Parturition Flashcards
Parturition
Begins when fetal size and nutritional demands exceed what the placenta can do
Describe the entire process of parturition.
-Fetal stress -> Increase in ACTH -> Increase in fetal cortisol -> increase in enzymes (enzymes cause placental P$ to convert to E2) and PGF2a
-E2 -> increase secretion by female reproductive tract -> lubrication
-E2 and PGF2a -> increased myometrial contractions -> increase pressure -> increase cervical stimulation -> increase oxytocin -> results in maximum pressure
-PGF2a -> causes luteolysis
-PGF2a -> increases relaxin -> causes pelvic ligament stretching and cervical softening
Know the 3 enzymes that are altered by cortisol for conversion of progesterone to estrogen.
-17a-hydroxylase
-17-20 desmolase
-aromatase
Know how the orientation of the fetus changes as parturition approaches and why this is important
-fetus moves where face and front feet exit first
-Failure to do this results in breech and may cause dystocia
Know the general distribution of prenatal losses
-2/3 occur in the embryonic stage
-1/3 occur in the fetal stage
Stage 1 of labor
-Preparative stage
-myometrial contraction
-abdominal discomfort
-contraction uterus pushes fetus towards the cervix
-cervix is dilating and the fetus is pushed into the cervical canal
Stage 2 of labor
-Expulsion of Fetal stage
-strong uterine and abdominal contractions are occurring
-animal is usually recumbent and straining
-Relaxin takes effect
-estradiol results in higher mucus production that lubricates the tract and washed away the cervial seal of pregnancy
-fetus puts pressure in the fetal membranes and allantochorion eventually breaks and allantoic and amniotic fluid are lost. These fluids further lubricate the cervix and vagina
-this movement cases more intense contraction until the neonate is born
Stage 3 of labor
-expulsion of the placenta stage
-weaker myometrial contraction continue
-uterine contractions
-chorionic villi loosen
-expulsion of placenta
-delayed in ruminants due to presence of cotelydons separating independently
-suckling induces oxytocin release which triggers further uterine contractions
Be able to define and describe dystocia including some factors that cause it
-Dystocia: Difficult birth
-Happens due to excessive fetal size (cattle), abnormal presentation, or multiple births
-Factors: maternal health, mechanical issues, or fetal size/position
Maternal causes
- uterine inertia primary or secondary
- cervical spasm, incomplete dilation
Mechanical causes
- fetopelvic disproportion
- uterine torsion
- stenosis of cervix and vagina
- congenital anomalies
fetal causes
- abnormal presentation, position and posture
- development defects
- oversize fetus, twins
What can dystocia cause
- premature labor
- prolonged labor
- arrest of labor
Be able to define retained placenta
-Failure of the placenta to be expelled following birth
-If placenta is not expelled within 24 hours it may be retained for 5-6 days
-most common in cattle
What are the causes of a retained placenta
-lack of blood flow to chorionic villi and this causes them to regress
-High incidence in premature or early delivery
-high milk producers
-twins
-dystocia
-induction of parturition
-nutritional deficiencies of vitamin A or selenium
