Maternal risk factors for small-for-gestational age newborns in Japanese dichorionic twins.

Aim: To investigate the maternal risk factors for small-for-gestational age (SGA) newborns in Japanese dichorionic (DC) twins.

Methods: A retrospective study was conducted from 2003 to 2008 on 340 DC twin pregnancies resulting in two live births. Newborns were classified as SGA if their birth weight was below the 10th percentile according to Japanese singleton norms. Statistical differences were evaluated between pregnancies resulting in appropriate-for-gestational age (AGA) pairs and those resulting in at least one SGA neonate.

Results: The study population consisted of AGA/AGA (50.8%), AGA/SGA (37.0%) and SGA/SGA pairs (12.0%). Logistic regression analysis identified significant interrelations for SGA with maternal nulliparity (odds ratio [OR] 0.52, 95% confidence interval [CI] 0.30-0.91), smoking (OR 3.25, 95% CI 1.09-9.66), assisted reproductive technology (OR 0.52, 95% CI 0.30-0.89), pregnancy-induced hypertension (OR 2.00, 95% CI 1.01-4.31), pregravid weight (kg) (unitary OR 0.94, 95% CI 0.91-0.97) and monthly weight gain (kg/month) (unitary OR 0.25, 95% CI 0.14-0.44). Bivariable receiver operating characteristic curves were generated for monthly weight gain (area under the curve [AUC] 0.626, cutoff 1.41 kg/month, P<0.001) and total weight gain (AUC 0.615, cutoff 14.0 kg, P<0.001).

Conclusion: Cigarette smoking and weight gain control are relatively modifiable factors for which interventional management is necessary to avoid perinatal problems arising from SGA pregnancy. Further studies are needed to investigate optimal nutrition, health guidance and subsequent weight gain control that lead to concrete improvement in maternal and infant prognoses.