When Did I Get Pregnant?

Is this a worrisome and stressful question that has been repeated over and over in your mind since the day you saw the positive lines on a pregnancy test? If so, kick your feet back and scroll down. This one is for you!

Through the years of working as a pregnancy center nurse, I have been met with this question many times. “When did I get pregnant?” If we are being honest, it is not an unlikely circumstance for men and women in this day to be sexually active with more than one partner. When pregnancy occurs in casual relationships, it can cause great stress for the man and woman in determining when the pregnancy occurred.

But there is good news! We are going to break down this question today. The first thing we need to do is define some key words.

1. What is Ovulation?

“Ovulation occurs when your ovary releases an egg. It happens around the 14th day of a 28-day menstrual cycle.” [1]

2. What is Conception?

According to the Cleveland Clinic, “Conception happens when sperm swims up through the vagina and fertilizes an egg in the fallopian tube. It happens in the hours or days after you have unprotected sex. After conception, the fertilized egg implants into the uterus and a pregnancy begins.” [2]

This term can be used interchangeably with fertilization. 

3. What is Gestational Age?

“The actual date of conception generally isn’t known for humans, so gestational age is the common way to measure how far along a pregnancy is. Where your baby is in their development — such as whether their fingers and toes have formed — is tied to gestational age.

Gestational age is measured in weeks from the first day of your last menstrual period. This means that your last period counts as part of your pregnancy. Even though you weren’t actually pregnant, your period is a signal that your body is preparing for pregnancy.

Fetal growth doesn’t actually start until conception, which is when sperm fertilizes an egg.”[3] 

Confusion often arises in medical facilities when we talk about gestational age. Gestational age is the MOST accurate, thus why it is used in medical offices for calculating how far along you are. Gestational age begins at the first day of your last menstrual period (LMP). Generally, women with typical 28 day cycles will have enough pregnancy hormone (hCG) in their body to test positive for pregnancy at 4 weeks gestation.

This means that it was 4 weeks from the first day of the woman’s last menstrual period (LMP) and approximately 2 weeks from the woman ovulating and conceiving (fetal age).

Healthline describes the difference between gestational and fetal age below:

“While gestational age is measured from the first day of your last menstrual period, fetal age is calculated from the date of conception. This is during ovulation, which means that fetal age is about two weeks behind gestational age.

This is the actual age of the fetus. However, it’s a less precise way to measure pregnancy, because in most cases it’s impossible to know when conception actually happens in humans.”

So Why Can Calculating Conception Dates Be Difficult?

Sources vary on the exact amount of time but can mostly agree that:

• An egg can survive approximately 24 hours after ovulation.
• Sperm can survive approximately 5-7 days AFTER intercourse.
• Not every woman has a typical, regular 28 day cycle. Some women ovulate early and others ovulate later. The time of ovulation greatly impacts the time of conception.
• Many women have unknown LMP’s due to irregular cycles or taking birth control.

Think You might be pregnant? Click here for a pregnancy quiz!

Let’s put our newfound knowledge to the test!

• Today’s date: 7-22-24.
• Last Menstrual Period: 6-1-24.

For a typical cycle, you would likely be approximately:

• 7 weeks 2 days gestation
• Estimated Due Date (EDD): March 8, 2025
• Probable Ovulation: June 15, 2024- most likely date.

Fertile/Ovulation Window: June 13-17, 2024.

Click Here to Calculate Gestational Age and Due Date

Click Here to Calculate a Possible Conception Date

Click Here for a Pregnancy Timeline Explanation

We hope this information on ovulation, conception, and gestational vs fetal age is helpful in understanding your body and cycle. The bottom line: we may not know the exact date you conceived but we can give an estimated range of time. It is important to think our decisions through and to understand that no birth control or method is 100% effective in preventing pregnancy.

If not knowing the day you became pregnant is a stressor for you, we are here to help! An ultrasound is the best way to determine how far along you are. We are here to help you navigate this journey, give you reassurance, support, and peace of mind.

Call us today to make an appointment!

-Nurse Ally

[1] https://my.clevelandclinic.org/health/articles/23439-ovulation

[2] https://my.clevelandclinic.org/health/articles/11585-conception

[3] https://www.healthline.com/health/pregnancy/what-is-gestation#gestation-period