The pelvis is the fixed part of birth; everything else has to fit through it. Three checks answer the question before mating rather than at 2 a.m. during labour: body condition on a 9-point scale, weight inside a 3 to 5 kg window, and one lateral radiograph at day 55 to 58 of gestation to compare the birth canal against the widest kitten skull. Together they sort queens into 3 groups: breed normally, breed with a planned caesarean booked, or do not breed.
Check 1: body condition, scored 4 to 5 out of 9
Fat narrows the canal from the outside in. A queen at 8 or 9 out of 9 has 1 to 2 cm of fat over the pelvic rim and around the perineum, and obese queens have longer labours and more retained placentas. A queen at 2 or 3 out of 9 has no reserves for 4 to 6 weeks of lactation and often cycles poorly. Aim for 4 to 5 out of 9 at mating: ribs felt under a thin fat layer, a waist visible from above, and a small abdominal fat pad. Score monthly, and score by hand rather than by eye, because a long-haired queen at 7 out of 9 looks identical to one at 4.
Check 2: weight inside 3 to 5 kg
Both ends of the range fail, for opposite reasons. Below 3 kg the pelvis is still growing, the canal is 10 to 20 percent narrower than it will be at maturity, and kittens are born at 90 to 120 g each, so a 5-kitten litter is 450 to 600 g of kitten against a 3 kg mother. Above 5 kg the risk shifts to obesity, gestational diabetes and a litter so large that the uterus cannot contract efficiently. Weigh at mating, then weekly: a gain of 15 to 20 percent by week 6 of gestation is normal, and 25 percent or more flags a litter of 6 or more kittens or excess fat.
Check 3: one radiograph, day 55 to 58
Fetal skeletons mineralise from about day 42, so a single lateral film taken between day 55 and day 58 shows every skull clearly without the crowding seen at term. One film is enough for 2 measurements: the number of skulls, and the widest skull diameter in centimetres against the pelvic inlet, which measures roughly 2.5 to 3.2 cm in a mature 3.5 to 4.5 kg queen. A skull within 10 percent of the canal width is a warning; a skull at or above canal width is a caesarean. Ask the vet to write both numbers on the report, because a photo on your phone loses the scale marker.
Do not skip the film because a previous litter went well. Canal width does not change between litters, but kitten size does: the same queen can pass 3 kittens of 100 g and fail on 5 kittens of 115 g, and a 15 percent increase in fetal weight is enough to change the decision.
The 2 referral categories
Sort every finding into one of 2 boxes. Category 1 is structural: a canal narrower than the fetal head, a previous pelvic fracture or malunion, a congenital narrowing, or a vaginal septum. Category 2 is maternal: obesity at 8 or 9 out of 9, a queen under 12 months old, a litter of 6 or more, or a history of 1 previous caesarean. Category 1 goes to a referral hospital before mating. Category 2 stays with you but books a caesarean date at day 58, so the clinic has 5 days of notice.
| Item | What you measure | Normal | Refer or plan surgery |
|---|---|---|---|
| Body condition | 9-point scale, hands on ribs and spine | 4 to 5 out of 9 | 8 or 9 out of 9 |
| Weight at mating | Same scale, same hour, grams | 3.0 to 5.0 kg | Under 3.0 kg or over 5.0 kg |
| Pelvic inlet | Lateral film at day 55 to 58 | 2.5 to 3.2 cm | Under 2.4 cm, or skull within 10 percent |
| Previous litters | Written history, 1 line per litter | 0 to 1 caesarean | 2 caesareans, or 1 stillbirth in canal |
| Age at first mating | Date of birth on the pedigree | 12 to 18 months | Under 12 months |
What the numbers change on the day
A queen cleared at 4 out of 9, 3.8 kg, with a 2.9 cm canal and 3 skulls of normal size, is a wait-and-watch labour with a phone number on the fridge. A queen with 5 skulls and a 2.6 cm canal should be at the clinic by day 60, with surgery planned for day 63 to 64 rather than after 4 hours of unproductive contractions. The cut-offs that mean call now, not later: 30 minutes of strong contractions with no kitten, 2 to 4 hours between kittens once labour starts, or a kitten visible in the vulva for 15 to 20 minutes without progress.
The 10 days before term
From day 53, take the queen's temperature every morning: a drop from 38.5 C to 37.5 C or below often precedes labour by 12 to 24 hours. Keep the car fueled and the clinic number saved, weigh the queen every 2 days, and have 2 clean towels and a box large enough for her to lie flat. Book the caesarean date in writing if any category 2 flag is present, and confirm the clinic handles feline surgery after 22:00, because a third of dystocias arrive at night.
- Score body condition by hand at mating, and again at day 30 and day 50 of gestation.
- Weigh weekly from mating; record grams, not impressions.
- Book 1 lateral radiograph for day 55 to 58 and ask for 2 numbers on paper.
- Write the 2 referral categories into the queen's file, with the date each was checked.
- Track the whole gestation against the weight curve in queen weight gain tracking, and check vaccine status in vaccination timing for breeding queens before mating, not after.
Budget the film, the consultation and a possible caesarean before the litter is conceived; the breeding cost calculator keeps the 3 line items visible. A pelvis assessment costs less than one emergency call, and it is the only part of labour you can still plan.
Frequently asked
Can I assess a queen's pelvis without an X-ray?
Partly. Body condition and weight catch the maternal risks, and palpation gives a rough idea, but only imaging measures the inlet against the fetal skull. One lateral film at day 55 to 58 gives both the kitten count and the comparison you need, and it should be read before labour starts.
Is 3 kg too small for a breeding queen?
For most breeds, yes. Below 3 kg the pelvis is still growing and the canal runs 10 to 20 percent narrower than at maturity, while a 5-kitten litter weighs 450 to 600 g. Wait until 12 to 18 months and 3.0 kg or more before the first mating.
What makes a queen a caesarean case?
A fetal skull at or above the pelvic inlet width, an inlet under 2.4 cm, a previous pelvic fracture or malunion, 2 earlier caesareans, or a litter of 6 or more in a small queen. Book the date at day 58 and confirm the clinic can operate at night.