As shown in Figure 6, in the keyword cluster analysis, keywords were divided into 20 clusters, including #0 cell therapy, #1 congenital diaphragmatic hernia, #2 expression, #3 gene therapy, #4 congenital heart disease, #5 HIV, #6 gestational diabetes mellitus, #7 fetal surgery, #8 gestational age, #9 pregnant women, #10 preterm birth, #11 twin–twin transfusion syndrome, #12 laser coagulation, #13 pulmonary hypoplasia, #14 differentiation, #15 risk factor, #16 mesenchymal stem cells, #17 myelomeningocele, #18 management, #19 fetal fibronectin, and #20 twin pregnancy. Here, FN1 is linked to Pulmonary hypoplasia.