How Do I Know How Many Weeks Pregnant I Am?

You and your OB/GYN can figure out how many weeks pregnant you are by calculating your ovulation and fertilization dates based on the date of your last menstrual period.

In order to determine how many weeks you are into your pregnancy you must first know the date of ovulation and fertilization. Calculating the date of ovulation and fertilization is typically done using the first day of your last menstrual period or an ultrasound date.

If a woman has a regular menstrual period and knows the first day of her last menstrual period, the baby’s gestational age can be calculated from this date. Many women do not know the date they ovulate so the first day of their last menstrual period, which is about 2 weeks before ovulation and is easy to know, is usually when doctors consider a pregnancy to have started. A doctor counts 280 days (40 weeks) from the first day of the last menstrual period to estimate the due date. 

The baby can also be measured by ultrasound as early as 5 to 6 weeks following the mother’s last menstrual period. This is most accurate earlier in pregnancy, with the best time to use ultrasound to estimate gestational age being between the 8th and 18th weeks of pregnancy. 

• The first trimester is weeks 1 to 13
• The second trimester is weeks 14 to 27
• The third trimester is weeks 28 to 40

Signs and symptoms of pregnancy month-by-month include: 

• Month 1
  • Missed period
  • Tiredness
  • Bloating 
  • Frequent urination
  • Mood swings
  • Nausea
  • Tender or swollen breasts
• Month 2
  • Same symptoms from month 1, but usually more noticeable
  • Heart beats faster
• Month 3
  • Earlier symptoms may continue to worsen, especially nausea
  • Breasts continue growing and changing
  • The area around your nipple (areola) may grow larger and darker
  • Acne outbreaks
• Month 4
  • Many earlier symptoms lessen or go away
  • Heartburn and constipation may worsen 
  • Breast changes (growth, soreness, and darkening of the areola) continue
  • Shortness of breath or faster breathing
  • Bleeding gums
  • Nosebleeds
  • Nasal stuffiness
  • Dizziness 
  • Fainting
• Month 5
  • Earlier symptoms continue
  • Breasts may be as much as 2 cup sizes larger
  • Fetal movements may be felt for the first time; feels like flutters or butterflies in the stomach (called quickening)
• Month 6
  • Earlier symptoms continue
  • Shortness of breath may improve
  • Breasts may start to produce tiny drops of early milk (colostrum)
  • Braxton-Hicks contractions may occur, which feel like a painless squeezing of the uterus or abdomen
• Month 7
  • Earlier symptoms continue
  • Back pain is common
  • Dizziness may lessen
• Month 8
  • Feeling tired 
  • More difficulty breathing as the uterus grows upward
  • Varicose veins, usually in the legs 
  • Hemorrhoids 
  • Stretch marks where skin has expanded
  • Braxton-Hicks contractions, heartburn, and constipation may continue
  • A small amount of urine may escape when sneezing or laughing because of pressure from the uterus on the bladder
  • Hair may appear fuller and healthier
• Month 9
  • Common pregnancy symptoms may continue through the end of pregnancy including fatigue, trouble sleeping, trouble holding urine, shortness of breath, varicose veins, and stretch marks