◈ Dog fertility clinic · Herne Bay, KentGood timingchanges everything.

As oestrogen climbs through pro-oestrus, the cells lining the vaginal wall change shape. They start round and plump and end up flat with sharp, angular edges — cornified. Under the microscope that shift is unmistakable.

• Repeated every 2–4 days, cytology tracks that climb. Once she's around 70% cornified and holding, we're into the window — and reading the slides in sequence is what makes it accurate.
• It confirms she's genuinely in season, and not showing something else that mimics it.
• At the other end it shows the dioestrous shift — the moment the window shuts. Breeding after that shift very rarely works, and knowing is far kinder than hoping.
• It's quick, it's kind, and it's far less invasive than sticking a needle in her every other day.

I don't push blood testing. Read the slides properly and cytology gets you there — my success rates say so.

A proper analysis covers volume, colour, concentration, total sperm count, progressive motility (how many are swimming forwards, not just wiggling) and morphology (what proportion are normally formed).

• As a rough yardstick, expect near 10 million sperm per pound of bodyweight — so a 30kg dog in the region of 650 million. Breeds vary enormously.
• For chilled shipping, the sperm-rich middle fraction is what we keep; the watery prostatic fraction is discarded because it shortens the sample's life.
• An extender is added, the sample cooled slowly — never dropped straight into a cold fridge — and packed with a gel pack for overnight courier.
• A good chilled candidate starts at 75%+ progressive motility and loses only around 10–15% over the first 24 hours.
• The analysis sheet travels with the sample so the receiving end can compare on arrival.

If a stud has never been analysed, do it before you time a bitch around him. It's the most common cause of a "mystery" missed litter.

Bitches are unusual: they ovulate immature eggs that need a further 48–72 hours inside the oviduct before they can be fertilised. So ovulation day is not breeding day.

• What matters is the trend across her slides, not any single reading in isolation. That's why I want to see her more than once.
• The semen type dictates how tight the window needs to be — fresh is forgiving, chilled less so, frozen least of all.
• Behaviour is a poor guide on its own. Plenty of girls flag days early or days late.

Please note: in the UK, artificial insemination in dogs is classed as an act of veterinary surgery, and surgical insemination has been banned since 2019. I work alongside your vet on timing, monitoring and preparation so everything happens on the right day.

• From day 21 small dark sacs become visible. Scanned earlier you risk a false negative and a miserable drive home.
• Days 24–26 is usually when we find heartbeats — the first real confirmation that the pregnancy is viable rather than just present.
• Days 28–30 is the most reliable single window, allowing for the fact nobody's ovulation date is ever perfectly known.
• A scan also picks up problems that have nothing to do with pregnancy — uterine infection such as pyometra being the important one. Early scanning has saved girls' lives.
• A second scan around 40–50 days checks growth, fluid and heart rates.
• And yes, I'll give you a number. Counting pups on a scan is a skill rather than a guess, and after dozens of litters mine come in right, or near as makes no difference. Breeders travel to me for it.

• Counting from ovulation, not mating. Gestation is far more predictable from the ovulation date — which is exactly why the timing work at the start pays off at the end.
• Kit list, whelping box setup and a run-through of the stages of labour, well before she's due.
• Temperature monitoring in the final week, and what the drop actually means.
• On the night: attendance or phone support, cord care, drying, first latch, and weighing every pup so we spot a fader early.
• Clear red lines for when to stop and ring your vet — hard straining with nothing produced, an over-long gap between pups, or a dam genuinely in trouble. I'd always rather you rang them too early than too late.

Bully breeds especially — have your vet's out-of-hours number on the fridge before you need it.

In England, Scotland and Wales every puppy must be microchipped and registered on a compliant database by eight weeks old, and it's illegal to hand a puppy over to a new keeper unchipped.

• The breeder must be recorded as the first keeper. The new owner then updates the record when the puppy goes home.
• Failing to comply can mean a notice giving 21 days to put it right, and a fine of up to £500.
• The chip doesn't replace a collar and tag — still a separate legal requirement in public.
• Keep your own details current on the database, and hand the registration paperwork over on collection day.

I hold the Defra-approved microchipping certification, so litters can be done here or at yours.