In early and mid pregnancy, maternal serum activin A levels are stable and low, rising dramatically from approximately 24 weeks of gestation, reaching peak levels proximate to term.

• 在妊娠早期和中期，孕妇循环中激活素A稳定于较低水平，大约从妊娠24周开始迅速升高，大约在妊娠足月时达高峰。