Asymmetrical intra-uterine growth restriction is a type of intra uterine growth restriction (IUGR) where some fetal biometric parameters are disproportionately lower than others as well as falling under the 10th percentile. The parameter classically affected is the abdominal circumference (AC).
It tends to present more in the 3rd trimester (later than the symmetrical IUGR pattern) and is the more commoner of the two main types of IUGR.
In this type there is classically relative preservation of the fetal brain (fetal head sparing theory) which pathologically characterised by an increased brain to liver ratio (BLR) 2. This can also result in decreased fetal subcutaneous fat 4,6. A paradoxical rare situation is with maternal cocaine use where the head circumference is reduced out of proportion to others 5.
The incidence of concurrent karyotypic abnormalities are low (or minimal 3) especially if asymmetrical IUGR is detected late in pregnancy.
Syndromes that can give an asymmetrical IUGR picture include
Features in the classical situation include:
- changes in fetal biometric parameters
- fetal abdominal circumference (AC) classically reduced out of proportion to other fetal biometric parameters and is below the 10th percentile
- certain fetal biometric parameters such as biparietal diameter (BPD) and head circumference (HC) may be normal
- increased HC:AC ratio
- fetal tachycardia (may be present in up to 50% of cases 4)
Oligohydramnios may be present as an ancillary sonographic feature.
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- 3. Anandakumar C, Chew S, Wong YC et-al. Early asymmetric IUGR and aneuploidy. J. Obstet. Gynaecol. Res. 1996;22 (4): 365-70. - Pubmed citation
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- 5. Little BB, Snell LM. Brain growth among fetuses exposed to cocaine in utero: asymmetrical growth retardation. Obstet Gynecol. 1991;77 (3): 361-4. - Pubmed citation
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- 7. Al-ghazali W, Chita SK, Chapman MG et-al. Evidence of redistribution of cardiac output in asymmetrical growth retardation. Br J Obstet Gynaecol. 1989;96 (6): 697-704. - Pubmed citation
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Synonyms & Alternative Spellings
|Synonyms or Alternative Spelling||Include in Listings?|
|Asymmetric intrauterine growth restriction||✗|
|Type II IUGR||✓|
|Head sparing IUGR||✓|
|Disproportional intra uterine growth restriction||✗|
|Asymmetrical intra-uterine growth restriction||✗|
|Asymmetrical intrauterine growth restriction||✗|