borderline significantP = 0.08
If only adjustment for conditional weight or length at 4 years were made, the increment in height for firstborns disappeared (Δ = 0 cm, 95% CI: −1.2, 1.2) ( P = 0.99), whereas the difference in blood pressure remained significant (diastolic blood pressure: Δ = 1.9 mm Hg, 95% CI: 0.4, 3.4) ( P = 0.01) or borderline significant (systolic blood pressure: Δ = 1.9 mm Hg, 95% CI: −0.3, 4.1) ( P = 0.08).