Development of early uteroplacental circulation

A crucial event in human development is trophoblast invasion, a process that will enable chorionic and maternal circulations to develop in a synchronized fashion. Early embryo and trophoblast are very sensitive to the conditions in which they grow, and progressive development of placental circulations is essential for normal pregnancy development. It has been demonstrated that inadequate trophoblast invasion is a major finding in many clinical deleterious conditions facing the obstetrician. Pathologic studies of placentas of pregnancies complicated by intrauterine growth restriction or preeclampsia demonstrate shallow trophoblast invasion of the spiral arteries. This has also been seen in early spontaneous miscarriages. In our study, we used color Doppler sonography to assess the uteroplacental circulation and predict outcome of first-trimester gestations. One hundred women with viable pregnancies of 7 to 12 weeks gestational age were prospectively evaluated. Color Doppler imaging was used to identify the location of blood flow within the uteroplacental circulation, and spectral Doppler imaging was used to analyze waveforms obtained from the decidual spiral arteries. Abnormal color Doppler findings were associated with a significantly higher prevalence of complicated pregnancies. Among women with abnormal Doppler findings, 12 (43%) of 28 pregnancies ended in miscarriage, whereas among women with normal findings only one (1.4%) of 72 women miscarried (p<.055). This study indicates that abnormal flow patterns of the early uteroplacental circulation due most likely to abnormal trophoblast invasion are associated with an increased prevalence of pregnancy complications. What causes inadequate invasion remains a mystery. Abnormal nitric oxide synthesis, due to possible endothelial cell dysfunction, has been demonstrated in some of these complicated pregnancies but, whether this is cause of effect, is not known. Every step of embryonal-maternal interaction from fertilization and onward has major implications on subsequent development of embryo, fetus, neonate and adult human being. Trophoblast invasions and transformation of the spiral arteries are possibly the most significant interactions and will have the most profound effect on pregnancy development.