Pregnancy During the First Trimester

Pregnancy, Trimesters and Fetal Development
Pregnant woman holding dummy

The average pregnancy lasts about 40 weeks. It is divided into three stages called trimesters. A trimester means three months. Dividing the pregnancy into trimesters gives it a beginning, middle and end stage. The first trimester, according to the University of Pennsylvania Penn Medicine, “is defined as from conception through week 14.”

First four weeks. In this earliest stage of the first trimester, your baby is a blastocyst, a tiny group of cells. However, you may begin to feel symptoms of the pregnancy. Even though you’re pregnant, cramping and even a bit of bleeding can occur. Don’t panic — many women experience this. If you are concerned, talk to your doctor. Other symptoms can include nausea and fatigue.

Weeks 5 and 6. As your little embryo continues to grow, increasing hormone levels can cause nausea and vomiting. Remember, even though it’s called morning sickness, it can occur any time of day, so be prepared. Your breasts may feel tender and even a bit swollen because of increased blood flow. Mood swings and frequent urination can begin during these weeks as well.

Weeks 7 and 8. Your pregnancy kicks into high gear. Nausea, vomiting and fatigue continue. Other digestive issues can develop such as constipation, bloating and heartburn. The need to pee frequently develops as your uterus grows. You may begin to crave certain foods and/or develop an aversion to other foods. Certain smells can trigger nausea.

Weeks 9 and 10. At nine weeks, the baby is considered a fetus. Mood swings caused by hormones are normal. Hormones can contribute to your nausea, headaches and fatigue as well. Expect a slight weight gain, as your baby is growing and so are you. Around 10 weeks, some women may start to develop a bit of baby “curve.” A condition called round ligament pain may occur as your body stretches with the developing fetus.

Weeks 11 and 12. As the first trimester winds down, the nausea and vomiting are likely to decrease or disappear. Your belly will look bigger, and a dark line may appear, running from about the pubic bone up toward your breasts. It’s the linea nigra, a common pregnancy symptom caused by hormones. It will go away after the baby is born, but can linger in breastfeeding moms. You may notice increased headaches and even suffer from bouts of dizziness. Other symptoms can include bloating and gas, vaginal discharge, spider veins and leg cramps.

Weeks 13 and 14. The wild roller coaster of pregnancy symptoms slows down at weeks 13 and 14. You may still have some nausea, but your queasiness and vomiting should be ending. It also is common to feel a few twinges or aches as your body stretches to fit the growing baby. Some women experience an increased sex drive at the end of the first trimester.

If you have any questions or concerns about your first trimester, consult your physician.


This article was originally published as Pregnancy During the First Trimester on

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