To enhance the early recognition of Prader-Willi syndrome by summarizing the clinical characteristics of Prader-Willi syndrome (PWS) during perinatal period.

Through a nationwide cross-sectional study in the Department of Pediatrics, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences,226 children diagnosed as PWS by molecular genetics were recruited from September 2019 to March 2020. Clinical data including fetuses Age, birth weight, fetal movement, fetal position, amniotic fluid, mode of bith, crying, muscle tension, feeding, and cryptorchidism were collected to analyze the clinical characteristics of Chinese PWS patients in the perinatal period, and according to the mode of birty, birth weight and genotypes to perform subgroup analysis. The clinical manifestations of different subtypes were statistically analyzed by t test, χ² test or Mann-Whitney U test.

Among the 226 PWS patients, 120 were males, and 106 were females. Among them, 100 (44.2%) patients were small for gestational age. Decreased fetal movement was the most common manifestation 202 cases (89.4%) during pregnancy, and other manifestations included polyhydramnios 71 cases (31.4%) and abnormal fetal position 58 cases (25.7%). One hundred and eighty-five (81.9%) patients were delivered by cesarean section and the frequency of abnormal fetal position was significantly higher (30.8%(57/185) vs. 2.4%(1/41),χ²=14.161,P<0.01). As for abnormal manifestations after birth included hypotonia 221 cases (97.8%),220 cases (97.3%) showing weak crying, 116 cases among the total 120 males patients (96.7%) wanifested with cryptordnildism and 206 feeding difficulties (91.2%). In terms of genetic subtype, most of them (184/226, 81.4%) had a paternal deletion, while maternal age (35±5vs. 29±5, t=-6.591, P<0.01) and the frequency of polyhydramnios (47.6% (20/42)vs. 27.7% (51/185), χ²=6.286, P=0.012) were significantly higher in the non-deletion group.

The main manifestations of PWS patients during the perinatal period are hypotonia, weak crying, feeding difficulties, decreased fetal movement, cryptorchidism and those patients are more likely to be born by cesarean section. In newborns with these characteristics, pediatricians should be aware of the possibility of PWS. In terms of the relationship between genotypes and phenotypes, polyhydramnios is more frequently observed in the non-deletion group.

Prader-Willi syndrome; Peripartum period; Muscle hypotonia