Glycohaemoglobin (GHb) levels were measured in 34 non-pregnant controls and 20 healthy pregnant Nigerian women in all the trimesters of pregnancy and the puerperium. In addition, cord blood GHb was determined in the new-born babies of the pregnant women. The mean (+/- s.d.) GHb levels, expressed as mmol fructose equivalents per gram of haemoglobin, for the controls and for the first, second and third trimesters and the puerperium respectively, were as follows: 89.9 (19.9), 82.1 (54.8), 88.2 (55.5), 85.7 (62.7), 96.7 (51.3). There were no significant differences between the values for the controls and the pregnant women and the results for the first, second and third trimesters were also not significantly different from each other. There was a significant positive correlation between the GHb levels in the second and third trimesters and the puerperium with the fasting blood glucose in the respective preceding trimester. The mean cord blood GHb value of 88.5 (46.7) was not significantly different from the maternal levels throughout pregnancy. There was a significant positive correlation between cord blood GHb and maternal GHb in the third trimester (r = 0.64, P less than 0.05) as well as the maternal third trimester fasting blood glucose (r = 0.69, P less than 0.05). However, there was no correlation between cord blood GHb and cord blood glucose or infant birth weight. The results of this study should prove useful in optimizing glycemic control in pregnant Nigerian diabetic women.