ABSTRACT
OBJECTIVE: To study the effect of gestational and perinatal exposures on thymic size in 366 normal birth weight and 426 low birth weight (LBW) neonates in Guinea-Bissau in West Africa. STUDY DESIGN: In a cross-sectional study, thymic size was measured at birth by the use of ultrasound. Information on possible determinants was collected from pregnancy cards, hospital records, and interviews with the mother. We used the log-transformed thymic index and thymus/weight index as outcome measures. Data were analyzed with adjusted linear regression models providing geometric mean ratios (GMRs) with 95% CI. RESULTS: Determinants of thymic size among normal birth weight infants were pathologic amniotic fluid (adjusted GMR for thymic index: 0.84 [0.74-0.96]) and male sex (GMR: 1.13 [1.06-1.22]). Among LBW infants, birth season (1.11 [1.01-1.22]), maternal body temperature (0.89 [0.79-0.98]), antibiotic treatment at the time of labor (0.84 [0.70-1.00]), number of pregnancy consultations (1.03 [1.00-1.05]), maternal age (0.91 [0.84-0.98]), Apgar score (1.06 [1.03-1.10]), and infant convulsions (0.44 [0.29-0.65]) were all independent determinants of thymic index but not all were determinants of thymus/weight index. Pathologic amniotic fluid and cesarean delivery were associated with thymus/weight index among LBW infants (0.85 [0.75-0.95] and 0.80 [0.67-0.96]) but were only borderline significant for thymic index. CONCLUSION: Exposures mainly related to stress and infections were associated with a smaller thymus, mainly in LBW infants.
Subject(s)
Thymus Gland/anatomy & histology , Thymus Gland/diagnostic imaging , Anti-Bacterial Agents/therapeutic use , Apgar Score , Body Temperature , Cohort Studies , Cross-Sectional Studies , Female , Guinea-Bissau , Hospitalization , Humans , Infant, Low Birth Weight , Infant, Newborn , Linear Models , Male , Organ Size , Pregnancy , Randomized Controlled Trials as Topic , UltrasonographyABSTRACT
BACKGROUND: There is increasing evidence that vaccines have an effect on general mortality which goes beyond specific disease protection. Oral polio vaccine (OPV) is widely used in low-income countries, but in observational studies in Guinea-Bissau we observed that not receiving OPV at birth was associated with reduced overall male infant mortality and enhanced immune response to BCG vaccine. We therefore initiated a randomized trial to test the overall effect of OPV at birth (OPV0). OBJECTIVE: A small thymic gland is a predictor of mortality in high-mortality settings. Within the trial we aimed to test whether no-OPV0 was associated with increased thymic size. METHODS: In 511 normal birth weight infants who were randomized to receive or not receive OPV0, thymic index and thymus/weight index were measured before randomization and after 2 weeks (N=49), 4 weeks (N=308) or 6 weeks (N=27). The association between OPV0 and the log transformed thymic size indicators were analyzed in ANCOVA models with thymic size at follow-up as the outcome and adjusting for thymic size at enrollment and age at follow-up. Estimates were reported as geometric mean ratios (GMR) with 95% confidence intervals, comparing no-OPV0 to OPV0. RESULTS: No-OPV0 was not associated with thymic index after 2 weeks (GMR: 1.14 (0.99-1.30)), after 4 weeks (GMR: 0.98 (0.93-1.05)) or after 6 weeks (GMR: 1.00 (0.81-1.23)). However, no-OPV0 was associated with increased thymus/weight index after 2 weeks (GMR: 1.22 (1.06-1.40)), but the effect was not seen after 4 weeks (GMR: 0.97 (0.92-1.03)) and 6 weeks (GMR: 0.99 (0.82-1.19)). There were no strong sex-differences. DISCUSSION: Overall there was no effect on thymic size of OPV0 when administered with BCG. The results could indicate that if an effect occurs, it is only within the first weeks after vaccination.
