A Methodical Study:
Aim of the study: To analyse the feasibility of colour and spectral Doppler assessment of blood flow in the fetal right (RPA) and left (LPA) main pulmonary arteries in relation to fetal position and to gestational age.
Study design: The fetal position was a priori divided into 3 types, depending on whether the fetal heart was visualised apically (Type 1), from the right side (Type 2) or from the left side (Type 3). Three groups A (19-25 weeks gestation), B (26-32) and C (33-39) including 33 consecutive pregnancies each, were examined to document the fetal position as well as the rate of the successful Doppler examinations of the RPA and/or LPA.
Results: The fetal position Type 2 was most common throughout gestation (in group A = 42%, B = 36%, C = 51%) followed by the type 3 and then type 1. The rate of successful Doppler records from the RPA and LPA depended on the fetal position: In Type 2 RPA in 98%; in Type 3, LPA in 100%; but the apical approach was not effective (< 40%). Depending on gestational age, the success rates for a Doppler examination of at least one vessel were high (> 85%), whereas successful examination of both vessels was unlikely (12%).
Conclusions: In the second half of pregnancy, independent of fetal position, Doppler examination of at least one pulmonary artery is successful in most cases, whereas the assessment of both vessels is rather difficult.