What Happens in the First Month of Pregnancy?
Pregnancy is divided into 3 trimesters. Each trimester is a little longer than 13 weeks. The first month marks the beginning of the first trimester.
Pregnancy is measured using “gestational age.” Gestational age starts on the first day of a woman’s last menstrual period (LMP).
Gestational age can be confusing. Most people think of pregnancy as lasting nine months. And it’s true that a woman is pregnant for about nine months. But because pregnancy is measured from a woman’s last menstrual period — about 3-4 weeks before she is actually pregnant — a full-term pregnancy usually totals about 40 weeks from LMP — roughly 10 months.
Many women do not remember the exact date of their last menstrual period — that’s OK. The surest way to tell gestational age early in pregnancy is with ultrasound.
These are the first two weeks of a woman’s menstrual cycle. She has her period. About 2 weeks later, the egg that is most mature is released from the ovary — ovulation. Ovulation may happen earlier or later, depending on the length of a woman’s menstrual cycle. The average menstrual cycle is 28 days.
After it is released, the egg travels down a fallopian tube toward the uterus. If the egg meets a sperm, they combine to form one cell. This is called fertilization. Fertilization is most likely to occur when a woman has unprotected vaginal intercourse during the 6 days that lead into ovulation.
The fertilized egg moves down the fallopian tube and divides into more and more cells. It reaches the uterus about 3–4 days after fertilization. The dividing cells then form a ball that floats free in the uterus for about 2–3 days.
Pregnancy begins when the ball of cells attaches to the lining of the uterus. This is called implantation. It usually starts about 6 days after fertilization and takes about 3–4 days to be complete.
Pregnancy does not always occur. Up to half of all fertilized eggs pass out of women’s bodies during regular menstruation before implantation is complete.
Learn more about how pregnancy happens.
|A Woman’s First Signs of Pregnancy|
For many women, the first sign of pregnancy is a missed period. Most pregnancy tests will be positive by the time a woman has missed her period. Other early signs of pregnancy include fatigue, feeling bloated, frequent urination, mood swings, nausea, and tender or swollen breasts. Not all women have all of these symptoms, but it is common to have at least one of them.