Failure To Conceive

If a bitch fails to conceive the two most common causes are:
- The bitch was mated at the wrong time of her season
- The male has a poor semen quality.
Both are easy to check. In the first case by means of a blood sample and a vaginal smear. In the second case by a semen sample.
Many breeders think that the cause may be an infection in the bitch but this is not likely.
There are, of course, preferences for particular partners among dogs but the most common reason for a bitch to reject the male, or why a male does not want to mate the bitch, is that the bitch is presented to the dog on the wrong day/days. Most often it is too early.

When should the bitch be mated?
Oestrus can vary from 4-20 days.
Many people believe that bitches should be mated between days 10-14 in the heat, but there are big differences. Some bitches allow mating when it seems too early and some when it is too late.
The bitch is ready for mating when she accepts the dog by turning her rear end towards him and moving her tail to the side.
A blood sample to check the bitch's progesterone levels can be helpful in determining the optimal day(s) for mating. (The progesterone level should be measured by a laboratory. The commercially available quick tests are not always reliable.)

Split Season
Another reason for a bitch not getting pregnant may be that she has a split season, or split oestrus, which is a fairly common problem particularly in young females.
Basically, what happens with these bitches is that instead of having a single season, they have 2 seasons which are 3-6 weeks apart. The 3-6 week gap between the season is the key to recognising this problem. The first season is unlikely to produce a pregnancy so the bitch must be mated on the second season.
This problem is often diagnosed when breeders bring their bitch to a vet for pre-mate testing - where the vet uses swabs from the vagina or blood test to determine when the bitch is ready to mate. What happens then is that the tests show that the bitch is never quite ready for mating, and if you try to mate her she will not stand, or if she does stand, she does not get pregnant. The season then seems to stop, but 3-6 weeks later the season starts again and this time the bitch will be ready to mate.
Sadly, most people only notice the first season and try to mate at this time. When this does not work, they are let to believe that their bitch is infertile and the second season goes unnoticed.
With bitches that go through split heats, she can be fertile when you are not prepared, and an unplanned litter could occur. Keep her secured and away from any intact males while she displays any signs of heat.

What you should watch out for:
You don't need to have any expensive tests to diagnose split seasons, good record keeping will suffice. If you have a bitch which has given some difficulties mating, keep a little diary of every day regarding her season (write down the colour of the discharge and if you tried to mate her). When she goes out of season, keep on checking her to see if she comes into season again a few weeks later - if she does, then she is likely to have had a split season - mate her again on the second season!!!
Having pre-mate swabs of the vagina and blood tests can help with this diagnosis, but, as mentioned earlier, if you keep a daily diary of the seasons of all your bitches, you may be able to detect this problem yourself and get puppies out of a bitch that you previously thought was infertile.

(Source of Split Season: Paolo Lencioni, BVSc MRCVS)