Answering the question of when a pregnancy begins is not always simple. Pregnancy starts when a female has ovulated, the egg meets sperm, and fertilization occurs. This generally takes place in the fallopian tubes and is not something we are aware of when it happens. If you are unsure of your conception date, this article will help to explain your options.
The timing of ovulation during the menstrual cycle differs from person to person. Most women ovulate around day 14, but it’s possible to ovulate anywhere between days 11 and 21. The egg remains viable for about twenty-four hours after being released from the ovary. Sperm can survive in the uterus and fallopian tubes for up to 7 days, which means it’s possible to conceive days after intercourse. All these factors make it very hard to pinpoint an exact date of conception.
Determining the gestational age of your baby is usually important for parents. It’s normal to want to know when you can expect the arrival of your bundle of joy. But gestational age is about more than determining your baby’s due date. Knowing the gestational age of a fetus helps to guide prenatal care. Healthcare providers want to pinpoint gestational age so they can accurately assess the growth of the fetus throughout the pregnancy, schedule checkups and prenatal screenings at the appropriate intervals and treat any conditions that may cause preterm birth.
Let’s learn different options when you are unsure of conception date.
Option #1: Human Chorionic Gonadotropin (hCG)
Human chorionic gonadotropin is otherwise known as the pregnancy hormone because even though this hormone can be present in your body at any time, the levels increase sharply early in a pregnancy. It is the hormone that a prenatal paternity test is typically designed to detect.
However, a blood test is the most accurate way to determine hCG levels. This is because there is more hCG present in blood than in urine. Blood tests are also more sensitive and can detect HCG at a much lower threshold. Your healthcare provider can usually estimate your baby’s gestational age by determining the hormone level in your blood. They can also track if pregnancy is progressing as expected by measuring the hormone level as it rises over time.
Option #2: Last Menstrual Period (LMP)
Because it is nearly impossible to pinpoint the exact date of conception, most healthcare practitioners will estimate your due date based on your LMP. On average, a menstrual cycle is 28 days long, and ovulation generally occurs around the 14th day.
However, if your cycle is shorter or longer than twenty-eight days, using LMP to determine the due date may be less accurate. To calculate your due date using your LMP, count 280 days from the first day of your last period.
Option #3: LMP Unknown
If you can’t remember when your last period started, or if your periods are irregular, it will be more difficult to determine your conception date and due date using the LMP calculations. In this case, your best option will be to get an ultrasound done to determine how far along your pregnancy is.
Option #4: Ultrasound
Ultrasounds are very helpful and, generally, an accurate way to determine your estimated due date. This is because an ultrasound allows the direct observation and measurement of the fetus. In early pregnancy, how a fetus grows and develops is relatively standard.
When you get an early ultrasound done, the technician will measure the crown-rump length of your baby. If the ultrasound occurs later in pregnancy, many measurements will be taken, including that of your baby’s head, abdomen, and thigh bone. These measurements help them to determine how many weeks along the pregnancy are. When an ultrasound is done in the first trimester, it is reasonably accurate at dating the pregnancy.
Option #5: In Virto Fertilization Pregnancy (IVF)
If you conceived through IVF, your practitioner would use the date of your transfer to determine your baby’s due date. This is just like the calculations done when using LMT, except when you have undergone IVF and embryo transfer, the due date will be two weeks shorter since there is no need to account for the last period or time of ovulation.
Instead, following the due date is calculated based on the age of the embryo, which is typically transferred at either day three or day five post-fertilization. The due date from an IVF procedure can be more accurate than a naturally conceived pregnancy since the actual date of conception is known.
Even after using the above methods to determine your due date, it’s essential to understand that it is only an estimate. The exact timing of your baby’s birth is impossible to predict; only about four percent of babies are born on their due date. It isn’t anything you need to be concerned about, though, as babies are considered term anywhere between 37 and 42 weeks of pregnancy.