Pregnancy by Trimester

Pregnancy is generally divided into three trimesters, each accounting for approximately 12 weeks, though the third trimester may last up to 16 weeks. Most women aren't even aware they're pregnant (or at least, aren't sure) until almost halfway through the first trimester. Still, pregnancy trimesters can be a handy guide for following the growth and development of your fetus and the changes within your own body. Here is a quick overview of pregnancy by trimester.

First Trimester

It may seem weird, but the first week of pregnancy is actually the week of your final menstrual period before conception. Because most women can't recall the actual date of conception but can remember the start of their last period, this method of dating pregnancy allows for a more accurate prediction of due date.

Conception, then, actually occurs somewhere around week 3, and most women suspect pregnancy somewhere around week 5 or 6. As soon as you suspect you're pregnant, confirm with a pregnancy test and then see your doctor or medical practitioner. The first trimester of pregnancy, and specifically weeks 6 through 10, is a crucial period of development in which most of the major systems of the body begin to form. Thus, it is especially important to maintain good health and avoid environmental factors (such as medications, smoke, alcohol, etc.) that could interfere with proper development.

Second Trimester

This stage begins at week 13, and by now most women are starting to show. The general rule of thumb is that once you've successfully cleared the first trimester, you can begin announcing your pregnancy because the risk of miscarriage decreases substantially. For most women, the morning sickness and fatigue of early pregnancy are also passing.

Between weeks 15 and 18, testing for many birth defects can be done. By week 19, conditions such as hydrocephalus and spina bifida can be seen by ultrasound. The 24- or 26-week ultrasound should reveal the sex, though the technician may not be able to get a clear read.

During this trimester, you may experience clumsiness, forgetfulness and the occasional discomfort (swollen feet, hot flashes, back pain) as your body changes and your belly grows. If, however, you experience severe pain, swelling or bleeding, contact your medical professional immediately.

Third Trimester

Around 28 weeks, the home stretch begins. Many women feel Braxton-Hicks contractions during this time, which is just the uterus's labor preparation. While your body prepares itself, it's a good idea to prepare your mind, too, especially if this is your first baby. Your healthcare provider can answer your questions and suggest resources such as books and classes.

Throughout the third trimester, you will be slowing down as your belly gets larger, your ligaments loosen and you gain weight. After week 30 or 32, it is not uncommon to gain a pound a week until birth. The vast majority of women give birth between week 38 and week 40.

By Trimester

By Month