Big questions for a bigger data set

We thank Drs Zhao and Li for their interest in our work and their accurate interpretation of our main message: babies born large for gestational age (LGA) arrive there through different patterns of fetal growth, which may inform the underlying mechanisms, as well as the newborns’ risk for adverse outcomes. As Drs Zhao and Li pointed out, each of the 4 groups of babies who were born LGA consisted of participants who had pregestational diabetes mellitus and also participants who did not. Although pregestational diabetes mellitus was not a perfect predictor for any group, babies with a profile of prenatal catch-up growth were born to participants who were more likely to have poor measures of glucose control, as determined by results of the glucose tolerance and glucose loading tests and a clinical diagnosis of gestational or pregestational diabetes mellitus. Thus, we disagree with the statement that “maternal glucose levels or controls are not the main factor for fetal overgrowth.” This conclusion cannot be drawn from our data. We agree that the additional questions raised by Drs Zhao and Li are of interest. Our limited sample sizes precluded addressing 2 of these questions. Pregestational diabetes mellitus was present in only 4 to 15 participants per LGA group in our study; thus, investigating diverse glucose control strategies and their success among these individuals would not have been statistically informative. Similarly, only 9 to 20 participants per LGA group were admitted to the neonatal intensive care unit (NICU) per LGA group in our study, and investigating differences in reasons for admission would not have been meaningful. Answers to these questions must be pursued in studies with larger sample sizes. The authors also asked about differences in NICU admission based on whether the participant had pregestational diabetes mellitus. Our approach for this analysis was to stratify LGA births based on patterns of fetal growth, not maternal characteristics. Thus, we did not examine neonatal outcomes in association with maternal characteristics in our study. Finally, the authors asked about gestational weight gain across the 4 LGA groups. We did not examine this factor because we do not have information on weight at delivery among participants in our data set. This is also an interesting question for future work. Born large for gestational age: not just biggerAmerican Journal of Obstetrics & GynecologyVol. 228Issue 3PreviewA large-for-gestational-age (LGA) birthweight, defined as a birthweight above the 90th percentile, is associated with remarkable maternal and neonatal morbidity.1 LGA increases the risk of low neonatal Apgar score at 5 minutes, shoulder dystocia, and neonatal intensive care unit (NICU) admission. Maternal risks include higher cesarean delivery rates, postpartum hemorrhage, and third- and fourth-degree perineal lacerations. Recently, Bommarito et al2 identified and described trajectories of fetal growth among LGA births in the LIFECODES Fetal Growth Study based on prenatal ultrasound measurements of head circumference, abdominal circumference (AC), and femur length (FL). Full-Text PDF