The World of Pregnancy

When Did I Conceive my Baby?

Finding out you are pregnant is a unique moment. In the next 9 months of pregnancy, your life will be filled with lots of unexpected moments. Various questions like “When did I conceive my baby?” will most likely pop up in your mind. when did I conceive my babyNormally, you would think that an online conception calculator would probably be able to offer the answer you want, but these things aren`t as reliable as you may hope.

The gestational age is calculated starting with the first day of your menstrual period. Because most of the times the conception date isn`t exactly known, it`s better if you`ll use the first day of the last menstrual period as a reference point.

When Did I Conceive My Baby?

When did I conceive based on last period? If you have a regular period and you know when it was the first day of your last menstrual period, questions like “What day did I conceive?” should not remain unanswered because you`ll be able to use this information to calculate the age of your pregnancy. Thus, the calculation isn`t made by using the date of ovulation. This will mean that although you might not have been pregnant at that moment, the first 2 weeks of the last menstrual period are taken into consideration.

When did I get pregnant based on ultrasound? The age of the fetus can be measured by ultrasound starting with the 5 or 6 week since the first day of the mother`s last period. This measurement can be even more exact with less time passed from the conception date and becomes less precise as the pregnancy evolves. The best period to determine the age of the pregnancy using ultrasound is between weeks 8 and 18. The most exact calculation method is by using the first date of the last period and confirming this date using the measurements obtained from ultrasound.

When Did I Conceive my Baby Based on Due Date? To calculate this date, the doctor will add 40 weeks or 280 days since the first day of the last menstrual cycle, or will add 7 days since that date minus 3 months. This is only an estimation – only 5% from all babies are born at the exact estimated due date.

Calculating your Pregnancy Weeks

How does the doctor calculate your pregnancy weeks? The usual 40 weeks of pregnancy start with the first day of your last period. Even though you may not have been pregnant, most doctors start the calculation of your pregnancy weeks with the beginning of the month and most probably with the 14th day from your last menstrual cycle. Still, the age of the pregnancy and the age of the embryo are 2 different things. The age of the pregnancy is usually 2 weeks bigger than the embryo`s age.

Talk to your doctor if you don`t know the first day of your last period. It`s important to know when was your first pregnancy week and the probable conception date, and your doctor can help you on this matter. Also, besides attempting to calculate a week of pregnancy mathematically, your doctor can use laboratory tests and tools to measure your hormones and find out in how many weeks you are pregnant or when you have conceived.

A doctor can evaluate and measure the uterus. Your doctor will be able to measure the distance between the pelvic bone and the top part of the uterus. Usually, the number of the centimeters will be the same as the number of the actual pregnancy weeks. For instance, in case your uterus measures 12cm, you are in the 12 weeks pregnant.

The heartbeats of the fetus. The first beats of his heart will be heard between the 9th and 12th weeks of pregnancy with a fetal Doppler monitor that will help assess the baby`s health. With it, the doctor can measure blood flow in various parts of his body, like brain, heart or umbilical cord.

When Did I Get Pregnant Exactly?

Last Menstrual Cycle: Women with an irregular period will find it rather difficult to estimate the age of the pregnancy with this method, and it will be the same with women who cannot remember the first day of their last period. In such cases, the age of the pregnancy is calculated by ultrasound.

The Development of the Fetus: In some situations it`s difficult to determine the age of the pregnancy because the fetus is either too small or too big for his gestational age. Also, sometimes the size of the uterus in early pregnancy or its height in late pregnancy don`t correspond with the first day of the last menstruation. In such cases, it`s pretty hard to calculate the age of the pregnancy precisely.

Normal Pregnancy: For women with a regular menstrual cycle, the conception takes place usually between the 11 and 21 day since the first day of the last period. Most women aren`t exactly aware of the date of ovulation and therefore, the conception date is simply estimated this way.

Special Cases: Women who practiced special procedures of fertilization, such as artificial insemination or IVF (in vitro fertilization), are aware of the exact date of the conception.

Due Date Calculator


If the above information doesn`t offer you the answers you need, the best way to find answers to questions like “When did I conceive my baby?” is to contact your doctor. He`ll be the only one who can tell you 100% if you are pregnant or not.

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4 Responses to When Did I Conceive my Baby?

  • I need advice. Is it possible for me to be pregnant I’m 42 yrs. Old n my tubes were tied 6 years ago. My last period was February 23,2017. My breasts hurt n have white stuff n itchy n sore. My belly is bigger. I’m nauseous n cry alot. Took a pregnancy test n was negative. Plz help

  • i would like to know if am preg or not please

  • I had a one night stand on april 19 could this person be the possible farther because this is saying i concieved on april 23 but I have a boyfriend and we’ve together everyday since April 20 is my boyfriend the father or one nightstand man

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