Table 3. Estimates of conditional probabilities for different stages of the reproductive process for reproductively normal subjects.

Estimates of hCG ( FEC _HCG) and clinical ( FEC _CLIN) fecundabilities and π _CLIN are derived from three hCG pregnancy studies as described in the text. π _LB is calculated from published values in Wilcox ⁶, Zinaman ⁷ and Wang ⁸ study reports. Estimates of fertilised egg loss up to implantation, clinical recognition and birth are provided, based on three scenarios: (i) high implantation probability ( π _HCG = 90%); (ii) equal implantation and fertilisation probabilities ( π _FERT = π _HCG); (iii) high fertilisation probability ( π _FERT = 90%). The probability of sperm-ovum-co-localisation ( π _SOC) was assumed to be 0.80.

Derived Fecundabilities and Conditional Probabilities For Fertile Women	Wilcox (1988)			Zinaman (1996)			Wang (2003)
FEC HCG FEC CLIN π CLIN π LB	0.432 0.339 0.783 0.877			0.381 0.333 0.875 0.790			0.462 0.349 0.754 0.871
% loss from implantation to live birth	31.3			30.9			34.2
If π SOC = 0.80, then π FERT × π HCG = If π FERT = π HCG, then π FERT = π HCG = If π FERT = 0.90, then π HCG = If π HCG = 0.90, then π FERT =	0.540 0.735 0.600			0.476 0.690 0.529			0.578 0.760 0.642
Estimated losses of fertilised eggs when…	π HCG = 0.90	π FERT = π HCG	π FERT = 0.90	π HCG = 0.90	π FERT = π HCG	π FERT = 0.90	π HCG = 0.90	π FERT = π HCG	π FERT = 0.90
% loss before implantation % loss before clinical recognition % loss before live birth	10.0 29.5 38.2	26.5 42.4 49.5	40.0 53.0 58.7	10.0 21.3 37.8	31.0 39.6 52.3	47.1 53.7 63.4	10.0 32.1 40.8	24.0 42.7 50.0	35.8 51.6 57.8