Small baby / IUGR

Question 1

How is neonate defined?

How is preterm baby defined?

Answer 1

1. Literal meaning = newborn in the first 28 days of life.
   => period of highest dependence and highest risk of mortality
2. A neonate whose calculated gestational age from the last menstrual period (LMP) is <37 weeks i.e. premature.

Question 2

Small baby:

Small babies may be normal due to parents being small.

Others are small regardless of parents size due to growth slowing/stopping in the uterus.

Answer 2

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Question 3

How is small for gestational age (SGA) calculated?

Answer 3

If weight is less than the 10th percentile, >2 standard deviation from the mean

Question 4

Definitions:

1. Low birth weight (LBW) = <2500g regardless of gestational age.

=> low birth weight baby may not be small for gestational age if it is born preterm

2. Very low birth weight (VLBW) = birth weight of <1500g regardless of age
3. Extremely low birth weight (ELBW) = birth weight of <1000g regardless of age

Answer 4

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Question 5

What happens in intrauterine growth restriction (IUGR)?

Answer 5

There is failure of growth in utero, which may or may not result in the baby being small for gestational age (SGA).

Question 6

Symmetrical (proportional) SGA = all growth parameters are symmetrically small (head circumference, weight, height equally reduced)

=> Suggests foetus was affected from early pregnancy

=> Early onset growth restriction (1st trimester)

=> Intrinsic cause i.e chromosomal abnormalities, constitutionally small (normal) or congenital infection.

Answer 6

Asymmetric (disproportional) SGA = the weight percentile < length and head circumference

=> Later onset growth restriction

=>Extrinsic cause i.e. insult later in the pregnancy e.g. placental, maternal (pre-eclampsia, hypertension, renal & cardio disease, maternal substance misuse)

=> These babies at a higher risk of complications

Question 7

What are the causes for asymmetric SGA / IUGR?

Answer 7

Poverty / poor social support account for 30% variance in birth weight

Constitutional factors

Malformation

Twins

Congenital infection

Placental insufficiency (maternal heart disease, hypertension, smoking, diabetes, sickle-cell disease, pre-eclampsia)

Question 8

Gestational age more important in predicting survival than birth weight alone.

Answer 8

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Question 9

Are SGA effects permanent?

Answer 9

90% of SGA catch up in growth in the first two years

BUT on average, adults are 1 standard deviation shorter than the mean adult height

Question 10

What is SGA / IUGR associated with / its complications?

Answer 10

Hypoglycaemia

Hypothermia

Genetic conditions

Poor postnatal growth => If severe, developmental problems

Risks from congenital infection / malformations if present

Polycythaemia (secondary to chronic intrauterine hypoxia)

Meconium aspiration

Necrotising enterocolitis (NEC)

Risk of foetal death

*may be an assoc. between SGA and adult risk of coronary heart disease and obesity