Canine Pregnancy in Thirteen Steps

Just for fun (a statement which cries out for the writer to get a real life, or at least some better hobbies), I thought I’d do a thorough break down on the steps involved in going from point ‘A’ (Bitch in Season) to point ‘B’ (litter of puppies).

It’s more complicated than you’d think.

First off, let’s tackle the issue of why we go through all of these steps. Theoretically, getting puppies isn’t hard – toss together a boy dog and girl dog at the right time, and 62 days later you’ve got puppies. We’re not dealing with backyard bred dogs here, however, so we do things the hard way, for the simple reasons that:

a) I want to make sure that the bitch gets pregnant, and in French Bulldogs that can be difficult, as their timing is a bit off from that of many other breeds

b) I’m usually either shipping semen in from across the country, or using frozen semen, so I need to make sure she is bred at exactly the right time in her cycle, which is a complex process

c) I’m going to want to ensure she is pregnant, once she’s been bred, so I can decide if it’s safe for me to have visitors to the house, or for me to continue going to dog shows or dog parks where we might be exposed to parvo or other illnesses harmful to pregnant bitches. Also, since we inevitably do a c section, it’s good for us and the vet to know she’s definately pregnant so I can give them a heads up on the impending c section dates. It also helpful to know if she’s carrying an extraordinarily large litter, so we can plan for extra helping hands during the section

Since I’ve established why we do the following steps, let’s now examine them in detail. Oh, and before I begin, let me point out that I am NOT a veterinarian, and don’t claim to be one, either, so there may indeed be some technical errors in this entry (although I’ve done my best to fact check it, and I have been breeding dogs using this method of testing for almost 18 years).

If I’ve made any errors, feel free to correct me via comments.

1. Determining where the bitch is in her cycle
For those who are new to this whole thing, I should establish a few facts about the canine heat cycle. Bitches come into season an average of once every six months, with wide variations in this schedule from dog to dog and breed to breed. Most French Bulldogs, for example, only come into season once every year, with a few cycling only once every 18 months. Bitches are only able to become pregnant during the final stages of their heat, not during other times of the year.

The first signs an owner has that her girl is in season is generally a blood droplet on the floor, combined with external puffiness that we fondly refer to as ‘baboon butt’. This isn’t foolproof, however. Some girls hardly bleed at all, other don’t swell, and some stay swollen all the time. I do a daily cotton pad check on all of my girls, to catch slight signs I might miss just looking for blood droplets. Having one girl in season also makes me more careful to check my other girls, as bitch heat cycles run through dog groups in clusters.

When I’m confident that my girl is in, I call my vet and arrange to come in and start testing in a few days. I make sure to note the first date I saw signs of her being in season, so I can tell my vet.

The normal reproductive cycle of the bitch is comprised of four stages: proestrus, estrus, diestrus, and anestrus. With the bitch we are breeding, we’re concerned with the first three of these stages –

Proestrus: (average duration = 9 days; range = 3-17 days) Swelling of the vulva, the external tissue of the vaginal opening, and bloody discharge marks the beginning of the proestrus stage, also known as the follicular stage. During proestrus, the ovarian follicles, each containing ova, increase in size. Increasing amounts of estrogen hormone, secreted by the ovarian follicles, cause the cells of the vaginal walls to take-on a distinctive shape, a process known as cornification. Both the level of estrogen and vaginal cornification are useful indicators of proestrus.

Estrus: (average duration = 9 days; range =3-21 days) Receptivity to mating marks the beginning of the estrus stage. Physiologically, estrus coincides with the predominant presence of cornified vaginal epithelial cells and an increase in serum progesterone levels to 2 ng/ml. Ovulation usually occurs 2 days following this increase in progesterone and hence, monitoring the levels of progesterone is an excellent indicator for timing breeding.

Diestrus: (average duration = 2 months) Approximately 6 days after ovulation, the cornified vaginal epithelial cells will revert to a non-cornified state. This condition marks the beginning of diestrus. This stage ends when progesterone levels fall to less than 1 ng/ml just prior to whelping in the pregnant bitch or approximately 2 months after ovulation in the nonpregnant bitch.

Progesterone testing, cell cytology to check for cornification, Draminski and LH testing all help us to determine which stage of the cycle a bitch is in.

2. Pinpointing her progesterone levels
Progesterone is a reproductive hormone that begins to increase in the bloodstream just prior to ovulation.Prior to coming in season (estrus), serum progesterone levels in the bitch are low, less than 2ng (ng=nanograms). As the cycle continues, progesterone levels slowly climb to a level of 5ng, upon which ovulation occurs. The ovulation date can be as early as day 7 and as late as day 27 of the estrous cycle, emphasizing the importance of the blood test. My vet usually likes to start with a base line progesterone level. This gives her a general idea of where the bitch is in her season. Unless she finds an unusually high reading for the beginning of the cycle, we usually then wait a few more days into her cycle before doing further progesterone readings, since they are sent out for lab analysis, rather than being done in house, which makes them rather pricey (about $50 a piece, and we’re going to do at least ten or so of them, plus all the other testing. It adds up fast.)

3. examining cell cytology

As the bitch progresses in her reproductive cycle, the cells lining her uterine wall undergo changes. Taking a swab of these cells, which is then examined under a microscope, is another tool that allows my vet to determine where in her cycle my bitch is.

This also helps us to determine when it’s necessary to begin taking blood samples for daily progesterone and LH testing. As I mentioned above, we don’t begin doing these initially, as it’s a waste of both time and money.

4. Draminski readings

Well, I don’t know much about how this one works, other than it takes reading in the viscosity levels of the vaginal mucosa, so this is from a Draminski dealer website –

As in most mammals, the vaginal mucus of the female dog remains quite viscous throughout most of her cycle in order to prevent germs etc from entering the uterus. As the eggs are released and start to ripen, the vaginal mucus thins in preparation to allow the sperm to enter the uterus. The Draminski Ovulation Detector records the viscosity of this mucus and a sharp drop in the readings indicates the start of the thinning of the mucus, about 1 day after ovulation.

5. Lutenizing Hormone (LH) levels
As all of these signs I’ve mentioned – cytology, progesterone and Draminski – start to show us we are progressing into the bitch’s cycle, we will start to do daily or initially semi daily LH level tests. LH is short for lutenizing hormone. It is the most important of all the clinical changes we are testing for, as this is the hormonal event by which we time all other occurrences (planning breedings and estimate the delivery date). The LH surge tells us that ovulation is about to occur, and the increase in progesterone levels tells us that the LH surge is due to occur. Can you see why testing for both is essential?

The LH level plods along at a relatively even level, with very few changes. The surge, when it comes, can be sudden, and one missed test (bad weather, a day your vet is away, etc) can be enough to miss it, which is what makes all of the above additional testing methods we’ve used essential to let us know when we are beginning to expect to see the surge occur.

Once it has, we know we can expect the bitch to ovulate within 48 hours.

Graph courtesy Dr. Fosters and Smith. Click image for link to original article.

6. The intersecting curve of LH and Progesterone
All of the above signs will culminate in one event – the intersecting curve of Progesterone levels rising, and LH surging. After the LH surge has occurred, our progesterone levels will begin to rise from baseline. These two key events lead us to the next step – planning the insemination.

7. Counting up four days to insemination
We know the date of the bitch’s ovulation based on her LH surge and steadily increasing progesterone levels. Now, we count up four days from surge to determine the optimum date for insemination. This is when the bitch’s egg will be ready for fertilization.

For artificial insemination of shipped or frozen semen, we do one insemination on day four. If we were doing a live breeding with an on hand stud dog, I’d likely do one insemination late on day three (the semen need seven hours after ejaculation before they are capable of fertilizing an egg. This period is referred to as the “capacitation time.”), and another breeding the next evening.

In theory, just one breeding should suffice, but if the dog was at hand and capable, I’d likely want to hedge my bets in this manner.

8. The insemination
Since most male French Bulldogs are rather inept romeos when it comes to mating, we generally do an artificial insemination, even when the dog and bitch are both in the same place. In most cases, however, the dog is far away (sometimes a continent away), so semen is collected by the stud dog owner or their vet, and shipped to mine. She calls me when it arrives, and I rush my dog in for insemination, which usually involves some silly comments about how I’d explain the speeding tickets, and an arm numbing 20 minutes holding my bitch’s rear end up in the air.

For frozen semen, the insemination is done surgically, via a small incision into the uterus. There, the semen is directly implanted. This is done because the frozen semen-sicles aren’t great swimmers, and die off quite quickly after they’ve been thawed out.

9. Morning sickness (but usually no pickle cravings)

The deed is done, and the bitch is bred. Now comes waiting and watching. Some bitches develop morning sickness about two weeks after insemination (Tessa did, regular as clockwork, and so did her daughter Sailor). Others show no signs at all. Some changes in appetite can also become apparent. For good measure, I start all of girls on an additional pregnancy multivitamin as soon as they’ve been inseminated, just in case.

10. The ultrasound
The earliest form of pregnancy detection is by ultrasound. Similar to that done on a human, the ultrasound can be done approximately 21 days into the (hoped for ) pregnancy. The downside of this is that two factors come into play – the skill of the person reading the ultrasound, and the bitch’s propensity to re-absorb her puppies. Dr. Khuly at Dolittler has a great entry on ultrasounds, and the need for skill. As for disappearing puppies, bitches can and indeed sometimes do re absorb litters after 21 days, so a sign of puppies doesn’t necessarily mean they’ll still be there on day 62.

Here’s an a video of a canine pregnancy ultrasound done late in the second term. You can see fetal heartbeats.

11. The x ray

At about day 51, or ten days before whelping, the skeletal systems of the puppies are developed enough to become visible via x ray. Not only does this allow us to confirm pregnancy without a doubt (and yes, I have had fat, piggy girls who were were still guessing about at day 50), it also allows us to count puppies, and see where they are placed in the uterus.

As I mentioned in the intro, this gives my vet an idea of what we are dealing with in terms of both litter size and potential issues with whelping.

I should note here that there is theoretically a third method of detecting pregnancy, and that’s palpation, but I’ve never had any luck with early palpation, and in the later stages of pregnancy an x ray just allows us to accomplish two goals with one procedure, so that’s usually what we do.

12. Reverse progesterone testing
The progesterone level of the bitch, which began to rise just before the LH surge, continues on its upward path until just before the bitch is due to whelp. Doing progesterone tests in the last days of the bitch’s pregnancy can be a useful tool to pinpoint her expected time of labour (useful in a c section breed, as taking pups too early can be life threatening).

From the Pet Education Veterinary Website –

After ovulation, progesterone concentrations continue to increase for 2-3 weeks, finally reaching 10-80 ng/ml. This level is necessary to maintain a pregnancy. In the dog, the progesterone level will remain at this level for about 60 days whether or not the dog is bred, and whether or not she is pregnant.

About 48 hours before whelping, the progesterone level drops to the 2 ng/ml range and within about 24 hours of whelping, the level drops to the 1 ng/ml range. This can help determine the proper timing of a c-section

The downside of this method is that it is expensive, and requires taking your dog to the vet for daily blood draws at a time when she needs as little stress as possible. For this reason, most breeders still rely on the time honored methods listed below to determine when the bitch is about to go into labour (and is, by extension, ready for her section).

13. Waiting, watching and temperature taking
There are a few signs that tell us when we should begin to expect labour in the bitch.

The first is one most people are familiar with – nesting. The bitch will sometimes become more interested in her whelping box, digging her blankets, fussing with the arrangement of the box, and, on occasion, deciding instead that your closet is far preferable to the pricey dura whelp box you paid over $200 for. Unfortunately, not all girls give us these signs.

We can generally rely on the temperature drop to be a much better indicator of impending labour.

On day 58 after the first breeding, you’ll want to start taking your bitch’s temperature three times a day. A bitch’s temperature will drop from around 101.4 to 99 degrees Fahrenheit or below a few hours before she is ready to whelp. A fluctuation in temperature is very normal, what you are looking for is a dramatic drop to below 99F. The temperature drop is the best indicator of imminent whelping. Once we’ve seen that drop, it’s into the car and off to the vet we go – which is another entry altogether.