severe heart failure (class II-IV, NYHA classification)
	History of eclampsia	5
	History of pyelitis	5
	Moderate heart failure (class I, NYHA classification)
	Moderate preeclampsia	5
	Acute pyelonephritis	5
	History of cystitis	1
	Acute cystitis	1
	History of preeclampsia	1
Metabolic disorders	Insulin-dependent diabetes	10
	Previous endocrine ablation	10
	Thyroid disorders	5
	Prediabetes (diet-controlled gestational diabetes)	5
	Family history of diabetes	1
Obstetric history	Fetal exchange transfusion in case of Rh incompatibility	10
	Stillbirth	10
	Post-term pregnancy (more than 42 weeks)	10
	Premature newborn	10
	Newborn, small for gestational age	10
	Pathological position of the fetus	10
	Polyhydramnios	10
	Multiple pregnancy	10
	Stillborn	10
	C-section	5
	Habitual abortion	5
	Newborn >4.5 kg	5
	Parity of births >5	5
	Epileptic seizure or cerebral palsy	5
	Fetal malformations	1
Other violations	Pathological results of cytological examination of the cervix
	Sickle cell disease	10
	Positive serological results for STIs	5
	Severe anemia (hemoglobin <9 g/dL)	5
	History of tuberculosis or injection site induration with purified protein derivative >10 mm
	Pulmonary disorders	5
	Moderate anemia (hemoglobin 9.0-10.9 g/dL)	1
Anatomical abnormalities	Malformations of the uterus	10
	Isthmic-cervical insufficiency	10
	Narrow pelvis	5
Maternal characteristics	Age 35 or <15 years	5
	Body weight <45.5 or >91 kg	5
	Emotional problems	1

Prenatal factors

Teratogenic factors	Viral infections	5
	Severe flu	5
	Overuse of drugs	5
	Smoking 1 pack a day	1
	Moderate alcohol consumption	1
Pregnancy complications	Rh sensitization only	5
	Vaginal discharge	5

During childbirth

Maternal factors	Moderate, severe preeclampsia	10
	Polyhydramnios (polyhydramnios) or oligohydramnios (oligohydramnios)	10
	Amnionitis	10
	Uterine rupture	10
	Pregnancy period >42 weeks	10
	Moderate preeclampsia	5
	Premature rupture of membranes >12 h	5
	Premature birth	5
	Primary weakness of labor	5
	Secondary weakness of labor	5
	Meperidine >300 mg	5
	Magnesium sulfate >25 g	5
	Labor >20 h	5
	Second stage of labor >2.5 h	5
	Clinically narrow pelvis	5
	Medical induction of labor	5
	Precipitous labor (<3 hours)	5
	Primary cesarean section	5
	Repeat cesarean section	5
	Elective induction of labor	1
	Prolonged latent phase	1
	Tetanus of the uterus	1
	Oxytocin overdose	1
Placental factors	Central placenta previa	10
	Placental abruption	10
	Marginal placenta previa	1
Fetal factors	Pathological presentation (breech, frontal, facial) or transverse position
	Multiple pregnancy	10
	Fetal bradycardia >30 min	10
	Breech birth, fetal extraction by the pelvic end
	Prolapse of the umbilical cord	10
	Fruit weight <2.5 kg	10
	Fetal acidosis <7.25 (stage I)	10
	Fetal tachycardia >30 min	10
	Meconium-stained amniotic fluid (dark)	10
	Meconium-stained amniotic fluid (light)	5
	Surgical delivery using forceps or vacuum extractor
	Breech birth, spontaneous or assisted
	General anesthesia	5
	Exit obstetric forceps	1
	Shoulder dystocia	1

¹ 10 or more points indicate high risk.

NYHA - New York Heart Association; STI - sexually transmitted infections.

Diabetes mellitus. Diabetes mellitus occurs in 3-5% of pregnancies, and its impact on pregnancy increases with increasing weight. Pregnant women with preexisting insulin-dependent diabetes mellitus have an increased risk of pyelonephritis, ketoacidosis, pregnancy-associated hypertension, intrauterine death, malformations, fetal macrosomia (weight >4.5 kg), and, if vasculopathy is present, fetal growth retardation. Insulin requirements usually increase during pregnancy.

Women with gestational diabetes are at risk of hypertensive disorders and fetal macrosomia. Screening for gestational diabetes is usually performed at 24–28 weeks of gestation or, in women with risk factors, during the first trimester. Risk factors include previous gestational diabetes, neonatal macrosomia in a previous pregnancy, family history of non-insulin-dependent diabetes, unexplained fetal loss, and a body mass index (BMI) greater than 30 kg/m ². A glucose tolerance test using 50 g of sugar is used. If the result is 140–200 mg/dL, the glucose is measured after 2 hours; if the glucose level is greater than 200 mg/dL or the results are abnormal, women are treated with diet and, if necessary, insulin.

Good blood glucose control during pregnancy minimizes the risk of developing adverse diabetes-related outcomes (treatment of diabetes in pregnancy).

Sexually transmitted infections. Intrauterine infection with syphilis can cause intrauterine fetal death, congenital malformations, and disability. The risk of HIV transmission from mother to fetus in utero or perinatally is 30-50% within 6 months. Bacterial vaginosis, gonorrhea, urogenital chlamydia during pregnancy increase the risk of preterm labor and premature rupture of membranes. Routine prenatal diagnosis includes screening tests to detect latent forms of these diseases at the first prenatal visit.

Syphilis testing is repeated during pregnancy if there is a risk of infection during delivery. All pregnant women with these infections are treated with antimicrobial drugs.

Treatment of bacterial vaginosis, gonorrhea, and chlamydia can prevent premature rupture of membranes during labor and reduce the risk of intrauterine infection of the fetus. Treatment of HIV infection with zidovudine or nevirapine reduces the risk of transmission by two-thirds; the risk is significantly lower (<2%) with a combination of two or three antiviral drugs.

These drugs are recommended for use despite their potentially toxic effects on the fetus and the woman.

Pyelonephritis. Pyelonephritis increases the risk of premature rupture of membranes, preterm labor, and fetal respiratory distress syndrome. Pregnant women with pyelonephritis are hospitalized for diagnosis and treatment. First of all, a bacteriological examination of urine with culture for sensitivity to antibiotics is performed.

Intravenous antibiotics (eg, third-generation cephalosporins with or without aminoglycosides), antipyretics, and hydration correction are used. Pyelonephritis is the most common non-obstetric cause of hospitalization during pregnancy.

Specific antibiotics for oral administration are prescribed, taking into account the pathogenic agent, for 24-48 hours after the cessation of fever, and a full course of antibiotic therapy is carried out for 7-10 days. Antibiotics for prophylactic purposes (eg, nitrofurantoin, trimethoprim-sulfamethoxazole) are prescribed for the rest of the pregnancy with periodic bacteriological examination of urine.

Acute surgical diseases. Major surgical interventions, especially intra-abdominal ones, increase the risk of premature birth and intrauterine fetal death. Physiological changes occur during pregnancy that complicate the diagnosis of acute surgical diseases that require emergency surgical intervention (e.g. appendicitis, cholecystitis, intestinal obstruction ), and thus worsen the treatment results. After surgery, antibiotics and tocolytics are prescribed for 12-24 hours. If planned surgical treatment is necessary during pregnancy, it is better to perform it in the 2nd trimester.

Pathology of the reproductive system. Malformations of the uterus and cervix (e.g., uterine septum, bicornuate uterus ) lead to fetal developmental disorders, abnormal labor, and increase the frequency of cesarean section. Uterine fibroid tumors may cause placental pathology, and growth may increase or nodes may degenerate during pregnancy; node degeneration leads to severe pain and peritoneal symptoms. Cervical insufficiency often leads to premature labor. In women who have had a myomectomy, spontaneousuterine rupture may occur during vaginal delivery. Uterine malformations that require surgical correction that cannot be performed during pregnancy worsen the prognosis for the course of pregnancy and labor.

Maternal age. Teenagers, who account for 13% of pregnancy rates, neglect prenatal care. As a result, the incidence of preeclampsia, premature birth, and anemia, which often lead to intrauterine growth retardation, increases.

In women over 35 years of age, the incidence of preeclampsia increases, especially in the setting of gestational diabetes mellitus, the incidence of uterine contractile abnormalities during labor, placental abruption, stillbirth, and placenta previa increases. These women also have the highest incidence of preexisting disorders (eg, chronic hypertension, diabetes). Genetic testing is necessary because the risk of chromosomal abnormalities in the fetus increases with increasing maternal age.

Maternal body weight. Pregnant women with a BMI of less than 19.8 (kg/m2) before pregnancy are considered underweight, which predisposes them to having a low birth weight baby (<2.5 kg). These women need to gain approximately 12.5-18 kg during pregnancy.

Pregnant women with a BMI greater than 29.0 (kg/m2) before pregnancy are considered overweight patients, which leads to hypertension, diabetes, post-term pregnancy, fetal macrosomia and increases the risk of cesarean section. Such women are advised to limit weight gain to 7 kg during pregnancy.

Influence of teratogenic factors. Teratogenic factors (agents that cause fetal malformations) are infections, drugs, and physical agents. Malformations most often form between the 2nd and 8th weeks after conception (4th to 10th weeks after the last menstruation), when the organs are laid down. Other unfavorable factors are also possible. Pregnant women who have been exposed to teratogenic factors, as well as those with increased risk factors, should be carefully examined using ultrasound to detect malformations.

Teratogenic infections include: herpes simplex, viral hepatitis, rubella, chickenpox, syphilis, toxoplasmosis, cytomegalovirus and Coxsackie virus. Teratogenic substances include alcohol, tobacco, some anticonvulsants, antibiotics and antihypertensive drugs.

Smoking is the most common addiction among pregnant women. The percentage of women who smoke moderately and heavily is increasing. Only 20% of women who smoke quit during pregnancy. Carbon monoxide and nicotine in cigarettes cause hypoxia and vasoconstriction, increasing the risk of spontaneous abortion (miscarriage or delivery before 20 weeks), intrauterine growth retardation (birth weight is on average 170 g less than that of newborns whose mothers do not smoke), placental abruption, placenta previa, premature rupture of membranes, premature birth, chorioamnionitis and stillbirth. Newborns whose mothers smoke are more likely to have anencephaly, congenital heart defects, cleft lip, delayed physical and intellectual development and behavioral disorders. Sudden infant death during sleep has also been reported. Limiting or stopping smoking reduces the risk of teratogenic effects.

Alcohol is the most common teratogen. Drinking alcohol during pregnancy increases the risk of spontaneous abortion. The risk depends on the amount of alcohol consumed; any amount is dangerous. Regular alcohol consumption reduces the birth weight of the child by approximately 1-1.3 kg. Even drinking as much as 45 ml of alcohol per day (equivalent to approximately 3 drinks) can cause fetal alcohol syndrome. This syndrome occurs in 2.2 per 1000 live births and includes intrauterine growth retardation, facial and cardiovascular defects, and neurological dysfunction. Fetal alcohol syndrome is the leading cause of mental retardation and can cause death in the newborn.

Cocaine use also has indirect risks (e.g., maternal stroke or death during pregnancy). Cocaine use can also lead to vasoconstriction and fetal hypoxia. Cocaine use increases the risk of spontaneous abortion, intrauterine growth restriction, placental abruption, preterm labor, stillbirth, and congenital malformations (e.g., CNS, urinary tract, skeletal malformations, and isolated atresia).

Although the major metabolite of marijuana crosses the placenta, occasional marijuana use does not increase the risk of birth defects, intrauterine growth restriction, or postnatal neurodevelopmental disabilities.

Previous stillbirth. Stillbirth (intrauterine fetal death >20 weeks) may be caused by maternal, placental, or embryonic factors. A history of stillbirth increases the risk of intrauterine fetal death in subsequent pregnancies. Monitoring fetal development and assessing fetal viability (using non-stress tests and fetal biophysical profile) are recommended. Treatment of maternal disorders (e.g., chronic hypertension, diabetes, infection) may reduce the risk of stillbirth in the current pregnancy.

Previous preterm birth. A history of preterm birth increases the risk of preterm birth in subsequent pregnancies; if the birth weight of the baby in the previous preterm birth was less than 1.5 kg, the risk of preterm birth in the next pregnancy is 50%. Causes of preterm birth include multiple pregnancy, preeclampsia or eclampsia, abnormalities in the placenta, premature rupture of membranes (resulting from ascending uterine infection), pyelonephritis, some sexually transmitted diseases and spontaneous uterine activity. Women with a history of preterm birth require ultrasound examination with measurement of cervical length, monitoring for pregnancy-induced hypertension should be carried out at 16-18 weeks. If symptoms of threatened preterm labor progress, it is necessary to monitor uterine contractility, test for bacterial vaginosis; determination of fetal fibronectin can identify women who need closer observation by a physician.

Previous birth of a newborn with a genetic or congenital disorder. The risk of having a fetus with a chromosomal disorder is increased for most couples who have had a fetus or newborn with a chromosomal disorder (diagnosed or undiagnosed) in a previous pregnancy. The risk of recurrence for most genetic disorders is unknown.

Most congenital malformations are multifactorial; the risk of having a subsequent fetus with a genetic disorder is 1% or less. Couples who have had a newborn with a genetic or chromosomal disorder in previous pregnancies may benefit from genetic screening. Couples who have had a newborn with a congenital malformation may benefit from high-resolution ultrasonography and evaluation by a prenatal care specialist.

Polyhydramnios and oligohydramnios. Polyhydramnios (excess amniotic fluid) can lead to severe dyspnea in the mother and preterm labor. Risk factors include uncontrolled maternal diabetes, multiple pregnancy, isoimmunization, and fetal malformations (e.g., esophageal atresia, anencephaly, spina bifida ). Oligohydramnios (deficiency of amniotic fluid) often accompanies congenital malformations of the fetal urinary tract and severe intrauterine growth retardation.

Pregnancy in patients with Potter syndrome in a fetus with pulmonary hypoplasia or superficial compression disorders may be interrupted (usually in the 2nd trimester of pregnancy) or end in intrauterine fetal death.

Polyhydramnios or oligohydramnios may be suspected in cases where the size of the uterus does not correspond to the gestational date or is discovered incidentally during diagnostic ultrasonography.

Multiple pregnancy. Multiple pregnancy increases the risk of intrauterine growth retardation, premature birth, placental abruption, congenital malformations, perinatal morbidity and mortality, uterine atony, and postpartum bleeding. Multiple pregnancy is detected by routine ultrasound at 18-20 weeks of pregnancy.

Previous birth trauma. Trauma to the neonate at birth (e.g., cerebral palsy, failure to thrive, or trauma from forceps or vacuum extractor delivery, shoulder dystocia with Erbe-Duchenne palsy) does not increase the risk in subsequent pregnancies. However, these factors should be evaluated and avoided in subsequent deliveries.