Some evidence suggests that aflatoxin may contribute to the high prevalence of stunting observed in low‐income countries. Whereas several studies have been conducted in West Africa, fewer exist in East Africa and even fewer in nonagricultural contexts. We analyzed serum samples from 400 iron‐replete, nonanemic pregnant women from a cohort in Dar es Salaam, Tanzania to determine the extent and magnitude of exposure to aflatoxin and to study the relationship between levels of aflatoxin exposure in utero and infant birth and growth outcomes. Ninety‐nine percent of women had detectable concentrations of aflatoxin B1‐lysine (AFB1‐lysine), with a median level of 1.4‐pg/mg albumin, indicating a much lower level compared to studies of rural populations in sub‐Saharan Africa. Our results do not show a statistically significant relationship between AFB1‐lysine levels and birth weight, small for gestational age, or prematurity. We observe a small statistically significant reduction in gestational age at delivery (0.47 weeks; 95% CI: −0.86, −0.07) as the natural log of AFB1‐lysine levels increases by 1 unit of pg/mg of albumin, after controlling for potential confounders. Among a nonrandom set of infants who had measurements for placental weight, haemoglobin at delivery, and follow‐up z‐score measurements, we find no association between aflatoxin plasma concentrations and these variables. These findings suggest a high prevalence of chronic low‐level exposure to aflatoxin, though its effect on birth outcomes in this population remains unclear. Our research adds to a growing body of literature finding mixed associations between aflatoxins on pregnancy outcomes and child growth.