The 200-pound English mastiff and the four-pound chihuahua share the same pregnancy cycles. Although some breeds and dogs have from one to three heat cycles in a year, pregnancy remains standard. Understanding the pregnancy cycle and timing helps to take care of the bitch during the pregnancy and prepare for whelping or birthing puppies, according to Marvista Animal Medical Center.
The first two stages of the estrous cycle prepare the bitch for mating. According to the University of Georgia, there are four stages: proestrus, estrus, diestrus and anestrus. In the first stage, when the vulva swells and has bloody discharge, your bitch may be attracted to but not allow a male to mate. This may last about nine to 14 days. During estrus, which lasts between five and 12 days, the bitch will allow mating. During this phase, the vulva is still swollen but the discharge becomes yellowish. The next phases involve pregnancy or preparing the uterus for the next heat.
Most breeds have heats every six to seven months, generally beginning at about five to six months old or over a year old in large and giant breeds. Some breeds such as the basenji generally have only one heat a year. Heat cycles vary, lasting as few as 12 days and up to 28 days.
After breeding, the sperm fertilizes the eggs. The eggs implant in the uterus, which has two horns that connect at the cervix. During diestrus, progesterone production helps the eggs grow. During this part of the pregnancy cycle, the fertilized egg cells continue to divide and grow as puppies develop.
According to Vetinfo, you should count from the last breeding date to estimate when puppies should arrive. Pregnancy may begin the first day or a few days after the last breeding, and lasts 58 to 68 days.
Ways to confirm pregnancy include hormone-testing, feeling for fetal sacs, ultrasound at around four to five weeks or X-rays after 45 days. According to Marvista, by the fifth week of pregnancy, the bitch begins to need about twice her normal amount of calories. Puppy food supplies necessary calories without increasing calcium and other supplements. Excess calcium problems include uterine inertia, which can result in a cesarean section, and seizures.
The final stage of pregnancy is labor. Generally, about 24 hours before whelping, your bitch’s rectal temperature will drop below 100 degrees Fahrenheit. The beginning of uterine contractions and full cervix dilation may last from six to 12 hours. During the second and third stage of labor, the contractions strengthen and birth begins. Puppies generally arrive 15 minutes to two hours apart. Contact your veterinarian if the bitch is exhibiting extreme pain, is in hard labor without producing a puppy for an hour, or takes more than four hours between birthing puppies.
Genetic and health testing of the potential parent dogs for hips, elbows, heart and thyroid problems prior to breeding helps increase chances for healthy puppies. During pregnancy, signs of problems include pregnancy lasting over 70 days, depression, green or dark discharge, discharge with a strong odor, temperature, bleeding, vomiting and diarrhea.