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Table 2 Multilevel linear regression equations for means and SDs of pregnancy weight gain for gestational ages in underweight, normal-weight, and overweight groups

From: Gestational weight gain charts for twin pregnancies in Southeast China

BMI category

Regression equation

Underweight

 Mean

2.867073 + 3.597614 × GA Spline term1–12.54554 × GA Spline term2+  19.79477 × GA Spline term3–22.73170 × GA Spline term4

 SD

Sqrt[16.108 +  0.04079 (GA Spline term1^2) + 4.132]

Normal weight

 Mean

2.867073 + 3.568180 × GA Spline term1–12.49818 × GA Spline term2+  19.7948319.79483 × GA Spline term3–22.73137-22.73137 × GA Spline term4

 SD

Sqrt[16.10812+  0.0410957 (GA Spline term1^2) + 4.132]

Overweight

 Mean

2.867073 + 3.357253 × GA Spline term1–12.09662 × GA Spline term2+  19.79483 × GA Spline term3–22.73169× GA Spline term4

 SD

Sqrt[16.17164+  0.0457317 (GA Spline term1^2) + 4.132]

  1. GA gestational age; sqrt square root
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BMC Pregnancy and Childbirth

ISSN: 1471-2393

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