Fetal growth restriction

By trimester

Weeks 1–13

1st trimester

First-trimester dating matters because an inaccurate due date can distort later growth percentiles. Major maternal conditions and early ultrasound findings may shape risk, but fetal growth restriction is usually identified later through ultrasound. Routine activity restriction and sildenafil are not recommended as ways to improve fetal growth.

Weeks 14–27

2nd trimester

Growth restriction found before 32 weeks is considered early onset and warrants a detailed obstetric ultrasound. SMFM recommends offering chromosome microarray testing when early unexplained isolated growth restriction is found and when growth restriction accompanies a malformation or excess amniotic fluid. Follow-up should evaluate growth, fluid, and placental blood flow.

Weeks 28–birth

3rd trimester

Serial growth ultrasound, umbilical artery Doppler, and fetal heart-rate surveillance guide third-trimester care. Birth timing ranges from preterm delivery for absent or reversed artery flow to 38 to 39 weeks for estimated weight between the 3rd and 10th percentiles with normal flow. These are clinician-directed pathways, not dates to calculate at home.

What does the evidence show for fetal growth restriction?

• SMFM defines fetal growth restriction as ultrasound estimated fetal weight or abdominal circumference below the 10th percentile. Once identified, serial umbilical artery Doppler is recommended; fetal heart-rate surveillance and birth timing vary with severity, Doppler flow, gestational age, and other maternal or fetal risks. 1
• Small-for-gestational-age describes size, commonly below the 10th percentile, while growth restriction implies pathologic failure to reach growth potential. Some constitutionally small fetuses are healthy, so clinicians combine size and interval growth with fluid, Doppler, maternal conditions, and fetal surveillance rather than relying on one percentile alone. 2
• ACOG's bulletin emphasizes the difficulty of distinguishing a constitutionally small fetus from one not reaching growth potential because of disease. It reviews causes, diagnostic and surveillance tools, and individualized birth timing rather than assuming every fetus below a size threshold has the same prognosis. 3
• In the randomized DIGITAT trial, 650 pregnancies with suspected growth restriction beyond 36 weeks were assigned to induction or expectant monitoring. Composite adverse neonatal outcomes and cesarean rates were similar between groups, but the trial was not large enough to settle rare outcomes or dictate care before term. 4
• CDC lists a clear reduction or stopping of fetal movement as an urgent maternal warning sign requiring immediate medical contact. Growth-restricted fetuses still need scheduled surveillance because normal movement at one moment cannot replace ultrasound, Doppler, or fetal heart-rate assessment. 5

When should I call my provider about fetal growth restriction?

Contact the obstetric team immediately if fetal movement clearly decreases or stops. Seek urgent assessment for heavy bleeding, fluid leakage, regular painful contractions before term, severe headache, vision changes, severe upper-abdominal pain, trouble breathing, fainting, or other symptoms the care team has linked to placental or blood-pressure complications. Do not wait for the next growth scan when an urgent warning sign appears. When in doubt, call your obstetric team the same day. Early input almost always beats waiting, and the on-call line exists exactly for this.