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Background: Historical background data of pregnancy loss, nonviable birth, premature and preterm births, and postnatal neonate mortality are essential for interpretation of reproductive and developmental toxicity (DART) studies. In this presentation, frequencies of these asessments in Cynomolgus monkeys under experimental conditions are summarized.
Methods: Frequencies of prenatal loss (PL, abortion, resorption and in utero embryo-fetal death before GD140), stillbirth (SB, birth of a nonviable neonate or in utero fetal death on or after GD140), premature birth (PMB, birth of viable neonate before GD140) and preterm birth (PTB, birth of a viable neonate between GD140 and GD154), normal birth (NB, birth of viable neonate after GD154), and postnatal neonate death (ND) were reviewed in control groups from 31 DART studies. This included a total of 510 maternal animals at GD0.
Results: Mean frequencies of all studies were 16.6 ±7.3% in PL, 14.1 ±9.1% in SB, 3.3 ±4.3% in PMB, 18.7 ±11.7% in PTB, and 67.3 ±15.1% in NB. Mean gestation length was 159 ± 8 days (including SB, PMB, and PTB). Thirteen neonates out of 216 live births died (6.0 ±5.3%), and 10 of the 13 NDs (77%) occurred within 7 days after birth. Frequencies of ND were 71.4% in PMB, 10.0% in PTB, and 2.3% in NB.
Conclusion: Frequency of ND clearly increased in PMB (71%) when compared with that of PTB (10%) or NB (2%). Since PTB was not uncommon (18.7%) and frequency of ND in PTB (10%) was generally comparable with that of NB (2%), PTB is considered to be within normal biological variation in Cynomolgus monkeys.
