Fetal movements during late gestation in the pig: a longitudinal ultrasonographic study.

Repeated ultrasonographic observation of fetal movements was used to distinguish movement patterns and to investigate the rate of occurrence and temporal organisation of these patterns (rest-activity cycles) during the last three weeks of gestation in the pig. By means of transabdominal ultrasonography with a 3.5MHz linear array transducer, motility in ten different fetuses (one per sow) was studied. Six (median; range 4-6) 1h recordings were made per fetus at 3-5 day intervals. Fifty-five 1h recordings were available for analysis. The occurrence of fetal general movements (GM), isolated head (HM), forelimb movements (LM), and rotations (ROT) was analysed from video tapes. For each movement pattern, the trend in occurrence over time was assessed by multilevel analysis. The temporal association between different movement patterns was studied by calculation of the kappa value. ROT occurred very infrequently and showed no particular trend over time. GM, HM, and LM showed a significant decreasing trend towards parturition (P<0.01). Total fetal activity (i.e., the sum of the four movement incidences) declined from an average of 25% of recording time to 9% over the last three weeks of pregnancy. Periods of fetal quiescence gradually increased with progressing gestation (P<0.05). There was no evidence of concordant association between the periods of rest and activity of GM, HM, and LM or of improved temporal linkage between these movement patterns with time. Fetal bodily activity decreases towards parturition mainly due to prolonged periods of rest. Fetal movement patterns show rest-activity cycles, but each pattern appears to cycle independently from the other throughout late gestation. The present results of spontaneous fetal movements in the pig provide reference data for future studies of fetal activity under different zoo technical conditions or pharmacological interventions.

Effects of morphine and naloxone on fetal heart rate and movement in the pig.

To test the hypothesis that an increasing opioid tonus is involved in decreases in fetal heart rate (FHR) and movement (FM) during late gestation, we studied the effects of intravenous bolus injections of morphine (1 mg) and naloxone (1 mg) on FHR and FM in the fetal pig. Twenty-one fetuses (1 per sow) were catheterized at 90-104 days of gestation (median 100 days). Recordings of FHR (electrocardiograph or Doppler-derived signals) and FM (ultrasonography) were made from 15 min before to 45 min after treatment. Morphine administration significantly decreased FHR, but it increased FHR variation and forelimb movements (LM). LM were clustered, and this stereotyped behavior has never before been observed in any mammalian fetus. Naloxone administration increased gross body movements and FHR without significant changes in FHR variation. It is concluded that FHR and motility are under opioidergic control in the pig fetus. Both morphine and naloxone induce hypermotility, suggesting that naloxone does not act as a pure opioid antagonist in the fetal pig.

Uterine responses to exogenous oxytocin before and after pre-partum luteolysis in the cow.

The aim of this study was to test the functional status of uterine oxytocin receptors in cows in vivo around parturition. The animals received consecutive, intra-arterial injections of 800, 1,600 and 3,200 mU of oxytocin at three different stages: during late gestation (days 260-274), at 12 h and at 24 h after intramuscular injection of a prostaglandin F2alpha analogue at day 275 to induce parturition. Cows (n = 6) had been provided with myometrial electrodes and a catheter had been installed in the aorta and in a branch of the uterine vein (UV). Regular blood samples were obtained from the UV from 5 min before until 45 min after each oxytocin injection to measure plasma levels of prostaglandin F2alpha (PGF2alpha) and oxytocin. Uterine electromyographic (EMG) activity was registered continuously during each experiment. The increase of oxytocin levels in UV plasma after intra-arterial injections was dose dependent (p < 0.02). Pre- and post treatment oxytocin levels at 24 h after induction of parturition were significantly increased (p = 0.0313). Both during late pregnancy and at 12 h after induction of parturition, oxytocin caused a significant increase in EMG activity (p = 0.022). After the 3,200 mU dose the increase was significantly higher than with the other 2 doses (p = 0.004). After each dose, EMG activity returned to baseline levels within some 15 min. At 24 h after induction of parturition, the pre-treatment level of EMG activity had increased. Doses of 800 mU and 1,600 mU of oxytocin produced a significant (p = 0.022) increment of EMG activity, which was of the same magnitude as during the preceding stages; after 3,200 mU of oxytocin the response was significantly higher than before (p = 0.008). No significant increases of PGF2alpha levels in UV plasma could be measured after oxytocin injections at any of the three stages. It is concluded that the myometrium of the pregnant cow responds in vivo to physiological doses of oxytocin. At 24 h after induction of parturition, when luteolysis has occurred and a parturient pattern of parturient myometrial activity has already started to develop, the response is enhanced. Physiological doses of oxytocin did not evoke a spurt release of PGF2alpha in uterine venous blood during the peripartal period.

Noninvasive monitoring of fetal heart rate during the last ten days of gestation in sows.

OBJECTIVE: To develop and evaluate a noninvasive technique for monitoring and analyzing porcine fetal heart rate (FHR) during late gestation. ANIMALS: 8 fetuses of 8 pluriparous sows in late gestation. PROCEDURE: With the sow positioned in lateral recumbency, the most caudal fetus was identified, using real time ultrasonography, and its heart rate was recorded for 60 minutes by use of Doppler cardiography. The same fetus was identified and monitored repeatedly during the last 10 days of gestation, excluding the 24 hours before delivery. Visual inspection and computerized analysis of the recordings were performed. RESULTS: 66 one-hour recordings were obtained from 8 fetuses, 1 in each of 8 sows. Mean signal loss was 37.5%. Episodes of low FHR and low FHR variation (FHR pattern A) alternated with episodes of high FHR and high FHR variation (FHR pattern B). This cyclic alternation between 2 distinct. FHR patterns was observed in 46 of 66 (69.7%) recordings, and suggests the presence of different behavioral states in fetal pigs. Basal FHR decreased toward parturition in 7 fetuses, but increased in 1 fetus with abdominal ascites. Basal FHR and long-term FHR variation were negatively correlated (r[S] = -0.73; P < 0.001). CONCLUSION: Noninvasive monitoring of FHR is possible and feasible during late gestation in pigs. This method permits longitudinal studies under pathophysiologic conditions and the evaluation of the effects of endogenous and exogenous influences on porcine FHR.

Induction of hydrometra in goats by means of active immunization against prostaglandin F2 alpha.

Hydrometra is a pathological condition of the uterus which is characterized by accumulation of aseptic fluid in the presence of a persistent corpus luteum. It forms a major cause of subfertility in goats. Active immunization against prostaglandin F2 alpha (PGF2 alpha), the luteolytic hormone in this species, was used to explore the possibility for artificial induction of this pseudopregnant condition. During the breeding season, 11 goats (group I) were immunized with 5 mg PGF2 alpha-ovalbumin conjugate in Freund's complete adjuvant, 4 goats were control-immunized (group CI) and 5 goats remained untreated (group C). Jugular blood samples were taken twice a week (monday and thursday) for measurements of plasma progesterone and binding of 3HPGF2 alpha. In conjunction with blood sampling, transcutaneous ultrasonographic examination of the uterus took place to detect the presence of fluid in the uterus. Before and immediately after immunization, the mean (+/-SD) duration of luteal phases (progesterone concentrations > or = 1 ng ml-1) was 16.7 +/- 1.6 (n = 39), 17.8 +/- 1.3 (n = 23) and 16.9 +/- 1.1 (n = 18) days in animals of group I, CI and C respectively. Ten goats of group I developed an antibody titre. Persistence of luteal function (mean duration +/-SD: 150.3 +/- 23.5 days) occurred in 6 of these animals and in 1 goat of group CI. Accumulation of fluid in the uterus in group I was first observed between day 31 and 38 of the prolonged luteal phase. Discharge of uterine fluid occurred as soon as the plasma progesterone concentration reached a level lower than 0.5 ng ml-1. It is concluded that immunization against PGF2 alpha is an effective method to induce pseudopregnancy in goats, providing a model for studies on luteal maintenance and uterine function in the absence of a conceptus.

Plasma prolactin, growth hormone and progesterone concentrations in pseudopregnant, hysterectomized and pregnant goats.

Jugular plasma prolactin (PRL), growth hormone (GH) and progesterone (P4) levels were estimated in goats under three different conditions with prolonged luteal function (P4 > or = 1 ng/ml): pseudopregnant animals (n = 4), goats hysterectomized during early pregnancy (n = 4) and does with normal pregnancy (n = 4). Mean duration (+/- S.E.M.) of luteal phases were 189 +/- 20, 171 +/- 10, and 147 +/- 2 days in the three groups, respectively. Until day 120, mean PRL levels were below 150 ng/ml in each group. After day 120 of the luteal phase, PRL concentrations were significantly higher than before, but continued to increase up to 800 ng/ml only in pregnant animals around parturition. Mean GH levels varied between 2 and 3 ng/ml in animals of each group during the luteal phase. Only after parturition, a significant elevation occurred. P4 levels in pseudopregnant animals were significantly lower than in the other two groups between days 10 and 55, and showed a gradual but continuous decline towards the end of the luteal phase. After hysterectomy of early pregnant animals, P4 concentrations decreased to levels measured in pseudopregnant animals but were significantly higher again as compared to pseudopregnant animals between days 121 and 150. It is concluded that a pseudopregnant condition, characterized by intrauterine fluid accumulation, is not related to increased plasma PRL and GH concentrations. The low and gradually decreasing plasma progesterone levels in the pseudopregnant animals probably reflect the absence of a luteotrophic stimulus by the conceptus. The progesterone profile in the animals that were hysterectomized during early pregnancy suggests that the corpora lutea of these does have been permanently changed by the presence of the conceptus during the first weeks of the luteal phase.

Serum prolactin concentration in pseudopregnant and normally reproducing goats.

Previous experiments with bromocriptine suggested that prolactin plays a role in the aetiology of pseudopregnancy in goats. Serum prolactin concentration was measured in a herd of white Dutch dairy (Saanen) goats when hydrometra (a typical characteristic of pseudopregnancy) was diagnosed by ultrasound, during the spontaneous development of pseudopregnancy, and in normally reproducing goats during the breeding season. In the normally reproducing does the prolactin concentration decreased at the beginning of the breeding season. In 12 of 14 pseudopregnant goats the prolactin concentration was within the range observed in the normally reproducing goats on the day that hydrometra was diagnosed. In two goats the prolactin concentration was low during the first few weeks of pseudopregnancy and in a third it fluctuated. There was no correlation found between the concentration of prolactin and the development or the presence of a persistent corpus luteum. These results suggest that prolactin does not play a crucial role in the aetiology of pseudopregnancy in the goat.

Feasibility of continuous recording of fetal heart rate in the near term bovine fetus by means of transabdominal Doppler.

A transabdominal Doppler technique for the recording of fetal heart rate (FHR) was investigated in the bovine fetus. During the last 2 weeks of gestation recordings were made once or twice per week in eight cows by placing a 1.5 MHz Doppler transducer on the right ventral abdominal wall. Continuous FHR recordings with a duration of more than 30 min were obtained in 29 of the 35 sessions. Major displacements of the fetus were the main cause of recording failure. The overall mean baseline FHR was 105 +/- 1.5 bpm with a range of 90 to 125 bpm. The mean bandwidth of the baseline FHR was 10.8 +/- 0.7 bpm with a range of < 5 to 20 bpm. Periods with different bandwidths alternated. The alternation of bovine FHR patterns pointed to the existence of different fetal behavioural states. The mean number of accelerations of FHR was 7.1 +/- 1.0 per hour. Many of the accelerations coincided with visible or perceptible fetal body movements. Decelerations of FHR occurred less frequently (range 0 to 4 per h). A period of tachycardia accompanied by an increased number of fetal movements occurred in 3 of the 29 FHR recordings. This non-invasive technique appears to be suitable to study FHR patterns during gestation and to investigate the presence and characteristics of behavioural states in the bovine fetus. It also provides the possibility to study effects on the fetus of drugs administered to the dam.

Fetal heart rate patterns and the influence of myometrial activity during the last month of gestation in cows.

Five cows in the last month of gestation, provided with uterine electrodes and in which catheters had been chronically installed in the fetal aorta, were used to study patterns of fetal heart rate (FHR) and the influence of periods of myometrial electrical activity during gestation (contractures) on FHR. The FHR was calculated by counting the number of blood pressure pulses on the tracings during alternate periods of 12 seconds. Three 1-hour recordings without contractures and 10 recordings during the time of a contracture were randomly selected for each cow. The calculated data points were plotted on a graph to display FHR patterns. In 41 periods associated with single contractures, FHR data points were taken every 72 seconds. Changes in absolute and relative FHR in these periods were determined to analyze a possible effect of contractures on FHR. Three types of variation in FHR patterns could be distinguished: a short-term, low-amplitude variation of basal FHR; a second type in which the duration was < 4 minutes and the amplitude was > or = 15 beats/min; and prolonged periods with increased or decreased FHR values (> 4 minutes and > or = 15 beats/min). The relationship between these types of variation and fetal activity states remains to be established for cows. During the 60 hours of recordings that were analyzed, a period of several minutes during which FHR values were extremely high (> 180 beats/min) was found 3 times. There were no significant differences in absolute or relative FHR before, during, or after a contracture.

Physiological aspects of pregnancy and parturition in dogs.

During late pregnancy (greater than 50 days) the pattern of uterine electrical activity is characterized by episodes of activity lasting 3-10 min and recurring at a low frequency (maximum 2.5/h). During the last 7 days before delivery there is a progressive qualitative change in activity which is correlated with the decrease in plasma progesterone concentration. Together with significant quantitative changes in uterine activity which occur during the last 24 h before parturition and after the sharp fall in progesterone concentration this suggests that progesterone plays a crucial role in the process of parturition in the bitch. Experiments with a calcium-channel antagonist have demonstrated the important role of Ca2+ ions in uterine contractility in dogs, but further investigations will be necessary to illustrate the clinical significance of hypocalcaemia in relation to primary uterine inertia. By marking all fetuses in utero before term by means of a radio-opaque substance, it was demonstrated that, when one or more pups were left in each uterine horn after birth of a pup, 78.2% of the pups were expelled from the contralateral horn. Assessment of the blood gas and acid-base status in spontaneously born puppies indicated that the initial state of acidosis is more severe than in several other domestic species. A mild to severe combined respiratory-metabolic acidosis occurs in almost every newborn puppy.