First Trimester

Guide to the first trimester of pregnancy

The early stages of pregnancy can be the most intense, as the excitement and physical changes can seem to hit you all at once. The first major physical symptoms will be the tell-tale missed period, along with breast tenderness, fatigue and morning sickness. Your mood can rise and fall quickly in the first trimester of pregnancy, and you may need to urinate more often.

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Your body will take some time to adjust to the higher hormone levels, but rest assured that the uncomfortable symptoms will likely not last for too long. Early pregnancy can bring lots of surprises, some of which may be frightening or worrisome. Here is an overview of what you can expect to experience in each week of your first trimester, from conception to week 13.

First Trimester of Pregnancy Week by Week

1 Week Pregnant – The first of your 40 weeks of pregnancy begins on the first day of your last period, which means that you are not yet pregnant. Conception typically occurs about two weeks after your period begins, but it is easier to project a due date based on the start of your period than on the specific date of conception.

2 Weeks Pregnant – The uterus is forming a new endometrial layer, and an egg is maturing in one of your ovaries, which will be released the following week.

3 Weeks Pregnant – Following ovulation, your egg will be fertilized by the sperm in one of the two fallopian tubes, forming a zygote made of 23 of your partner's chromosomes and 23 of your own. During this week, your progesterone levels will spike and prevent menstruation.

4 Weeks Pregnant – The zygote will become a blastocyst and will burrow into your uterine lining. Although spotting during pregnancy can indicate complications, some women experience what is known as implantation bleeding at this stage, which is typically a very small amount of spotting around the time of your expected period and nothing to be worried about.

5 Weeks Pregnant – The blastocyst turns into an embryo at this stage, and your period is about a week late. Many women begin to experience breast soreness, fatigue and morning sickness as the level of the HCG hormone increases rapidly.

6 Weeks Pregnant – The embryo is growing and its heart begins to pump blood; you may notice that your waistline has started growing, too. Your sense of smell is heightened, and you may feel faint or dizzy when you stand up too quickly. Now is the time to assess your pregnancy diet and lifestyle because embryonic development is particularly vulnerable to what you put in your body at this stage.

7 Weeks Pregnant – Your hormonal changes could begin to give your skin a healthy glow or, if you are unlucky, result in a breakout of acne. Although you may not be showing yet, you may be feeling constipated as a result of slowing digestion and an increasing blood supply. The embryo's organs, limbs and facial features are developing quickly.

8 Weeks Pregnant – Your uterus is growing, putting pressure on your bladder. Your breasts might still be tender, and you may notice that your nipples are becoming darker. The embryo, now about an inch long, will form eyes and teeth. This is the week that the gender will be determined.

9 Weeks Pregnant – Although some women may lose a little weight due to morning sickness, most will be gaining weight steadily. When women experience bleeding during the first trimester, it is usually during this week, and a small amount of spotting or breakthrough bleeding is completely normal. The embryo will begin to develop bones and form fingers and toes.

10 Weeks Pregnant – Your veins may become more noticeable as your blood volume increases even more, and you might feel warmer and moodier. You should continue to gain weight, but be sure to eat a nutritious diet to keep your energy up and both of you healthy. Moderate pregnancy exercise will help tame mood swings.

11 Weeks Pregnant – Your uterus is over twice its usual size, and you may be able to feel it if you press your belly just above the pubic bone. The embryo is now a fetus, and the genitals will be formed by the end of the week.

12 Weeks Pregnant – Some of your discomfort will finally be relieved – the uterus will shift away from your bladder, your morning sickness may let up and you will soon begin to feel energetic and content. Many of the fetus's vital processes are developing now that the kidneys and intestines are fully functioning, and its face now has a recognizably human profile.