How to Calculate Due Date Using a Maternity Wheel?

Pregnancy is a time of excitement and anticipation in any woman's life. One of the most common questions expectant parents ask during the pregnancy is, “When is the baby due?”

Healthcare providers use many different tools to answer this question. One such commonly used tool is the maternity wheel, also known as the gestational wheel. Evidence proves that these wheels are inexpensive ways to calculate the due date accurately [1].

In this article, we will learn how to use the maternity wheel to determine the due date and explore some other ways to calculate the delivery date. This article also includes some tips for expectant women to support first pregnancy.

What Is a Maternity Wheel?

A maternity wheel, or gestational wheel, is a simple tool healthcare providers use to estimate a baby’s due date. You can also use this tool at home to get insights on your pregnancy and calculate the delivery date.

A maternity wheel is actually a circular chart made of two movable disks — an outer wheel and an inner wheel. The outer wheel lists the months and days of the year, while the inner wheel contains information about the weeks and trimesters of pregnancy. The inner wheel has two important marks, "first day of last menstrual period" and "due date of delivery," and there is a 40-week or 280-day calendar between these two marks.

How to Use the Maternity Wheel?

The maternity wheel works by using the first day of your last menstrual period (LMP) as a starting point [2]. Here is a step-by-step guide on how to use the maternity wheel:

1. The first step is to locate the first day of your last menstrual period on the outer wheel.
2. The next step is to align the "first day of last menstrual period" or "0-week" mark on the inner wheel with the LMP date on the outer wheel.
3. Now locate where the due date mark or the 40-week mark on the inner wheel aligns with the calendar on the outer wheel. This is your calculated due date according to the gestational wheel or conception calendar.

The pregnancy gestation wheel is based on the average length of a pregnancy, which is about 280 days or 40 weeks [3]. It assumes a regular 28-day menstrual cycle.

Other Ways to Calculate the Due Date

While the pregnancy gestation wheel is an inexpensive and effective tool, women look for other ways to calculate the due date to confirm the findings of the gestational wheel. Here are some other options for you to get an estimate of the delivery date:

1. Online Due Date Calculators

There are many online tools and apps that can help you calculate your due date based on the first date of your last menstrual period. All you need to do is enter the first date of your last menstrual period on the tool, and you will get an estimated delivery date.

2. Ultrasound Scans

Ultrasound scans can provide an accurate estimate of the due date. In such scans, the measurement of the baby’s crown-to-rump length (CRL) helps determine gestational age [4].

3. Physical Examination

If you are not sure about your LMP date and ultrasound is also not accessible, a healthcare provider may estimate the due date based on the size of the uterus during a pelvic exam, or by using a picture of the uterus for further analysis.

4. IVF Due Date Calculation

In the case of in-vitro fertilization (IVF), the due date is calculated based on the date the embryo is transferred into the uterus. Usually, a 3-day embryo is transferred in IVF, which means that you need to add 263 days on the day of embryo transfer, and you will get the due date.

Tips to Support a Healthy Pregnancy

Once you determine the due date, it’s important to focus on maintaining a healthy pregnancy. Here are some tips to support your health and the development of the baby during pregnancy:

1. Attend Prenatal Checkups: Prenatal checkups help ensure the baby is growing properly and the mother stays healthy. They allow doctors to catch and address any potential problems early. Regular visits also provide guidance and support for a safe and healthy pregnancy.
2. Eat a Balanced Diet: A balanced diet helps your body obtain essential nutrients for the pregnancy [5]. Fruits, vegetables, lean proteins, and whole grains are some of the nutrient-rich food options excellent for pregnancy.
3. Prenatal Vitamins: A balanced diet may not always be enough to fulfill the increased nutritional demands during pregnancy [5]. This is why doctors recommend taking prenatal vitamins, which are dietary supplements that provide essential vitamins and minerals for pregnancy.

4. Exercise Regularly: Gentle activities like walking, swimming, or prenatal yoga can help improve circulation, reduce stress, and prepare your body for labor. However, it is essential to avoid intense exercises during pregnancy as they can harm the growing baby in the womb.
5. Avoid Harmful Substances: Stay away from alcohol, smoking, and recreational drugs, as they can harm the baby. Such substances can significantly increase the risk of miscarriages and birth problems in the baby [6].

Conclusion

The maternity wheel is an effective tool that helps you determine the baby's due date quickly and easily. It determines the due date by adding 40 weeks or 280 days on the first day of your last menstrual period.

If you want to confirm the findings of the maternity wheel, there are many other ways to calculate the estimated delivery date. These include online tools, pregnancy apps, and ultrasound scans. Knowing the due date can help you prepare for the delivery phase and child care after birth.

Resources Used

1. Stokes, M., Olson, A., Chan’gombe, M., Rajab, B., Janmey, I., Mwalwanda, C., Levison, J., & Pope, R. (2021). Reinventing the Pregnancy Wheel to Improve Pregnancy Dating and Antenatal Care Visits: A Pilot Randomized Trial in Malawi. International Journal of Maternal and Child Health and AIDS, 10(1), 139–145. https://doi.org/10.21106/ijma.474 
2. Methods for Estimating the Due Date. (n.d.). ACOG. https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2017/05/methods-for-estimating-the-due-date 
3. Declercq, E., Wolterink, A., Rowe, R., De Jonge, A., De Vries, R., Nieuwenhuijze, M., Verhoeven, C., & Shah, N. (2023). The natural pattern of birth timing and gestational age in the U.S. compared to England, and the Netherlands. PLoS ONE, 18(1), e0278856. https://doi.org/10.1371/journal.pone.0278856 
4. Kang, J., Park, E., Yang, Y., Park, M., & Park, W. I. (2013). Crown-Rump Length Measured in the Early First Trimester as a Predictor of Low Birth Weight. Yonsei Medical Journal, 54(4), 1049. https://doi.org/10.3349/ymj.2013.54.4.1049 
5. Marshall, N. E., Abrams, B., Barbour, L. A., Catalano, P., Christian, P., Friedman, J. E., Hay, W. W., Hernandez, T. L., Krebs, N. F., Oken, E., Purnell, J. Q., Roberts, J. M., Soltani, H., Wallace, J., & Thornburg, K. L. (2021b). The importance of nutrition in pregnancy and lactation: lifelong consequences. American Journal of Obstetrics and Gynecology, 226(5), 607–632. https://doi.org/10.1016/j.ajog.2021.12.035 
6. Odendaal H, Dukes KA, Elliott AJ, et al. Association of Prenatal Exposure to Maternal Drinking and Smoking With the Risk of Stillbirth. JAMA Netw Open. 2021;4(8):e2121726. https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2783302