Table 1.

Allometric growth relationships between different tissue compartments and the volume, V_p, of human placenta during gestation. Values represent allometric exponents (B) and constants (A) calculated using the linear regression equation log Y = B · log V_p + log A where Y refers to the compartment variable and log A is the intercept on the log Y axis

Compartment	Exponent B (SEM)	Constant A	P-value (B is not 1)
Volume IVS	0.939 (0.0314)	0.6538	NS
Volume Villi	1.002 (0.0286)	0.4882	NS
Volume Tro	1.076 (0.0309)	0.0821	*
Volume Str	0.916 (0.0279)	0.3690	**
Volume FC	1.544 (0.0460)	0.0038	***
Surface Villi	1.323 (0.0294)	0.0032	***
Surface FC	1.618 (0.0448)	0.0005	***
Length Villi	1.534 (0.0421)	0.0071	***
Length FC	1.622 (0.0502)	0.0145	***
Number All	1.069 (0.0143)	0. 2005	***
Number Tro	1.096 (0.0174)	0.0684	***
Number Str	1.026 (0.0233)	0.1181	NS
Number FCE	1.135 (0.0312)	0.0190	***
Arith thickness VM	−0.338 (0.0263)	40.88	***
Arith thickness Tro	−0.333 (0.0230)	20.97	***
Arith thickness Str	−0.340 (0.0353)	19.48	***
Harm thickness VM	−0.177 (0.0147)	2.097	***
Harm thickness Tro	−0.498 (0.0341)	45.98	***
Harm thickness Str	−0.497 (0.0430)	25.59	***
Ratio VM	0.169 (0.0168)	0.4651	***
Ratio Tro	0.165 (0.0173)	0.4561	***
Ratio Str	0.157 (0.0234)	0.7614	***

IVS, intervillous space; Villi, terminal and intermediate villi; Tro, villous trophoblast; Str, villous stroma; FC, fetal capillaries; FCE, fetal capillary endothelium; Arith, arithmetic mean; Harm, harmonic mean; Ratio, index of thickness variability; VM, villous membrane (trophoblast + stroma).

NS, not significantly different from B = 1

^*P < 0.05

^**P < 0.01

^***P < 0.001.