During the first week of pregnancy, symptoms are still very few and subtle. Many women may not even notice that their body is undergoing change.

In the first days following fertilization, hormone levels change significantly so that menstruation can stop and the body can prepare for fetal development in the wound.

Some of the most common symptoms experienced by women in the first week of pregnancy include abdominal cramping, increased breast sensitivity, excessive fatigue, mood swings and aversions to certain smells.

Symptoms in the first week

Symptoms that many women may report, if felt, can include:

1. Abdominal cramps

This is a very common symptom in women in general, as it occurs during any period of major hormonal fluctuations, like menstruation and even pregnancy. Unlike menstruation, however, abdominal cramps are usually not accompanied by bleeding.

In addition to abdominal cramps, women may also notice light bloating or abdominal swelling. This is not due to the growing fetus yet, as it is is still a microscopic embryo. The swelling occurs due hormonal action on the uterine tissues and the female reproductive tract.

2. Breast sensitivity

Soon after fertilization, the woman’s body undergoes many significant changes triggered by hormonal fluctuations. One noticeable change is an increase in breast sensitivity. This occurs due to changes in mammary tissue in preparation for breastfeed.

Although this sensitivity can be felt in the first week, many women may only notice this discomfort after 3 to 4 weeks. The nipples and areola may also undergo some changes and often become darker in color.

3. Excessive fatigue

Many women often notice a sudden surge in fatigue after only 3 or 4 weeks, however some may report inexplicable fatigue soon after fertilization.

Usually, this fatigue is related to increased progesterone in the body, which can increase drowsiness and decrease energy levels throughout the day.

4. Mood swings

Mood swings are another symptom that can emerge in the first week of pregnancy. Many times, these changes in mood may go unnoticed as a pregnancy symptoms, and may only be caught later on, after a positive pregnancy test.

These changes occur due to fluctuations in hormones, which can trigger emotions of joy, followed by sudden sadness or irritability.

5. Aversion to strong odors

Fluctuating hormones can make women more sensitive and even repulsed by specific smells, like perfume, cigarettes, strong-smelling foods or gasoline.

These aversions can go unnoticed, like the mood swings, until a pregnancy test is completed. Learn about other early pregnancy symptoms that can occur before a missed period.

How to confirm pregnancy

Although there are many symptoms that are commonly experienced among women in the first week of pregnancy, these symptoms are not a reliable way to confirm pregnancy.

Ideally, women should complete a pharmacy test in the first 7 days after a late period. They can also solicit a pregnancy blood test from their doctor to determine hCG levels in the blood, which is a hormone that is only produced during pregnancy.

Read more about the different types of pregnancy tests and the pros and cons of each type.

When is the first week of pregnancy?

Obstetricians usually consider the first week of pregnancy to be the first day of the last period. It means that during this week, the woman is not in fact pregnant, as the new egg has still not been released for fertilization by a sperm.

Nonetheless, women often consider their first week of pregnancy to be the 7 days immediately following fertilization. This lines up with the obstetricians' measurement of 2 or 3 weeks of gestation. .