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Pregnancy Due Date Calculator

Find our your Expected Due Date (EDD) and the best time to have your first scan using simply the first day of LMP (Last Menstrual Period.) Little extra – find our your little ones anticipated Zodiac sign with our Pregnancy Due Date Calculator!

London Pregnancy Clinic - Pregnancy Due Date Calculator for early pregnancy scans.

Enter your LMP


Book your first scan

You can get some early reassurance about your pregnancy by booking your first scan with us at around the time the calculator indicated 6 weeks - book now!

If you are at later stages of your pregnancy, please visit our Early Pregnancy Scans page to find out what other scans you can have in the first trimester and our general scans page for scans in the 2nd and 3rd trimesters.

What if I don't know my LMP?

When it comes to estimating your Estimated Due Date (EDD) without knowing the date of your last menstrual period (LMP), particularly in cases of IVF (In Vitro Fertilisation) pregnancies, there are specific methods used to calculate this important milestone. Understanding your EDD is crucial as it helps in monitoring the development of your pregnancy and planning for the arrival of your baby. Estimating EDD without LMP For those who might not know their LMP or have irregular cycles, the EDD can still be estimated using  First Ultrasound Scan: An early ultrasound, often done between 6 to 12 weeks, can provide an accurate estimate of your due date. During this scan, measurements of the baby, specifically the crown-rump length (CRL), help in determining how far along the pregnancy is and estimating the due date. This method is widely used and considered reliable.

In the case of an IVF pregnancy, estimating the EDD is more straightforward due to the known elements of the conception process. Here's how it's done: Date of Embryo Transfer: In IVF treatments, the exact date of the embryo transfer is known. If you had a Day 5 embryo transfer (blastocyst transfer), your EDD is calculated by adding 261 days (or 37 weeks) to the transfer date. For a Day 3 transfer, add 263 days (or about 37 weeks and 2 days). Egg Retrieval Date: Alternatively, the EDD can be estimated based on the egg retrieval date. This method considers the egg retrieval day as the equivalent of ovulation in a natural cycle. Ultrasound Confirmation: Regardless of the method used, an early ultrasound is recommended to confirm the pregnancy's viability, number of embryos, and to fine-tune the EDD based on the embryo's development.

Frequently Asked Questions

You have a question? We have an answer.

How does our Pregnancy Due Date Calculator work?

If you're pregnant or planning a pregnancy, one of the first things you'll want to know is when your little one is expected to arrive. Our Pregnancy Due Date Calculator is here to help you mark that all-important date on your calendar. But how does it work? Let's break it down in simple terms, making sure you understand every step of the way.

Understanding the Basics

At its core, our calculator needs just one crucial piece of information from you: the first day of your last menstrual period (LMP). Why? Well, it turns out that this date is a key anchor in predicting when your baby is likely to be born. It's all based on a standard calculation used by healthcare professionals around the world.

The Calculation Explained

From the date you provide, the calculator adds 280 days (or 40 weeks). This number isn't plucked from thin air; it's grounded in medical research that shows it's the average length of human pregnancy. So, by counting 280 days from your LMP, we get an estimated due date (EDD) - the day your baby is likely to make their grand entrance.

How Accurate Is It?

While our Pregnancy Due Date Calculator gives you a good estimate, it's worth remembering that every pregnancy is unique. Factors like your menstrual cycle length and the baby's growth rate can influence the actual birth date. That's why health professionals often recommend an early pregnancy scan, which can provide a more precise EDD based on the baby's development.

What About IVF Pregnancies?

For those who've embarked on their pregnancy journey through IVF (In Vitro Fertilisation), the calculator is still a handy tool. Since IVF procedures have known dates (like when the embryo was transferred), the calculator adjusts its magic formula to work with these dates, ensuring you still get an accurate EDD.

How accurate is the EDD estimation from ultrasound?

The accuracy of the Estimated Due Date (EDD) from ultrasound is a pivotal concern in prenatal care, influencing a wide array of clinical decisions and maternal expectations. Ultrasound-based EDD estimation is renowned for its precision, particularly when performed in the first trimester of pregnancy. This period is considered the golden window for EDD estimation through ultrasound due to the uniformity of fetal growth across pregnancies, making early ultrasounds the most reliable method for dating a pregnancy.

First-trimester ultrasounds, typically conducted before 14 weeks of gestation, can predict the due date with an accuracy of +/- 5 to 7 days. The crown-rump length (CRL), which measures the length of the fetus from the top of the head (crown) to the bottom of the buttocks (rump), serves as the cornerstone for this estimation. Due to the standardised rate of fetal growth during these initial weeks, the CRL provides a precise benchmark for calculating the gestational age and, subsequently, the EDD.

The accuracy of ultrasound-based EDD estimations slightly diminishes as the pregnancy progresses. In the second trimester, the margin of error increases to approximately +/- 7 to 14 days. By the third trimester, the variability in fetal growth rates among different pregnancies can lead to an accuracy range of +/- 2 to 3 weeks. Despite this gradual decrease in precision, ultrasound remains a crucial tool for EDD estimation throughout pregnancy, offering significant advantages over other methods such as the date of the last menstrual period, especially when the menstrual cycle is irregular or the conception date is uncertain.

Moreover, ultrasound examinations provide additional benefits beyond EDD estimation, including the assessment of fetal growth, detection of congenital anomalies, evaluation of the placenta, and monitoring of the pregnancy's health. The integration of ultrasound in prenatal care exemplifies its indispensable role in modern obstetrics, facilitating informed clinical decisions, optimising maternal and fetal outcomes, and enhancing the antenatal care experience.

Use our Pregnancy Due Date Calculator to find out your EDD!

What if I already gone past my EDD as estimated by ultrasound or LMP, should I be worried?

Going past your Estimated Due Date (EDD) as determined by ultrasound or Last Menstrual Period (LMP) can be a source of concern for many expectant mothers, but it is a relatively common occurrence. It's important to understand that the EDD is an estimate, not a guaranteed delivery date. In fact, only about 5% of babies are born on their precise due date. Most babies are born within a week or two before or after the estimated due date, with a significant number arriving safely after this period.

If you have gone past your EDD, it's crucial not to panic. Here are several reasons why being past your due date is usually not a cause for immediate concern:

  1. Variability in Pregnancy Length: Every pregnancy is unique, and the length can vary. The EDD is based on a 40-week gestational period, starting from the first day of the last menstrual period, but this is an average rather than a rule.

  2. Accuracy of EDD: Both the methods of using LMP and ultrasound have their margins of error. Early ultrasound (in the first trimester) is generally more accurate than LMP for dating a pregnancy, but it's still an estimate with a margin of error.

  3. Natural Variation: There is a natural variation in the length of pregnancy. It's common for pregnancies to extend beyond 40 weeks, and most of these prolonged pregnancies result in healthy deliveries.

However, while it's often not a cause for immediate concern, ongoing monitoring is essential to ensure the continued health of both the mother and the baby. Healthcare providers typically recommend increased surveillance if a pregnancy extends too far beyond the EDD. This can include:

  • Non-stress tests to monitor the baby's heart rate and movements.
  • Amniotic fluid checks using ultrasound to ensure the baby still has enough amniotic fluid.
  • Biophysical profiles, which are more comprehensive exams that assess the baby's breathing, movement, muscle tone, heart rate, and amniotic fluid levels.

In some cases, if a pregnancy extends significantly beyond the EDD (usually beyond 41 or 42 weeks, depending on the healthcare provider's policies and the mother's health), induction of labour may be suggested. The decision to induce labour is based on the balance between the risks of prolonged pregnancy (such as increased risk for stillbirth, decreased amniotic fluid, and the potential for a larger baby, which can complicate delivery) and the readiness of the baby and the cervix for birth.

It's essential to maintain open communication with your healthcare provider if your pregnancy goes past your EDD. They can provide guidance, reassurance, and care tailored to your specific situation, ensuring the best outcomes for you and your baby. Remember, the goal is a healthy delivery, and sometimes that means waiting a bit longer for your little one to decide it's time to make an appearance.

What is classified as pre-term birth?

Pre-term birth, classified as the delivery of a baby before the completion of 37 weeks of pregnancy, is a critical concern in the field of obstetrics and neonatal care. Unlike full-term pregnancies, which culminate after 37 to 42 weeks, pre-term births occur when a baby is born prior to the 37th week, marking a significant deviation from the expected gestational period. This early delivery can lead to various health challenges for the newborn, including respiratory issues, digestive problems, and developmental delays, highlighting the importance of specialised care and attention for these infants.

Pre-term birth is further categorised into three subgroups based on the gestational age at birth: extremely pre-term (less than 28 weeks), very pre-term (28 to less than 32 weeks), and moderate to late pre-term (32 to less than 37 weeks). The categorisation helps healthcare professionals in tailoring the care and interventions necessary for the optimal development of pre-term infants, addressing the unique needs based on the degree of prematurity.

The causes of pre-term birth are multifaceted, encompassing a range of factors such as genetic predispositions, maternal health issues (e.g., infections, chronic conditions like diabetes or high blood pressure), lifestyle factors, and complications in pregnancy like preeclampsia or placental problems. Preventive measures and early detection of risk factors play a crucial role in mitigating the incidence of pre-term births, underscoring the importance of comprehensive prenatal care.

Addressing the health challenges associated with pre-term birth requires a multidisciplinary approach, involving obstetricians, neonatologists, paediatricians, and a host of other healthcare specialists. The management and care of pre-term infants are tailored to their specific needs, ranging from respiratory support for those with underdeveloped lungs to specialised nutritional support to promote growth and development.

Pre-term birth remains a leading cause of neonatal mortality and morbidity worldwide, making it a significant public health issue. The ongoing research and advancements in neonatal care continue to improve the outcomes for pre-term infants, emphasising the importance of access to quality prenatal and postnatal care in reducing the prevalence and impact of pre-term births.

What is the first scan offered by the NHS?

Your first scan with the NHS is likely to be the Nuchal Translucency/Dating scan at 11-14 weeks. This scan is predominantly designed to screen for the same chromosomal anomalies as NIPT using an older methodology developed in the 1990s. NIPT is a far more advanced test developed in 2011 with a much higher accuracy.

Most crucially, majority of NHS Trusts have no protocols for structural anomalies screening until ~20 weeks. Our scans are specially designed to screen for every anomaly detectable from an early gestational age and will improve the management of the pregnancy.

Learn more about our 10 week scan. Use our pregnancy due date calculator to get the best possible dates for your scans!

What is the earliest scan I can have during pregnancy?

A Viability Scan, also known as an early pregnancy scan, is an ultrasound examination that is usually carried out between 6 to 9 weeks of pregnancy. This scan plays a crucial role in confirming the presence of your baby's heartbeat, determining the number of babies you're expecting, and estimating the gestational age of your pregnancy, helping to establish a more accurate due date.

What Happens During a Viability Scan?

During a Viability Scan, a small ultrasound device called a transducer is either passed over your belly or, more commonly in early pregnancy scans, used internally via the vagina to get a clear view of your womb. The procedure is safe, painless, and non-invasive. The internal scan does not harm the baby or interfere with the pregnancy.

Why Is a Viability Scan Important?

  1. Confirmation of Pregnancy and Heartbeat: One of the primary reasons for this scan is to confirm the pregnancy is developing inside the womb and to detect the baby’s heartbeat. This can provide immense reassurance to expectant parents.

  2. Determine the Number of Babies: Whether you're carrying one baby, twins, or more can be identified during this scan.

  3. Assessing Pregnancy Viability: The scan assesses the health and viability of the pregnancy. It checks for any signs of an ectopic pregnancy (where the embryo implants outside the womb) and can help in identifying any early signs of potential complications.

  4. Estimating Gestational Age: The scan provides an estimation of how many weeks pregnant you are based on the size of the embryo. This helps in calculating a more accurate due date.

What Are the Outcomes?

Following a Viability Scan, you should have a clearer understanding of your pregnancy’s health status. Most parents find this early scan a comforting confirmation of their pregnancy's progression. However, if there are concerns, such as signs of an ectopic pregnancy or lack of heartbeat, your healthcare provider will discuss the next steps with you, offering support and advice on how to proceed.

What is the most common Zodiac sign in the world?

The most common Zodiac sign in the world is often considered to be Scorpio or Virgo, but this can vary depending on the birth rate in different months across different years. The birth rate can fluctuate significantly due to various factors, including cultural, social, and economic conditions that influence family planning decisions. Therefore, pinpointing the exact most common Zodiac sign globally with a specific number of people under that sign can be challenging without access to up-to-date and comprehensive birth data from all around the world.

However, it's generally noted that September (Virgo and part of Libra) tends to have a higher number of births in many countries, largely due to the timing of conception around holidays in December. This observation suggests that Virgo might be among the most common Zodiac signs, given its period from August 23 to September 22. If we assume a uniform distribution of births, which is admittedly a simplification, each Zodiac sign would have approximately 1/12th of the world's population. With the world population exceeding 7.9 billion people as of 2024, each sign would theoretically encompass around 658 million people. However, due to the aforementioned fluctuations in birth rates, the actual number for the most common sign could be slightly higher.

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