Abstract
The effects of gestational age on placental oxidative balance throughout gestation were investigated in women with uncomplicated pregnancies. Placental tissues were obtained from normal pregnant women who delivered at term or underwent elective pregnancy termination at 6 to 23 + 6 weeks of pregnancy. Placental tissues were analyzed for total antioxidant capacity (TAC) and lipid peroxide (malondialdehyde, MDA) levels using commercially available kits. Two hundred and one placental tissues were analyzed and the mean ± SD MDA (pmol/mg tissue) and TAC (µmol Trolox equivalent/mg tissue) levels for first, second, and third trimester groups were 277.01 ± 204.66, 202.66 ± 185.05, and 176.97 ± 141.61, P < 0.004 and 498.62 ± 400.74, 454.90 ± 374.44, and 912.19 ± 586.21, P < 0.0001 by ANOVA, respectively. Our data reflects an increased oxidative stress in the placenta in the early phase of normal pregnancy. As pregnancy progressed, placental antioxidant protective mechanisms increased and lipid peroxidation markers decreased resulting in diminution in oxidative stress. Our findings provide a biochemical support to the concept of a hypoxic environment in early pregnancy. A decrease in placental oxidative stress in the second and third trimesters appears to be a physiological phenomenon of normal pregnancy. Deviations from this physiological phenomenon may result in placental-mediated disorders.
Highlights
During the first trimester of pregnancy, the conceptus develops in a low oxygen environment that favors organogenesis in the embryo and angiogenesis in the placenta [1]
106 placental tissues were collected from women up to 13 weeks of gestation and were grouped as first trimester; 48 placental tissues were collected from women from 13+ to 23 weeks + 6 days of gestation and were grouped as second trimester; and 47 tissues were obtained from term normal placentas which were selected from deliveries of a newborn without maternal or fetalneonatal pathologies and were grouped as third trimester
On the other hand placental total antioxidant capacity (TAC) levels were found to be the lowest in the first and second trimester but the levels steadily increased as pregnancy progressed (Table 1 and Figure 1)
Summary
During the first trimester of pregnancy, the conceptus develops in a low oxygen environment that favors organogenesis in the embryo and angiogenesis in the placenta [1]. This low oxygen environment is created when maternal arterial blood is prevented from entering the intervillous space of the placenta by plugs of cytotrophoblast cells that invade the uterine spiral arteries. The normoxic environment created in the placenta is maintained until term [1] Perturbations in such an oxidative environment as pregnancy continues are suggested to play a role in the pathophysiology of pregnancy disorders such as preeclampsia, intrauterine growth restriction, and early pregnancy loss [1]
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