High-Risk Pregnancies

A high-risk pregnancy is a pregnancy in which the mother, fetus, or**, newborn is or will be at an increased risk of morbidity or mortality**, happening before, during, or after delivery. They can lead to serious maternal, obstetric, and neonatal complications if left undetected. Keep in mind that pregnancy itself predisposes and puts the mother at a health risk. Leading causes of maternal mortality include hemorrhage, indirect medical conditions, hypertension, sepsis, and DVT. Leading causes of infant mortality include prematurity, sepsis, and congenital anomalies. High-risk pregnancies can be classified as maternal factors, maternal health conditions, and obstetric conditions.

• Maternal factors
  • Age < 16 yo and > 35 yo
    • Adolescent pregnancy = increased risk of PET, IUGR, and malnutrition
    • Advanced maternal age = increased incidence of DM, PET, Obesity, and other medical conditions
  • Low SES
  • Weight < 50kg
  • Poor nutrition
  • Smoking, drug, and alcohol addiction
  • Uterine anomalies (including incompetent cervix)
• Maternal health conditions
  • Diabetes mellitus
  • Hypertension
  • Severe anemia (Hb < 7 g/dL)
  • Heart disease
  • Sickle Cell Disease
  • STDs
  • Renal, Thyroid, and Autoimmune disease
  • Acute surgical problems
• Obstetric conditions
  • Multiple gestation (increased risk of congenital abnormalities, prematurity, PPH)
  • Polyhydramnios
  • Oligohydramnios
  • PPROM
  • IUGR
  • Abnormal presentation
  • Rhesus incompatibility
  • Fetal anomalies
  • Placental anomalies
  • Antepartum Hemorrhage
  • Prior birth trauma
  • Stillbirth
  • Previous miscarriage
  • Pre-eclampsia

Maternal Screening for High-risk Pregnancies

• Preconceptions screening
  • Medical conditions (DM, HTN, HIV, Epilepsy and their medications)
  • Life-style issues (drug abuse, alcohol abuse, weight)
  • Genetic issues
• Age
  • Age <16 yo: Associated with stress, poor nutrition, PET/Eclampsia, LBW d/t placental abnormalities, and poor nutrition
  • Age > 35 yo: Increased risk of DM, Obesity, HTN, PET/Eclampsia, Chromosomal abnormalities, C-section
• Mode of conception
  • Artificial Reproductive Technologies (ARTs) are associated with multiple pregnancies, preterm delivery, and Low Birth Weight
• Past Obstetric history
  • Recurrent miscarriages ( 2 or more consecutive pregnancy losses)
  • Previous stillbirths or neonatal deaths: due to recurring events like DM, Chronic renal disease, chronic hypertension, lupus anticoagulant
  • Previous preterm or SGA: due to hypertension, renal disease, cigarette smoking, alcohol, or infection
  • Previous LGA: increased risk of DM
  • Previous infant with damage (CP, genetic disorder, congenital anomaly, or neonate requiring special care)
  • Rapidly successive pregnancies (< 3 months btw birth and conception)
  • Operative deliveries
  • Previous pre-eclampsia
• Genital tract disorders
  • Cervical insufficiency
  • Uterine abnormalities (septate uterus, bicornuate uterus)
  • Fibroid
• Medical History
  • Chronic Hypertension
  • Renal disease
  • DM
  • Heart disease
  • Epilepsy
  • Sickle Cell Disease
  • Pelvic fractures
  • Thyroid disease

Antenatal Fetal Assessment

• Genetic testing
  • Nuchal translucency (11-14 weeks)
  • B-hCG
• Maternal serum analyte testingAt 15-22 weeks for open NTDs
  • Serum AFP
  • B-hCG
  • Estriol
• Syndromic testing
  • Hb electrophoresis for SCD
• Preterm labor detection
  • Cervical length (unlikely preterm birth if 30 mm at 34-45 weeks)
  • Fetal fibronectin (unlikely if negative within 2 weeks)
• Diabetic screen
  • OGTT or Fasting blood sugar (at 24-28 weeks)

Antenatal Surveillance using Ultrasound

• First-trimester scan (12/40 dating scan)
  • Confirm the site of fetal implantation and viability (by demonstrating cardiac activity)
  • Estimate gestational age (crown-rump length is accurate for fetus < 12 weeks)
  • Diagnose multiple pregnancies and chorionicity (number of sacs)
  • Identify markers for increased risk of chromosomal abnormalities (nuchal thickness > 6 mm)
  • Identify gross structural abnormalities
• Second-trimester scan (18 – 22/40 anomaly scan)
  • Estimate gestational age if not done in the first trimester
    • Biparietal diameter (BPD)
    • Head circumference (HC) – used to date pregnancy btw 14-20/40
    • Femur length (FL)
  • Survey for chromosomal abnormalities (the main reason for the scan)
  • Diagnose multiple pregnancies and chorionicity (if not already done)
  • Identify the location of the placenta (5% have low-lying placenta)
  • Estimate amniotic fluid volume
    • Polyhydramnios = anencephaly, esophageal atresia
    • Oligohydramnios = renal agenesis, Pregnancy of uncertain viability (PUV)
  • Measure cervical length
    • < 1.5 cm: 50% chance of preterm birth
    • Treatment is offered if cervical length < 2cm at 24 weeks
• Third-trimester scan
  • Assess fetal growth and estimate weight
    • Abdominal circumference (AC)
    • Head circumference (HC)
    • Biparietal diameter (BPD)
    • Femur length (FL)
    • HC/AC = marker of IUGR
  • Assess fetal well-being using amniotic fluid volume
    • Amniotic fluid volume: a single maximum vertical measure of the deepest pocket of fluid
      • < 2cm: oligohydramnios
      • 2 – 8 cm: normal volume
      • 8 cm: polyhydramnios
    • Amniotic fluid index (AFI): sum of all maximum vertical pools of amniotic fluid measurements in the 4 quadrants of the uterus
      • < 5 cm: oligohydramnios
      • 5 – 10 cm: reduced amniotic fluid volume
      • 10 – 25 cm: Normal
      • 25 cm: polyhydramnios
  • Site of placenta implantation and abnormal invasion into the myometrium
    • The placenta tends to grow towards the fundus as pregnancy progresses
    • Low-lying placenta in the third trimester have a higher risk of placenta previa than in the 2nd trimester ****
• Why isn’t the third-trimester ultrasound accurate for determining gestational age?
  • Due to genetic influence on fetal growth
  • Due to influence of Intrauterine Growth Restriction