Oxygen carrying capacity of blood is a function of hemoglobin concentration. Pregnancy being a condition with enormous physiologic, biochemical and anatomic adaptations require normal levels of hemoglobin for optimal pregnancy outcome. However, each trimester and parity may have effect on the hemoglobin concentration. Studies have however shown a physiologic anemia in the second trimester of pregnancy. This adversely affects the oxygen carrying capacity of blood, resulting in gestational anemic hypoxia. We designed this study to assess the oxygen carrying capacity of blood in various groups of parous women as pregnancy advances. We used a multistage sampling technique to group pregnant women attending antenatal clinic into seven groups: primigravida, para1, para2, para3, para4, para5 and >para5. We randomly selected thirty-eight subjects from the various groups. We selected forty control subjects from a group of women attending family planning clinic. Subjects gave informed consent and the Ethical Committee of the hospital gave ethical clearance for the study. 2mls of blood was collected into an EDTA bottle for hemoglobin concentration measurement using standard method. We multiplied hemoglobin concentration by 1.34ml to get the oxygen carrying capacity of hemoglobin. We adopted 95% hemoglobin saturation for all subjects. Since hemoglobin concentration less than 10g% is anemia, subjects with values less than 12.73ml% were regarded as having gestational anemic hypoxia. Para2 subjects had the highest percentage (31.5%, n=12) of second trimester gestational anemic hypoxia. This was followed by para3 with a percentage (26.32%, n=10).The difference in these values was not statistically significant (p>0.05). Para1 and para4 had percentages 13.16%; n=5 and 10.53%; n=4 respectively. The primigravida, para5 and >para5 had no records of second trimester gestational anemic hypoxia. The oxygen carrying capacity of 13.14 ±2.10ml% and 13.21± 2.07ml% for para2 and para3 for second trimesters respectively, were significantly (P<0.05) lower than that of control (15.70±2.10ml%). Para2 and para3 had more pronounced tendency of causing gestational anemic hypoxia. .This may be due to inadequate residual iron stores in these parities. Routine antenatal hematinics should be increased in these parities during the second trimester to forestall possible effects of gestational anemic hypoxia.