It is known that the prevalence of CSs in some breeds approaches 100%. In addition, this study identified previous CSs, fewer than eight and more than 11 puppies per litter in Boerboel bitches as obstetric risk factors (resulting in emergency CSs and stillbirths). It also showed that a trial of labour after caesarean section was associated with considerable obstetric risks. In such high-risk pregnancies, using the signs of parturition to time elective CSs in the bitch is problematic, as by then there may already be foetal distress or demise. Also, the signs of parturition may present at an inconvenient time of the day, when staff shortages may impede professional service. This study aimed at solving these problems by investigating various means of predicting the day and time of onset of parturition (cervical dilatation) in the bitch. This study showed that a chemiluminescent immunoassay (Immulite® 1000 LKPW1) is a reliable replacement for a discontinued radio immune assay to measure PC in serum or plasma. It proved that the first day of cytological dioestrus (D0) is the most precise peri-oestrous predictor of the day of cervical dilatation. This study showed that the variation in the foetal biparietal diameter is too large to accurately predict readiness for CS and that the preparturient PC may be used to predict the time of cervical dilatation, thereby allowing timeous planned CSs in bitches where D0 is unknown. The use of medetomidine hydrochloride as premedicant combined with propofol as induction agent and sevoflurane as maintenance, is safe and is associated with good maternal and puppy survival rates at delivery, 2 h and 7 d after CSs. Performing elective CSs upon the first appearance of any degree of cervical dilatation proved successful. For bitches in this study with high-risk pregnancies, we proved that it is safe to perform fixed date preparturient CSs on D57 if the cervix has not dilated by then. This study showed that bitches have haematocrits at the time of cervical dilatation that are at the lower end of the normal reference ranges for non-pregnant dogs and that the decline in haematocrit associated with CS is similar for parturient (open cervix) and preparturient (closed cervix) CSs. As incidental findings, this study discovered two puppies sharing one placenta in each of two litters. The one case of placenta sharing proved to be monozygotic twins whilst the other case proved to be a case of dizygotic monochorionic canine foetuses with blood chimaerism and suspected freemartinism. This study provides the veterinary obstetrician with a protocol that can be used to safely perform elective CSs in a large proportion of the obstetric population at a convenient time of the day but more research is required with larger numbers to establish whether this practice is routinely safe and safe in all breeds.
Die voorkoms van keisersnitte bereik 100% in sommige rasse. Hierdie studie het getoon dat
ʼn vorige keisersnit, kleiner werpsels as agt en groter werpsels as 11 in die Boerboel,
verloskundige risikofaktore is. Dit het ook getoon dat ʼn poging tot spontane kraam nadat ʼn
teef voorheen ʼn keisersnit ondergaan het, geassosieer is met 'n aansienlike risiko van noodkeisersnitte
en doodgebore hondjies. Om in sulke hoë risiko dragtighede te wag vir tekens
van kraam voordat ʼn elektiewe keisersnit uitgevoer word is riskant, omdat fetale nood of
dood reeds kon intree. Die tekens van kraam verskyn dikwels op ʼn ongeleë tyd van die dag,
wanneer ʼn personeeltekort ʼn professionele diens belemmer. Hierdie studie was daarop
gemik om hierdie probleme op te los deur verskeie metodes te ondersoek om die dag en tyd
van aanvang van servikale ontsluiting in die teef te voorspel. Verskeie bevindings spruit uit
die studie: ʼn Chemiluminessensie immunotoets (Immulite® 1000 LKPW1) is ʼn betroubare
plaasvervanger vir ʼn gestaakte radioimmunotoets. Die eerste dag van sitologiese diestrus
(D0) is die mees presiese en praktiese peri-estrus voorspeller van die dag van servikale
ontsluiting. Die bipariëtale deursnit van honde fetusse tydens laat dragtigheid varieer soveel
binne rasse en binne werpsels dat dit ongeskik is vir die akkurate en betroubare voorspelling
van gereedheid vir keisersneë. Die voorgeboortelike progesteroon konsentrasie in die
bloedplasma of serum dien as ʼn voorspeller van kraam in tewe waarvoor D0 nie bekend is
nie. Die binneaarse toediening van 7 mg/kg medetomidine hidrochloried as premedikasie, gekombineer met 1–2 mg/kg propofol as induksiemiddel en 2% sevoflurane in suurstof vir
die onderhoud van narkose vir keisersnit in tewe is veilig en lewer hoë oorlewings peile in
tewe en kleintjies by geboorte, 2 ure en 7 dae na keisersnit. Keisersnitte wat uitgevoer word
sodra die eerste tekens van servikale ontsluiting waargeneem word, is suksesvol. Hierdie
studie het getoon dat vir tewe met hoë risiko swangerskappe, dit veilig is om preparturiente
keisersnitte uit te voer in tewe met n geslote serviks, sewe en vyftig dae (D57) na D0 vir
tewe met werpsels > 1 as die serviks teen daardie tyd nog nie ontsluit het nie. Tewe se
hematokrit aan die begin van kraam stem ooreen met die laer normale waardes van vir
nie-dragtige honde en dat vermindering in hematokrit geassosieer met parturiente
keisersnitte (oop serviks) soortgelyk is aan bloedverlies geassosieer met preparturiente
(geslote serviks) keisersnitte. Toevallige bevindings was dat twee fetusse uit elk van twee
werpsels ʼn plasenta gedeel het. In een geval was die fetusse monosigotiese tweelinge en in
die ander geval was hulle monochorionies en disigoties, met moontlike freemartinisme.
Hierdie studie stel die veterinêre verloskundige in staat om elektiewe preparturiënte
keisersnitte op ʼn geleë tyd van die dag uit te voer in ʼn hoë persentasie van die obstetriese
populasie maar verdere navorsing met groter getalle word benodig om vas te stel of dit
roetine gewys veilig is en veilig is in alle rasse.
