IUGFR Flashcards
Define IUGFR and SGA
- SGA: birth weight < 10th centile
* FGR: Failure of the fetus to achieve its predetermined growth potential for various reasons
What are the key features of early IUGR
Early IUGR • Size
• Umbilical
Doppler- abnormal umbilical arteries
AC<10th centile
AC<3rd centile - severe
What is meant by low birth weight
Low birthweight (LBW): Less than 2,500g at delivery. Currently ~7% of live births (UK).
Very low birthweight (VLBW): Less than 1,500g at delivery. Currently ~1% of live births (UK).
Extremely low birthweight (ELBW): Less than 1,000g at delivery. Currently ~0.2% of live births (UK).
Describe low birth weight
- Epidemiological studies use BW alone, not GA
- Most LBW neonates are NOT growth restricted
- Many FGR babies are delivered prematurely
- 3-10 fold increase in perinatal morbidity and mortality- associated with early delivery
- LBW, FGR and preterm delivery have closely associated pathologies
Describe the issues with regarding low birth weight and why is this important
The last two definitions take no account of gestational age, they simply refer to the weight of the infant at delivery. This is very important – for example, an infant of 2,500g at term would be considered SGA, whereas if delivered at 33 weeks this would be an appropriate weight for a normal infant
Infants who are inappropriately small at delivery are at increased risk of a range of neonatal complications. In many cases, treatment is best started as soon as possible, so identifying the at-risk infants is important.
It is important to differentiate between infants born preterm, who are of low birthweight simply because they have been born early, and those who are growth restricted; the latter are a greater risk of morbidities and mortality after delivery, and most low birthweight infants are in the former group (and hence at lower risk).
What type of definition is SGA
- The terms ‘small for gestational age’ (SGA) and ‘small-for-dates’ are statistical definitions of weight at birth (below a subjective centile on charts of birth weight standards)
- The centiles most commonly employed are the tenth, fifth or third.
Describe the importance of the choice of centiles for SGA
- When choosing which centile to use, a balance between sensitivity and specificity is being made – the tenth centile is most sensitive and the third centile is most specific.
- The tenth centile will capture all babies with FGR, but will also include those babies that are just small for gestational age, i.e. you get a number of false positives.
- All babies recorded using the third centile will have FGR, but some FGR babies may be missed, i.e you get a number of false negatives.
which centile is used for large gestational age
> 90th centile
When should the term FGR be used
• The term FGR should only be used for fetuses with definite evidence that growth has altered.
• Growth is a dynamic process of a change of size over time and, therefore, it can only be assessed by serial observation (ie over a period of 10-14 days)
the serial measurements show that the infant is not growing ‘along a centile’, but is growing less than would be expected.
Describe the overall outcomes for babies with FGR
- IUGR is the most common factor identified in stillborn babies.
- In addition, it has serious consequences for babies who survive.
- Furthermore, there is an increased risk of IUGR and intrauterine death (IUD) in mother’s subsequent pregnancy.
What are the short term problems of LBW/FGR/Prematuritry
Respiratory distress Intraventricular haemorrhage Sepsis- start on antibiotics Hypoglycaemia- give dextrose drip Necrotising enterocolitis- ischaemic bowel Jaundice- weight loss Electrolyte imbalance
Describe the longer term problems of LBW/FGR/Prematuirty
Medium term
Respiratory problems
Developmental delay
Special needs schooling
Long term
Fetal programming- problems in adult life
Describe the different causes of SGA
Dating problem - growth normal, wrong date (normal fluid/dopplers) consistent growth
Normal - growth may reduce normally (normal fluid/dopplers)
Foetal problems (5%) - abnormality/infection
Placental insufficiency (20%) - reduction in AC/FL, with deranged dopplers (blood flow diverted to essential organs-mover less)- reduced liquor- infrequent urination
AC decreased due to loss of centripetal fat
HC decreases last
When does IUFGR usually occur
IUGR generally develops in the second and third trimesters of pregnancy. The first trimester concentrates on the development of embryonic and fetal structures, so the fetus weighs about 50g at the end of the first trimester. Almost all weight gain occurs in the later stages of pregnancy, so this is when the main causes are apparent.
What is important to remember about the risk factors for IUGR
These factors may be present in combination, in which case the risk of IUGR may be increased.
Describe the maternal medical factors that can lead to IUGR
- Chronic hypertension •Connective tissue disease •Severe chronic infection •Diabetes mellitus •Anaemia
- Uterine abnormalities •Maternal malignancy •Pre-eclampsia •Thrombophilic defects
Describe the fetal factors that can lead to IUGR
- Multiple pregnancy
- Structural abnormality •Chromosomal abnormalities •Intrauterine (congenital) infection •Inborn errors of metabolism
iNFECTIONS- CMV, toxoplasmosis
Describe the placental factors that can lead to IUGR
- Impaired trophoblast invasion •Partial abruption or infarction •Chorioamnionitis
- Placental cysts
- Placenta praevia
Describe the maternal behavioural factors that can lead to IUGR
- Smoking
- Low booking weight (<50 kg) •Poor nutrition
- Age <16 or >35 years at delivery •Alcohol
- Drugs
- High altitude
- Social deprivation
Summarise the changes that take place during the pregnancy
The first half of pregnancy is a time of preparation for the demands of rapid fetal growth in the second half of pregnancy
Alterations in maternal physiology to facilitate transfer of nutrients to the fetus
Increased mass of maternal stores of glucose and adipose tissue
Increased placental mass
Increased mass of fetus
Summarise placental development
- 10-12 weeks is the period of placentation
- Rapid early growth prepares way for fetal growth
- Trophoblast cells use same molecular mechanisms as tumors (invasion), but are highly regulated and controlled- interruptions in this- early onset IUGR
Two phases of placentation:
1st- primary implantation
2nd- 14-16 weeks- last for 4 weeks
Describe the roles of the placenta
- Maintains immunological distance between mother and fetus
- Special endocrine organ: produces protein-peptides and steroid hormones and functions as a “transient hypothalamo-pituitary-gonadal axis”
- Responsible for exchange of nutrients, gases & metabolic waste products between maternal and fetal circulation
Outline a schemata for the relationship between fetal nutrition and fetal growth
nutrition demand and placental supply influence fetal nutrition, depends on: fetal genome maternal body composition utero-placental blood flow dietary intake and placental transfer
fetal nutrion influences:
oxygen blood flow
nutrient supply (glucose, amino acids, fatty acids)
endocrine regulation (IGFs, PGH, leptin)
in turn, these all influence fetal growth.
Explain the link between IUGR and pre-eclampsia
There is a close link between pre-eclampsia (pre-eclamptic toxaemia, PET) and IUGR, so that these complications often occur together. The reason seems to be that the main cause of pre-eclampsia is diminished remodelling of the spiral arteries by cytotrophoblast (Figure 6.13), which causes decreased blood flow and hence decreased nutrient supply to the placenta and fetus.
Increased resistance in the spinal arteries as they stay narrow.
Summarise the key features of pre-eclampsia
• Hypertension • Proteinuria
HBP in 10% all pregnancies Only 1-2% severe form “Fetal syndrome” is relatively rare
What is the current definition of pre-eclampsia
The International Society for the Study of Hypertension in Pregnancy: gestational hypertension of at least 140/90 mmHg on two separate occasions ≥4 hours apart
Describe pre-eclampsia
Multisystem disease that usually manifests as hypertension and proteinuria
BP>140/90mmHg and proteinuria >0.3g/24hour (PCR>30)
Mild140-149/90-99mmHg Moderate 150-159/100-109mmHg Severe ≥160/110mmHg
arising de novo
after the 20th week of gestation in a previously normotensive woman and resolving completely by the 6th postpartum week
Describe the epidemiology of pre-eclampsia
IUGR can occur independently of pre-eclampsia; sometimes this may be because of altered placental function, without any maternal symptoms, but mostly it will be the result of some complication within the fetus itself.
Pre-eclampsia occurs in ~5% of pregnancies, which makes it one of the most common complications of human pregnancy. This makes link between pre-eclampsia and IUGR important, given that pre-eclampsia and IUGR are both risk factors for preterm delivery
Which foetuses need growth monitoring
Bad Obstetric History
Previous maternal hypertension
Previous FGR Stillbirth
Placental Abruption
Concerns in index pregnancy
Abnormal serum biochemistry PAPP-A <0.3 MoM
Reduced symphysis fundal height
Maternal systemic disease e.g. hypertension, renal, coagulation
Antepartum haemorrhage
Describe how you can predict which foetuses will be growth restricted
Poor Obstetric History • Primips • Obese • Afro-Carribean / African • Strong Family History • Essential hypertension • Diabetes / Impaired Glucose Tolerance • Systemic vascular disease • Renal disease • Thrombophilias
Describe the concerns that may arise in the index pregnancy which should indicate that the foetus needs to be monitored
Abnormal serum biochemistry • Reduced symphysis fundal height • Maternal systemic disease e.g. PET • Antepartum haemorrhage • Multiple pregnancy
Describe the screening for at risk pregnancies at 24 weeks.
- PAPP-A < 0.3 MoM, POHx PET / FGR
- Maternal systemic disease e.g. HT, renal, sickle
- Uterine artery Doppler 1st/ 2nd trimester – blood flow through uterine arteries: identify high resistance flow
Describe how to analyse uterine artery doppler screening
Normal- clear spikes with good diastolic flow (no notched between spikes)
Pre-eclampsia- early diastolic notches, poor diastolic flow- lower reading than that of normal between the spikes due to higher resistance.
Describe the results from a meta-analysis linking the uteroplacental doppler screening to Pre-eclampsia
Likelihood Ratio: Positive test = 4.89 (95% CI: 4.33-5.48) Negative test = 0.55 (95% CI: 0.50-0.61)
Describe the results from a meta-analysis linking the uteroplacental doppler screening to FGR
Likelihood Ratio: Positive test = 3.68 (95% CI: 3.32-4.07) Negative test = 0.73 (95% CI: 0.70-0.76
Describe the sequence of events in FGR
Increased uterine artery resistance- increased umbilical artery resistance.
Blood is redirected to the brain- so middle cerebral artery resistance decreases- fetal movement decreases and reduced liquour volume (less urination)
Blood in the fetus becomes more acidotic- increasing ductus venous pressure- IUD
PI= pulsatility index, if high- associated with increased risk of pre-eclampsia and thus impaired placentation.
How do we calculate PI
Arteries: Peak systolic veolicty (S)- end diastolic velocity (D) / Vm
Veins- s-a/vm
When does increased impedance in the umbilical arteries become evident
Increased impedance in the umbilical arteries becomes evident only when at least 60% of the placental vascular bed is obliterated
What is seen in the umbilical artery proper
PI lower at the placental end
Hypoxia to acidosis- negative flow- flow from mother into the fetus.
How does the fetus respond to hypoxia
Aortic body chemoreceptor stimulation leading to the redistribution of cardiac output
Increased flow • Brain • Heart • Adrenals
Decreased flow • Lungs • Kidneys • Gut
Hypoxia also causes CNS dysfunction:
• Poor tone • Altered breathing • Altered movement patterns • Changes in heart rate patterns on CGT
What happens to the middle cerebral artery in FGR
Decreased PI
Hypoxic- less gaps between peaks
Describe 25% flow in the umbilical vein
Ductus venosus Intrahepatic AC growth
• Fetal lungs inactive in utero • Right ventricle dominant • Blood shunted through foramen ovale
• Fetal perfusion of renal system • Amniotic fluid production
Describe the ductus venosus
• Longitudinal through upper abdomen • Parallel, anterior to the right of the aorta • Receives 40% of umbilical venous flow • Directs oxygenated blood to the L ventricle
Describe the monitoring of fetal movement
• A reduction in fetal movements may precede fetal death by a day or more; therefore, fetal movement counting may be of value in assessing fetal wellbeing. • In the UK, the Cardiff kick chart is the most commonly used method. • Mothers record the time taken each day to feel ten fetal movements. • Women who report a reduction in fetal movements, and particularly those who report an absence of fetal movements, need cardiotocography and/or an ultrasound assessment of the fetus to reassure the mother and ensure fetal wellbeing.
Summarise the general principles of managing a fetus with FGR
- Problems in the index pregnancy Manage according to serial fetal biometry, fetal Doppler, BPP and CTG
- Screening of “at risk” pregnancies 24/40 Ut A screening - growth every 2 weeks, US weekly
- Delivery Aim to deliver when ≥28 weeks and / or ≥500g Caesarean section for compromised foetuses
Describe how deliveries in pregnancies are complicated by FGR
Timing delivery in these pregnancies depends on balancing the risks to the fetus if it remains in utero and the hazards from the prematurity, which decrease as the gestation advances
• Evidence of fetal compromise on CTGs or abnormal Dopplers/ ultrasound finding / maternal compromise
• Corticosteriods should be administered (if not already given) at gestations < 36 weeks in order to improve neonatal wellbeing - for lung surfactant
What will the mode of delivery depend upon
Gestation of the pregnancy • Condition of the pregnancy • State of the cervix • Presentation of the fetus • Other factors: oligohydramnios – labour may be poorly tolerated due to cord compression
Describe the survival and morbidity trends in preterm infants
Later gestation delivery associated with increased survival and less morbidity (less risk from RDS, intraventricular haemorrhage, necrotising enterocolitis and sepsis)
Describe early IUGR
• Low incidence 1% • Highly correlated to maternal disease (preeclampisa) • Difficult to manage – Balancing risks of severe prematurity and morbidity with risk of in utero death
Describe late IUGR
• More common 5-7% • Rarely correlated to preeclampisa • Difficult to differentiate from constitutionally SGA • Easy to manage: deliver • But when and how?
What is important to remember about pre-eclampsia
In the particular case of pre-eclampsia (with or without IUGR), as the placenta is the primary cause, the ultimate ‘treatment’ is delivery. As indicated above, it is the balance between risks that is important in making the decision about the timing of delivery. In some pregnancies, the health of mother or infant (or both) can deteriorate rapidly, making an emergency Cesarean section a necessity.
Once IUGR or pre-eclampsia have been identified, it is very difficult to treat these complications and reverse their impact on the infant.
Describe the risk of CMV
- 30% risk of transmission of CMV in pregnancy and the risk to the baby is highest in the first trimester
- Normal outcome or associated with neurodevelopmental delay and deafness • Cannot be excluded by ultrasound alone • Amniocentesis: for CMV PCR • Ideally >6 weeks from the point of infection • Miscarriage (0.5-1%) or rupture of membranes • Patient is committed to pregnancy and declined invasive testing
Describe cystic hygroma (excessive nuchal skin)
Referred with increased NT of 9mm Findings: Septated cystic hygroma Associated with underlying genetic conditions such as Turner's syndrome or trisomies, cardiac abnormalities as well as maternal infection There is an increased IUD For CVS
Describe a rare skeletal dysplasia that may explain the cystic hygroma
Desbuquois skeletal dysplasia, confirmed by genetic testing
This is an exceedingly rare condition with uncertain prognosis
Describe pentasomy X
49,XXXXX, is a rare chromosomal abnormality in which a female has five X chromosomes instead of the normal two
Variable phenotype
Signs may include intellectual disability, short height, low-set ears, decreased muscle tone, and developmental delay
