Problem It is unknown whether maternal cytokine production differs between twin and singleton gestations in the implantation phase. A difference in maternal serum cytokine concentrations in twins would imply a dose‐response to the invading embryos, as opposed to a general immune reaction. Method of study A prospective longitudinal cohort of women aged 18‐45 at an academic fertility center undergoing in vitro fertilization and embryo transfer (IVF‐ET) underwent routine collection of serial serum samples starting 9 days after ET and then approximately every 48 hours thereafter. Cryopreserved aliquots of these samples were assayed for interleukin‐10 (IL‐10), tumor necrosis factor‐alpha (TNF‐α), and C‐X‐C motif chemokine ligand 10 (CXCL10) using the SimplePlex immunoassay platform. Pregnancies were followed until delivery. Serial measures of serum concentrations of IL‐10, CXCL10, and TNF‐α in singleton or di‐di twin pregnancies from 9 to 15 days after IVF‐ET were compared. Results Maternal serum levels of CXCL10 are significantly lower in women with di‐di twin pregnancies in early implantation compared to those with singleton gestation (day 9‐11, P = .02). Serum levels of TNF‐α and IL‐10 were comparable at all studied time points (P > .05). Conclusion Maternal serum levels of CXCL10 are significantly lower in the earliest implantation phase in di‐di twins compared to singleton conceptions. Given the known anti‐angiogenic role of CXCL10, we hypothesize that lower CXCL10 levels in twin implantations allow an environment that is conducive for the greater vascularization required for the establishment of dual placentation in di‐di twins.