Conrad KP, Petersen JW, Chi YY, et al. - Researchers compared in vitro fertilization pregnancies without a corpus luteum (CL) with pregnancies conceived spontaneously or by ovarian stimulation, resulting in 1 and > 1 CL, respectively (n = 19–26 participants per cohort), to investigate if there was generalized impairment of cardiovascular adaptation in the former group. During the first trimester, women who conceived without a CL demonstrated significant reduction or absence of the expected increases of cardiac output, left atrial dimension, peak left ventricular filling velocity in early diastole (E wave velocity), peripheral/central arterial pulse pressure ratio, and global AC, as well as reduction in augmentation index. This was noted in comparison with the 1 and > 1 CL cohorts, which were similar. Overall, the importance of CL factor(s) in the transformation of the maternal cardiovascular system in early gestation was strongly supported in this study. Better cardiovascular function and lower risk of preeclampsia in vitro fertilization pregnancies could result from regimens induce development of a CL or replacement of missing CL factor(s).