Pulmonary hypoplasia in fetuses with congenital conotruncal defects

Objectives We sought to investigate pulmonary hypoplasia ( PH ) and associated risk factors in fetuses with congenital conotruncal defect ( CTD ). Methods A total of 75 fetuses with CTD (gestational age (GA): 22–32 weeks) and 150 normal GA‐matched fetuses as the control group were studied. We measured diameters of aorta (Ao); main, left, and right pulmonary artery ( PA ); and their Z‐scores by fetal echocardiography ( FE ). We also measured the lung area, lung area/chest area ratio ( LCR ), lung‐to‐head circumference ratio ( LHR ), right lung area/head circumference 2 (quantitative lung index, QLI ), and Z‐scores. Results The PA , left pulmonary artery ( LPA ), RPA , and their Z‐scores and the lung area measurements (except for QLI ) were significantly smaller in the CTD group, compared with the normal control group. Subgroup analysis showed the following: (1) CTD with right ventricular outflow tract obstruction ( RVOTO ) had smaller main and branch PA dimensions and small lung areas in contrast to CTD without RVOTO . (2) CTD with pulmonary atresia had smaller LPA and RPA dimensions but no difference in lung areas. (3) In the common types of CTD , lung area variables were mostly smaller in double outlet right ventricle ( DORV ) and tetralogy of Fallot ( TOF ), but there was no difference in transposition of the great arteries ( TGA ). Conclusions CTD is associated with hypoplastic main and branch pulmonary arteries as well as PH . Risk factors for PH included defect types ( DORV and TOF but not TGA ) and RVOTO . It is plausible that pulmonary blood flow, rather than the type of CTD , RVOTO , or pulmonary artery dimensions, plays a key role in PH .