Fetal adrenal gland volume and preterm birth: a prospective third-trimester screening evaluation.

Objective: Given the importance of the fetal adrenal gland in producing hormones critical to labor, we sought to evaluate whether sonographic three-dimensional measurements of the adrenal gland are a useful screening tool for spontaneous preterm birth (SPTB).

Method: We prospectively screened 128 non-anomalous singletons from 24 to 36 weeks' gestation with volumetric measurements of the fetal adrenal gland at their indicated antenatal sonogram. Labor and delivery outcomes were assessed and compared with respect to adrenal volume.

Results: When corrected for estimated fetal weight, the 11 women (9%) who delivered following SPTB had smaller adrenals than those who did not, 0.33 cm(3)/kg compared with 0.57 cm(3)/kg, respectively (p = 0.006). There was no difference in volumes between those who delivered by SPTB within 7 days or greater than 14 days from measurement (0.34 cm(3)/kg versus 0.33 cm(3)/kg, p = 0.79). Among women at increased risk of SPTB, those with SPTB had smaller adrenals than those who did not: 0.32 cm(3)/kg versus 0.53 cm(3)/kg, p = 0.06.

Conclusion: We found fetal adrenal glands significantly smaller for those delivering preterm. Given the prior literature and our asymptomatic population, our data support multiple pathways leading to SPTB.