Determining the due date in the bitch: can we do this?

Yesterday I was lecturing to vet students at the Ontario Veterinary College in Guelph.
The topic? Clinical cases in canine/feline obstetrics: should I be afraid if a breeder calls in the middle of the night for this? What was the purpose of this talk? Show the students that they SHOULD NOT be afraid to face these situations because we now have in veterinary medicine the tools to answer all these questions.

Interesting discussion then, and during the talk one of the student asked me a very good question. “OK, I don’t know much about obstetrics in canines yet, but can’t we determine the due date in the bitch to make things easier for everybody?” I told her that was an excellent question… because today we can!

Pregnancy length in the bitch is 63±1 days from the day of ovulation. This is important because most of the time when I speak with our breeder partners, they will determine the pregnancy length from the day of 1st breeding… while in this case, pregnancy length can go from 58 to 72 days. Large range here: more difficult to accurately predict the due date. As you see, this is another reason why performing a timing of ovulation can be so valuable. Not only will it optimize the fertility of your animals, but moreover if you know when the bitch ovulated, you can almost tell when parturition will take place!

And we can be even more accurate than that depending on the size of the bitch. You can see here a graph I borrowed from my former sidekick Dr Fernando Mir at the Alfort Vet School. Small dogs will usually deliver earlier (around 62 days post-ovulation) while larger dogs will tend to deliver around 64 days post-ovulation.

Influence of the size on the pregnancy length (from Mir et al 2011)

And what happens if you did not do a timing of ovulation? Well, we still have ways to estimate the due date (it will however then only be an estimate we will definitely lose in accuracy):

-          We can do what we call biometric measures under ultrasounds (typically we will measure the size of the skulls – what we call the biparietal diameter): these measures are entered in an equation that will give us an approximative due date (different equations are available depending on the size of the animal, if your vet is interested in this they can reach out to me).

-          More expensive but an interesting tool when we are dealing with an at-risk bitch, we can assay progesterone. 24h before parturition progesterone levels will drop below 2ng/mL: when we have this result, we know that parturition is about to start and if needed, we know that we can safely perform a C-section because it means that the bitch is soon due.

I often recommend clients to monitor the body temperature of their animals a week before the expected parturition date. The progesterone drop I just described is usually associated to a drop of 0.3-1ºCin the body temperature of this animal. This is something that will be observed in 98% of the parturient bitches and can be a very simple tool you guys can use at home. If you have any doubt however, good news, we can give you a more accurate answer at the vet clinic. That’s what I was telling these young vet students yesterday: there is nothing here to be afraid!

Remember we are all part of the same PRO community! Don’t hesitate then: share with us your experiences, ask your questions and let us know what you think! Social networks enable us to keep the discussion going, so whether you are a Facebooker or a Twitter-addict, you can – and should!- be part of it!

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Comment by Emmanuel PRO Technical Service on October 9, 2013 at 7:55am

Thanks for your feedback. I think timing of ovulation using progesterone assays is an exceptional tool that has many advantages, the point I wanted to make here is that thanks to that we can clearly define the due date in bitches. That's something I would always advise when it is possible to do so, I totally get that we cannot perform this all the time (even if I would like it to be so!!!). In cases where we know the bitch is at risk (because of breed-specific related issues like in brachycephalic breeds), history of uterine inertia, very large litters (>12) or small litters (what we call the single puppy syndrom), it's good to know we have ways to determine the due date! Even if there was no timing of ovulation performed, when can still estimate the due date: one of my colleague in Spain uses a lot the fetal biometry technique for instance, and he is very satisfied with it. 

Comment by Catherine Betts on October 8, 2013 at 2:21pm

It is very fun to try to guess due dates for my bitches.  I don't do progesterone testing but will monitor the length of the ties.  For my first time moms, I generally do at least three natural breedings with a day in between each one spread over the days I feel are likely the best for the bitch based on her behavior and discharge.  I then look at the length of the ties over the three breedings and count 59 days from the longest tie...+1 - that is the estimated due date.  With repeat moms, I count back 63 days from the date they delivered their first litter, figure out  where that was in their cycle (ie, day 8, day 11, day 15 etc) and then set up my breedings accordingly next time around.  So, if 63 days from delivery was day 11 in their cycle, I set up breeding for day 13 and day 15 of the heat.  I expect day 15 to be the longest tie...count forward 59 days and that day +1 is the estimated delivery date.  Not very scientific I know but I have been able to pick due dates for most of my litters that have been accurate within that two day window.  The exception has been some of my first time moms where behavior has been flirty for the whole heat or there is little or no discharge to go by.  For the most part, this has worked for me.  With the change to the Royal Canin HT42D food, and this type of planning, we average larger than normal litter size for our breed - Miniature Schnauzers.  Very fun!


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