Since transthyretin (TTR) was discovered, it has been regarded as a serum protein carrier of thyroid hormones and retinol. However, many other important functions of TTR have been found recently, and current evidence suggests that it plays a role in human receptivity and normal pregnancy. TTR is abundant in the uterine cavity, uterine secretion, placenta, and serum of pregnant females in the peri-implantation uterus and the first trimester of pregnancy. It may be involved in the delivery of maternal thyroid hormones to the fetus. In addition, it appears to play a key role in the preeclampsia mechanism and may be involved in spiral artery remodeling. This review will summarize what is currently known about TTR and normal pregnancy; it will focus on our findings regarding the role of TTR in the spiral artery remodeling process and the additional research required in the future.