Placental Growth Measures in Relation to Birth Weight in a Latin American Population

Abstract

Introduction The placenta, translates how the fetus experiences the maternal environment and is a principal influence on birth weight (BW). Objective To explore the relationship between placental growth measures (PGMs) and BW in a public maternity hospital. Methods Observational retrospective study of 870 singleton live born infants at Hospital Maternidad Sardá, Universidad de Buenos Aires, Argentina, between January 2011 and August 2012 with complete data of PGMs. Details of history, clinical and obstetrical maternal data, labor and delivery and neonatal outcome data, including placental measures derived from the records, were evaluated. The following manual measurements of the placenta according to standard methods were performed: placental weight (PW, g), larger and smaller diameters (cm), eccentricity, width (cm), shape, area (cm(2)), BW/PW ratio (BPR) and PW/BW ratio (PBR), and efficiency. Associations between BW and PGMs were examined using multiple linear regression. Results Birth weight was correlated with placental weight (R(2) = 0.49, p < 0.001), whereas gestational age was moderately correlated with placental weight (R(2) = 0.64, p < 0.001). By gestational age, there was a positive trend for PW and BPR, but an inverse relationship with PBR (p < 0.001). Placental weight alone accounted for 49% of birth weight variability (p < 0,001), whereas all PGMs accounted for 52% (p < 0,001). Combined, PGMs, maternal characteristics (parity, pre-eclampsia, tobacco use), gestational age and gender explained 77.8% of BW variations (p < 0,001). Among preterm births, 59% of BW variances were accounted for by PGMs, compared with 44% at term. All placental measures except BPR were consistently higher in females than in males, which was also not significant. Indices of placental efficiency showed weakly clinical relevance. Conclusions Reliable measures of placental growth estimate 53.6% of BW variances and project this outcome to a greater degree in preterm births than at term. These findings would contribute to the understanding of the maternal-placental programming of chronic diseases.

Placental measurements and their association with birth weight in a Brazilian cohort

“…After adjustment for maternal and infant factors, R 2 raised to 74%. This result is in agreement with previous Argentinian findings 13 . In contrast, an American study with a similar methodology found that the adjustment for covariates diminished the power of association between PM and BW 28 .…”

“…Although BW was correlated with PW, Figure 1 shows a wide variation in PW for any given BW; e.g., infants weighing around 3000 g had placentas ranging from 300 to 900 g. This finding suggests a wide variation in placental efficiency, which corroborates previous data 13 . The caloric intake and dietary composition during pregnancy affect the size of the human placenta at term 29 .…”

“…Previous studies conclude that a placenta with a low average thickness has decreased functional efficiency, leading to a smaller newborn for a given PW 15,23,28 . However, this and another Latin American study have found a low explanatory power of BW by placental thickness 13 . The speculated reason is that this measurement incompletely captures the variability that characterizes the human placenta.…”

“…Small placentas are more likely to be dysfunctional, and PW is closely correlated to birth weight (BW). Studies conducted in populations from various geographic and historic backgrounds confirm such association [11][12][13] . Besides, placental to birth weight ratio (PW/BW) is an important marker of fetal growth and a proxy of placental efficiency.…”

“…Placental morphometry has been extensively explored in developed countries, where PW percentile curves have been reported 15,16 . However, there is limited data from Latin American populations, including Brazilian ones 13,17,18 .…”