You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

For most bitches mating between 9 and 16 days after the first show of blood (the onset of pro-oestrus) will coincide with ovulation and result in pregnancy - but for some bitches this method will miss ovulation.

The "average" time for ovulation in the bitch is 12 days after the first show of blood - in which case mating should take place between days 14 and 16 because the oocytes released from the ovary require 2 days to mature before they can be fertilised. However, recent studies conducted at the University of London have shown that some bitches ovulate as early as 5 days after pro-oestrus starts, and some ovulate as late as 30 days after pro-oestrus starts.

So, for bitches which are not "average" other methods for detecting the best time for mating have to be used - otherwise attempts to get such a bitch pregnant are likely to fail.

To some extent observation of behaviour, and swelling of the vulva can be used. Bitches will only stand and allow a male to mount her, and will get obvious swelling of the vulva about 2 days before ovulation occurs. So mating should take place 4 days after these signs are noted.

In bitches that prove difficult to get pregnant your veterinarian can analyse blood samples for hormone changes that will indicate when ovulation will occur :

• Increase in oestrogen - onset of pro-oestrus - attractive to male dogs
• Fall in oestrogen, slight increase in progesterone - bitch allows mating
• Increase in luteinising hormone (LH) - ovulation occurs 24-72 hours after this peaks

Veterinarians can use progesterone concentrations as a good indicator of when LH is likely to increase. Progesterone concentrations of 2-4 ng/ml are reached about 2 days before ovulation (so mating should occur 4 days after these concentrations are reached),  and 5-10 ng/ml are reached during the fertile period (mating should occur within 24 hours of these concentrations being reached). Commercial kits are available for this hormone test.

Other tests that can be used include 

• Examination of cells removed from the vagina using a swab (smear test). This technique is not reliable at predicting ovulation and the best time for mating
• Direct examination of the vaginal wall using an endoscope - this is not used often but it is an accurate way to assess when the fertilisation period has started
• Ultrasound - can be used but the precise timing of ovulation is difficult to see
• Other tests including measuring the electrical resistance of vaginal secretions, and examination for crystallisation of mucus are not in common use at this time but may be useful in the future, .
• Measuring changes in glucose concentrations in the vaginal discharge has failed scientific scrutiny and appears to be a useless test

Updated October 2013