Pregnancy is a challenging time for the breeder and the bitch. Inadequate serum progesterone concentrations are often associated with pregnancy loss or premature birth, without evidence to confirm them. In this study, a large number of bitches were monitored during pregnancy, and serum progesterone concentrations were determined to infer what concentration is considered normal. Three samples were taken during early, mid and late gestation.The results indicate that progesterone concentrations may be lower than previously reported as adequate in the veterinary literature, with the bitch showing no signs of pregnancy failure and giving birth to healthy pups at the expected term.
Pregnancy and lactation are among the most challenging periods in a bitch's life. Most studies on the endocrinological aspect of pregnancy have focused on only a small number of animals. The aim of this study was to evaluate progesterone (P4) concentrations in a large number of bitches during early, mid and late pregnancy. A total of 126 bitches of different breeds were included in the study after a thorough clinical and gynecological examination during estrus. Blood samples were collected three times (T1-T3) during gestation or from non-pregnant bitches in diestrus and P4 was measured by chemiluminescence. At T1 (11-19 days post ovulation (dpo)), serum P4 concentrations were 30.23 ± 6.65 ng/ml and 28.45 ± 6.26 ng/ml, respectively, and at T2 (23-32 dpo) they were 22.73 ± 6. 27 ng/ml and 22.59 ± 5.77 ng/ml, and at T3 (52-60 dpo) they were 6.68 ± 2.18 ng/ml and 3.17 ± 2.26 ng/ml, respectively, in pregnant (n = 98) and non-pregnant (n = 23) subjects. P4 concentrations were significantly different between pregnant and non-pregnant animals at the last examination (p ≤ 0.001). In the context of hypoluteoidism, the collected data yielded interesting results. A total of 28 out of 98 pregnant females showed a significant decrease (> 15 ng/ml) in P4 concentrations from early to mid-pregnancy and 56 females showed P4 concentrations lower than what is considered adequate according to current recommendations (> 20 ng/ml at T1 and T2, > 5 ng/ml at T3). Although P4 was not supplemented, no abortion or preterm birth occurred in any of these animals. Because P4 supplementation may pose a significant risk to bitches and puppies, further research regarding the patterns of P4 concentration, the diagnosis of hypoluteoidism, and indications and treatment options is warranted.
Hinderer, J.; Lüdeke, J.; Riege, L.; Haimerl, P.; Bartel, A.; Kohn, B.; Weber, C.; Müller, E.; Arlt, S.P. Progesterone Concentrations during Canine Pregnancy. Animals 2021, 11, 3369.https://doi.org/10.3390/ani11123369
