Your first pregnancy will probably leaving you feeling excited and a bit nervous. There is so much to look forward to and learn about. One of the things you might be wondering is how much weight you should gain. This will vary depending on your starting weight. Obese women should gain less than underweight women. In general, doctors recommend gaining between 25 and 40 lbs, according to WebMD.

Size

Your doctor is the best person to tell you how much weight you should gain during your first pregnancy. You will be weighed at each appointment. Women of average weight usually gain between 25 and 35 lbs during the course of a healthy pregnancy. Overweight women should have a target weight gain of between 15 and 25 lbs. Women who are very obese should aim for between 10 and 20 lbs, according to MayoClinic.com. Underweight women might need to gain as much as 40 lbs, with a minimum weight gain of around 28 lbs.

Time Frame

Most women gain about 4 lbs during the first trimester, according to AskDrSears.com. This is mostly due to fluid retention, but some women who experience severe nausea actually lose weight. During the second trimester, it is common to gain about a pound per week as the baby grows rapidly in size. The seventh and eighth months of pregnancy are also often a time of rapid weight gain as the baby puts on fat. Many women do not put on much, if any, weight during the last month of pregnancy, as space is tight and the focus is more on the maturation of the baby’s organs, especially the lungs.

Function

Obviously, much of that weight gain goes to the baby’s body (an average of 7.5 lbs), but much of it also goes to help your body nurture the baby. Your blood flow increases dramatically when you are pregnant. In fact, about 3 lbs of your increased weight is blood, according to the March of Dimes. Two lbs goes to your breasts, 2 lbs is the increased size of your uterus and the placenta takes up about 1.5 lbs. The amniotic fluid weights around 2 lbs, and the water you retain (usually in your feet and ankles) can add up to as much as 4 lbs. Finally, your body retains fat and protein to the tune of about 7 lbs. Much of this is stored to make breast milk.

Considerations

Most women gain less during a first pregnancy than subsequent ones. This is due in part to the fact that women are younger during their first pregnancies. Increased weight gain during a second pregnancy is also attributed to the fact that your uterus is already “stretched out,” which is also why you show earlier, according to Parents.

Warning

Excess weight gain during pregnancy can lead to dangerous conditions such as high blood pressure and gestational diabetes, both of which can cause the baby to grow larger than is healthy. This may necessitate a Cesarean section. In addition, too much weight gain can cause other problems such as backaches, leg pain, varicose veins and increased fatigue.