How can I figure out for sure when I got pregnant?

Pregnancy can often feel like a big mystery. What is happening to my body? Why do I feel this way? When did I even get pregnant? 

Maybe you’ve never been pregnant before; maybe you have. Either way, each pregnancy requires attention, care, and understanding. One of the first things to do after finding out you’re pregnant is to calculate gestational age–which will help you understand the timeline of your pregnancy.  

Pregnancies are measured in weeks and trimesters. Healthcare providers measure from the first day of your last menstrual period to calculate gestational age. This information helps you plan prenatal care, understand milestones, and track your pregnancy as it progresses.  

What is Gestational Age?

Gestational age refers to the number of weeks and days that have passed since the first day of your last menstrual period, also known as your LMP.

Healthcare providers utilize this crucial measurement to monitor the progress of the pregnancy. It’s important to note that gestational age is not the same as conceptional age. 

Conceptional age, also known as fetal age, is the actual age of the fetus. This is calculated from the date of conception (the scientific term for the beginning of pregnancy, which occurs when a sperm fertilizes an egg). This age is usually about two weeks less than the gestational age, because conception typically occurs about two weeks after the first day of the last menstrual period. The main differences between gestational and conceptional age include: 

• Calculation: Gestational age is calculated from the first day of the last menstrual period, while conceptional age is calculated from the date of conception.
• Usage: Gestational age is widely used in medical practice for monitoring pregnancy and scheduling tests, whereas conceptional age is more specific to the actual development of the fetus.

While gestational age can be measured with more precision, conceptional age can be challenging to clearly identify. Sperm can survive up to 5 days in the female body. If you ovulate within 5 days after a sexual encounter, it’s possible to become pregnant from that encounter. Thus, even if you had only one sexual encounter during a given cycle, it’s still challenging to pinpoint the exact day you conceived.  

Knowing gestational age, however, allows for accurate tracking of fetal development, essential screenings, and milestones to optimize prenatal care for mother and baby.

By calculating gestational age, expectant parents gain insights into their baby’s growth, fostering a well-informed and prepared journey through pregnancy.

Calculating Gestational Age

Various methods exist to determine the gestational age of your pregnancy.

The first piece of information you need is the date of the first day of your last menstrual period (LMP). Whether or not you are trying to get pregnant, it’s wise to keep track of your periods. Missed periods not due to pregnancy may signal other health concerns that should be addressed. There are many options of period tracking apps that you can download that are simple to use and help you monitor your cycle. 

LMP alone is not sufficient information to accurately calculate gestational age, for a few reasons. 

• Irregular Cycles: Many women have irregular menstrual cycles, which can make it difficult to pinpoint ovulation and conception dates. LMP assumes a regular cycle, typically around 28 days, but variations are common.
• Timing of Ovulation: Conception occurs when sperm fertilizes an egg, which typically happens within 12-24 hours after ovulation. If a woman has a longer or shorter cycle, ovulation may not occur at the expected time based on her LMP.
• Variability in Menstrual Flow: The start of the menstrual period can vary based on a range of factors, including stress, illness, or changes in routine, leading to inaccuracies in calculating fertile windows.
• Sperm Viability: Sperm can live in the female reproductive tract for up to five days. Therefore, even if LMP is known, conception could occur several days after the assumed ovulation date.
• Uncertainty in LMP Reporting: Women might not accurately remember their LMP, leading to potential discrepancies in dating a pregnancy.
• Medical Conditions: Certain medical conditions or hormonal imbalances can affect menstrual cycles and ovulation, further complicating the relationship between LMP and conception. 

For these reasons, you should verify gestational age through a more accurate method, namely ultrasound. 

Ultrasound examinations stand out as an accurate method for determining gestational age, especially when performed in the first trimester. Measurements of the embryo or fetus can yield precise developmental timelines.

In cases where menstrual history or early ultrasounds are not available, physical examinations and estimations based on uterine size can serve as helpful indicators of gestational age.Gestational age is essential information to help you navigate your pregnancy journey safely and successfully.

If you are considering abortion, it is especially necessary to determine gestational age accurately. Medical abortions (abortion pills) are not FDA-approved beyond 10 weeks gestation. If you are further along than you think, the abortion pills may be ineffective and can cause additional complications that will need further medical care.

Common Mistakes When Calculating Gestational Age 

One common error involves miscalculating the last menstrual period (LMP). 

Failing to remember this date can lead to a significant discrepancy when calculating gestational age.  

Women’s cycles can vary widely, and an irregular period can further complicate this estimation, leading to confusion and potential miscalculations of the due date. The use of emergency contraception can also alter menstrual cycles, making dating of the pregnancy especially difficult. 

For women who are considering abortion, miscalculating gestational age can pose risks to your health and safety. The types of abortion available depend heavily on how far along you are, and you should never utilize any abortion option without verifying your pregnancy via ultrasound first.  

Another pitfall is relying exclusively on physical symptoms to gauge gestational age. For instance, nausea, breast tenderness, and fatigue can vary significantly between individuals and pregnancies, making these markers unreliable without professional medical assessments and ultrasounds.

Finally, some people might prioritize unofficial mobile apps or online calculators over professional medical advice to determine gestational age. While technology can be beneficial, these tools should complement, not replace, medical consultations. Accurate, professional guidance ensures optimal prenatal planning and well-being.

Pregnancy Signs & Symptoms

Among the most indicative signs of early pregnancy is a missed menstrual period. (Note: If you have missed your period, we offer free pregnancy testing and pregnancy confirmation ultrasounds at Clearway.)

Additionally, tender, swollen breasts are another common symptom often experienced by expectant mothers.

Nausea, sometimes referred to as morning sickness, frequently occurs (although it can happen at any time of the day). Fatigue and increased need for rest may be noticeable as your body channels energy into supporting the developing fetus.

Finally, heightened senses, such as an amplified sense of smell and taste, may also indicate pregnancy. Monitoring these signs can help you identify early pregnancy and seek timely medical care.

Ultrasounds for Early Pregnancy

Ultrasound measurements use sound waves to produce images of the uterus. If you have an intrauterine pregnancy, it should be measurable via ultrasound. Generally, sonographers measure the crown-rump length (CRL) of the fetus to establish gestational age, providing precise data that correlates with standardized growth charts.

Clinical guidelines suggest performing subsequent ultrasounds to monitor consistent fetal growth, reinforcing the initial estimates. 

At times, an early ultrasound might not show the results you’re expecting. This may be due to a pregnancy that’s too early to measure. It may also signal an ectopic pregnancy, which would require immediate follow up and emergency care.

When to Consult a Healthcare Provider

Determining gestational age as early as possible is vital. Consulting a healthcare provider promptly after suspecting pregnancy significantly enhances prenatal care and outcomes. At Clearway, we offer free pregnancy testing and ultrasounds to determine the gestational age of your pregnancy. 

In particular, if you experience any concerning symptoms or have irregular menstrual cycles, a timely consultation allows for accurate assessment of your gestational age. This ensures a tailored care approach, pivotal for managing both typical pregnancies and those requiring specialized attention.

Moreover, early detection and regular monitoring by a healthcare provider can help identify any potential complications. It’s crucial to guarantee both maternal and fetal health through consistent and professional oversight.

Finally, engaging with a healthcare provider early on fortifies your pregnancy journey with informed decisions and emotional support. If you’re feeling unsure about whether or not you want to continue this pregnancy, schedule a consultation at Clearway. 

We offer free medical services (including pregnancy confirmation ultrasounds) and a safe space to process your decision and receive resources and support. You’re not alone in this! 

Schedule your appointment today. 

Reviewed by Kate O., BSN RN

This information is for educational purposes only. It is not a substitute for medical advice. Please contact your doctor for more information.