What is the recommended frequency of fetal growth ultrasound surveillance in patients with hypertension?

From the Guidelines

For pregnant patients with hypertension, fetal growth ultrasounds should be performed every 2 to 4 weeks starting from 26 weeks’ gestation, with the frequency of monitoring adjusted based on the presence of fetal growth restriction or other high-risk factors, as recommended by the most recent guidelines 1.

Key Principles of Management

The management of patients with hypertension in pregnancy involves controlling blood pressure, monitoring for the development of preeclampsia, and assessing fetal growth, especially if maternal uric acid is elevated.

• Control blood pressure to levels of 110 to 140/85 mm Hg.
• Monitor for development of preeclampsia using urinalysis at each visit along with clinical assessment and blood tests at 28 and 34 weeks as a minimum.
• Assess fetal well-being with ultrasound from 26 weeks’ gestation and thereafter at 2 to 4 weekly intervals if fetal biometry is normal and more frequently in the presence of suspected fetal growth restriction.

Fetal Monitoring and Management

Fetal biometry, amniotic fluid volume assessment, and fetal Doppler waveform analysis should be performed at the first diagnosis of preeclampsia, with serial evaluation of fetal growth, amniotic fluid volume, and umbilical artery Doppler recommended from 26 weeks’ gestation until birth, as stated in 1.

• The ideal scanning schedule thereafter is determined by the presence or absence of fetal growth restriction at the initial assessment and the gestation at diagnosis.
• Fetal biometry should be assessed no more frequently than every 2 weeks, with more frequent ultrasound measurements needed if there is high umbilical artery resistance or absent or reversed end-diastolic flow.

Surveillance Schedule

The surveillance schedule is important because hypertensive disorders in pregnancy increase the risk of placental insufficiency, which can lead to fetal growth restriction, decreased amniotic fluid, and potential fetal compromise, as noted in 1.

• Regular monitoring allows for timely intervention, including possible early delivery if fetal wellbeing becomes compromised.
• Twice-weekly antenatal testing (non-stress tests or biophysical profiles) is recommended starting at 32 weeks for chronic hypertension and earlier (26-28 weeks) for preeclampsia or growth restriction.

From the Research

Frequency of Fetal Growth Ultrasound Surveillance

• The frequency of fetal growth ultrasound surveillance in patients with hypertension is crucial for detecting intrauterine growth restriction (IUGR) and preventing stillbirth and hypoxic sequelae in the fetus 2.
• According to a study published in 2003, sonographic estimated fetal weight (EFW) is slightly to moderately useful in detecting fetal growth restriction in patients with chronic hypertension 3.
• The American College of Obstetricians and Gynecologists recommends antepartum testing for patients with hypertensive disorders, including those with chronic hypertension or pregnancy-induced hypertension, starting at 33 to 34 weeks gestation 2.
• For patients with complications such as intrauterine growth restriction, preeclampsia, diabetes, systemic lupus erythematosis, or chronic renal disease, antepartum testing should begin when intervention for fetal indications is judged to be appropriate, usually starting at about 26 weeks gestation 2.
• A study published in 2021 found that the incidence of preeclampsia decreases dramatically from early preterm fetal growth restriction to late preterm and term fetal growth restriction, highlighting the importance of regular fetal growth ultrasound surveillance 4.

Recommendations for Fetal Growth Ultrasound Surveillance

• Patients with chronic hypertension or pregnancy-induced hypertension should undergo fetal growth ultrasound surveillance every 3 to 4 weeks starting at 28 to 30 weeks gestation 3, 2.
• Patients with complications such as intrauterine growth restriction, preeclampsia, diabetes, systemic lupus erythematosis, or chronic renal disease should undergo more frequent fetal growth ultrasound surveillance, typically every 1 to 2 weeks 2.
• Doppler velocimetry may be helpful in further evaluation of patients with abnormal primary testing 2.
• Regular fetal growth ultrasound surveillance can help identify IUGR and prevent stillbirth and hypoxic sequelae in the fetus 3, 2, 4.