Table 3.

Characteristics of relaxin secretion in non-pregnant and pregnant cycles of humans and selected non-human primate species.

Species	Days to peak serum relaxin concentrations (Ovulation = D0)	Peak serum relaxin concentrations (ng/ml)	Normal term gestation (Days)	Reference
Human
Non-pregnant cycle	10	0.06		[200]
Pregnant cycle	56–77	1.0–3.5	280	[201]
Chimpanzee
Non-pregnant cycle	8–13	0.15–1.40		[202]
Pregnant cycle	30	2.0	230	[202]
Baboon
Non-pregnant cycle	12	0.45		[48]
Pregnant cycle	25–35	1.0–1.5	177	[203]
Rhesus macaque
Non-pregnant cycle	13	0.05		[204]
Pregnant cycle	45–60	1.0–1.5	165	[43]
Cynomolgus macaque
Non-pregnant cycle	16	0.03		[43]
Pregnant cycle	45–60	1.0–1.5	165	[43]
Common marmoset
Non-pregnant cycle	10–11	1.0–2.5		[205]
Pregnant cycle	84–98	12.0–16.0	155	[51]