Parturition in the Cow: Endocrine Changes in Animals With Chronically Implanted Catheters in the Foetal and Maternal Circulations

Abstract

Intravascular catheters were placed in the umbilical, uterine and maternal peripheral circulations of 16 Jersey cows between 240 and 260 days of gestation. Foetal plasma cortisol, blood gases and pH, and maternal plasma oestrogen, progesterone and cortisol were measured in ten animals during late pregnancy and throughout spontaneous parturition; all delivered live foetuses although parturition was earlier than normal and the placenta was generally retained. The gradual pre-partum rise in foetal plasma cortisol during the last week of gestation (from 10\p=n-\20 ng/ml 7 days before parturition to 51 \ m=+-\5 ng/ml in the last 3 h before delivery) was much less marked than the abrupt increase immediately after birth when the cortisol concentration invariably doubled. Maternal plasma oestrogen rose from 0.35 \ m=+-\ 0.04 ng/ml to 1\m=.\20\ m=+-\ 0.11 ng/ml during the week before parturition. Progesterone concentrations remained stable until a sudden fall 1\p=n-\2 days before delivery. The slight alterations in maternal plasma cortisol during this period were not statistically significant. The maternal plasma oestrogen levels were higher in the uterine vein than in the periphery, whereas uterine venous progesterone concentrations were significantly lower than in the peripheral circulation.The hormonal changes associated with the artificial induction of labour were investigated by the administration of cortisol, dexamethasone or corticotrophin to the foetus (four animals). In each case premature delivery occurred 5-6 days later; the maternal hormonal changes were very similar to those in untreated catheterized cows. These findings contrasted sharply with the known, rapid effect of dexamethasone given directly to cows in late pregnancy. This action of dexamethasone was confirmed in two catheterized cows (at 257 and 260 days of gestation); one dose of 25 mg (i.m. to the cow) was sufficient to cause delivery within 40 h. No changes in foetal plasma cortisol concentration occurred until the increase immediately after delivery but the usual maternal hormonal changes were telescoped into a sudden rise in oestrogen and fall in progesterone. The changes in foetal and maternal hormone levels during induced and naturally occurring parturition are discussed in relation to findings in other species.

The relation between the birth process and the condition of the newborn piglet and calf

“…Blood gas values and pH in samples taken from the umbilical cord (Schuijt 1992) or the dorsal digital vein of a front leg (Szenci et al 1988) during calving confirmed earlier data from experiments with chronically catheterized foetal calves (Comline et al 1974) that no significant changes take place in the oxygenation and acid base balance during the most part of an uncomplicated birth process. It is only during the last hour before expulsion that a more sustained hypoxia and acidosis develops, most probably as the result of a more permanent reduction in uterine blood flow.…”

Prepartum Maternal Plasma Glucose Concentrations and Placental Glucose Transporter mRNA Expression in Cows Carrying Somatic Cell Clone Fetuses

“…A high incidence of gestational loss in early to mid-pregnancy is the most remarkable feature of the cloning of cattle [1], but problems in the peripartum period, such as delayed parturition, large offspring syndrome (LOS) and neonatal death, are also factors in decreasing the production efficiency [1][2][3][4]. LOS and poor sign of parturition in pregnant cows cause dystocia leading to losses of dams and newborn calves.Cortisol, a glucocorticoid secreted from the fetal adrenal cortex, plays an important role in the initiation and progression of parturition [5,6]. The secretion of cortisol from the fetal adrenal cortex is facilitated particularly during the last week of gestation and reaches a peak just before parturition [5].…”

“…The secretion of cortisol from the fetal adrenal cortex is facilitated particularly during the last week of gestation and reaches a peak just before parturition [5]. In the placenta, cortisol promotes the synthesis of estrogens that induce relaxation and dilation of the birth canal [7].…”

“…Cortisol, a glucocorticoid secreted from the fetal adrenal cortex, plays an important role in the initiation and progression of parturition [5,6]. The secretion of cortisol from the fetal adrenal cortex is facilitated particularly during the last week of gestation and reaches a peak just before parturition [5].…”

Multilevel regulation of steroid synthesis and metabolism in the bovine placenta

“…Because this coincides with an increase in circulating oestrogens, it was suggested that pregnenolone, the common precursor substrate for the synthesis of both steroids, is diverted from progesterone to oestrogen synthesis (Schuler et al, 1994). The more abrupt decrease in circulating progesterone 2-3 days prior to parturition is interpreted as being due to luteolysis and increased progesterone metabolism, likely precipitated by the increase in foetal cortisol production and release, a crucial component of the foetal endocrine signals that initiate parturition (Comline et al, 1974;Fairclough et al, 1975;Hunter et al, 1977).…”