Is maternal anemia associated with small placental volume in the first trimester?

Anaemia in the first trimester and poor physiological plasma expansion during pregnancy negatively impact foetal weight and newborn anthropometrics: An observational cohort study in Tanzania

OBJECTIVES

Anaemia during pregnancy is a major health challenge affecting pregnancy outcome worldwide. The objectives of this study were to investigate the impact of severe-moderate anaemia in the first trimester, as well as changes in haemoglobin during pregnancy among non-anaemic women, on foetal weight, placental blood flow and newborn anthropometrics.

METHODS

In a prospective cohort study, 346 women residing in rural Tanzania were followed throughout pregnancy with serial ultrasound and newborn anthropometrics assessed within 24 h of delivery. Associations between placental blood flow, foetal weight and newborn anthropometrics with either first trimester severe-moderate anaemia (haemoglobin≤9.5 g/dL) or changes in haemoglobin from the first to the third trimester among non-anaemic women, were assessed by mixed model regression and multiple linear regression, adjusting for maternal and foetal co-variables. Foetal weights and birthweight were converted to z-scores using a population based sex-specific weight reference.

RESULTS

Severe-moderate anaemia in the first trimester was associated with significantly reduced foetal weight z-scores (adjusted mean difference (aMD) -0.44 (95% CI -0.81, -0.07)) and newborn anthropometric indices (birth weight z-score aMD -0.55 (-0.9, -0.13), abdominal circumference aMD -11 mm (95% CI -20, -3)). There were no association between first trimester severe-moderate anaemia and placental blood flow. Among women who were non-anaemic in the first trimester, women with the least reduction in haemoglobin (Δ ≥ -0.3 g/dL) delivered significantly smaller newborns (birthweight z-score aMD -0.55 (-0.91, -0.20), abdominal circumference aMD -10 mm (95% CI -17, -3), compared to women with the greatest reduction (Δ haemoglobin ≤ -1.4 g/dL)).

CONCLUSIONS

Severe-moderate anaemia in early pregnancy was associated with smaller newborn anthropometrics which was reflected in smaller mean foetal weights in the second and third trimester. Furthermore, among women who were non-anaemic in the first trimester, there was an association between smaller newborn anthropometrics and limited haemoglobin decrease during pregnancy, possibly reflecting insufficient plasma expansion.

Mild anemia during pregnancy upregulates placental vascularity development

The connection between maternal hematological status and pregnancy outcome has been shown by many independent researchers. Attention was initially focused on the adverse effects of moderate and severe anemia. Interestingly, some studies revealed that mild anemia was associated with optimal fetal development and was not affecting pregnancy outcome. The explanation for this phenomenon became a target for scientists. Hemodilution, physiologic anemia and relative decrease in hemoglobin concentration are the changes observed during pregnancy but they do not explain the reasons for the positive influence of mild anemia on a fetomaternal unit. It is hypothesized that hemodilution facilitates placental perfusion because blood viscosity is reduced. Subsequently, it may lead to a decline in hemoglobin concentration. Anemia from its definition implies decreased oxygen carrying capacity of the blood and can result in hypoxemia and even hypoxia, which is a common factor inducing new blood vessels formation. Therefore, we raised the hypothesis that the lowered hemoglobin concentration during pregnancy may upregulate vascular growth factor receptors expression such as VEGFR-1 (Flt-1) and VEGFR-2 (FLK-1/KDR). Consecutively, increased fetoplacental vasculogenesis and angiogenesis provide further expansion of vascular network development, better placental perfusion and hence neither fetus nor the mother are affected.

Maternal hemoglobin concentration and hematocrit values may affect fetus development by influencing placental angiogenesis

OBJECTIVE

Vasculogenesis and angiogenesis are crucial for maintaining proper placental perfusion and optimal fetal development. Among other physical and chemical factors, hypoxia is known to stimulate angiogenic processes. Preplacental type of hypoxia is often associated with maternal anemia and is thought to enhance vascularization within the fetoplacental unit. The goal of this study was to establish the correlation between the local expression of vascular endothelial growth factor (VEGF) and placenta growth factor (PlGF) receptors (flt-1, flk-1) with maternal hemoglobin (Hb) concentration, hematocrit (Ht) values and the infant birthweight.

METHODS

In total, 43 specimens of term placentas obtained from normal course pregnancies delivered at term were included in the study. The expression of flt-1 and flk-1 receptors was analyzed by immunohistochemical staining. Vascular/extravascular tissular index (V/EVTI) was measured by assessing a total vascular area. Nonparametric Mann-Whitney U-test and Spearman's rank correlation were used to compare the various parameters and their differences between the groups.

RESULTS

Among the patients with low Hb concentration, nearly 2-fold greater expression of the flt-1 receptor was positively correlated with infants birthweight (p = 0.028).

CONCLUSIONS

Increased placental vascular density (increased flt-1 expression), during a physiological course of gestation, may be an adaptive response to lowered maternal Hb concentration and Ht values encountered during pregnancy.

Influence of maternal anemia during pregnancy on placenta and newborns

Introduction:

Sideropenic anemia is a common pregnancy disorder. Depending on severity, maternal anemia can significantly influence morphometric characteristic of placental tissue, pregnancy course and outcome. Objectives: to estimate if maternal anemia a) results with significant placental changes; b) influence on newborn weight, length and vitality.

Patients, material and methods:

Research included 100 women and their newborns, 50 anemic, and 50 women in the control group. Sixty placentas were collected, placental mass and volume was determined, and blood vessels of terminal villi were stereologically analyzed. Newborns mass and body length, and Apgar scores within 1 and 5 minutes after delivery were recorded.

The results:

Placentas of anemic pregnant women showed significant increase of terminal villi blood vessels (224,18 vs. 197,00 cm³; p<0,0001), but total placental mass and volume did not differ significantly. Anemic mothers’ newborns were significantly shorter (51,76 vs. 55,54 cm; p<0,0001), smaller body mass (3048,00 vs. 3615,60 g; p<0,0001) and delivered one week early (38,2 vs. 39,2 GW; p<0,0001), but not significantly poorer vitality (p>0,05) comparing with the control group.

Conclusion:

Sideropenic anemia increase placental maturity, that could be a possible cause of earlier spontaneous delivery among anemic women. The anemic mothers’ newborns are shorter and lower body mass, but not poorer vitality index.