Abnormal Maternal Body Mass Index and Customized Fetal Weight Charts: Improving the Identification of Small for Gestational Age Fetuses and Newborns.

BACKGROUND: Obesity and thinness are serious diseases, but cases with abnormal maternal weight have not been excluded from the calculations in the construction of customized fetal growth curves (CCs). METHOD: To determine if the new CCs, built excluding mothers with an abnormal weight, are better than standard CCs at identifying SGA. A total of 16,122 neonates were identified as SGA, LGA, or AGA, using the two models. Logistic regression and analysis of covariance were used to calculate the OR and CI for adverse outcomes by group. Gestational age was considered as a covariable. RESULTS: The SGA rates by the new CCs and by the standard CCs were 11.8% and 9.7%, respectively. The SGA rate only by the new CCs was 18% and the SGA rate only by the standard CCs was 0.01%. Compared to AGA by both models, SGA by the new CCs had increased rates of cesarean section, (OR 1.53 (95% CI 1.19, 1.96)), prematurity (OR 2.84 (95% CI 2.09, 3.85)), NICU admission (OR 5.41 (95% CI 3.47, 8.43), and adverse outcomes (OR 1.76 (95% CI 1.06, 2.60). The strength of these associations decreased with gestational age. CONCLUSION: The use of the new CCs allowed for a more accurate identification of SGA at risk of adverse perinatal outcomes as compared to the standard CCs.

Maternal Thinness and Obesity and Customized Fetal Weight Charts.

OBJECTIVE: The aim of the study was to determine if customized fetal growth charts developed excluding obese and underweight mothers (CC(18.5-25)) are better than customized curves (CC) at identifying pregnancies at risk of perinatal morbidity. MATERIAL AND METHODS: Data from 20,331 infants were used to construct CC and from 11,604 for CC(18.5-25), after excluding the cases with abnormal maternal BMI. The 2 models were applied to 27,507 newborns and the perinatal outcomes were compared between large for gestational age (LGA) or small for gestational age (SGA) according to each model. Logistic regression was used to calculate the OR of outcomes by the group, with gestational age (GA) as covariable. The confidence intervals of pH were calculated by analysis of covariance. RESULTS: The rate of cesarean and cephalopelvic disproportion (CPD) were higher in LGAonly by CC(18.5-25) than in LGAonly by CC. In SGAonly by CC(18.5-25), neonatal intensive care unit (NICU) and perinatal mortality rates were higher than in SGAonly by CC. Adverse outcomes rate was higher in LGAonly by CC(18.5-25) than in LGAonly by CC (21.6%; OR = 1.61, [1.34-193]) vs. (13.5%; OR = 0.84, [0.66-1.07]), and in SGA only by CC(18.5-25) than in SGAonly by CC (9.6%; OR = 1.62, [1.25-2.10] vs. 6.3%; OR = 1.18, [0.85-1.66]). CONCLUSION: The use of CC(18.5-25) allows a more accurate identification of LGA and SGA infants at risk of perinatal morbidity than conventional CC. This benefit increase and decrease, respectively, with GA.