Uterine involution and return to cyclicity Flashcards
What has to happen in the post-partum period (puerperium)
- Uterine involution
- Elimination of bacterial contamination
- Resumption of ovarian function
- Lactation/suckling
Outline the features of uterine involution
- Reduction in uterine size
- Coordinated atrophy
- Endometrial repair
- Expulsion of lochia
Describe the bovine reproductive tract day 1 post partum
- Brown mucus from cervical plug
- Ovary still present (was present throughout pregnancy)
- Will lyse after parturition
- Uterus too big to palpate at this stage
Describe the bovine reproductive tract day 4 post-partum
- Cervix starting to close off
- Some reduction in size
- Lochia is normal fluid (bloody discharge in conjunction with foetal fluids)
- Discharged via the vagina then the vulva
Describe the bovine reproductive tract day 10 post partum
- Haemorrhaging of vagina greatly reduced
- Cervix much smaller
- Uterus much smaller
- CLs of pregnancy mostly gone
- Antral follicles starting to appear (starting to return to cyclicity)
- Gravid and non-gravid horn return to oestrus at different rates, non-gravid first
Describe the bovine reproductive tract day 20 post partum
- Similar to non-pregnant
- Cervix and vagina repaired
- CL disappeared
- Lots of ovarian activity
Describe the myometrial contractions in the uterine involution mechanism
- Peristaltic waves towards cervix
- Discharge of fluid/debris
- Compress vasculature preventing further bleeding
- Stimulated by oxytocin and PGF2a
- Stimulated by suckling
Outline the coordinated atrophy involved in the uterine involution mechanism
Reduction in myometrial cell size
Describe the lochia in the cow
- Second cleansing
- Blood tinged
- Remnants of foetal placena and endometrial tissue
- Odourless
- Forms as a result of caruncular sloughing between day 5-10, leaves stubs
Describe endometrial repair
- Restoration of caruncle
- Sloughing of cotyledon
- Necrosis
- Tissue remodeling
- Intercaruncular endometrium thins during pregnancy
- Early necrosis and destruction of epithelial lining of caruncles
- Top surface sloughs away
- Vascular stubs left, repaired and reorganised - get smaller
Describe uterine involution in teh mare
- Extremely rapid
- Little endometrial disruption
- Post-partum infection normal and frequent and eliminated by foal heat
Explain why there is little endometrial disruption in the mare
- Diffuse placenta
- Contents of lumen of endometrial glands reabsorbed
- Autolysis and shrinkage of the maternal crypts
Describe uterine involution in the bitch
- Restored to size by 4 weeks
- 2 lochia
- First is immediate, second 4-6 weeks later (has normal appearance)
- Endometrial repair slow (3 months)
Describe the first lochia in the bitch
- Immediate
- Green
- Caused by uteroverdin
- Only green immediately post-partum
- D1-2 PP red and water, then mucoid appearance
Describe week 1 of endometrial repair in the bitch
- Eosinophilic necrotic layer over placental sites
- Few decidual like cells
Describe week 2 of endometrial repair in the bitch
- Collagen fibre proliferation
- Mononuclear cell infiltration
- Glands start to dilate, any mass within glands get infiltration and proliferation to make collagen masses
Describe week 3 and 4 of endometrial repair in the bitch
- Increased collagen lining
- Irregular lobulated masses
- Dilated endometrial glands
- Absence of decidua cells
- Myometrium starting to repair self
Describe weeks 5-7 of endometrial repair in the bitch
- Sloughing of collagen mass (second lochia)
- Once removed, endometrium has new epithelial lining and is repaired
- Mononuclear cell infiltration
- Glands return to normal size
- Whole process can take 3 months to completion
Describe weeks 8-12 of endometrial repair in the bitch
- Sloughing
- Replacement of endometrial lining
- Complete at week 13
Why does bacterial contamination of the uterus occur at parturition?
- Cervix dilated
- Non-sterile
What infections are normal in the mare following parturition?
- Coliforms and Streptococci
- Eliminated by foal heat
Describe elimination of uterine bacterial contamination following parturition in teh cow and mare
- Increased by myometrial contractions
- Phagocytosis by leukcytes, promoted by oestradiol
What may predispose the uterus to bacterial contamination in relation to parturition?
- Retained foetal membranes
- Prolonged uterine involution period
- Weak uterine contractions
What are the effects of excessive uterine bacterial contamination following parturition?
- Metritis/endometritis
- Prolonged uterine involution period
- Delayed return to cyclicity and thus delayed establishment of pregnancy
Describe endometritis (whites)
- Persistent infection (>3 weeks)
- Attentuated uterine defence mechanism
- Deviatlised tissue e.g. retained foetal membranes
- Inflammation of endometrium
- Opportunistic pathogens e.g. Trueperella pyogenes
- High incidence
- Significant cause of infertility
- White mucoid discharge with odour
Outline treatments for endometritis (whites)
- Cleansing
- Antibiotics
- Oxytocin or PGs to stimulate contraction and elimination of infection
Describe the hormonal changes that occur to resume cyclicity
- P4 falls
- E2 falls after parturition
- Release of GnRH (no suppression from P4)
- Early stages pit not responsive to GnRH
- Release of LH and FSH (FSH first)
- Aids development of follicles
- Follicular wave recruited
- E2 increases as follicle grows
- LH increases and becomes dominant
- Dominant follicle producing E2 and inhibin
- E2 stimulates at threshold LH surge and thus ovulation
- CL present and P4 increases
- Cyclicity has resumed
Describe the nature of the first cycle/heat
- In most species is short and silent
- Mare is exception to this
List factos that may delay ovarian rebound
- Periparturient abnormalities
- Milk yield (greater NEB, lower IGF1 impact on ovary development)
- Nutrition (BCS, NEB, IGFs)
- Parity
- Suckling
- Season
- Climate
