Background and aims Intrauterine growth restriction (IUGR) continues to be one of the major complications of pregnancy. Utero-placentary ischemia is the most common cause of IUGR in developed countries. Infection is one of the most important causes of morbidity and mortality in early life of IUGR infants. Thymus is the main organ involved in the cellular immunity response during the newborn period.

The aim of this study was to describe the consequences of IUGR on the development of the thymus.

Methods On day 17, pregnant Wistar rats were divided into two groups. IUGR was induced by two meso-ovarian vessels cauterizations, and sham surgery was performed on control animals. Dams were allowed to deliver at term gestation. Four pups of each group were killed on day 2, 4, 6 and 10. Weight and organ weight data were collected. Thymus was paraffined and HE staining was made.

Results A global and relative thymus’ weight diminution was observed in IUGR animals (p<0.05). The ratio control/IUGR thymus weight was 2.05 (Day 2), 1.73 (Day 4), 1.1 (Day 6) and 0.78 (Day 10).

An alteration of the medulla and stroma structure was observed in the histological study of the IUGR thymus. Progressive thymus structure maturation appeared in the consecutive days. A structure similar to controls was achieved on day 10.

Discussion

• IUGR pups show a thymus weight and relative thymus weight smaller than control pups.

• The histological thymus immaturity may play a role in the increased risk of infection in IUGR babies.

Discussion