How Long is The First Trimester of Pregnancy?

Understanding the First Stage of Your Pregnancy Journey

When you receive a positive result on a pregnancy test, you probably go through a range of thoughts and emotions all at once: joy, fear, uncertainty, excitement and wonder. And you may begin to ask, “What now?” Before you get too far ahead of yourself—planning the nursery, dreaming about gender and the baby shower—you’ve got the first trimester in front of you. The first 12 weeks of pregnancy is officially considered the first stage of pregnancy, although the manner in which trimesters are measured can get confusing.

How Trimesters Are Measured

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A standard full-term pregnancy is measured at 40 weeks, although it’s usually not exact. Not only are babies notorious for not arriving on their due dates, but the trimester system can be a bit confusing. You’re technically not “pregnant” until you’re about two weeks in.

The beginning of pregnancy is measured from the first day of your last menstrual period. Ovulation typically takes place about two weeks after that, which is when fertilization of the egg takes place, followed by the implantation of the embryo.

Most women find out they are pregnant four weeks or more after their last period, which is the earliest that an at-home pregnancy test will show up as positive. In other words, you can go through the first four weeks of pregnancy without even knowing you’re pregnant!

You'll be in your first trimester from the day you started your last menstrual period (which marks the beginning of week one) until 12 weeks later. The second trimester takes place between weeks 13 and 27, and the third trimester is week 28 to birth.

What to Expect Your First Trimester

Once you receive positive test results, you can relax a bit. Celebrate with your partner and any family members or friends with whom you want to share the news. It probably won’t be long before you start noticing the first symptoms of pregnancy, which can include nausea, morning sickness, bloating, exhaustion, breast tenderness and moodiness. You might not look pregnant yet, but you will almost certainly feel the effects! Everyone experiences this stage a little differently.

It’s very important during this time to eat nutrient-dense food (if you can stomach it), continue to take prenatal vitamins, stay hydrated and take all other possible measures to care for your body. No need for extra calories yet. Avoid alcohol, tobacco and chemicals. You may need more rest and sleep, but you should also try to exercise several days a week.

Your baby will go through a phenomenal amount of growth and change during this short time period. It transforms from a single-cell zygote into a miniature person in just a couple of months. The first trimester is the period in which your baby begins a heartbeat, grows limbs, and develops bones, nails, hair, a brain and other internal organs.

Talking to Your Doctor or Midwife

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You should be in close communication with your OB-GYN or midwife throughout the pregnancy. You can make an appointment as soon as you have a positive pregnancy test; most practitioners will schedule an appointment when you're between six and 10 weeks. Notify them before then if you notice any spotting or bleeding, as this can be a sign of an early miscarriage. Other unusual symptoms you’ll want to get checked immediately include severe abdominal pain, sudden thirst, painful urination, a fever over 101.5 degrees F, chills, backache, severe puffiness in the hands and face, or disturbances in your vision. Otherwise, you might experience discomfort because of the changes your body is going through, but this is not cause for concern.

When you go in for your first appointment, you can expect to get an ultrasound and hear those first heartbeats. You’ll also take several tests, including a Pap smear, urinalysis and bloodwork to ensure that all systems are on "go."

You will probably have a long list of questions for your practitioner, so don’t be afraid to ask. Be sure to disclose your full medical history as well as to ask about any medications, supplements and foods to avoid. Make yourself aware of these restrictions as early as possible, preferably even before you’re pregnant, to ensure your optimal health as well as your child’s.

The first trimester is an exciting time that goes by very quickly, since you won’t even be sure you’re pregnant until at least four weeks in. Enjoy this time, take care of yourself, and get ready for one of the biggest but most wonderful changes in your life.