Changes in antithrombin III levels in pregnancy, labour and in women on the contraceptive pill.

Antithrombin III activity as determined by the modified Mancini technique is reported for the first time in different groups of Nigerian women as well as in a group of male blood donors. The mean level of activity (78.69%) observed in women during their second and third trimesters was lower than the mean value in the same group of women at parturition (93.18%) and significantly lower than a control group of non-pregnant women who were also not on the contraceptive pill (109.67; P less than 0.05). There was no significant difference between the mean activity of the female control group and that of women on the contraceptive pill and that of a group of male blood donors of the same age range.