Parity and lactation cause transient bone loss but are not risk factors for osteoporosis later in life
Bibliographic record
Abstract
The skeleton is a storehouse of minerals and alkali that is borrowed from when needed.1 To a marked extent during lactation, and to a modest degree during pregnancy, a woman’s skeleton is resorbed to provide calcium and other minerals to her offspring. Whereas most calcium in a newborn’s skeleton derives from the maternal diet during pregnancy, most calcium in milk is resorbed from the maternal skeleton during lactation.1 Bone resorption similarly provides rapidly needed calcium to other lactating mammals, egg layers, and animals with antlers and horns. After these physiologically programmed losses, the skeleton is later restored to its prior mineral content and strength. Longitudinal cohort studies in women have shown that during pregnancy, areal BMD (aBMD) declines slightly or remains unchanged, while during 6 mo of breastfeeding, the lumbar spine drops 5%-10% with smaller losses at the hip and radius.1 These reductions in aBMD and implied bone strength are usually without clinical consequences, although women do rarely present with fragility fractures during reproductive cycles. About 20% of such fractures (largely vertebral compressions) occur during pregnancy or puerperium, while 80% occur while lactating.2 Longitudinal studies also show that the skeleton typically returns to its prior aBMD within 6-12 mo after weaning.1 Limited HR-pQCT studies have found post-weaning improvement in skeletal microarchitecture, but some reductions in microarchitecture appear to persist.3
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.005 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.005 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".