95. The endocrinology of parturition; birth

Question 1

Phases of parturition

Answer 1

0. (initial) phase: before parturition 1. phase: preparatory phase 2. phase: phase of contraction 3. phase: after-phase

Question 2

0. (initial) phase: before parturition

Answer 2

-Oedema of the vulva -Mucus is hanging out of the vagina -Edematous udder -dripping of colostrum

Question 3

1. phase: preparatory phase

Answer 3

Opening of cervix (Dilation) • Cow: 2-6 hours; mare: 1-3 hours; bitch: 6-12 (36) hours Infiltration and swelling of birth canal, the cervical plug is dissolved and appears in vagina, pelvic ligament relaxed, abdominal wall is lowered, body temp. is decreased with 0.5- 1 degree. Uterus reaches a tonic status!  Opening (Dilation): • Birth canal is further dilated, uterus has now rhythmic contractions developing the so called „labor-pains”. Connections between the fetal and maternal parts of the placenta gets looser. Fetal membrane move towards the uterine orifice, open it, slide through the cervix and appear in the vaginal slot. Usually first the allantoic, then the amniotic sac appears. The so called preparsatory pains begin. The upper limbs may be pushed out already.

Question 4

2. phase: phase of contraction

Answer 4

Oxytocin • doloresadpartum • cow–2hours,mare5-60mins, bitch – 30 mins (each fetus), sow – 15 mins (each fetus) Oxytocin stimulated rhythmic uterinal contraction is increasing, combined with increased abdominal pressure: expulsion of fetus (begins with rupturing of allantoic sac; ends with release of fetus) • First the head is pushed out (usually).Ends with release of fetus to the environment. • That is the most intensive phase, with the most severe pain (dolores ad partum), followed by short break and gathering of strength. Phase length: • Cow – 2 hrs, Mare 5-60 min., Bitch – 30 min.(betw fetuses), Sow – 15 min. between fetuses

Question 5

3. phase: after-phase

Answer 5

After-pains,expellingthemembranes. • Following parturition morphological recovery of uterus begins (puerperium), in order to reach pre-gravid status (involution). The ovary is reactivated, new cycle begins. • End of process: the expel of fetal membranes to the environment  Length: • The duration depends on the type of connection between maternal and fetal placenta. • (Cow - > 8 hrs, Mare – 1-3 hrs, Sow and Bitch – 1 to 3 hrs (membranes may be expelled between birth of separate fetuses).

Question 6

End of parturition

Answer 6

Contraction of the uterine muscles result in the separation of the allantochorion from the endometrium.  Then, allantochorion is inside out transferred to the environment  This indicates that the parturition is finished The vet carefully checks the allantochorion whether all parts are expelled Even the smallest piece could lead to fatal endometritis

Question 7

Normal birth position of a fetus

Answer 7

Normal Orientation: Presentation: -Longitudinal -head or bottom first Position: -Abdominal position Deportment: - Stretched deportment

Question 8

Parameters describing the position of fetus

Answer 8

There are three parameters for the description of the position of the fetus. • Presentation -describes the position of the fetus in the birth canal. • Position -describes the location of the fetal vertebral column and the birth canal. • Deportment -describes the position of the fetal limbs and the head in relation to the birth canal.

Question 9

Presentation

Answer 9

Presentation describes the position of the fetus in the birth canal. • The fetus occupies its final position at the end of pregnancy (just before the start of parturition). • head first: this is the normal presentation in large animals. • bottom first: a presentation occurs in 40% of multiparous species. It may cause complications in the phase of contractions, since clamping of the umbilical cord may cause hypoxia in the fetus.

Question 10

Position:

Answer 10

Position describes the location of the fetal vertebral column and the birth canal. • Normal position: abdomen down. During position: abdomen up (or back down) clamping of the umbilical cord may cause complications. • The bovine fetus is in “abdomen down” position during pregnancy. • The horse fetus is in “abdomen up” position during pregnancy, therefore it should rotate by 180 degrees before parturition. Horse: • “abdomen up” position during pregnancy, it rotates by 180 degrees before parturition Cow: • in “abdomen down” position throughout the whole pregnancy

Question 11

Deportment

Answer 11

Deportment describes the position of the fetal limbs and the head in relation to the birth canal. • Normal deportment: stretched limbs. • During pregnancy, appendages of the fetus are in bent position. This should become stretched (or extended) directly before parturition. If this is omitted, difficulties take place and help is needed.

Question 12

The endocrinology of parturition

Answer 12

End of Pregnancy • high P4, low E2. • Uterus is insensitive to contracting effect of E2 and Oxytocin. Initiator of Changes: • fetal stress (At the end of pregnancy in utero life gets „inconvenient”) -(can be: mechanical stress (growing size of fetus), chemical stress (lack of nutrients and oxygen),high environmental temp., maturation of Hypothalamus, maturation of fetal adrenal cortex

Question 13

Regulators of Parturition

Answer 13

Labor onset - Stretch stimulus -Oxytocin -Prostaglandins -Positive feedback • Cervicalstretch • Oxytocin • parturition

Question 14

Hormonal role: (picture)

Answer 14

Question 15

Endocrinological changes in horse

Answer 15

Unlike other domestic animal species, the factors that initiate parturition in the mare have not been elucidated

Incontrasttoruminantspecies,maternalestrogenand progesterone concentrations do not change markedly, and a well-defined fetal cortisol surge is not observed just prior to parturition in the mare

P4increasesbeforeparturition,whileE2decreases

 Parturition is associated with large increases in prostaglandin and oxytocin concentrations, which induce uterine contractions and delivery of the foal.