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

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

	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)	< 0.001	0.48 (0.06, 0.89)	0.025
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)	< 0.001	0.36 (-0.22, 0.95)	0.241
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)	0.076	-0.29 (-0.76, 0.19)	0.032
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)

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
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
P values are calculated from an omnibus chi-squared test that parameter estimates are simultaneously zero
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

ISSN: 1741-7015