An enlarged fetal thymus may be the initial response to intrauterine inflammation in pregnant women at risk for preterm birth.

OBJECTIVE

Fetal thymus involvement in prematurity has been studied, and this study aimed to evaluate its relationship with short cervix and amniotic fluid sludge in the second trimester of pregnancy.

METHODS

In this prospective cross-sectional study, 79 pregnant women (19+0 to 24+6 weeks) were included, and cervical length and the presence or absence of amniotic fluid sludge were evaluated. In the three-vessel view of the fetal thorax, the thymus was identified, and its perimeter and transverse diameter were measured and transformed to a zeta score based on gestational age.

RESULTS

Data from 22 women with short cervix (<25 mm) and 57 patients with normal cervix (≥25 mm) were analyzed. The transverse diameter of the fetal thymus was significantly greater in the short cervix group compared to that of the normal cervix group (z-score 2.708 vs. -0.043, p=0.003). There were no significant differences in the perimeter (z-score -0.039 vs. -0.071, p=0.890) or the transverse diameter (z-score 1.297 vs. -0.004, p=0.091) of the fetal thymus associated with the presence (n=21) or absence of sludge (n=58).

CONCLUSION

A short cervix is associated with an increased transverse diameter of the fetal thymus during the second trimester of gestation.