 [ Symptoms ] how common is a false positive pregnancy test my expected period was suppose to be sept 25 it never came so i took a test fives days later it came up positive could i really be pregnant [ Disease ] most doctors base their recommendation of weight gain on the weight of the mom before pregnancy women with a normal bmi body mass index should gain anywhere between 25 and 35 pounds and up to 45 for twins overweight women may be able to safely gain between 15 and 25 pounds but should not use pregnancy as a time to diet or lose weight check with your doctor to determine if it is safe for you to gain less or more than the recommended range