The effect of parity status on δ15N: looking for the “pregnancy effect” in 18th and 19th century London

This study examined the effect of parity status on δ15N using the well-characterised 18th and 19th century skeletal collection from the crypt of Christ Church, Spitalfields, London. We tested whether the cumulative effect of multiple pregnancies and breastfeeding could significantly reduce female δ15N values compared to males. The results from stable isotope analysis of 92 adult ribs show that the population of Spitalfields had relatively little variation in diet, compared to contemporary urban populations, and had abundant animal and marine protein. We were able to rule out any effect attributable to socio-economic status, date or age at death on the stable isotope ratios. There were no significant differences in δ15N due to parity status, nor were there any differences between males and females. Models of collagen turnover rates in ribs suggest that the effect of δ15N depletion due to pregnancy would be undetectable except in ideal circumstances, where bone of the optimal turnover period was sampled, and in cases where multi-parous individuals died shortly after parturition.