Fetal Growth Restriction — When the Baby Stops Growing but Keeps You Up at Night

ntro — The Awkward Pause After Biometry

You finish measuring.
You stare at the screen.
The baby’s head is the size of a strawberry, but it’s supposed to be a lime.
You check again, remeasure, whisper a prayer to Hadlock,
and finally mutter:

“Hmm… growth a bit below average.”

Congratulations, doctor — you’ve just entered the world of Fetal Growth Restriction (FGR),
where centimeters become moral judgments and every Doppler trace feels like a heartbeat polygraph.

🔹 Step 1: Let’s Define the Drama

Fetal Growth Restriction (FGR) = a baby that doesn’t reach its genetically expected growth potential.

Now, this sounds poetic — until you realize you have to quantify “potential.”

So we use percentiles, because numbers make anxiety official:

FGR: Estimated Fetal Weight (EFW) < 10th percentile.
Severe FGR: EFW < 3rd percentile.
Small but OK (SGA): <10th percentile but normal Doppler & growth pattern.

💬 OBGYNX humor:
If EFW <10th but Doppler’s perfect, that baby’s not sick — it’s just petite and European.

🔹 Step 2: Types — The Two Personalities of FGR

Mnemonic: “Early vs Late — Villain vs Victim.”

Early FGR (<32 weeks):
→ Usually placental insufficiency.
→ Classic Doppler villain.
→ Associated with preeclampsia and abnormal UA flow.
Late FGR (≥32 weeks):
→ The quiet type.
→ Normal Doppler until it’s not.
→ Usually missed until the baby starts lagging behind.

💡 OBGYNX tip:
Early = Doppler nightmare.
Late = deceptively normal baby who just stops getting RSVPs from the placenta.

🔹 Step 3: The Root Cause — “The Placenta Is Tired”

Most FGRs start with placental dysfunction —
the ultimate burnout organ.

It’s supposed to deliver oxygen, but ends up sending excuses.
Think of it as a lazy delivery app:
The fetus keeps ordering nutrients,
the placenta keeps saying, “Out for delivery.”

Other causes include:

Genetic or structural abnormalities.
Infections (TORCH, CMV, Zika — the usual suspects).
Maternal disease (hypertension, lupus, renal disease).
Multiple pregnancy (the “share your pizza” effect).

🔹 Step 4: The Diagnosis — “When the Numbers Start Falling”

You suspect FGR when:

The fundal height stops increasing.
EFW or AC <10th percentile.
Growth lag on serial ultrasounds.

But let’s be real — biometry alone is just gossip.
The truth comes from Doppler.

🔹 Step 5: The Doppler Chronicles — Reading the Placental Drama

Mnemonic: “U-M-D = Umbilical, MCA, Ductus venosus.”

Umbilical Artery (UA):
- Low diastolic flow → resistance ↑
- Absent EDF → placenta’s on strike.
- Reversed EDF → placenta declared bankruptcy.

💬 OBGYNX humor:
If the UA waveform looks flat, so is your night — because you’re not going home.

Middle Cerebral Artery (MCA):
- PI ↓ = brain-sparing.
- The fetus literally reroutes blood to the brain — survival mode activated.
CPR (Cerebroplacental Ratio = MCA PI / UA PI):
- Normal >1.0
- <1 = “Houston, we have redistribution.”
Ductus Venosus (DV):
- Reversed a-wave = fetal cardiac failure warning.

Mnemonic: “RED = Reversed = Emergency Delivery.”

🔹 Step 6: The Stages of FGR (Simplified ISUOG 2025)

Mnemonic: “Restless Placenta Syndrome.”

Stage I:
Just high resistance in UA, normal MCA → keep calm, scan weekly.

Stage II:
Absent EDF in UA, CPR <1 → high risk → monitor every 2–3 days.

Stage III:
Reversed EDF in UA → admit, steroids, prepare delivery.

Stage IV:
Abnormal DV flow → delivery now, do not collect $200.

💬 OBGYNX truth:
If the DV looks like Morse code, the fetus is already sending SOS.

🔹 Step 7: The Growth Patterns — “It’s Not Always the Placenta’s Fault”

Mnemonic: “CHIPS.”
C – Chromosomal
H – Hypertension
I – Infection
P – Placental problems
S – Structural defects

If none of these fit → it’s SGA, not FGR.
Translation: “Small, but thriving — don’t panic.”

🔹 Step 8: The Management — “How Not to Kill the Calm”

The holy trinity:

Timing of delivery
Antenatal steroids (for lung maturity)
Doppler-based follow-up.

Early FGR → manage in tertiary center.
Late FGR → follow closely, deliver when CPR drops <1 or fetal heart tracing worsens.
Always individualize — no cookie-cutter placenta.

💬 OBGYNX mantra:

“If Doppler says go, you go.
If it says wait, you wait nervously.”

🔹 Step 9: The Prognosis — Hope with a Side of Anxiety

Good Dopplers = good outcomes.
Abnormal UA + abnormal DV = prepare for NICU drama.
Late FGR often recovers beautifully.

💡 OBGYNX pearl:
Never underestimate a small fetus with a big attitude — they often grow up to run the ward.

🔹 Step 10: The Mnemonic Recap — “SMALL”

S – Slow growth
M – Measure biometry
A – Assess Doppler (UA/MCA/CPR/DV)
L – Look for cause
L – Launch delivery when time is up

Resident version:
“If it’s small and Doppler’s scary — steroids, scan, and stand by.”

⚡️ OBGYNX Closing Thought

FGR is not about size — it’s about struggle.
It’s the story of a fetus negotiating with a lazy placenta,
fighting for every heartbeat, every millimeter, every week.

As long as you measure, monitor, and manage with precision —
you give that baby the only thing that matters: a fair chance.

“Don’t chase perfection. Chase perfusion.” — OBGYNX 2025

Create it