Objective:The purpose of this study was to explore the effect and mechanism of maternal chorioamnionitis on placental microvasculature and platelet activation among preterm infants by activating Wnt-Flt1 signal pathway .

Methods:With clinical randomized controlled trial (RCT), the cases were matched with 1:1 according to gestational age and divided into 2 groups according to the placental pathology result: chorioamnionitis group and control group. (1) To observe the platelet parameter, birth weight, thrombrocytopenia and hemorrhage complication, such as intracranial hemorrhage, retinal hemorrhage, pulmonary hemorrhage and gastrointestinal hemorrhage. (2) To observe the miscrovascular density (MVD) in placenta, platelet activating factor (CD62p,CD63) and thrombopotetin (TPO) in preterrn infants.The placental MVD was assessed by immunohistochemical method. The platelet activating factors were detected by flow cytometry. TPO was detected by ELISA. (3) To observe Wnt5a, Flt1 and VEGF in placenta and fetal circulation.The measurement data were analyzed by pair t test and conditional logistic regression. Pearson correlation analysis was used for relationship.

The exclusive criteria included :(1) born to mother with no any other maternal complications; (2) no congenital abnormalities and neonatal asphyxia; (3) died or discharged within 72 hours.

Inclusion Criteria:

1. gestational age<37weeks
2. admitted to the NICU at Guangdong Women and Children Hospital, with a date of birth from June 2016 to December 2016
3. whose mothers were diagnosed chorioamnionitis by placental histopathology

Exclusion Criteria:

1. born to mother with no any other maternal complications
2. no congenital abnormalities and neonatal asphyxia;
3. died or discharged within 72 hours.

Chorioamnionitis contributes to the high morbidity and mortality in preterm infants, thrombocytopenia is one of the acute morbidity