2 Profiles of pregnancy-associated glycoproteins for Holstein embryo recipients with pregnancy losses in different periods during the first two months of gestation

The aim was to provide biological insight into pregnancy loss (PregLoss) in Holstein embryo recipients with circulating pregnancy-associated glycoproteins (PAGs) from 1003 embryo transfers (fresh IVF) using a modified 5-day CoSynch protocol in the recipients. Overall pregnancy/embryo transfer (ET) was 42.3% (424/1003), 39.1% (392/1003), 37.0% (371/1003), and 35.5% (356/1003), respectively, for Days 28, 33, 47, and 63 of gestation using visualisation of embryonic heartbeat by rectal ultrasound. Thus, PregLoss was 7.5% (n = 32) from Day 28 to 33 (first period), 5.4% (n = 21) from Day 33 to 47 (second period), and 4.0% (n = 15) from Day 47 to 63 (third period). Based on a case-control experimental design, each PregLoss event where matched (timed ET date, embryo quality, embryo development, and times of timed ET for each PregLoss recipient) with positive and negative controls selecting nonpregnant (NP) embryo recipients (NP on Day 28 and with circulating progesterone that was lower than 1 ng/mL on Day 19) and one pregnant (Preg) in all pregnancy diagnoses in the experiment. Blood samples were collected on Days 21, 28, 33, 47, and 63 to measure circulating progesterone (RIA) and PAGs (ELISA BioPRYN). Heifers were designated as having embryonic attachment on Day 21 when PAGs were greater than the highest PAGs value for the nonpregnant group (0.06 ng/mL). Data were analysed with GLIMMIX and MIXED procedures of SAS. Significant differences were considered with P ≤ 0.05, whereas P ≤ 0.10 as a tendency. There was a similar percentage of heifers with attachment on Day 21 for Preg (80% [55/68]) compared with PregLoss during the second period (76.2% [16/21]) and the third period (80% [12/15]). However, for the PregLoss in the first period, the percentage of heifers with attachment on Day 21 was lower (50%, 16/32) compared to Preg (P = 0.01) or compared by contrast with PregLoss on the second and third periods 77.8% (28/36 [P = 0.02]). PregLoss in the first and second periods had intermediary circulating PAGs compared to NP and Preg on Day 21 (Table 1). Nevertheless, on Day 28, only PregLoss in the first period had lower circulating PAGs compared with Preg (Table 1), with a tendency between PregLoss and Preg in the second period. In summary, heifers that would experience PregLoss in the first period already had signs of underdevelopment placentation early on Days 21 and 28. Alternatively, PregLoss in the second period had lower circulating PAGs on Day 21 but not on Day 28, able to pass through the first PregLoss period. There is no sign of underdevelopment placentation in the third period of PregLoss.