Background: Early and late-onset preeclampsia is thought to be different disease entities. This study aimed to determine the effects of early-onset preeclampsia-like symptoms on feto-placental outcomes and the adverse impacts of various factors on placental and fetal growth and development at different gestational stages in a mouse model.
Methods: Pregnant C57BL/6J mice were divided into control and preeclampsia (PE) groups, and injected subcutaneously with the nitric oxide synthase inhibitor L-arginine methyl ester (L-NAME) 50 mgxkg(-1)d(-1). The PE group was divided into early-, mid- and late-PE groups with L-NAME injections starting on days 7, 11 and 16 of pregnancy, respectively. Corresponding control groups were injected with saline at the same time points. Blood pressure was measured until days 14 and 18, when the fetuses and placentas were removed under anesthesia. Blood pressure, urinary protein, and fetal and placental conditions were analyzed.
Results: Blood pressure and urinary protein increased following L-NAME injection. The fetal survival rate and fetal weight were reduced and the fetal absorption rate was increased in the early-PE group on days 14 and 18 of pregnancy, compared with the control group. There were no significant differences in these parameters between the late-PE group and the respective control group. Placental weights in the early- and mid-PE groups were significantly reduced at days 14 and 18 of pregnancy compared with the control groups, but there was no significant difference in placental weight between the late-PE group and the respective control group. Morphologic examination of placentas from the early- and mid-PE groups showed varying degrees of fibrinoid necrosis and villous interstitial edema, but no significant pathologic changes were found in the placentas from the late-PE or control groups.
Conclusion: Preeclampsia-like symptoms occurring during the early stage of pregnancy are more likely to affect placental and fetal development, whereas late onset preeclampsia-like symptoms have a direct impact on the mothers.