There temperature will usually drop a day or two after they begin producing colostrum though isn't set in stone. How many days in is she? I'd start taking her temperature now. Here is a basic run down and lots of links for you.
Average gestation is 59 to 63 days from the first tie (calculator in first link below) though can be a little earlier around 57 (earlier may be a bit of concern for puppy development) or up to 68 (time to be concerned and are more likely to need assistance or c-section at that length and even more a concern on smaller breeds. Some of the standard prenatal care consists of things like confirmation by ultrasound or blood test earlier around 3 or 4 weeks to confirm and try and be sure she doesn't have something like pyometra and possibly STD (absorption, miscarriage and other problems) if dogs weren't tested before breeding instead. It also helps with distinguishing a false pregnancy which has some of the complications of a real one and indicates the thyroid or hormones may be off and dogs who go through false pregnancy are usually recommended spayed for those reasons and their comfort.
Towards the end of pregnancy you will do an x-ray or ultrasound. This is where we try to evaluate for likelihood of difficulty and c-section based on the pups themselves and things like their size and rate of growth leading to the whelp and how many and if she is likely to run into difficulty from exhaustion and things if not known you are doing a C before even breeding based on breed. Knowing how many is exciting but it is an important detail to know during free whelp. If your girl is only carrying one or two pups she may be more likely to have problems and of course, likely to become exhausted and unable to continue if there are many, it also gives you an idea of when she's done or if there is a pup left to decay and cause infection and even helps evaluate distress when she has stopped or seems to tired to continue or there is too long a period in between pups and you know there are more during a free whelp and things like that so is imperative and invaluable (and standard) when whelping. About a week before the due period is often best for evaluation and being able to figure out if size ect. May be a big problem once they’ve grown even more. The second link is a quick run down of danger signs during whelp. Colostrum usually appears a week or so before or not until right at whelp when the pups arrive but most often appears a day or two before the temperature drop. Colostrum is where the pups get the bulk of their antibodies from and is less in volume than milk which comes in day 3 or 4 after whelp. It is a good idea to begin taking temperature ( a couple times or so a day and preferably at the same time each day) when the colostrum appears no matter how many days in if you weren’t before that.
During early labor the females temperature will usually drop to around 98 (it goes back up as thing’s proceed) and may only drop by a degree or two if your girl doesn't follow typical patterns. It is important to know when a temperature drop occurs since if there are no pups within 24 hours of the temperature drop (active labor) there is likely a problem and the vet should be called (or if c-section breed that it is time to head in). If your gut says it's time and your girl is in labor she probably is, even with only a minor temperature drop on some very rare occasions. If the pups are free whelped (non c-section) the dam is examined 24 hours after to be sure there are no complications (rupture, torsion, prolapse hemorrhage ect.) and retained placenta's or pups to cause deadly infection. She may need or benefit from an injection to help clean her out faster at that time (also to try and prevent infection). The veterinarian will usually go over the next steps and more common danger signs and problems (like mastitis and eclampsia) for the nursing stage at that time. Usually around 2 to 5 days the pups go in to the vet for a look over and to have dew claws removed and tails docked if that's done.
The earliest any pup can be placed is 8 weeks, having been started on their shots and dewormings and recent vet check. This is for health, socialization and behavioral purposes and many breeds and most breeders keep them beyond the 8 week minimum though breed can factor in how long. This is for health, socialization and behavioral purposes, they learn some things like the meaning of no (from Dam), pack placement and bite inhibition through interaction with the family unit. Bite inhibition doesn't begin until 7 to 8 weeks. 6 to 8 weeks with Dam and litter mates is critical for starting to learn normal behavior that makes for a good companion. Many breeds are recommended a minimum of 12 weeks.
http://www.askabreeder.com/Dog+Gestation+Calculator
http://drnelsonsveterinaryblog.com/2009/01/01/canine-labor--when-to-call-the-vet.aspx
http://www.terrificpets.com/forum/47517.asp
q6300945.html
q3929338.html
http://www.learntobreed.com/
http://www.dogbreedinfo.com/whelpingmain.htm
http://www.marvistavet.com/html/body_brucellosis_in_dogs.html
http://www.marvistavet.com/html/body_canine_herpes_infection.html
http://www.lowchensaustralia.com/breeding/eclampsia.htm
http://www.bullmastiffsonline.com/bitches.html
http://www.wildheirlabradorrescue.org/readingroom/what-is-a-back-yard-breeder.php
http://members.tripod.com/antique_fcr/goodbreeder.html
http://healthgene.com/canine/
http://www.irvinevetservices.com/education_spaying.php
http://www.dogfoodanalysis.com/dog_food_reviews/
http://www.bornfreeusa.org/facts.php?more=1&p=359
http://www.terrificpets.com/forum/57502.asp
Average gestation is 59 to 63 days from the first tie (calculator in first link below) though can be a little earlier around 57 (earlier may be a bit of concern for puppy development) or up to 68 (time to be concerned and are more likely to need assistance or c-section at that length and even more a concern on smaller breeds. Some of the standard prenatal care consists of things like confirmation by ultrasound or blood test earlier around 3 or 4 weeks to confirm and try and be sure she doesn't have something like pyometra and possibly STD (absorption, miscarriage and other problems) if dogs weren't tested before breeding instead. It also helps with distinguishing a false pregnancy which has some of the complications of a real one and indicates the thyroid or hormones may be off and dogs who go through false pregnancy are usually recommended spayed for those reasons and their comfort.
Towards the end of pregnancy you will do an x-ray or ultrasound. This is where we try to evaluate for likelihood of difficulty and c-section based on the pups themselves and things like their size and rate of growth leading to the whelp and how many and if she is likely to run into difficulty from exhaustion and things if not known you are doing a C before even breeding based on breed. Knowing how many is exciting but it is an important detail to know during free whelp. If your girl is only carrying one or two pups she may be more likely to have problems and of course, likely to become exhausted and unable to continue if there are many, it also gives you an idea of when she's done or if there is a pup left to decay and cause infection and even helps evaluate distress when she has stopped or seems to tired to continue or there is too long a period in between pups and you know there are more during a free whelp and things like that so is imperative and invaluable (and standard) when whelping. About a week before the due period is often best for evaluation and being able to figure out if size ect. May be a big problem once they’ve grown even more. The second link is a quick run down of danger signs during whelp. Colostrum usually appears a week or so before or not until right at whelp when the pups arrive but most often appears a day or two before the temperature drop. Colostrum is where the pups get the bulk of their antibodies from and is less in volume than milk which comes in day 3 or 4 after whelp. It is a good idea to begin taking temperature ( a couple times or so a day and preferably at the same time each day) when the colostrum appears no matter how many days in if you weren’t before that.
During early labor the females temperature will usually drop to around 98 (it goes back up as thing’s proceed) and may only drop by a degree or two if your girl doesn't follow typical patterns. It is important to know when a temperature drop occurs since if there are no pups within 24 hours of the temperature drop (active labor) there is likely a problem and the vet should be called (or if c-section breed that it is time to head in). If your gut says it's time and your girl is in labor she probably is, even with only a minor temperature drop on some very rare occasions. If the pups are free whelped (non c-section) the dam is examined 24 hours after to be sure there are no complications (rupture, torsion, prolapse hemorrhage ect.) and retained placenta's or pups to cause deadly infection. She may need or benefit from an injection to help clean her out faster at that time (also to try and prevent infection). The veterinarian will usually go over the next steps and more common danger signs and problems (like mastitis and eclampsia) for the nursing stage at that time. Usually around 2 to 5 days the pups go in to the vet for a look over and to have dew claws removed and tails docked if that's done.
The earliest any pup can be placed is 8 weeks, having been started on their shots and dewormings and recent vet check. This is for health, socialization and behavioral purposes and many breeds and most breeders keep them beyond the 8 week minimum though breed can factor in how long. This is for health, socialization and behavioral purposes, they learn some things like the meaning of no (from Dam), pack placement and bite inhibition through interaction with the family unit. Bite inhibition doesn't begin until 7 to 8 weeks. 6 to 8 weeks with Dam and litter mates is critical for starting to learn normal behavior that makes for a good companion. Many breeds are recommended a minimum of 12 weeks.
http://www.askabreeder.com/Dog+Gestation+Calculator
http://drnelsonsveterinaryblog.com/2009/01/01/canine-labor--when-to-call-the-vet.aspx
http://www.terrificpets.com/forum/47517.asp
q6300945.html
q3929338.html
http://www.learntobreed.com/
http://www.dogbreedinfo.com/whelpingmain.htm
http://www.marvistavet.com/html/body_brucellosis_in_dogs.html
http://www.marvistavet.com/html/body_canine_herpes_infection.html
http://www.lowchensaustralia.com/breeding/eclampsia.htm
http://www.bullmastiffsonline.com/bitches.html
http://www.wildheirlabradorrescue.org/readingroom/what-is-a-back-yard-breeder.php
http://members.tripod.com/antique_fcr/goodbreeder.html
http://healthgene.com/canine/
http://www.irvinevetservices.com/education_spaying.php
http://www.dogfoodanalysis.com/dog_food_reviews/
http://www.bornfreeusa.org/facts.php?more=1&p=359
http://www.terrificpets.com/forum/57502.asp