Prior Term Birth Weight: Is It Useful for Predicting Fetal Weight in Subsequent Pregnancies?

摘要

Objectives: To investigate the relationship between birth weights in successive pregnancies.Methods: Successive, full-term pregnancies were examined in 54 non-diabetic, non-hypertensive women. Birth weights in prior pregnancies were used to predict subsequent birth weights, both alone and after correcting for differences in gestational age and fetal gender between the two pregnancies.Results: Prior birth weight predicted subsequent birth weight with a correlation of 0.39 and a mean absolute prediction error of ±330 g (±9.6%). Correcting for changes in gestational age and fetal gender increased the correlation to 0.51 and reduced the mean absolute prediction error to ±291 g (±8.4%). Conclusions: Term birth weight in multiparous women can be predicted to within ±291 g (±8.4%) using only prior birth weight and two other variables that describe the current and preceding pregnancies. This routinely available information may explain why mothers can estimate the birth weights of their current fetuses with reasonable accuracy. Introduction Recently, it has been reported that pregnant women are able to predict the birth weight of their offspring with an accuracy ranging from ±305-402 g (±8.7-11.5%) at term. 1,2,3,4,5 By contrast, obstetrician's abilities to predict birth weight using clinical palpation have ranged between ±277-336 g (±7.5-10.3%), 1,2,3,4,5,6,7,8,9 and when obstetrical ultrasonography is employed, it's accuracy has ranged between ±285-564 g (±8.2-15.6%) in the same and similar studies. 3,4,5,6,7,8,9This study was undertaken to examine the paired birth weights of term offspring born to non-diabetic, non-hypertensive women who had two deliveries within a four-year period at a single academic institution in the United States. In addition, a prediction model was developed for estimating term fetal weight based on a combination of factors during the current and prior pregnancies to address the question of whether multiparous women can make birth weight estimations based on the integration of routinely available pregnancy-specific information that can also potentially be used by clinicians. Subjects and Methods The women included for study were delivered between August 1998 and April 2001 by one of the general obstetrical faculty practices within the Duke University Health System. All subjects were delivered at Duke University Hospital (elevation 106 m) and all were private patients. Approximately 700 women were delivered by this group during this period. Sixty-one of these women had term deliveries between 37-42 weeks of gestation and were also identified as having prior term deliveries at Duke University Hospital. The medical records of these patients were reviewed retrospectively to extract the following information for both pregnancies: maternal age, gravidity, parity, pre-pregnancy weight, final pregnancy weight, 50-g 1-hr glucose screening test result, 100-g 3-hr glucose tolerance test results (when necessary), medical illnesses, complications of pregnancy, fetal gender, birth weight, all standard pregnancy dating criteria, and maternal height and race.This study made use of archival, de-identified patient information that was obtained before 2003. The study was retrospective in nature and had no impact on either the routine clinical care that was provided or to the type of information that was gathered. Thus, it conforms to the standards established by the NHMRC for ethical quality review 10 and was exempted from institutional review board evaluation.During their prior pregnancies, two patients were diagnosed with gestational diabetes. Both were eliminated from further analysis due to the significant and highly variable effect of this condition on fetal weight. 11 Two additional patients were diagnosed with mild pre-eclampsia (1 in a prior and 1 in a subsequent pregnancy), and three others were diagnosed with chronic hypertension (2 in a prior and 1 in a subsequent pregnancy). These five patients were also eliminated f