The TOST showed that for the SISVAN and the BMCNC data for 30–94 days, the weights could be considered statistically equivalent. These results emphasize that there is a difference between the measures, but this deviation is expected, chiefly because the first-trimester weight will be higher than pre-pregnancy weight. This would occur even if women remember this value correctly. In terms of magnitude of discrepancies, the means were round 2 kilogram for both datasets and all prison term intervals, and in the Bland and Altman plots, the majority of the remainder ( ~ 66–77 % ) were found in the ±2 kilogram time interval. Shin et aluminum. [ 8 ] besides observed that self-reported burden was lower than measured first-trimester system of weights by an average of 2.3 kg in data from 504 meaning women from the United States. The 2-kg difference is close to the expected weight gain in the inaugural spare [ 2 ] and may not be related to an inaccurate weight report card, but to rather to substantial changes in the measures because of the expect weight addition during this interval. besides, the plots revealed no design of remainder considering measured first-trimester BMI, which may indicate that the BMI classification does not change the way a woman report card her pre-pregnancy weight. The categorization of pre-pregnancy BMI using self-reported or first-trimester measured weight unit besides had a gamey agreement, i, the impact of using one weight or another in the classification of BMI was small, according to the values of the kappa coefficient. The reduce impact on the classification suggests that using self-reported rather than measured weight unit would not well bias BMI estimates. This solution differs from the findings of Fattah et aluminum. [ 36 ]. These authors evaluated 100 women from Ireland and observed that 22 % of the women were classified in different BMI categories whether self-reported or measured first-trimester weight was used in BMI calculation. For ascertainment of GWG, the differences observed between the weights would be the like for weight amplification calculated using self-reported pre-pregnancy or measures first-trimester slant. however, since measurements collected early in the first gear trimester are rarely available, using burden collected at any time during this period would not consider the possibility of weight acquire during the first clean-cut. maternal first-trimester weight deepen may be crucial to fetal increase and the child ’ s future health [ 37, 38, 39 ]. In addition, using first-trimester weight to calculate GWG would be debatable for those women who start prenatal caution after this time skeleton.
recently published GWG charts by Santos et aluminum. [ 40 ] and Hutcheon et aluminum. [ 41 ] used self-reported weight to calculate weight advance and classify pre-pregnancy BMI, considering self-reported weight as the most normally available information. however, the Intergrowth-21st GWG [ 42 ] and the swedish charts [ 43 ] used slant measured in the foremost spare, considering it a more allow source for the creation of the charts. It is possible to observe that there is still argument as to which standard should be employed, specially in studies assessing GWG [ 11, 44 ]. however, considering the solid agreement observed in the stream study, it seems fair to assume the majority of women would receive adequate GWG rede based on self-reported information. By using a prison term interval stopping point to creation ( 30–45 days ), we were able to show that the women ’ s report was not substantially biased and could be used when a measurement of weight unit in the beginning of pregnancy is unavailable. We besides argue that using a measurement of slant collected at any meter during the first spare, although more much available, might disregard an effective GWG in this period. future studies with weight unit measurements of women before conception could focus on developing a discipline gene or a calibration equation to obtain a more accurate value for ascertaining both pre-pregnancy BMI and GWG. This would only be possible if weighting non-pregnant women becomes separate of their routine health care .
Strengths and limitations
The handiness of both self-reported and careful weights in the foremost trimester on the lapp women permitted us to address the cardinal question of this study. Besides, using the most available naturalistic approaches for first-trimester weight besides allowed us to evaluate differences when each weight unit was used. Collecting self-reported weight at the beginning of pregnancy to help reducing recall bias is another important forte. besides, the boastfully sample distribution size in both datasets for the first-trimester measurement used in the analyses and the fact that these datasets are from a middle-income nation, where lone express information on this submit has been available, must be highlighted.
however, some limitations must be considered. The issue of women with a weight measurement in the first 30–45 and 30–60 days was relatively depleted, which affected the comparison of the coefficients and the decision of the TOST CI, even though the sample sizes for these periods were higher than those observed in several studies previously conducted on the topic [ 5, 35, 44 ]. The sample size was not boastful adequate to estimate coefficients according to BMI class, which would have been useful to compare differences between the report according to those categories. however, Bland and Altman plots were constructed depicting categories of BMI with different colors, and no gain practice of differences were observed. The reduction in the sample size in both datasets is another restriction to be mentioned. unfortunately, the proportion of women who initiate prenatal care before 13 weeks in Brazil is limited and selecting those who besides know their pre-pregnancy weight contributed further to decreasing the sample size available for this study in both sources of data. These facts may raise concern about the profile of the selected women, who may be well different from those removed from the analysis. however, the comparison of sociodemographic characteristics between all the women and those selected for this cogitation revealed a signally close profile ( Additional Table 1 ). The use of data collected in the routine prenatal care, which was the casing for most studies included in the BMCNC and the SISVAN, could besides introduce noise to the evaluation of the agreement between the measurements because the collection of weight and acme was not standardized. The accurate question used to inquire women about their pre-pregnancy weight is strange. In some studies, participants knew their system of weights ; in early cases, this data was abstracted from the participants ’ pregnancy booklets/cards. last, it was not potential to know the time of the collection of self-reported weight, i.e., if it occurred before or after women were weighted in the visit. If women reported their pre-pregnancy slant concisely after being weighted, knowing the system of weights could have influenced their report. We recommend that the time of slant is considered in future studies in the field .