There are no official guidelines to assist in answering this question. I will search for relevant research papers instead.
From the Research
Significance of Microcephaly in a Fetus with Intrauterine Growth Restriction (IUGR)
- Microcephaly is a significant prognostic factor in fetuses with intrauterine growth restriction (IUGR) and deserves special attention and separate evaluation 1
- The incidence of microcephaly varies widely due to differences in definition and population being studied, and it is strongly related to neurodevelopmental disorders 1
- Microcephaly in growth-restricted fetuses is not necessarily part of the general growth retardation, and its diagnosis can be challenging due to differences in definitions and measurement techniques between fetuses and newborns 1
Risk Factors and Associations
- Severe intrauterine growth restriction, delivery for preeclampsia, placental infarction, and being female are associated with microcephaly in extremely low gestational age newborns 2
- Characteristics associated with fetal growth restriction and preeclampsia are among the strongest correlates of microcephaly among children born at extremely low gestational ages 2
- Microcephaly is also associated with nonwhite race, and the risk factors for a head circumference between <1 and >2 SD below the median are similar to those of microcephaly 2
Diagnosis and Management
- Deceleration of the head circumference growth rate, even when the head circumference is still within normal limits, might be the only clue for developing microcephaly and should be considered during fetal head growth follow-up 1
- Combining additional parameters such as a positive family history, associated anomalies, and new measurement parameters can improve prediction in about 50% of cases, and thus should be part of the prenatal workup 1
- Advances in imaging modalities and in prenatal genetic investigation, along with the emergence of new growth charts, can also improve diagnostic accuracy 1
Outcomes and Complications
- Children born with fetal growth restriction (FGR) or small for gestational age (SGA) have a higher risk of minor cognitive deficits, school problems, and metabolic syndrome in adulthood 3, 4
- The risk of neonatal mortality is two to four times higher in SGA newborns than in non-SGA preterm and full-term infants 4
- Initial management of an SGA newborn includes combatting hypothermia, ventilation with a pressure-controlled insufflator if necessary, and close monitoring of capillary blood glucose 4