Investigation of maternal mortality and stillbirth in feline dystocia after emergency obstetric care interventions: a retrospective analysis

Abstract

Objectives

The aim of this study was to investigate the efficacy and success of emergency obstetric care interventions for feline dystocia and to analyse the effects of therapeutic interventions on maternal mortality and stillbirth.

Methods

This retrospective, observational study included 153 queens of various breeds and ages that presented to the clinic with dystocia. Anamnesis, signalment, physical examination, ultrasonography, radiography and subsequent intervention data were also collected. Differences in stillbirth rates between the treatment groups were evaluated using the χ² test. The mean litter size, mean duration of labour and number of stillbirths were calculated in each case. In addition, to obtain information on further breeding of dystocia patients, 51 queen owners were contacted by telephone.

Results

Medical treatment was successful in 17% of patients, and 83% underwent surgical treatment for dystocia. Ovariohysterectomy (59%) was the most common surgical method, followed by conservative caesarean section (35%). En bloc resection was performed in 6% of patients. A total of four (2.4%) queens died. Of 542 kittens from 153 deliveries, 210 (39%) were stillborn. Singleton pregnancies were associated with a high risk of difficult labour. Similarly, prolonged duration of labour increased the stillbirth rate. The fertility status of queens after caesarean section was assessed by interviewing 51 owners, 27 (53%) of whom provided information. Of these, 12 were mated again and nine successfully (they became pregnant with successful natural births in five).

Conclusions and relevance

Similar to previous studies, our data showed that medical management led to success in only a minority of cases. In addition, mortality data for emergency births under modern standardised treatment conditions were provided. Singleton pregnancy is a suspected risk factor for dystocia. Pregnancy after caesarean section is possible with natural unassisted birth.

Keywords

Dystocia therapeutic interventions maternal mortality stillbirth

Introduction

The primary responsibility of obstetricians is to identify difficulties early and initiate the appropriate therapeutic procedures.¹ Difficult labour (dystocia) occurs when the dam is unable to deliver without assistance.^2
–6 Dystocia ideally requires the use of well-defined protocols for clinicians to follow; however, in contrast to human medicine, such guidelines do not exist for cats. To obtain insights that could aid in clinical decision-making for obstetrics in queens, retrospective literature, personal and third-party experience, and in some cases, data from studies on human medicine and other animal species are used, which may lead to errors. The causes of maternal mortality and stillbirth related to dystocia in queens are multifactorial and there are limited data in the literature. Generally, the longer the labour process, the higher the maternal mortality and stillbirth rates in queens.² Data from older studies may be misleading because examination methods (eg, the use of ultrasound) and medication have changed over the past few decades, warranting the need for current data to guide therapy. In a recent study,³ feline dystocia was evaluated in a series of 28 cats, but larger-scale studies of feline dystocia are required. Given the literature gap, our objectives for this study were:

to analyse maternal mortality and stillbirth rate;

to analyse the results of therapeutic interventions;

to assess the relationship between litter size and stillbirth in feline dystocia; and

to determine the status of a dam’s fertility after emergency interventions for dystocia.

Materials and methods

Animals

In this retrospective study, data from 153 queens of various breeds and ages, with dystocia, were analysed. The animals were treated at a single veterinary clinic between January 2000 and March 2021. The inclusion criteria were stage 2 of labour and dystocia diagnosed according to the criteria of Bailin et al.³ The animals did not receive any veterinary treatment before visiting the clinic. Of the 166 initially admitted animals, 13 were excluded: nine cats gave birth after arrival at the clinic without intervention, one had an extrauterine pregnancy and three had prolapsed uteri postpartum.

Data collection

Examinations were carried out according to a standardised protocol over the entire study period, which was defined in an electronic documentation programme (EasyVET; VetZ). This resulted in the standardised data collection. A diagnostic method was not used if the owner refused one because of cost. After anamnesis, general health examinations, clinical gynaecological examinations, blood analyses, abdominal ultrasound and radiography were performed. The number and viability of the kittens in the genital canal were also investigated.

Anamnesis

The following information was obtained from the owners through anamnesis: age, breed, number of labours, presence or absence of prior dystocia, time of first mating to determine the duration of gestation, beginning of labour, birth of kittens before presentation to the clinic and interventions before presentation. Details of the labour were collected via the following questions: When did labour start? What were the clinical signs at the onset of labour? Were there any stillbirths or live births? The duration between labour onset and visit to the clinic was determined. It was also determined if there was any intervention administered during labour.

Palpation

Before any diagnostic imaging, the presence of kittens was checked using manual abdominal palpation.

General clinical examinations

Respiratory rates, heart rates (HRs) and body temperature were measured and recorded. The birth canal was checked for discharge, putrefaction and the presence of kittens. The results from general haematological and biochemical analyses were also recorded. Rectal temperatures were measured using a digital thermometer.

Radiography

Radiography was used to determine the presence, number and size of fetuses in the uterus and birth canal, and to detect the presence or absence of fetal-pelvic disproportion and fetal transverse position. Maternal pelvic and fetal head diameters were compared using radiographic images to determine fetal-pelvic congruence, which was subjectively assessed because, currently, there are no reference data for different age groups of cat breeds.

Ultrasonography

Ultrasonography was used to check for the presence and viability of fetuses and to exclude ectopic pregnancies. Fetal HRs were determined in at least two fetuses. In each case, fetal HRs were measured twice, 2 mins apart.

Therapeutic interventions for dystocia

Treatment decisions were based on clinical findings and diagnosis. Treatment approaches for dystocia are shown in Figure 1 and explained in detail below. In cases where the general health of the queen was assessed as being at appreciable risk, surgical methods were always used instead of medical treatments (Figure 1). Where the queen was assessed as being in good or adequate general health, medical treatments were preferred if the birth canal was open and there was no fetal-pelvic disproportion or fetal transverse position. Fetal HRs were considered when determining the treatment intervention in particular. Surgical treatment interventions were also preferred in cases with fetal HRs <130 beats/min (Figure 1).

Figure 1

Treatment approaches to dystocia cases. Four clinicians were involved in the management of these cases, and all evaluated the instances based on standardised protocols. **OHE = ovariohysterectomy: the uterus and ovaries are removed after delivering the kittens. Indications for this type of caesarean section included severe changes in the uterine wall, massive bleeding from the placentation sites and the owner’s desire for spaying. *^XThe lowest fetal heart rates (HRs) were used for decision-making. ^XEn bloc resections: delivery of the kittens after removal of the uterus

Medical management

Medical management was performed if the following conditions were met: the queen was in good general health with an open birth canal, fetal-pelvic disproportions and fetal transverse position were excluded, and fetal HRs were >130/min. Medical intervention included mild to moderate traction and administration of oxytocin (Veyx-Pharma; up to 2 U SC) in combination with glucose 5% SC (Selectavet) and oral calcium administration (350 mg/500 mg calcium lactate pentahydrate and calcium gluconate per 10 ml, Frubiase; Boehringer Ingelheim). A maximum of two doses of oxytocin were administered 45 mins apart. If no kitten was born within 45 mins of the second injection, medical treatment was deemed to have failed and surgery was performed.

Surgical management

If medical treatment failed, the fetal HRs decreased to <130 beats/min or parturition with natural unassisted birth was not possible owing to incorrect fetal positions (eg, transverse position, fetomaternal disproportion), a caesarean section (caesarean section conservative, ovariohysterectomy [OHE], en bloc resection) was performed immediately. En bloc resection was performed if there was foul-smelling vaginal discharge or an accumulation of gas in the uterus. This surgical method was used to prevent contamination of the abdominal cavity. Indications for OHE included severe changes in the uterine wall, heavy bleeding from placentation sites and the owner’s desire for spaying.

Anaesthetic protocol

The two anaesthetic protocols below were used for surgery.

Protocol 1: in well-manageable queens, intravenous (IV) cannulation was performed in conjunction with preoxygenation, and anaesthesia was induced with propofol (up to 6 ml/10 kg; Zoetis). In addition, meloxicam (Metacam; Boehringer Ingelheim) was administered as a single dose (0.3 mg/kg SC). The cat was intubated and ventilated with oxygen. After removal of the kitten, anaesthesia was maintained using inhalation anaesthesia (isoflurane and oxygen), while analgesia was maintained using butorphanol (0.1 mg/kg IV) administered slowly.

Protocol 2: midazolam (0.1–0.3 mg/kg; Dechra Regulatory BV) and ketamine (5–10 mg/kg; Selectavet) were used as intramuscular premedication. These animals then underwent venous cannulation, and anaesthesia and analgesia were induced as described in protocol 1. Anaesthetic protocols were not evaluated in the analysis of outcomes. Postoperative analgesic treatment was provided for 1–3 days. Metamizole (25 mg/kg), meloxicam (0.2 mg/kg), carprofen (4 mg/kg) or butorphanol (0.1 mg/kg) was preferred for analgesia.

Outcomes

The following data were collected for all queens with dystocia: maternal mortality, number of kittens born alive or dead, and stillbirth rates.

Follow-up of queens after discharge

To obtain information on further breeding of dystocia patients after caesarean section, 51 owners were contacted by telephone to conduct a survey comprising the following questions:

Has the queen been mated again?

To what extent was mating successful?

What was the status of repeat pregnancies and births?

Was dystocia present or was the birth natural (unassisted)?

Statistical analysis

Differences in stillbirth rates between the treatment groups were evaluated using the χ² test. Statistical significance was set at P <0.05. Descriptive statistics were used to determine the number of stillbirths. In this context, stillbirths for different gestation durations and litter sizes were calculated as means and percentages. All statistical analyses were performed using Minitab version 21.4.1 (Minitab). All mean numerical values were expressed by adding the standard deviation (mean ± SD).

Results

Animals

The exact age of 123/153 queens was known by the owners and ranged from 6 months to 12 years, with a mean of 2.8 ± 2.3 years. The domestic shorthair queen was the most frequently affected breed (46%). Parity information was available for 93 queens. Of these, the majority (n = 55) had not previously had a litter. In total, 15 animals had a litter once; 10, twice; five, three times; and six, >three times. Two animals presented during their seventh pregnancy. Overall, 64% of the queens showed moderate to severe tachycardia (160–260 beats/min). In many cases (n = 35), patients with tachycardia had an increased respiratory rate (44–180 beats/min). Bradycardia (68 beats/min) was diagnosed in only one case. The queens’ internal body temperature was within the reference interval (38.0–39.3°C) in 62% of cases. An increase in internal body temperature was observed in 7% of the queens. Moreover, 31% of the queens showed slight hypothermia (37.3–37.8°C), while three presented with a very low temperature (34.3–36.4°C).

Litter size

Litter size was in the range of 1–8 kittens being born (mean 3.3 ± 1.6). Singleton pregnancies were observed in 22 queens.

Gestation and labour duration

The mean duration of gestation in 59 of the included cases was 65 ± 5.4 days. The mean duration of labour (onset to birth of first kitten) until presentation at the clinic (n = 76) was 18 ± 0.3 h.

Treatment of dystocia

As shown in Table 1, the 153 dystocia patients were divided into three groups.

Table 1

Treatment of queens with dystocia

Therapy	Absolute number	Relative number (%)
Medical management	26	17
Medical management with subsequent caesarean section	23	15
Caesarean section	104	68
Total	153	100

Medical obstetric care was successful in only 17% of the patients, and 83% underwent surgical treatment for dystocia. Table 2 presents the distribution of the surgical methods used.

Table 2

Distribution of the surgical methods in queens with dystocia

Type of surgical incision	Absolute number	Relative number (%)
Caesarean section	44	35
Ovariohysterectomy*	75	59
En bloc resection^†	8	6
Total	127	100

Ovariohysterectomy after delivery of the kittens

†

Delivery of the kittens after removal of the uterus

Of the 127 queens that had a caesarean section, 23 were initially treated medically before surgery was required. Twelve patients (52%) underwent conventional caesarean section, whereas 11 (48%) underwent OHE. In all cases, the decision to perform OHE was made at the owner’s request and was not medically indicated.

Maternal mortality

Four queens (2.4%) died as a result of severe general malaise (hypothermia, anaemia and lateral positioning), uterine torsion (hypothermia, shock) and uterine rupture. Two animals died during the initiation of anaesthesia and two died during surgery.

Stillbirths

Of the 542 kittens from 163 deliveries, 210 (38.8%) were stillborn (Table 3). As shown in Figure 2, stillbirths were highest in singleton pregnancies (59%), where 13/22 kittens died. Notably, 18/22 queens with singleton pregnancies required surgical treatment. As can be seen from the data on stillbirths presented in Table 3 and Figure 2, our overall findings suggest that an increased litter size was associated with a reduced probability of stillbirth.

Table 3

Distribution of stillbirths and live kittens in queens with dystocia (n = 542 kittens)

Litter size	Stillbirths (%)	Total number of kittens	Total live kittens	Total dead kittens (x, y)
1	59	22	9	13 (10, 3)
2	36	64	41	23 (19, 4)
3	42	114	66	48 (41, 7)
4	33	128	86	42 (39, 3)
5	42	135	79	56 (51, 5)
6	48	42	22	20 (18, 2)
7	24	21	16	5 (4, 1)
8	17	16	13	3 (3,0)
Total		542	332	210 (185, 25)

x = number of kittens that were diagnosed as dead in the genital tract; y = number of kittens that died after being removed from the genital canal

Figure 2

Litter size and stillbirth in queens with dystocia (n = 542 kittens from 163 births)

The mean duration of labour until presentation to the clinic (n = 76) was 18 ± 0.3 h (range 2–96) for 76 queens with this information available. A prolonged duration of labour was found to increase the stillbirth rate in these cases (Table 4).

Table 4

Stillbirths in queens with dystocia by the duration of labour and treatment of dystocia

Treatment method	Duration of labour (h)	Stillbirth (%)
Total (n = 76)	18 ± 0.3	31.0
Medical management (n = 13)	10.0 ± 8.0	25
Surgical management (n = 63)
Medical labour assistance with	19.2 ± 18.8	32.3
Subsequent caesarean section (n = 11)	10.6 ± 6.2	25
Immediate surgical therapy (n = 49)	19.0 ± 17.3	32.9
En bloc resection (n = 3)	56 ± 36.6	66.6

Data are mean ± SD unless otherwise indicated

Stillbirths observed across different treatment methods in dystocia patients

Table 5 shows the number of stillbirths associated with different treatment methods. Stillbirth was more frequent after surgical therapy for dystocia than after medical labour assistance (P <0.001). In contrast, when the methods of assisted labour alone were considered, en bloc resection was found to be associated with significantly more stillbirths than the other methods (P <0.001) (Table 5).

Table 5

Stillbirths observed across different treatment methods in queens with dystocia (n = 153)

Treatment method	Stillbirths (%)	Total number of kittens	Living kittens	Dead kittens	χ² test	P value
Medical management (n = 26)	25.9^a	85	63	22	18.765	<0.001
Medical management with subsequent caesarean section (n = 23)	30.1^a,b	83	58	25
Caesarean section (n = 96)	39.5^b	309	187	122
En bloc resection (n = 8)	70.8^c	24	7	17

Values with different letters indicate significant differences (P <0.05)

Fertility after dystocia

The fertility status of the cats was analysed by interviewing 51 animal owners, of whom 27 provided information. A total of 12 queens were mated again, of which nine became pregnant, all in the first oestrus after the dystocia episode. Of those, five (55.5%) gave birth naturally (unassisted), whereas four (44.5%) developed dystocia and underwent OHE.

Discussion

The prevalence of dystocia in queens is in the range of 0.4–20% in the literature.^7,8 It is typically an emergency; consequently, veterinarians must act and advise quickly and comprehensively. As treatment routines are rarely developed in practice, literature on feline obstetrics is very important. Comparable studies either date back many years^7,9
–11 or refer to a long period of evaluation,² and the diagnostic and therapeutic standards do not correspond to the current situation. A more recent study that evaluated feline dystocia included only 35 cases,³ and 7/35 queens did not receive any intervention, while 28 underwent obstetric interventions, which were subjected to stillbirth analysis. In the present study, we analysed 153 queens with dystocia and addressed important limitations of the study by Bailin et al³ (eg, relationship between litter size and stillbirth, duration of labour and stillbirth, and follow-up of subsequent fertility of queens after assisted delivery). Our patient evaluation was based on data collected after a standardised examination procedure. These results are intended to provide information on the outcomes of obstetric interventions in queens.

Studies have reported that maternal mortality rates in queens with dystocia are in the range of 2–6.3%.^2,3,12,13 In the present study, maternal mortality (2.4%) occurred in queens that were already in critical general health on admission to the clinic, including shock. Two patients had poor preoperative general health (uterine rupture and torsion). A third patient presented with shock that could not be successfully treated. A fourth animal presented with severe anaemia in the lateral position and died during preparation for a caesarean section. The study by Bille et al¹⁴ investigated the general mortality risk under general anaesthesia and confirmed that mortality is closely correlated with the health status (American Society of Anaesthesiologists [ASA] classification for assessing perioperative risk) of animals. Animals with an ASA level of ⩾3 had a significantly higher mortality rate than those with an ASA level of 1–2. In this study, the mortality rate increased from 2.9% (ASA level 3) to 7.58% (ASA level 4) and 17.33% (ASA level 5) in correlation with ASA levels. Overall, maternal mortality depends on the dam’s preoperative health status. The worse the initial situation, the worse the chance of success. Similarly, Bailin et al³ reported that the general health of queens with dystocia has an impact on maternal mortality, indicating the importance of early dystocia detection and treatment for its prevention, which queen owners should be informed about.

Stillbirth is a widely defined term in the literature. Whether only stillbirths, postpartum deaths in the first hours of life up to the fourth day of life, or death occurring during the first 3–4 weeks or the rearing phase (4th to 6th week of life) up to weaning are recorded makes a significant difference.^{4,11,15
–20} The present study refers to stillbirths including deaths occurring until the end of the birthing process.

In the present study, surgical treatment was performed in 83% of queens with dystocia, while 15% were initially treated medically. This is in line with the data published by Ekstrand and Linde-Forsberg,¹⁰ based on which 79.9% of patients were treated surgically, of which 44.2% were initially treated medically. Sohst et al² also performed an incisional delivery in 78.9% of cats in their series, 35.6% of which were treated medically. In a study by Zamponi,²¹ surgery was necessary in 74.7% of cats, 8.9% of which had been previously treated medically without success. Collectively, the data from these studies suggest an increase in the proportion of patients treated with surgery alone without previous attempts at medical therapy. Lorin and Wollrab²² postulated that caesarean section be performed in 95% of cats with dystocia. In summary, it can be stated that caesarean section is necessary in the majority of cats with dystocia and that medical management has a lower success rate. Any veterinarian who initiates medical obstetric treatment for a queen should anticipate that it may not be successful. Indeed, in a recent study of 28 queens with dystocia requiring urgent intervention,³ medical treatment was used in 75% (n = 21) and was successful in only six (29%) patients, which supports our results. Bailin et al³ reported that stillbirths occur in approximately 34% of queens with dystocia. The same researchers³ also report that the proportion of stillbirths delivered by medical (32%) and surgical (34%) means was higher than that delivered without assistance (22%). In the present study, when the methods of assisted labour alone were evaluated, en bloc resection was found to be associated with a significantly higher incidence of stillbirth than the other methods. This is because this surgical approach is typically used when dead kittens are present, as well as foul-smelling vaginal discharge, in order to avoid abdominal cavity infection.^11,23 In these cases, it can be assumed that the cat had already been in labour for some time, which explains the higher mortality rate.

In our study, surgical therapy for dystocia was associated with a significantly higher stillbirth rate than medical labour assistance,²⁴ similar to the observations of Bailin et al.³ However, we cannot conclude that surgical interventions are the only cause of increasing neonatal deaths because many different factors may be involved, one of which is the anaesthetic agent administered to the queen. Because almost all anaesthetics cross the placental barrier and lead to temporary depression in the fetus, maternal anaesthesia may ultimately cause the development of depression in kittens after birth, delaying the onset of suckling. Anaesthesia is obviously one potential cause of death in the kittens, but presumably the kittens may also be more compromised (or already dead), contributing to the need for surgery.^25,26

When the mean duration of labour and stillbirth rates were compared, stillbirth tended to increase in proportion to the duration of labour (Table 4). However, this positive correlation was not significant in the present study, but nevertheless our observations support the statement by Sohst et al,² that prolonged labour is a negative prognostic factor for neonatal survival.

In the present study, 59% of fetuses in singleton pregnancies died (Figure 2). In conjunction with the findings of Lawler and Monti,¹⁷ it can be confirmed that litter size influenced the risk of dystocia.²⁷ Sparkes et al²⁸ reported a higher risk of caesarean section in pregnancies with smaller litter sizes. Other authors have not found a correlation between litter size and dystocia risk in queens.^10,26 A single pup increases the risk of dystocia in bitches.²⁹ This is because the puppies grow too big.

There is a significant gap in the literature concerning the fertility of queens after caesarean section. To address this, we called owners whose cats gave birth by caesarean section or medical management. However, from the owners contacted, only 12 cats were mated. Of these, 75% (9/12) became pregnant, corresponding to the physiological fertility rate of queens.³⁰ Surprisingly, 55% were spayed after dystocia. The owners perceived dystocia as a dramatic,³¹ memorable experience, and the spay was intended to prevent the circumstances from being repeated. Overall, our data suggest that pregnancy after caesarean section is possible and, in some cases, with a natural unassisted birth. Future systematic studies on more cases may minimise the limitations of this study.

Conclusions

In queens with dystocia, medical management plays a much smaller role than caesarean section. Even in cases where medical treatment is initially possible, the situation may change such that caesarean section becomes necessary. Singleton pregnancies are associated with a high risk of difficult labour. Early diagnosis of such pregnancies and the management of labour are important for reducing maternal mortality and stillbirths. Similarly, there is a significant risk of stillbirth associated with delayed labour interventions in queens with dystocia, of which cat owners should be aware.

Footnotes

Acknowledgements

The authors extend their heartfelt gratitude to the entire team for their invaluable support in the data follow-up and the successful completion of this study. In addition, the authors gratefully acknowledge all the cat owners for participating in the study.

Accepted: 16 October 2024

Author note

The data presented in this study are available on reasonable request from the corresponding author.

Conflict of interest

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Ethical approval

The work described in this manuscript involved the use of non-experimental (owned or unowned) animals. Established internationally recognised high standards (‘best practice’) of veterinary clinical care for the individual patient were always followed and/or this work involved the use of cadavers. Ethical approval from a committee was therefore not specifically required for publication in JFMS. Although not required, where ethical approval was still obtained, it is stated in the manuscript.

Informed consent

Informed consent (verbal or written) was obtained from the owner or legal custodian of all animal(s) described in this work (experimental or non-experimental animals, including cadavers, tissues and samples) for all procedure(s) undertaken (prospective or retrospective studies). For any animals or people individually identifiable within this publication, informed consent (verbal or written) for their use in the publication was obtained from the people involved.

ORCID iD

Sait Sendag

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