Customised birthweight centiles are useful for identifying small-for-gestational-age babies in women with type 2 diabetes.
BACKGROUND
Customised birthweight centiles identify small-for-gestational-age (SGA) babies at increased risk of morbidity more accurately than population centiles, but they have not been validated in obese populations.


OBJECTIVE
To compare the rates of SGA by population and customised birthweight centiles in babies of women with type 2 diabetes and examine perinatal outcomes in customised SGA infants.


METHODS
Data were from a previous retrospective cohort study detailing pregnancy outcomes in 212 women with type 2 diabetes. Customised and population birthweight centiles were calculated; pregnancy details and neonatal outcomes were compared between groups that delivered infants who were SGA (birthweight < 10th customised centile) and appropriate weight for gestational age (AGA) (birthweight 10-90th customised centile).


RESULTS
Fifteen (7%) babies were SGA by population centiles and 32 (15%) by customised centiles. Two babies of Indian women were reclassified from SGA to AGA by customised centiles. Nineteen babies were reclassified from AGA to SGA by customised centiles; of these, 15 (79%) were born to Polynesian women, five (26%) were born less than 32 weeks and two (11%) were stillborn. Customised SGA infants, compared with AGA infants, were more likely to be born preterm (19 (59%) vs 20 (16%), P < 0.001) and more likely to be stillborn (4 (13%) vs 0 P = 0.001). After excluding still births, admission to the neonatal unit was also more common (19 of 28 (68%) vs 43 of 127 (34%), P < 0.001).


CONCLUSIONS
In our population more babies were classified as SGA by customised compared with population centiles. These customised SGA babies have high rates of morbidity.
Department of Obstetrics, National Women's Hospital, Auckland, New Zealand. jrowan@internet.co.nz
Janet A
JA
Rowan
Steven
S
Luen
Ruth C
RC
Hughes
Lynn C
LC
Sadler
Lesley M E
LM
McCowan
D000328:Adult; D001724:Birth Weight; D015992:Body Mass Index; D015331:Cohort Studies; D003924:Diabetes Mellitus, Type 2 / Q000150:complications* / Q000188:drug therapy; D005260:Female; D006801:Humans; D007004:Hypoglycemic Agents / Q000627:therapeutic use; D007231:Infant, Newborn; D007234:Infant, Premature; D007236:Infant, Small for Gestational Age; D008687:Metformin / Q000627:therapeutic use; D011247:Pregnancy; D011254:Pregnancy in Diabetics; D012016:Reference Values; D012189:Retrospective Studies
D007004:Hypoglycemic Agents; D008687:Metformin