Gestational Age Calculator

Q: Question: My menstrual cycle is 35 days long. Is this calculator accurate for me?

Answer: This is an excellent question. Standard calculators are based on a 28-day cycle, assuming ovulation on day 14. In a 35-day cycle, ovulation would occur around day 21. This means your actual gestational age might be about one week less than the LMP-based calculation. This is precisely why a first-trimester ultrasound is more reliable in such cases.

Q: Question: How long does "morning sickness" last? Is it a cause for concern?

Answer: Morning sickness (which can occur at any time of day) usually subsides by 12-14 weeks. It's a normal part of pregnancy. However, if you are vomiting excessively (a condition called hyperemesis gravidarum), leading to weight loss or dehydration, you must contact your doctor immediately.

Q: Question: When should I feel the baby's first movements?

Answer: First-time mothers typically feel movement between 18-22 weeks. If this is your second pregnancy, you might feel it as early as 16 weeks. After 28 weeks, you should pay attention to the baby's movements every day.

Calculate how far along the pregnancy is based on the Last Menstrual Period (LMP). Accurate, easy to use, and includes PDF report.

Hello! I am Dr. Anuja Dokras (MBBS, DNB – Obstetrics & Gynaecology). As a doctor, I believe that accurate information is the greatest source of empowerment, especially during a journey as significant as pregnancy. This is not just a physical transformation; it is an emotional and mental journey where every day and every week counts.

This webpage is much more than just a calculator. It is a comprehensive guide, designed to help you understand every aspect of your pregnancy. Here, we will not only calculate your gestational age and due date, but we will also delve into the science behind it, the changes you can expect each trimester, and the critical milestones that matter for you and your baby.

The Foundation of Pregnancy Planning: Why Every Day Matters

Accurate tracking of gestational age is not just for satisfying your curiosity. It is crucial for ensuring the healthy development of your baby and your own well-being.

Tracking Fetal Development: Every week, your baby follows a specific developmental path. Knowing the gestational age helps your doctor confirm that your baby is growing at the right pace.
Scheduling Vital Medical Tests: Pregnancy involves several critical tests that must be performed within a specific timeframe.
- NT Scan (Nuchal Translucency): Weeks 11-13
- Double Marker Test: Weeks 11-13
- Anomaly Scan (TIFFA): Weeks 18-22
- Glucose Tolerance Test (GTT): Weeks 24-28
Monitoring Maternal Health: Based on the gestational age, your doctor monitors your health needs, such as nutrition, weight gain, and potential complications (like gestational diabetes or pre-eclampsia).
Planning for Birth: It helps you prepare mentally and physically for labor and delivery.

Your Interactive Calculator: A Step-by-Step Guide

Method 1: Based on Last Menstrual Period (LMP)

Select “By LMP”.
Enter the LMP Date: Choose the date of the first day of your last menstrual period.

Dr. Anuja’s Tip: “The LMP method is most accurate for women with regular menstrual cycles (28-30 days). If your cycle is much shorter or longer, your due date might vary slightly, which your doctor will advise you on.”

Method 2: Based on Ultrasound Date

Select “By Ultrasound”.
Enter the Ultrasound Date.
Enter Gestational Age: Input the weeks and days from your ultrasound report.

Dr. Anuja’s Tip: “In early pregnancy, fetuses grow at a very consistent rate. That is why a first-trimester ‘dating scan’ (around 7-9 weeks) is considered the ‘gold standard’ for determining gestational age.”

Understanding the Results: A Medical Perspective

Estimated Due Date (EDD): This date is based on Naegele’s rule (LMP – 3 months + 7 days + 1 year). However, a pregnancy is considered ‘term’ when it is between 37 and 42 weeks.
- Early Term: 37 weeks 0 days to 38 weeks 6 days
- Full Term: 39 weeks 0 days to 40 weeks 6 days
- Late Term: 41 weeks 0 days to 41 weeks 6 days
- Post-Term: 42 weeks 0 days and beyond
Trimester: The three stages of pregnancy:
- First Trimester: The foundational period for your baby’s body.
- Second Trimester: A phase of growth and maturation.
- Third Trimester: A time for rapid weight gain and preparation for birth.

The Trimester-by-Trimester Blueprint: A Doctor’s Guide

First Trimester (Weeks 1-13): The Miracle Begins

Fetal Development: From a fertilized egg, your baby develops into a tiny fetus. The heart begins to beat around 5-6 weeks. By 12 weeks, nearly all organs are formed, and it looks like a miniature human.
Maternal Changes: Hormonal changes are intense. You may experience fatigue, nausea (morning sickness), breast tenderness, and frequent urination.
Key Medical Check-ups: Initial blood tests (hemoglobin, blood group, thyroid, infectious diseases), urine tests, and the dating/NT scan.

Second Trimester (Weeks 14-27): The Golden Period

Fetal Development: The baby grows rapidly. You might feel the first movements (‘quickening’), usually around 18-22 weeks. He or she can now hear and react to external stimuli.
Maternal Changes: Energy levels often increase. The baby bump becomes more prominent. Skin changes (like the linea nigra) and mild backaches are common.
Key Medical Check-ups: The Anomaly Scan (TIFFA) to ensure all of the baby’s organs are developing correctly, and the Glucose Challenge Test.

Third Trimester (Weeks 28-40+): The Final Stretch

Fetal Development: The baby gains weight rapidly, the lungs mature, and he or she begins to descend into the correct position for birth (head down).
Maternal Changes: The growing belly can cause discomfort, such as shortness of breath, difficulty sleeping, and Braxton Hicks contractions (practice contractions).
Key Medical Check-ups: More frequent doctor visits (weekly after 36 weeks), growth scans, Group B strep test, and monitoring of the baby’s position.

Special Scenarios and Considerations

Irregular Menstrual Cycles: If you have irregular periods, the LMP method can be unreliable. In such cases, it is best to rely entirely on the ultrasound results.
IVF Pregnancies: In IVF cases, the EDD is calculated based on the date of the embryo transfer. Your fertility specialist will provide you with an accurate date.

Q&A with Dr. Anuja

Answer: This is an excellent question. Standard calculators are based on a 28-day cycle, assuming ovulation on day 14. In a 35-day cycle, ovulation would occur around day 21. This means your actual gestational age might be about one week less than the LMP-based calculation. This is precisely why a first-trimester ultrasound is more reliable in such cases.

Answer: Morning sickness (which can occur at any time of day) usually subsides by 12-14 weeks. It’s a normal part of pregnancy. However, if you are vomiting excessively (a condition called hyperemesis gravidarum), leading to weight loss or dehydration, you must contact your doctor immediately.

Answer: First-time mothers typically feel movement between 18-22 weeks. If this is your second pregnancy, you might feel it as early as 16 weeks. After 28 weeks, you should pay attention to the baby’s movements every day.

Final Words: Stay Informed, Be Empowered

This calculator and the information provided here are meant to make you an active participant in your pregnancy journey. Knowledge gives you the power to ask the right questions, understand your body, and make the best decisions in partnership with your doctor.

Your pregnancy is a unique and precious experience. Enjoy every moment of this beautiful journey.

Dr. Anuja Dokras
MBBS, DNB (Obstetrics & Gynaecology)

Disclaimer: This tool and its content (medically verified by Dr. Anuja Dokras) are designed for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your physician or another qualified health provider with any health concerns regarding your pregnancy.