This trial is a continuation of the investigators' previous clinical trial (NCT02772289). In the previous three-arm randomized clinical trial involving women with primiparous singleton pregnancies, the investigators found umbilical cord mesenchymal stem cells was not significantly different from placebo for the reduction of cesarean section skin scar and did not increase recognition of participants'satisfaction at the sixth month follow-up. Although there was no statistical difference, the trial study found that the total vancouver scar scale rating was lower with the dose increased.~Some studies have suggested that it usually took 18-24 months for a typical scar matures. In this trial, the investigators want to continue to investigate the efficacy of perinatal tissue mesenchyme stem cells treatment on the appearance of a caesarean scar as compared to a similar untreated scar at the three years follow-up.
The study is to investigate the long-term efficacy of perinatal tissue mesenchyme stem cells treatment on the appearance of a caesarean scar as compared to a similar untreated scar.