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Definitions Control of fetal growth Determinants of birth weight Causes of IUGR Causes of 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
Control of Fetal GrowthControl of Fetal Growth
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).
Control of Fetal GrowthControl of Fetal Growth
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
2000
2500
3000
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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4000
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
Causes of IUGR:Causes of IUGR:3. Maternal factors3. Maternal factors
Hypoxemia- Severe anemia- Chronic lung disease- Cyanotic heart disease- High altitude (>2000 m)
Causes of IUGR:Causes of IUGR:3. Maternal factors3. Maternal factors
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
Causes of IUGR:Causes of IUGR:3. Maternal factors3. Maternal factors
Substance abuse Cigarette smoking Alcohol Illicit drugs ? Caffeine (>100 mg)
Causes of IUGR:Causes of IUGR:3. Maternal factors3. Maternal factors
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)
Causes of IUGR:Causes of IUGR:3. Maternal factors3. Maternal factors
Causes of IUGR:Causes of IUGR:3. Maternal factors3. Maternal factors
Other causes Vitamin D deficiency ART conception Radiotherapy Uterine malformations Extremes of reproductive life Short inter-pregnancy interval Chronic maternal stress
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
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Prevention Screening Diagnosis Management Long term complications
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
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
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
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
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
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