Purpose: To describe the performance-related physiological and haematological changes in a well-trained cyclist (peak oxygen uptake, VO_2peak: 54.9 ml min⁻¹·kg⁻¹) performing endurance training during pregnancy and postpartum. 

Methods: Training data was systemized by training form (endurance and resistance), intensity (low- (LIT), moderate-, and high-intensity training), and modality (cycling, running, hiking, XC-skiing, strength training and other). Power output at 4 mmol L⁻¹ [BLa⁻] (L₄), maximal aerobic power (W_max), and VO_2peak as well as haemoglobin mass, blood volume, plasma volume and red blood cell volume (RBCV) were measured at different time points during pregnancy and 12 weeks postpartum. 

Results: L₄ and W_max increased by 3% while absolute VO_2peak was unaltered from gestational wk 2 to 14, despite 12 and 14% increases in RBCV and BV. After delivery, BV was reduced by 7% but RBCV was maintained 5% above start-pregnancy levels, while VO_2peak almost returned to (-1%), and W_max increased by 5% above start-pregnancy levels 12 weeks postpartum. 

Conclusion: This case-study illustrates a disassociation between increases in haematological values and VO_2peak during pregnancy. Furthermore, a quick resumption of LIT and a gradually increasing intensity of training in the 12 weeks following delivery ensured a return to start-pregnancy levels of VO_2peak and corresponding improvements in W_max. Although general recommendations cannot be given on the basis of these data, this study provides a framework for investigating pregnant endurance athletes and contributes to the generation of new hypotheses in this field.