Prenatal acetaminophen affects maternal immune and endocrine adaptation to pregnancy, induces placental damage, and impairs fetal development in mice.

Acetaminophen (APAP; ie, Paracetamol or Tylenol) is generally self-medicated to treat fever or pain and recommended to pregnant women by their physicians. Recent epidemiological studies reveal an association between prenatal APAP use and an increased risk for asthma. Our aim was to identify the effects of APAP in pregnancy using a mouse model. Allogeneically mated C57Bl/6J females were injected i.p. with 50 or 250 mg/kg APAP or phosphate-buffered saline on gestation day 12.5; nonpregnant females served as controls. Tissue samples were obtained 1 or 4 days after injection. APAP-induced liver toxicity was mirrored by significantly increased plasma alanine aminotransferase levels. In uterus-draining lymph nodes of pregnant dams, the frequencies of mature dendritic cells and regulatory T cells significantly increased on 250 mg/kg APAP. Plasma progesterone levels significantly decreased in dams injected with APAP, accompanied by a morphologically altered placenta. Although overall litter sizes and number of fetal loss remained unaltered, a reduced fetal weight and a lower frequency of hematopoietic stem cells in the fetal liver were observed on APAP treatment. Our data provide strong evidence that prenatal APAP interferes with maternal immune and endocrine adaptation to pregnancy, affects placental function, and impairs fetal maturation and immune development. The latter may have long-lasting consequences on children's immunity and account for the increased risk for asthma observed in humans.

Effect of prenatal steroid treatment on the developing immune system.

UNLABELLED: Prenatal steroids have an undisputed positive effect of decreasing neonatal morbidity and mortality by improving fetal lung maturation. Some concerns have been raised on long-term consequences on the hypothalamic-pituitary-adrenal axis and cognition, but there are no studies addressing effects on the immune system. The thymus is an essential organ for the development and selection of T cells, and thymocytes are extremely sensitive to steroids. Using a mouse model for prenatal steroid administration, we show here that betamethasone treatment to the mother has a profound effect on the thymus of the offspring. We find the thymus volume reduced, affecting mostly the developing CD4+ CD8+ double-positive thymocytes and a compensatory accelerated transition of the earlier stages to replenish the depleted compartment. This effect lasts for at least 3 days, which correspond to a very relevant period for the selection of the T cell repertoire. Moreover, we show that low doses of betamethasone have similar effects on human thymocytes in vitro. Therefore, further studies are needed to analyze possible long-term consequences of this treatment on the immune system of the offspring. KEY MESSAGE: Betamethasone administered to the mother before birth reaches the fetal thymus. Prenatal betamethasone results in massive loss of developing thymocytes. The effects of betamethasone on thymus development are visible for several days. Human thymocytes are also sensitive to low doses of betamethasone. Altered thymocyte development around birth may have an effect on the immune system.