Gestational age-specific reference intervals for placental growth factor and its application in singleton and twin pregnancies: a population-based cohort study​Kaiqi Wu Shaomin Zhou Yongying Bai Binbin Yin Baohua Li Bo Zhu Shuai Li a Department of Clinical Laboratory, Women’s Hospital, School of Medicine, Zhejiang University, Hangzhou, Chinab Department of Obstetrics and Gynecology, Women’s Hospital, School of Medicine, Zhejiang University, Hangzhou, Chinaon October 9, 2025 at 10:24 am