Factors associated with gestational weight gain in women with morbid obesity

Figures & data

Figure 1. STROBE flow chart of study participant selection.

Table 1. Maternal characteristics of women with and without gestational weight gain outcome recorded.

Variable	Category	With GWG (n = 618)	Without GWG (n = 117)	p-value
Body mass index		44.0 (±3.7)	44.0 (±3.7)	0.719 ʃ
Gestation at first antenatal weight (weeks)		9.1 (±3.3)	8.9 (±3.2) (n = 116)	0.515
Maternal age (years)		28.3 (±5.4)	29.1 (±5.3)	0.171
Smoking status at first antenatal appointment				0.109
	Smoker	129 (20.9%)	32 (27.6%)
	Non-smoker	489 (79.1%)	84 (72.4%)
Parity				0.004**
	0	190 (30.8%)	30 (25.6%)
	1	219 (35.4%)	29 (24.8%)
	2 or more	209 (33.8%)	58 (49.6%)
Ethnicity				0.952
	White British	587 (95.6%)	112 (95.7%)
	All other ethnicities	27 (4.4%)	5 (4.3%)
Deprivation quintile				0.123
	Quintile 1: Most deprived	339 (54.9%)	78 (66.7%)
	Quintile 2	127 (20.5%)	21 (17.9%)
	Quintile 3	78 (12.6%)	9 (7.7%)
	Quintile 4	53 (8.6%)	8 (6.8%)
	Quintile 5: Least deprived	21 (3.4%)	1 (0.9%)
Highest household occupation				0.077
	Professional or higher occupations	107 (17.8%)	15 (13.3%)
	Intermediate occupations	141 (23.5%)	17 (15.0%)
	Routine and manual occupations	197 (32.8%)	46 (40.7%)
	Housewife/ Unemployed/ student	156 (25.9%)	35 (31.0%)
Education				0.589
	GCSE/ equivalent or lower	102 (43.4%)	17 (44.7%)
	AS/A level or equivalent	60 (25.5%)	12 (31.6%)
	Degree, postgraduate or equivalent	73 (31.1%)	9 (23.7%)
Marital status				0.508
	Married/civil partnership	210 (34.2%)	46 (39.3%)
	Partner	334 (54.4%)	57 (48.7%)
	Single ‡	70 (11.4%)	14 (12.0%)
Preterm birth (<37 + 0 weeks gestation)				0.000***
	No	592 (95.9%)	54 (54.0%)
	Yes	25 (4.1%)	46 (46.0%)

Data are mean ± standard deviation or n (%). Abbreviations GWG: gestational weight gain; IMD: Index of Multiple Deprivation.

^ʃ Mann Whitney U test used as data not normally distributed.

^‡ - The single category included 10 women who were divorced/ separated/widowed.

** statistically significant at p < 0.01 level,.

*** statistically significant at p < 0.01 level.

Table 2. Crude regression coefficients and 95% confidence intervals for each variable with gestational weight gain.

Variable	Category	n	β (95% CI)	p-value
Number of healthy lifestyle clinic appointments attended	0	618	REF
	1		0.02 (-1.75, 1.80)	0.979
	2		0.49 (-1.32, 2.30)	0.596
	3+		0.78 (-0.97, 2.53)	0.380
Body mass index		618	−0.18 (-0.33, −0.03)	0.021*
Maternal age (years)		618	0.05 (-0.05, 0.16)	0.328
Smoking status at first antenatal appointment	Non-smoker	618	REF
	Smoker		−0.22 (-1.60, 1.16)	0.754
Parity	0	618	REF
	1		−2.50 (-3.86, −1.14)	0.000***
	2 or more		−3.23 (-4.61, −1.86)	0.000***
Ethnicity	White British	614	REF
	All other ethnicities		4.24 (1.52, 6.97)	0.002**
Deprivation quintile	Quintile 1: Most deprived	618	REF
	Quintile 2		1.98 (0.53, 3.43)	0.007**
	Quintile 3		0.58 (-1.16, 2.33)	0.512
	Quintile 4		0.89 (-1.16, 2.95)	0.395
	Quintile 5: Least deprived		0.64 (-2.49, 3.77)	0.688
Highest household occupation	Professional or higher occupations	601	2.62 (0.87, 4.36)	0.003**
	Intermediate occupations		1.95 (0.34, 3.57)	0.018*
	Routine and manual occupations		2.33 (0.84, 3.82)	0.002**
	Housewife/ Unemployed/ student		REF
Education	GCSE/ equivalent or lower	235	REF
	AS/A level or equivalent		2.13 (-0.16, 4.41)	0.068
	Degree, postgraduate or equivalent		1.35 (-0.81, 3.50)	0.220
Marital status	Married/civil partnership	614	0.44 (-1.49, 2.36)	0.657
	Partner		−0.66 (-2.48, 1.17)	0.482
	Single ‡		REF
Infant sex	Female	617	REF
	Male		0.97 (-0.15, 2.09)	0.090 §

Abbreviations: β: regression coefficient; 95% CI: = 95% confidence interval; REF: referent;.

Removing the outlier(s) and / or point(s) of high leverage, did not change the direction of the effect or the significance except in the case detailed below:.

^§ Further away from reaching significance when removing the 2 cases with large standardised residuals [0.826, 95% CI -0.281, 1.933) p = 0.143, n = 615].

^‡ - The single category included 9 women who were divorced/ separated/widowed.

* statistically significant at p < 0.05 level,.

** statistically significant at p < 0.01 level,.

*** statistically significant at p < 0.01 level.

Table 3. Multiple regression model of factors associated with gestational weight gain in women with a BMI ≥ 40kg/m² (n = 596).

Variable	Category	β (95% CI)‡	p-value
Constant		14.71 (-2.62, 32.04)	0.096
Body mass index		−0.22 (-0.36, −0.07)	0.003**
Maternal age		0.12 (0.005, 0.24)	0.041*
Smoking status at first antenatal appointment	Non-smoker	REF
	Smoker	1.33 (-0.07, 2.73)	0.062
Parity	0	REF
	1	−3.10 (-4.44, −1.76)	<0.001***
	2 or more	−3.96 (-5.47, −2.44)	<0.001***
Ethnicity	White British	REF
	All other ethnicities	3.07 (0.47, 5.67)	0.021*
Deprivation quintile	Quintile 1: Most deprived	REF
	Quintile 2	2.00 (0.63, 3.37)	0.004**
	Quintile 3	0.21 (-1.46, 1.89)	0.803
	Quintile 4	0.13 (-1.91, 2.17)	0.899
	Quintile 5: Least deprived	0.16 (-2.84, 3.16)	0.915
Highest household occupation	Professional or higher occupations	1.41 (-0.35, 3.18)	0.117
	Intermediate occupations	1.17 (-0.42, 2.76)	0.149
	Routine and manual occupations	1.56 (0.14, 2.98)	0.032*
	Housewife/ Unemployed/ student	REF
Number of healthy lifestyle clinic appointments attended	0	REF
	1	−0.54 (-2.26, 1.18)	0.537
	2	−0.12 (-1.86, 1.62)	0.890
	3+	−0.02 (-1.74, 1.70)	0.982
Infant sex	Female	REF
	Male	0.39 (-0.68, 1.45)	0.478

^‡ Adjusted for birthweight, gestation at first antenatal weight, gestation at final recorded weight and gestation at birth.

R2 = 0.211 F = 7.328 p < 0.001, n = 596 df = 21.

Within the final model, normality of the residuals was checked graphically. Durbin Watson = 1.981. Collinearity tolerance ranged from 0.426 to 0.953 and variance inflation factors ranged from 1.05 to 2.35, therefore no concerns with multicollinearity were indicated within this model.

No cases with extreme Cook’s values were identified, 3 cases had standardised residuals > ± 3 and 10 cases had Mahalanobis distances where p < 0.001. For analysis removing these outliers/ points of leverage please see Table S1.

Data availability statement

The datasets used and/or analysed during the current study are not publicly available within a repository as they belong to the Hospital Trust, but the data is available from the corresponding author on reasonable request.