Intrauterine Growth Restriction

Eric H. Dellinger, MD

Greenville Hospital System

IUGR: Introduction

• IUGR 2nd leading contributor to PNM rate• PNM rate increased 6-10 fold• PNM rate 8/1000 background:

– 120/1000 for all IUGR– 60-80/1000 when anomalies excluded

IUGR: Introduction

• 40% of stillbirths have IUGR– 53% of preterm stillbirths– 26% of term stillbirths

• Intrapartum asphyxia reported in up to 50% of IUGR fetuses

• > 60% of IUGR fetuses with FHR tracing abnormalities have hypoxia/acidosis

• Pardi, NEJM 328:692, 1993

When is small, too small? Defining IUGR

IUGR: Definition

• Birth weight < 10th percentile used to define growth restriction at birth

• Definition carried over to fetuses using ultrasound measurements (+/- 15%)

• Using 10th percentile, 70% will be constitutionally small (no increase risk)

• Two SD = less than 3rd percentile• AC < 2.5th percentile has 95% sensitivity

IUGR: PNM and EFW

020406080

100120140160180200

> 10 10 9 8 7 6 5 4 3 2 1 0.5

Birth Weight (percentile)

Per

inat

al M

orta

lity

/ 10

00 L

B

Background Information

Normal Versus Abnormal

Normal Versus Abnormal

< 10th Percentile

70% Normal 30% Abnormal

(Constitutional IUGR) (Pathological IUGR)

IUGR: EtiologyFetal / Placental Maternal

Chromosomal / Genetic History of IUGRTwins HypertensionCongenital malformation DiabetesInfectious disease MSAFP increase

CMV APSToxoplasmosis Chronic illnessRubella Weight < 90% IBW

Placental pathology HemoglobinopathyPrevia Substance abuseAbruption Anemia/HypoxiaMosaiacismInfarction

Past History of IUGR

• Prior history #1 risk factor for subsequent IUGR

• 1 prior episode: 25% recurrence• 2 episodes: Fourfold increase• 1/3 population “at risk”: 2/3 IUGR babies• 2/3 population “low risk”: 1/3 of the IUGR

babies, but most are constitutional

IUGR: Diagnosis

• The Fundal Height Myth:– best from 20-32 weeks: lightening– lag of 4 cm suspicious– Sensitivity of 27%, PPV of 18%

• Fundal height of limited value– risk factors more predictive

IUGR: Fetal Measurements

• Have you weighed a fetus lately?– EFW derived indirectly

• “Normal” growth curves difficult to establish• PTL strongly associated with IUGR

– BW derived charts inaccurate

• U/S growth curves more accurate over preterm age ranges

IUGR: Fetal Growth Patterns

When did you last watch a fetus grow?

Strategy

Strategy

• Normal versus abnormal• Symmetric versus asymmetric• Fetal causes

– Anomalies, arrhythmias, infection

• Placental problems• Amniotic fluid• Dopplers• Fetal surveillance

HC/AC Ratios

Weeks Ratio

<32 > 1.0

32-34 ~ 1.0

>34 < 1.0

Asymmetric HC preserved, ratio > 1.0Symmetric HC, AC both small, ratio ~ 1.0

IUGR: HC/AC Ratios

Asymmetric Symmetric

HC HC

AC AC

HC/AC HC/AC

Asymmetric vs. Symmetric

Asymmetric

Utereo-placental

Symmetric

Constitutional

Aneuploidy Infection

Fetal Causes

• Aneuploidy• Anomalies• Arrhythmias• Infection

Aneuploidy

Anomalies

Arrhythmias

Infection

Placental Causes

Amniotic Fluid Volume

IUGR: Oligohydramnios

• Initial harbinger of doom– IUGR, preeclampsia– may precede abnormal HC/AC

• Fluid pocket of BPP:– >2 cm 6% IUGR– 1-2 cm 20% IUGR– <1 cm 39% IUGR– also predicts intrapartum distress