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Table 3 Growth rates of singleton births from fresh ART transfers, frozen transfers (FET) and naturally conceived (NC) babies between birth and 6–8 weeks, and 6–8 weeks and primary school entry

From: The growth of assisted reproductive treatment-conceived children from birth to 5 years: a national cohort study

  Birth/6–8 weeks 6–8 weeks/school entry
Coefficient (95% CI) P Coefficient (95% CI) P
Constant (growth rate for a NC baby with ‘Reference’ characteristics) 254.8 (250.5, 259.1)   54.4 (53.9, 54.9)  
Type of conception
 Naturally conceived Reference 0.023 Reference 0.363
 ART—fresh cycles 7.2 (2.1, 12.7) 0.25 (-0.34, 0.88)
 ART—frozen cycles 4.9 (-3.5, 13.9) 0.74 (-0.39, 1.90)
Gender
 Male Reference < 0.001 Reference 0.025
 Female -46.2 (-49.4, -42.9) 0.48 (0.06, 0.89)
IMD Quintile
 1 (most deprived) 8.2 (3.1, 13.3) 0.026 0.46 (-0.23, 1.20) 0.102
 2 6.7 (1.4, 11.9) 0.90 (0.23, 1.58)
 3 6.8 (1.5, 12.4) 0.52 (-0.10, 1.20)
 4 5.4 (-0.1, 10.9) 0.21 (-0.41, 0.80)
 5 (least deprived) Reference Reference
Smoked during pregnancy
 No Reference < 0.001 Reference 0.241
 Yes 19.6 (14.9, 24.5) 0.36 (-0.22, 0.95)
Maternal age
 (Linear term) 2.9 (-0.2, 6.4) 0.076 0.42 (0.01, 0.84) 0.032
 (Quadratic term) -2.4 (-6.7, 1.8) -0.29 (-0.76, 0.19)
Feed type at 10 days
 Breast Reference < 0.001 Reference 0.236
 Bottle 22.8 (18.7, 26.5) 0.12 (-0.35, 0.57)
 Breast and bottle 11.7 (4.6, 18.4) 0.78 (-0.10, 1.66)
  1. Results from multiple linear regression models for growth (change in weight) between birth and 6–8 weeks (average weekly growth rate) and 6–8 weeks and primary school entry (average monthly growth rate), adjusting for type of conception, Scottish Index of Multiple Deprivation (IMD), maternal age and smoking status during pregnancy, feed type at 10 days and the ART-NC matching variables: gender, year and month of delivery and delivery hospital. Full model details are available in Additional file 1: Table S4
  2. Quoted effect sizes represent the difference from the indicated reference category. The ‘Constant’ coefficient represents the average rate of growth for a naturally conceived boy, breast-fed at 10 days by a non-smoking mother who resided in an area belonging to the least deprived quintile
  3. P values are calculated from an omnibus chi-squared test that parameter estimates are simultaneously zero
  4. Note that for ease of interpretation, the effect sizes for the linear and quadratic components of maternal age represent the change in outcome for a 10-year change in maternal age