The effect of bladder volume on the angle between the placenta and the abdominal surface in patients placenta referred with posterior for chorionic villous sampling through the abdomen

Abstract

A significant number of pregnancies require cytogenic examinations for various reasons , considering the possibility of performing this method early, CVS is preferable to other sampling methods of fetal tissues and amniotic fluid, and it should be one of the most important methods of examining the fetus. This method is usually performed between 12 and 14 weeks of pregnancy. Afull bladder acts as an acoustic window, which makes it possible to perform this procedure from the side of access to the placenta without the need to enter the needle into the amniotic fluid. In posterior placenta, it may not be possible to access the placenta. Due to the fact that the bladder is located in the anterior part of the uterus and its fullness or emptiness directly affects the position of the uterus, the current study was conducted to investigate the effect of bladder filling on changing the angle of the uterus in cases of posterior placentas and as a result access to the placenta in casas of CVS. Materials and Methods: This study is prospective and cross-sectional and the research method is full count. About 40 pregnant women with a BMI<30 and a gestational age of 11 to 14 weeks, which has an indication of CVS and having a posterior placenta and in the period from April to March 2022, those who visited AL-Zahra Hospital after obtaining written consent were included in the study. Before performing the CVS, the initial ultrasound performed by the perinatologist, the volume of bladder and the placement angle of the placental axis were evaluated in the midsagittal section relative to the horizontal surface of the mother,s abdomen. The mentioned angle was measured ones with a full bladder and another time with an emoty bladder, sampling was done when the placenta had an angle of 90 degrees or less with the horizon. At the end, the angle was measured and empared in two states of full and emoty bladder and the amount of access to the placenta in these two states. Results: The average angle of the placenta with the horizontal surface of the mother,s abdomen in patients with posterior placenta referred for CVS, it is 111/624 degree when the bladder is empty and 74/625 degree when the bladder is full, which showed that by filling the bladder, the angle between the axis of the placenta and the horizon of the mother’s abdomen decreases and helps to make the placenta available. Pearson’s correlation test also showed that, there is a correlation between the mentioned angle in two states of full and empty bladder. P=0/000 and N=40 and r=0/62, the relationship between these two variables is inverse and moderate. As a result, by increasing the volume of the bladder, the angle between the placenta and the horizon decreases and a better view of the placenta is provided for sampling. In 4 patients with a retroverted uterus. Access to the placenta was better with an empty bladder.