IUD insertion forces: effects of recent childbirth and lactation

This investigation compared the force required to insert an IUD in women who were breastfeeding and who had recently delivered a child with that required in control women who were not breastfeeding and who had not recently delivered. Twenty-eight women who had recently delivered and who were breastfeeding were compared with twenty-eight controls. The women were matched for age and parity and for the type of IUD used. The mean IUD insertion force in the breastfeeding, recently-delivered women was 1.75 newtons (N) as compared to 2.80 N in the controls. The difference was statistically highly significant (paired t-test, p less than 0.01). Recent childbirth and lactation are associated with a reduction in IUD-related insertion pain, probably due to a reduction in the force required for insertion. This reduction in IUD insertion force is not necessarily related to lower uterine perforation rates in IUD insertion in this group. A number of physiological mechanisms may be responsible for this finding.