Table 3.

Hydration and densities of fat-free mass from prepregnancy to postpartum^a,^b

	Prepregnancy	Weeks				Postpartum	Density component	Population
		10–14	~ 20	30–32	35–40
Hydration (%) Longitudinal studies
van Raaij et al.19 c
No/only leg edema		0.725	0.732	0.740	0.750			Derived by van Raaij et al.19 from data on chemical analysis of six adult humans (five male, one female), BMI not reported84
Edema		0.725	0.734	0.748	0.765
Fidanza et al.21 c	0.738	0.738		0.752	0.761			Derived from reference body85 (based on three male cadavers): mean BMI: 20.9 kg/m2
Lof et al.43	0.718	0.723	0.747	0.747		0.732		Swedish women (n = 19), pregravid BMI: 24.2 kg/m2
Paxton et al.22		0.738			0.757			US women (n = 200): 55% Hispanic; 21% non-Hispanic White; 25% non-Hispanic Black; pregravid BMI: underweight (<19.8): 10.5%; normal (19.8–26.0): 61.5%; overweight (>26–29.0): 14.5%; obese (>29): 13.5%
Sohlström and Forsum42 d	0.669 ± 3.3e					0.697 ± 5.0e		Swedish women (n = 16); pregravid BMI: 23.7 kg/m2
Hopkinson et al.48					0.76 ± 0.02	0.75± 0.02		US women (n = 56); pregravid BMI: 22.8 kg/m2
Cross-sectional studies
Prentice et al.46					0.768			British women (n = 8); pregravid BMI: 23.1 kg/m2
Catalano et al.20				0.762				Predominately white US women (n = 20); pregravid BMI: 25.7 kg/m2
Density (g/cm3)
Paxton et al.22 f		1.100			1.091		Maternal and fetal	Estimates based on the Selinger four-compartment model;86 population details above
Fidanza et al.21 c	1.100	1.100	1.097	1.092	1.087		Maternal and fetal	Derived from reference body (based on three male cadavers) and based on Hytten’s report:25 mean BMI: 20.9 kg/m2
Hopkinson et al.48g					1.087 ± 0.006	1.094 ±0.007	Calculated maternal	Estimates based on the Fuller four-compartment model corrected according to the estimates by van Raaij et al. at 36 weeks;19 US women (n = 56); pregravid BMI: 22.8 kg/m2
Density (g/l) of fat-free mass gain
van Raaij et al.19 c, f
No/only leg edema		1.022	1.027	1.032	1.030		Maternal and fetal	Estimates derived from Hytten, population details not reported
Edema		1.022	1.020	1.023	1.019

^aHydration factor for fat-free mass calculated as total body water/ fat-free mass.

^bValues reported are mean ± s.d.

^cEstimates derived from Hytten’s estimates of composition of tissues.²⁵

^dFat-free mass estimated with magnetic resonance imaging (MRI).

^eBecause fat-free mass was estimated with MRI, these values are based on different assumptions and are not comparable with the other values in the table.

^fDensity estimated with underwater weighing and estimated using the Goldman and Buskirk equation.⁸⁷

^gDerived from equations from Van Raaij et al. (1988) developed according to the Hytten’s estimates of composition of tissues.²⁵