If your girl is pregnant, I like to put them onto a high quality puppy food during the pregnancy and while she is nursing the pups. I tend to increase her calories by doing the following:
up to 4th week of pregnancy: normal calories
5 -7 weeks: normal + 25%
8- birth: normal + 50%
birth - 3rd week of lactation: normal + 100%
4th week lactation and on: gradually taper the number of calories back to normal.
I do not recommend vitamins or supplements during pregnancy, it tends to cause more problems than it is worth.
The methods of determining pregnancy include:
Serum relaxin measurement: after 24 days (this test is not offered by every lab, you will need to check with your vet)
Ultrasound: after 21 days
Palpation (by feel): after 25 days, this is not always accurate. It can be harder to determine in large or obese dogs.
X-rays: after 42 days
I do think that it is a good idea to have an ultrasound done on her as it will confirm weather she is pregnant and will help you recognize it she running into any problems while giving birth.
You may find this link helpful in learning how to provide for a pregnant dog: http://www.VeterinaryPartner.com/Content.plx?P=A&A=1459
Finally, here is a bit of information about whelping (birthing) and caring for new born puppies:
THE PET HEALTH LIBRARY
By Wendy C. Brooks, DVM, DipABVP
Educational Director, VeterinaryPartner.com
Preparing for your dog's labor and puppy care can be both exciting and fun; still, awareness of potential problems is of paramount importance. It is a good idea to keep track of your dog's breeding date so as to know when to expect what.
After about 35 days of pregnancy, the mother's caloric requirements will begin to increase. In general, she should require about twice as much food as usual whereas, when she begins nursing, she will need three times as much food. Do not supplement calcium as this can cause metabolic imbalances; also, excess vitamins may be harmful to the puppies. The best nutritional plan is to buy a dog food approved for growth and feed according to the package; such diets are balanced and require no supplementation. Exercise of the pregnant bitch need not be restricted until after the first 4 to 6 weeks of pregnancy.
Some time around the 45th day, your dog should be examined by a veterinarian. At this time, the skeletons of the unborn pups will have mineralized and are thus visible on a radiograph. Your dog's abdomen should be x-rayed so that you know how many pups to expect. Ultrasound may be used to confirm pregnancy much earlier (after 25 days, the embryonic heart may be seen beating) but it is more difficult to count the number of pups using this method.
A comfortable area should be set aside for whelping and raising the puppies. The bitch should feel at home here and should be able to come and go as she likes while the puppies must remain confined.
The gestation period of the dog is considered to be 63 days though this is not written in stone and a normal range might be 58 to 68 days.
When your dog's due date is approaching, you should begin monitoring her rectal temperature. When her temperature drops below 100F (normal canine temperature is 101F-102F), labor may be expected within 24 hours.
The First Stage of Labor
During this stage, uterine contractions begin. The bitch will appear very restless and may pace, dig, shiver, pant, or even vomit. This is all normal and all an owner can do is see that the bitch has water available should she want it.
The Second and Third Stages of Labor
The second stage is the hard labor stage in which the puppy is expelled. The third stage refers to the expulsion of the placenta and afterbirth. Each pup may not be followed by afterbirth; the mother may pass two pups and then two placentas. This is normal.
Puppies are born covered in membranes that must be cleaned away or the pup will suffocate. The mother will bite and lick the membranes away. Allow her a minute or two after birth to do this; if she does not do it, then you must clean the pup for her. Simply remove the slippery covering and rub the puppy with a clean towel. The umbilical cord may be tied in a knot about one inch from the pup and cut with scissors on the far side of the knot.
Expect one pup every 45 to 60 minutes with 10 to 30 minutes of hard straining. It is normal for bitches to take a rest partway through delivery, and she may not strain at all for up to 4 hours between pups. If she is seen straining hard for over an hour, or if she takes longer than a 4-hour break, consult a veterinarian.
Expect some puppies (probably half of them) to be born tail first. This is not abnormal for dogs.
Call Your Veterinarian If:
30 to 60 minutes of strong contractions occur with no puppy being produced.
Greater than four hours pass between pups and you know there are more inside.
She fails to go into labor within 24 hours of her temperature drop.
She is in obvious extreme pain.
Greater than 70 days of gestation have passed.
It is normal for the bitch to spike a fever in the 24 to 48 hours following birth. This fever should not be accompanied by clinical signs of illness.
Normal vaginal discharge after parturition should be odorless and may be green, dark red-brown or bloody and may persist in small amounts for up to 8 weeks.
Problems to Watch For
Metritis (Inflammation of the Uterus)
Signs of this condition are as follows:
foul-smelling vaginal discharge
loss of appetite
no interest in the puppies
decreased milk production
If these signs are noted, usually in the first day or two postpartum, a veterinarian should be consulted. Your dog may have retained a placenta or have suffered some trauma during delivery. Animals who have required assistance with delivery are often predisposed to metritis.
This condition results when the bitch has trouble supporting the calcium demand of lactation. Calcium supplementation predisposes a bitch to this condition. Usually affected animals are small dogs. They demonstrate:
nervousness and restlessness
no interest in or even aggression towards the pups
stiff, painful gait
This progresses to:
inability to stand
This condition generally occurs in the first 3 weeks of lactation and a veterinarian should be consulted immediately.
Mastitis (Inflammation of the Breasts)
Normal nursing glands are soft and enlarged. Diseased glands are red, hard, and painful. In general, the bitch does not act sick; the disease is confined to the mammary tissue. The bitch may be sore and discourage the pups from nursing; however, it is important to keep the pups nursing the affected glands. This is not harmful to the puppies and helps flush out the infected material. Hot packing may be helpful.
Problems with the Puppies
Newborn puppies should spend their time feeding and sleeping; they are not very playful or active for the first week. Puppies that nurse poorly, cry constantly, or do not sleep with the rest of the litter are in trouble and should be examined by the veterinarian. Ideally the puppies should be weighed shortly after birth and should be expected to gain 5% to 10% of their birth weight daily. (A small weight loss in the first day of life is normal but this should be less than 10% of their initial weight.) Puppies that do not gain weight properly are in trouble and should be checked by the veterinarian. It is helpful if puppies are weighed at least daily to be sure they are growing properly. Very young puppies have clear or slightly yellow-tinged urine. Obviously yellow urine is a sign of dehydration.
If you think there is a problem with the mother or any of the puppies, contact your veterinarian. Examination may be needed for the mother and entire litter, not just the individual who appears sick.
Most dogs are excellent mothers and problems are few. The basic rule is to seek veterinary care if she seems to feel sick or if she ceases to care for her young. Puppies nurse until they are about 6 weeks old and then may be adopted by new homes.
Please let me know if you have any further questions.