How Far Along Am I in My Pregnancy?

Some different symptoms appear, breasts larger than usual, morning sickness begins, and a missed period is noticed. You take a pharmacy pregnancy test and it’s positive! Congratulations, you’re pregnant! And soon the question arises: how far along am I in my pregnancy?

Changes in the body in the first few days are not always noticeable and are easily confused with PMS symptoms, especially for those who suffer every month from very strong symptoms such as cramps, severe headaches, and nausea as well. These symptoms can also occur in the early days of pregnancy¹.

According to experts, symptoms usually only begin to appear about 15 to 20 days after fertilization. The calculation that will tell you how far along you are is done from the date of your last menstrual period, also called by the gynecologist/obstetrician as LMP (Last Menstrual Period), and it will be referred to this way in your prenatal booklet as identification².

Everyone knows that a pregnancy should last about 9 months, of course, there are risks of preterm labor, but this is the expected length of time. However, your gynecologist will not calculate pregnancy in months, but rather in weeks.

Some may think this change was made to confuse mothers who can’t understand these calculations and even less how many weeks equals a certain month. But believe it or not, the purpose of this change is to define more precisely the baby’s gestational age, since the fetus undergoes significant and important changes each week such as the development of the heart, separation of fingers and toes, and the emergence of eyes. Counting gestational age by weeks allows parents and the obstetrician to track the exact development of the baby.

How to Calculate Gestational Age?

The calculation that will let you know your pregnancy length is the date of your last menstrual period, as we’ve mentioned. However, it’s impossible to know the exact date the sperm fertilized the egg and give a precise date, but through an ultrasound exam it is possible to check fetal development and inform you of the gestational week you are in.

At the very first ultrasound, which usually happens by the gynecologist’s request around the 7th week, the gestational sac and embryo measurements will be checked. The exam device itself will make calculations through graphs that indicate how many weeks along the embryo is. With the ultrasound report, your gynecologist can verify this information to see if it matches what’s been recorded during your appointment, such as the estimated date of conception.

From the calculation of gestational age, an estimated due date for the baby’s birth will be established. This date is set for when, according to medical calculations, the pregnancy reaches 40 weeks. Remember, this is not the deadline for the baby to be born and should not cause concern or require a C-section for this reason; after all, the baby can be born up to 42 weeks, as long as properly monitored by the doctor.

Because it’s not possible to be certain of the exact date of fertilization, the calculation may have small errors in dates, either before or after the actual date, so the baby may take a little longer to be born and people may think it’s overdue. Many women with irregular menstrual cycles also cannot identify their true fertile period or even the correct date of their last menstrual period, which makes it harder for doctors to inform the exact gestational age.

It’s also important to point out that pregnancy does not always start on the day of conception, since sperm can survive in the female reproductive tract for about 5 to 7 days and fertilization may only happen days later, when ovulation occurs³. This means there is not 100% certainty in calculations even when a woman remembers the day of conception, as it may not have actually occurred on that exact date.

See also: How to Calculate Gestational Age? – Understand the Medical Calculation