LGA, SGA and IUGR Flashcards
Define LGA.
A baby which is >95th centile for weight or 4,000-4,500g at or after 36 weeks of pregnancy
What are the causes of LGA?
- FH of LGA or previous LGA baby
- High BMI (>35)
- GDM
How do you diagnose LGA?
If SFH is greater than expected on customised growth chart on two or more occassions or significant increase on one occasion –> growth scan
Growth scan then looks at:
- the fetal growth,
- amniotic fluid volume
- blood flow in placenta
What if the US for LGA showsn normal growth?
Refer back to midwife for continuing assessment for SFH (if the mother does not have diabetes)
At what gestation with LGA should the mother have OGTT?
If <36 weeks gestation - above this the OGTT is not reliable and any high blood glucose should be monitored with diet and exercise
What are the complications of LGA?
- Shoulder dystocia - 6-7/100 in LGA
- Erb’s palsy - due to brachial plexus damage in shoulder dystocia
- PPH
- Need for CS (1 in 3) or instrumental delivery (1 in 6)
- Perineal tears extending into the bowel
- Neonatal hypoglycaemia
- Neonatal polycythaemia
- Meconium aspiration
What is the management of LGA?
Depends on the patient - IOL may be recommended early or elective CS.
Monitoring for neonatal hypoglycaemia after delivery.
Define IUGR.
Describes a fetus that has not reached its growth potential because of genetic or environmental factors
Define SGA.
<10th centile for weight
Severe SGA is <3rd centile
Define low birth weight (LBW).
Defined as a birth weight < 2500g, regardless of gestational age
Describe VLBW.
A birth weight < 1500g, regardless of gestational age (although these babies are almost always premature).
What is SGA vs IUGR?
SGA - weight is less than the 10th percentile for that particular gestational age or two standard deviations below the population norms on the growth charts. Does not take into account in-utero growth of physical characteristics at birth
IUGR - neonates born with clinical features of malnutrition and in-utero growth restriction, irrespective of their birth weight percentile. Refers to fetus not reaching potential weight
- e.g. A baby may not be SGA but may still be considered to have had IUGR if they have features of in-utero growth restriction and malnutrition at the time of birthNot all babies with IUGR will be classified as SGA due to reference population standards used
- NB: SGA babies can be constitutionally small but actually normal e.g. when born to parents who are small ot into ethnic population that is smaller than the reference
What are the causes of SGA?
Constitutionally small
Non-placental mediated growth restritcion:
- Chromosomal disorders
- Congenital anomalies
- Multiple gestation
- Infection (e.g. TORCH*, malaria, varicella)
- Inborn errors of metablism
Placenta mediated growth restriction:
- Maternal factors e.g. low BMI, malnutrition, substance abuse, severe anaemia and medical conditions (e.g. PET, AI disease, thrombophilia, renal disease, essential HTN. )
- Other placental problems
*TORCH: Toxoplasmosis, Other (syphilis), Rubella, Cytomegalovirus, Herpes simplex virus
What placental factors contribute to IUGR?
- Uteroplacental insufficiency
- Abnormal implantation
- Vascular anomalies
- Placental abruption
- Infarction
- Tumour
- Villous placentitis (bacterial, viral, parasitic)
- Confined placental mosaicism
What are the minor and major risk factors for SGA? How many warrant monitoring for SGA?
1 major or 3 minor
What investgations are used to assess for SGA in women with risk factors for it?
1st and 2nd trimester:
- History and examination
- Ensure accurate dating by LMP (Nagele’s rule ) or CRL
- Maternal serum screening e.g. PAPP-A
- US for echogeneic bowel
- Uterine artery doppler
2nd and 3rd trimester:
- SFH and customised charts
- Serial US (if 1 major RF) from 26-28 weeks of pregnancy
- Uterine artery doppler (if 3 minor risk factors)
What is PAPP-A?
Pregnancy-associated plasma protein A (PAPPA)
Low levels in 1st trimester assocuated with chromosomal abnormalities
Which biochemical markers are good for screening of SGA?
Those tht have a placental origin e.g.
- PAPP-A - if <0.415MoM then major risk factor for delivery
- AFP - >2.5MoM or <0.15MoM
- High hCG
- High inhibin A
- Low unconjugated oestriol
- Combined triple test
What is the pathophysiology of SGA <3rd centile?
Usually failure of trophoblast invasion of the myometrial uterine spiral arteries and reduced uteroplacental blood flow - when persistent notching or abnormal flow velocity ratios are seen after 24 weeks
Other:
- karyotype
- CMV
- Toxoplasmosis
- Syphilis
From how many weeks should SFH be measured?
What if measuring small?
24 weeks of pregnancy onwards AND plotted on a customised chart rather than a population-based one
If measuring small refer for fetal USS to assess size
What are some reasons why SFH may be inaccurate?
bMI>35
Large fibroids
Hydramnios
Refer for ultrasounds to assess fetal size
Can SGA be prevented? How?
Antiplatelets - if high risk of PET, commenced at or before 16 weeks of pregnancy (1 high or 2 moderate RFs)
Lifestyle advice - smoking and alcohol reduction (no evidence for dietary)
What interventions should be considered in the preterm SGA fetus?
Cosrticosteroid infection if 24+0 to 35+6 weeks gestation
