Figure 3. Clock/Clock pregnancies are characterized by increased rates of fetal reabsorption, reduced serum levels of estradiol and progesterone, and possible dysregulation of prolactin release.

A, The percentage of Clock mutant dam pregnancies showing any signs of fetal reabsorption is significantly greater than wildtype at dpc 14 (** indicates p < 0.01) and full-term (* indicates p ≤ 0.05), as determined by chi square analysis. In many cases, both wildtype and Clock pregnancies showed some signs of reabsorption by full-term, but reabsorbing fetuses occurred more frequently in Clock pregnancies. While all wildtype pregnancies delivered normally, 40% of Clock mutant dams carried to full-term but failed to deliver. Importantly, Clock mutant females exhibited copulatory plugs as frequently as wildtype females, indicating that mating behavior was intact in the mutants. Additionally, the average number of fetuses per genotype at dpc 11 was almost identical between genotypes (7.6 fetuses per wildtype dam, 7.75 fetuses per Clock/Clock dam), indicating that the early stages of pregnancy, including ovulation, fertilization, implantation, and early fetal development, occur normally in Clock mutants. WT = wildtype, CL = Clock/Clock, DPC = days post copulation. B, Estradiol levels are significantly reduced in Clock/Clock (closed circles) mice compared to wildtypes (open circles) (p < 0.001). Estradiol in both genotypes is elevated in late pregnancy (dpc 17, 19) compared to mid-pregnancy (dpc 11, 14) (p < 0.01). C, Progesterone is significantly lower in Clock/Clock females compared to wildtypes (p < 0.05) due to very low progesterone levels in Clock/Clock females at dpc 11. In both genotypes, progesterone levels at dpc 14 are elevated compared to dpc 11 and dpc 19 values (p ≤ 0.01). For both B and C, * indicates p < 0.05. Prior to testing the hypotheses, data were checked to verify that they met the assumptions of normality and equality of variance required for analysis of variance. Because the data violated one or more of the assumptions, data were transformed using logarithms and statistical analysis (two-way ANOVA and Fisher’s LSD) was performed on the log transformed data. D, The duration of pseudopregnancy is significantly shorter in Clock/Clock females compared to wildtype controls as determined by t-test (** indicates p ≤ 0.001). Wildtype (n = 10) and Clock/Clock (n = 26) females were mated with vasectomized CD-1 males and the length of pseudopregnancy, as indicated by leukocytic vaginal cytology, was measured by vaginal lavage. The presence of a copulatory plug was designated as dpc 1, and the final day of leukocytic smears was designated as the last day of pseudopregnancy.