Changes in Bone Mineral Status and Bone Size During Pregnancy and the Influences of Body Weight and Calcium Intake

Abstract

Previous studies have found a significantly increased risk of preterm delivery and low birth weight after cervical conization. Most of these studies were case-control studies or were small, hampering the ability to detect significant differences between gestational age groups. This population-based cohort study evaluated the adverse consequences of cervical conization on subsequent pregnancies. The investigators linked data from the Medical Birth Registry of Norway and the Cancer Registry of Norway for the years 1967 to 2003 on 15,108 births occurring in women who had previously had cervical conization and 57,136 who subsequently had the procedure. The 2,164,006 births during the study period by women who had never had cervical conization served as controls.The proportion of preterm birth (delivery before 37 weeks of gestation) was 17.2% [95% confidence interval (CI); 16.6%-17.8%] among women who gave birth after cervical conization; 6.7% (95% CI, 6.5%-6.9%) in women who gave birth before cervical conization; and 6.2% (95% CI, 6.2%-6.3%) in women who never had the procedure. The relative risk (RR) of premature delivery after cervical conization compared with women who never had cervical conization increased with decreasing gestational age: RR 2.5 (95% CI, 2.4-2.6) at 33 to 36 weeks; RR 3.4 (95% CI, 3.1-3.7) at 28 to 32 weeks; and RR 4.4 (95% CI, 3.8-5.0) at 24 to 27 weeks. The risk of a late abortion (Ͻ24 weeks of gestation) was higher after cervical conization compared with no conization; the RR was 4.0 with a 95% CI of 3.3 to 4.8. During the study period, the RR of preterm delivery declined, particularly for delivery before 28 weeks of gestation. These findings show that cervical conization increases the risk of preterm delivery in subsequent pregnancies, especially early in pregnancy when the clinical significance is highest. EDITORIAL COMMENT(As one would expect, the data that we have relating ablative and excisional procedures for cervical dysplasia to late abortion and prematurity were not derived from randomized studies. That is to say, reproductive age women with cervical dysplasia deemed to require cervical ablation or excision have not been randomized to therapy or to expectant management for the purposes of evaluating their subsequent preg-nancy performance. Nor has a study been done wherein women have been randomized to different methods of cervical ablation or excision for the purposes of comparing subsequent pregnancy outcomes. Clearly, randomized trials of this nature would be logistically extremely difficult to do, and, in some situations, ethically problematic. But they would be the best way to overcome the major problem in evaluating the OBSTETRICS Volume 64 Number 2 OBSTETRICAL AND GYNECOLOGICAL SURVEY ABSTRACTPrevious studies have shown that during cesarean section, the concentration of lactate in myometrial capillary blood is higher among women with dysfunctional labor compared with normal labor. Small increases in lactate concentrations have been associated with impairment in the strength an...

Calcium economy in human pregnancy and lactation

“…When used to study change over time within an individual, the value unadjusted for weight change provides a measure of net or actual change in mineral content, and therefore of Ca mobilisation from or accretion into the skeleton, provided that there is no accompanying change in bone size. Adjustment for weight change allows the effects of pregnancy and lactation on the skeleton to be considered independently of weight effects (11) .…”

“…Because of this volume effect, the interpretation of aBMD in longitudinal studies can be complicated, especially when there are changes in bone size, for example, during growth or, potentially, in pregnancy or lactation. In such studies, BA can be used to adjust BMC for bone size (BA-adjusted BMC) and the influence of body weight and weight change considered separately (11) . Third, the skeleton is responsive to changes in body weight (the greater the weight gain the greater the BMC and aBMD) (11) .…”

“…In such studies, BA can be used to adjust BMC for bone size (BA-adjusted BMC) and the influence of body weight and weight change considered separately (11) . Third, the skeleton is responsive to changes in body weight (the greater the weight gain the greater the BMC and aBMD) (11) . Finally, because of technicalities associated with bone-edge detection, BA, and hence BMC and aBMD, is influenced by the amount of mineral present and the depth of overlying soft tissue and may change slightly when the mineral content or the tissue depth changes (the greater the mineral present or overlying tissue, the greater the BA) (27,30) .…”

“…However, interpretation is more difficult when DXA data are not reported in full and may account for some of the inconsistencies in results and conclusions between different studies. Estimates of Ca content, and the contribution of the skeleton to Ca economy, are obtained by making assumptions about the proportion of Ca present in the mineral phase of human bone, generally considered to be about 38 % (11) . In addition, there are systematic differences in aBMD measurements between different DXA manufacturers.…”

Interrelationships between Tooth Properties and Biochemical Bone Turnover Markers Investigated on Six-Month-Old Pig Model

“…As shown in previous studies, long-term treatment with glucocorticoids and dexamethasone inhibits bone formation and accelerates bone resorption [28]. Contrary to dexamethasone treatment, calcium administration in rational dosages in mammals improves bone formation processes leading to higher bone mass acquisition and improved bone mineral density [14,23].…”