normal and abnormal fetal growth

Fetal Growth

Max MongelliWomen & Childrens’ Health

Nepean Hospital

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Definitions Control of fetal growth Determinants of birth weight Causes of IUGR Causes of macrosomia

Definitions:Definitions:

SGA LGA LBW VLBW IUGR MACROSOMIA

Control of Fetal GrowthControl of Fetal Growth

Classic studies by Walton and Hammond (1938) on crosses between the Shire horse and the Shetland pony:

Birth weights of foals born to Shetland dams of Shire sires were close to those of pure Shetlands

Conversely, foals of Shire dams by Shetland sires were close to those of the pure breed


Evidence in humans: Preponderance of the maternal effects on

fetal growth ( Cawley 1954; Ounsted 1966;) Paternal contribution minimal (Wilcox ) HLA sharing/consanguinity: significant

reduction in birth weight (Shami et al, 1991; Morton, 1958; Magnus et al, 1985).


Early fetal growth is controlled by fetal genetic mechanisms

Maternal effects operate mostly late in gestation

Determinants of birth weightDeterminants of birth weight

Gestational age Maternal size (height & weight) Fetal gender Parity Ethnic group

Fetal Growth : Fetal Growth : GenderGender

500

1000

1500

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2500

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3500

4000

0

24 26 28 30 32 34 36 38 40 42

Males Females

EFW

weeks

Fetal Growth : ParityFetal Growth : Parity

weeks

500

1000

1500

2000

2500

3000

3500

4000

0

24 26 3028 32 34 36 38 40 42

Primip

Multip

EFW

Fetal Growth: Ethnic GroupsFetal Growth: Ethnic Groups

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0

24 26 28 30 32 34 36 38 40 42

Average

Indian

weeks

EFW

Genetic Chromosomal Congenital malformations Multiple Pregnancy

Causes of IUGR:Causes of IUGR:1. Fetal1. Fetal

Genetic factors contribute to 30-40% of the variation in birth weight

Risk of IUGR is inheritable: women who were SGA at birth have x2 increase risk of having a IUGR baby

Mutations in GCK and HNF- beta genes

Genetic Causes of IUGRGenetic Causes of IUGR

Karyotype anomalies account for up to 20% of cases with IUGR

Often early-onset Most cases symmetric

Chromosomal Causes Chromosomal Causes of IUGRof IUGR

Causes of IUGR:Causes of IUGR:Congenital anomaliesCongenital anomalies

Major or multiple anomalies – 1-2% The combination of IUGR and structural

and chromosomal anomalies is common.

Causes of IUGR:Causes of IUGR:2. Placental factors2. Placental factors

Ischemic placental disease Multiple infarcts Umbilical-placental vascular anomalies Abnormal cord insertion Circumvallate placenta Chorioangiomata

Causes of IUGR:Causes of IUGR:3. Maternal factors3. Maternal factors

Reduced utero-placental flow PET, renal disease SLE, collagen vascular disease Hypertension, diabetes Antiphospholipid syndrome


Hypoxemia- Severe anemia- Chronic lung disease- Cyanotic heart disease- High altitude (>2000 m)


Malnutrition Severe starvation affects fetal growth Dutch famine 1944 Caloric intake reduced to 600 kcal/d Birth weights reduced by 250 g Siege of Leningrad Calories reduced to 300 kcal Birth weight reduced by 500g


Substance abuse Cigarette smoking Alcohol Illicit drugs ? Caffeine (>100 mg)


Medications Warfarin Anticonvulsants Chemotherapy Beta-blockers

InfectionsInfections Account for <5% of all cases of IUGR Early in pregnancy have the greatest effect Transplacental or across fetal membranes CMV most common virus Rubella,varicella, toxo, malaria, syphilis

less common Bacteria: rare (eg listeria)



Other causes Vitamin D deficiency ART conception Radiotherapy Uterine malformations Extremes of reproductive life Short inter-pregnancy interval Chronic maternal stress

MacrosomiaMacrosomia

Prevalence of MacrosomiaPrevalence of Macrosomia

10% for > 4000g 1.5% for > 4500g

Causes of Macrosomia:Causes of Macrosomia:

Constitutional Gestational Diabetes Hyperinsulinemia in non-

diabetics Genetic Disorders

Neonatal AnthropometryNeonatal Anthropometry

Infants of diabetic mothers have different body shape

Greater shoulder and extremity circumference

Greater body fat Decreased HC: FAC ratio

Genetic DisordersGenetic Disorders

Beckwith-Wiedemann Syndrome Sotos SyndromeSotos Syndrome Weaver Syndrome Simpson-Golabi-Behmel Berardinelli lipodystrophia

Risk Factors for Macrosomia:Risk Factors for Macrosomia: High BMI Multiparity Advanced maternal age Maternal diabetes Post-term pregnancy Male infant Previous macrosomic infant Excessive weight gain in pregnancy Pacific islanders Maternal birth weight over 4000g

Abnormal Fetal Growth:Clinical Practice

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Prevention Screening Diagnosis Management Long term complications

Prevention of IUGRPrevention of IUGR

Prevention of IUGRPrevention of IUGR

Stop smoking Avoid D & A Aspirin, folate if indicated Minimize risk of multiple pregnancy Minimize risk of infections ?Treat thrombophilias Treat vit. D deficiency Pre-conceptional counselling

NotNot effective in prevention: effective in prevention:

Bed rest Antihypertensive therapy Long-chain PU fatty acids Beta-mimetics

Prevention of MacrosomiaPrevention of Macrosomia

Prevention of MacrosomiaPrevention of Macrosomia

Normalise BMI prior to conception Early detection of GDM Good control of GDM Moderate exercise during

pregnancy

Screening for Abnormal Screening for Abnormal Fetal GrowthFetal Growth

Screening for Abnormal Screening for Abnormal Fetal GrowthFetal Growth

Fetal size estimation by palpation alone can be inaccurate

Better results by measuring the symphysis-fundus height (SFH)

Technique of SFH Technique of SFH MeasurementMeasurement

Patient supine, bladder empty. Measuring tape should be blank on one side,

cm markings on other side. Blank side up. SFH measured in cm from top of uterine

fundus to the top of symphysis pubis. Measurement plotted on reference chart.

Reference Charts for Antenatal Reference Charts for Antenatal Screening for Abnormal Fetal GrowthScreening for Abnormal Fetal Growth

Unadjusted, population – based charts Individually adjusted charts: customised

growth charts Customised charts have lower false positive

rates than unadjusted charts.

Antenatal Diagnosis of Antenatal Diagnosis of SGA/IUGRSGA/IUGR

SFH measurements alone cannot confirm. Possibility of IUGR if there is a growth

deceleration pattern or a single small SFH measurement.

Ultrasound examination is indicated if there is clinical suspicion.

Ultrasound Diagnosis of Ultrasound Diagnosis of SGA/IUGRSGA/IUGR

Fetal biometry: HC, BPD, FAC, FL Can be converted to an estimated fetal

weight (EFW) Amniotic fluid index (AFI) Doppler studies of umbilical arteries Screen for fetal anomalies (10% of IUGR) Cardiotocography (non-stress test)

KaryotypeKaryotype

Fetal karyotype may be indicated if: IUGR is of early onset Severe (< 3rd pct) Associated with polyhydramnios Structural anomalies are present

Doppler StudiesDoppler Studies

Examination of umbilical arteries and MCA Proven to reduce PNM by 30% Abnormal if absent or reversed diastolic flow If abnormal in ductus venosus fetal risk is

very high

ASSESSMENT OF AMNIOTIC FLUID VOLUME

Management of IUGR:Management of IUGR:InvestigationsInvestigations

Management of IUGR:Management of IUGR:InvestigationsInvestigations

FBC, EUC, LFT’s, urate LAC, antiphospholipid antibodies TORCH/viral studies Chromosome studies

Management of IUGR:Management of IUGR:Conservative or elective Conservative or elective

delivery?delivery?

Management of IUGR:Management of IUGR:Conservative or elective Conservative or elective

delivery?delivery?

Depends on severity of IUGR If close to term and fetus not

compromised, induction of labour If there are signs of fetal distress

cesarean section is indicated.

Management of IUGR:Management of IUGR:ConservativeConservative

Twice weekly U/S for AFI/flows Daily CTG’s 2 -weekly EFW measurements Antenatal steroids Pregnancy should not extend beyond 37

weeks’ gestation

Complications of IUGR:Complications of IUGR:Short termShort term

Hypoglycemia Hypothermia Hyperviscosity syndrome Impaired immune function RDS / NEC if preterm Birth asphyxia

Complications of IUGR:Complications of IUGR:long termlong term

Cerebral palsy Small decrease in IQ Reduced scores for executive cognitive functions Risk related to severity of IUGR

Developmental Origins of Adult Diseases Developmental Origins of Adult Diseases (The Barker Hypothesis)(The Barker Hypothesis)

IUGR fetuses compensate for adverse intrauterine environment by endocrine-metabolic reprogramming

In adult life this leads to increased risk of hypertension, hypercholesterolemia, IGT, IHD

Management of Management of MacrosomiaMacrosomia

Differential Diagnosis of Differential Diagnosis of High SFHHigh SFH

Macrosomia Polyhydramnios Multiple pregnancy Uterine fibroids Pelvic masses Maternal obesity

Diagnosis of Diagnosis of LGA/MacrosomiaLGA/Macrosomia

Ultrasound biometry Conversion to an estimated fetal weight Some centres use FAC only Cut-off for LGA is EFW>90th pct Cut-off for macrosomia 4500 g or 5000 g

Accuracy of UltrasoundAccuracy of Ultrasound

Less accurate for big babies Sensitivity ranges from 22% to 69% May not be more accurate than clinical

palpation alone

Complications of MacrosomiaComplications of Macrosomia Birth trauma Erbs’ Palsy Birth asphyxia Neonatal hypoglycemia Polycythemia Neonatal jaundice Hypercalcemia, hypomagnesemia RDS Meconium Aspiration Syndrome

Maternal Complications of Maternal Complications of MacrosomiaMacrosomia

Genital tract trauma PPH Increased risk of emergency CS

Complications of Macrosomia:Complications of Macrosomia:Long TermLong Term

In GDM offspring Neurodevelopmental delay Reduced head circumference at 3

years of age Greater risk of type 2 DM Obesity

Management of Macrosomia:Management of Macrosomia:Vaginal Delivery or C/S ?Vaginal Delivery or C/S ?

Controversial issue Shoulder dystocia difficult to predict Some centres use 4500 g or 5000 g RCOG does not recommend C/S for

suspected macrosomia

Management of Macrosomia:Management of Macrosomia:Induction of Labor ?Induction of Labor ?

Common request from patients No evidence that it reduces the risk of

shoulder dystocia

normal and abnormal fetal growth

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