How it departed

From its pre-registered plan, under plan/

• Not stated

  The plan says the placebo distribution calibrates M and M is raised if placebo jumps exceed the honest CI more than expected, but gives no threshold. Rule fixed in code before outcomes were computed: if 2 or more of the 5 placebo cutoffs (31, 32, 33, 37, 38) have honest CIs excluding 0, M is raised to the smallest value in {0.15, 0.2, 0.3, 0.5, 1, 2} pp per year squared that leaves at most 1. Result: 1 of 5 excluded 0 (cutoff 38, whose window contains age 40), so M stayed at the preregistered 0.1.

  Bears on C1 and C2

• Not stated

  Falsification set and family: the plan lists race/ethnicity without categories. We used four indicators (non-Hispanic White, non-Hispanic Black, Hispanic, non-Hispanic Asian), so 11 covariates per cutoff with one Holm family each. Covariates are measured in the primary (nulliparous) sample, except nulliparity share, which can only vary in the all-parity singleton 37-44 week sample.

  Bears on C1 and C2

• Not stated

  The plan gives M only in probability units. For BMI and log birth counts, M is the largest absolute second difference of the variable's own single-age series over ages 28-46, excluding second differences that straddle 35 or 40. This rule gives very wide bias bounds, so the BMI and density tests are uninformative; they cannot fail and do not drive any verdict.

  Bears on C1 and C2

• Done differently

  The plan names an ART-use subgroup. The parsed extract kept rf_inftr (any infertility treatment, which includes ART) rather than rf_artec, so the subgroup is infertility treatment yes/no.

• Not stated

  Data-quality fix: the 2016 and 2017 NBER files code mrace6 as two digits (10, 20, 30, 40/41, 51, 61); the first digit is taken as the six-group race code used in 2018-2024.

• Not stated

  The plan says no benefit is claimed only when the CI excludes the benefit implied by Geiger et al. (perinatal mortality -0.39 pp). That benchmark maps only to stillbirth, so the check is applied to term stillbirth; for the other key secondaries we report the honest CIs without a no-benefit verdict.

  Bears on C5

• Not stated

  Holm adjustment for the key secondary benefit outcomes is done within each cutoff (five outcomes per family).

  Bears on C3 and C4

• Not stated

  Stillbirth rate = fetal deaths / (fetal deaths + live births), singleton, nulliparous, 37-44 weeks, US residents, non-imputed age, 2018-2024 (the fetal-death files obtained); the same honest RD with M = 0.1 pp.

  Bears on C5

• Not stated

  Outcome codings: induction ld_indl Y vs N; cesarean dmeth_rec 2 vs 1; delivery at 39 weeks combgest = 39; NICU ab_nicu Y vs N; Apgar apgar5 0-6 vs 7-10 (99 excluded); maternal morbidity any Y among mm_mtr, mm_plac, mm_rupt, mm_uhyst, mm_aicu, with records where they are unknown excluded; BMI 99.9 excluded. Unknown values are dropped per outcome.

  Bears on C1, C3, and C4

• Not stated

  The reproduction step re-runs the analysis from single-year age cell counts (data/cells_*.csv, about 130 KB) built by code/build_cells.py from the 20 GB of public microdata. The full pipeline (download, checksum, parse, build cells) is in code/full_pipeline.sh with checksums in code/SHA256SUMS_raw, and the cells were rebuilt byte-identically on two machines.

• Not stated

  The plan's SESOI line says about 2.3% relative to a ~43% baseline; the pooled baseline it reports elsewhere is 37.9%. The SESOI of 1.0 pp used in the decision rule is unchanged.

  Bears on C1

• Not stated

  The plan file's first line still reads as a draft heading; this exact file is what was registered, so it is carried unchanged under plan/.