Physiology of Pregnancy, Labor and Puerperium Changes in Joint Laxity Occurring during Pregnancy

Abstract

Relaxation of the pelvic joints is an essential and normal accompaniment of pregnancy and may be related to hormonal changes. The authors of this report have found no studies of peripheral joint laxity during pregnancy. They have, therefore, quantified peripheral joint laxity in a group of 63 women, both during pregnancy and after delivery, each subject acting as her own control. Since laxity may fall with age at certain joints, the study population was divided into five age groups: less than 22; 22 to 25; 26 to 28; 29 to 31; and 32 or older. Generalized joint laxity was assessed by a standard scoring system, and extension of the metacarpophalangeal joint of the left index finger was quantified with a finger hyperextensometer. The mean reading for each of the groups after delivery was 65, 63, 63, 65, and 67, respectively. It was concluded that there was little natural reduction in laxity within this age range, and no subsequent factor was applied because of age. No significant change occurred in laxity during and after pregnancy as assessed by the scoring system, although the more precise hyperextensometer showed a higher degree of hyperextension at the metacarpophalangeal joint during pregnancy than after delivery, and this difference was statistically significant. When the degree of hyperextension at the metacarpophalangeal joint was correlated with the duration of pregnancy, there was a slight trend for readings to be highest between the 28th and the 30th weeks. At no time, however, was there a significant difference from any other time during the period of pregnancy studied. There was a highly significant difference in the degree of hyperextension between primigravidae and multigravidae, the latter showing almost three times as much as the former. Since there is some evidence that inherited hyperlaxity prevents the formation of abdominal striae after delivery, the abdomens of all subjects were examined on the second assessment. Forty-one subjects displayed striae, and 27 had none. There was no significant difference in the mean hyperextensometer readings between these two groups either during or after pregnancy (71/65 degrees and 70/64 degrees, respectively).