On average, pregnancy lasts 40 weeks (or 38 weeks from conception).

If one fetus develops and grows in the uterus, pregnancy is called a singleton pregnancy , and if it is a pregnancy with two or more fetuses, we are talking about a multiple pregnancy. Multiple pregnancies are generally considered to be at increased risk of complications.

Pregnancy can be determined in different ways – with urine tests, with blood tests and with an ultrasound examination (vaginal or transabdominal).  An urine or blood test are not enough to confirm pregnancy. A positive urine or blood test only indicates the presence of ß-hCG or PREGNANCY HORMONE, but they do not represent a guarantee that the pregnancy will continue or proceeded normally. Pregnancy is confirmed with an ultrasound examination and visualization of the fetus in the uterus.  

WHAT IS β-hCG?

Human chorionic gonadotropin or β-hCG is called the pregnancy hormone. It is secreted by the developing placenta shortly after the embryo implants in the uterus. The presence of β-hCG in the bloodstream shortly after conception and the subsequent increase in its concentration during early gestational development is an excellent indicator for early detection of pregnancy. The measurement of β-hCG in the blood serum is more accurate than the urine pregnancy test, as it shows the actual values ​​and their decline or rise, not just their presence.

What if β-hCG value is too low?

Two weeks after the embryo transfer, when the blood test is performed, the woman is somewhere between the 4th and 5th week of pregnancy. β-hCG values ​​for these weeks of pregnancy have a very large range. 

There is no normal or ideal value of β-hCG and no value can clearly predict a successful or unsuccessful course of pregnancy. However, values ​​below 100 IU/L measured two weeks after embryo transfer usually do not indicate a good prognosis. 

Much more than the first measured value of β-hCG, the increase or duplication of value. Within 48 hours, a satisfactory increase in value by at least 66% is expected, and the value is expected to double every 48-72 hours. In the case of (too) low values, it makes sense to repeat the blood test in 2 to 3 days and closely monitor the development of the pregnancy.

What if β-hCG value is too high?

If the β-hCG values ​​for a certain gestational age or weeks of pregnancy significantly higher than expected (e.g. 100,000 IU/L and more), a molar pregnancy is suspected .

The value of β-hCG reaches its peak 1-2 weeks before the end of the first trimester of pregnancy (12 weeks) and then begins to decline in the second trimester.

Table of increasing β-hCG values ​​by weeks of pregnancy:

URINE PREGNANCY TESTS

Urine pregnancy tests are a simple and accurate way that a woman can confirm pregnancy at home. The test only needs to be soaked with urine – a stick or the slip is placed under a stream of urine or placed in a glass containing a urine sample.

Pregnancy tests are available in different forms, have different sensitivity and display results in different ways (two parallel lines, plus, text, weeks of pregnancy, etc.). They are available in most specialty stores, drugstores and pharmacies.

Pregnancy tests detect the presence of β-hCG in the urine. The most sensitive tests detect as little as 10 mIU/ml, but most will clearly show pregnancy at values ​​higher than 25 mIU/ml.

When should a woman take a urine pregnancy test?

In the case of spontaneous conception (which also includes conception after IUI), the pregnancy test should be performed after the absence of menstruation, despite the fact that some test manufacturers promise reliable results by testing several days before the absence of menstruation. If a woman has irregular cycles, it is recommended that she take the test 3 weeks after the last sexual intercourse or 3 weeks after the supposed onset of ovulation/fertile days.

In the case of conception after IVF, a woman can take a pregnancy test on the 9th day after the transfer of a 5-day-old embryo (blastocyst) or day 11 after transfer of a 3-day-old embryo . Taking the test earlier is not recommended, as the β-hCG values ​​are usually not yet high enough.

How accurate are pregnancy tests?

Urine pregnancy tests are accurate (99%) assuming they are used correctly. 

A pregnancy test will be less accurate if it has expired or if it is not used correctly. Therefore, it is always necessary to check the expiration date on the packaging and carefully read the instructions that come with the pregnancy test.

Despite their accuracy, urine tests are a limited indicator of pregnancy. To confirm pregnancy or to confirm the normal course/development of pregnancy, especially in MAR procedures, a blood test is required, and later an ultrasound examination for confirmation.

BLOOD TEST TO CONFIRM PREGNANCY

In spontaneous pregnancies a blood test to confirm pregnancy is rarely performed, usually:

• in case of prolonged unexplained absence of menstruation and negative urine tests
• urine tests with unclear results 
• in the event of unusual bleeding or unusual course, pregnancy complications (to rule out ectopic, molar pregnancy, etc.)

On the contrary, in the process of fertilization with medical assistance (MAR), after the transfer of the embryo, the woman reports to the clinic in about 14 to 16 days to take a blood test to check the presence or value of pregnancy hormone. This is an extremely important step in the entire MAR process. Even if most laboratories value the blood test as positive already at values ​​above 5-10 IU/L, infertility clinics set this level a little higher and talk about pregnancy only if the result is 40 IU/L or more.

PREGNANCY CONFIRMATION WITH ULTRASOUND EXAMINATION

The importance of the first ultrasound examination

Regardless of the method of conception (spontaneous or through the MAR procedure), the first ultrasound examination represents an important milestone in every pregnancy. Its purpose is primarily to confirm pregnancy inside the uterus. 

Women who become pregnant through MAR procedure will usually have their first ultrasound examination between the 7th and 8th week of pregnancy and will have it performed at an infertility clinic. All subsequent ultrasound and systematic examinations are performed by their chosen gynecologist.

Women who conceive spontaneously are usually scheduled for their first ultrasound examination between the 9th and 10th week of pregnancy, unless there is a need for an earlier examination due to complications.

What is determined by the first ultrasound examination?

Depending on the weeks of pregnancy at the first examination:

• the presence, size and shape of a gestational sac (or multiple gestational sacs)
• the presence, size and shape of the yolk (a round structure that supplies the embryo with nutrients until the placenta develops)
• the presence and size of the fetus or fetal echo
• the presence of a fetal heartbeat

During the 4th week of pregnancy (at the onset of a missed period or a positive pregnancy test), pregnancy cannot be detected by ultrasound, but a thickened uterine lining can be observed.

Gestational sac

The display of the gestational sac is the earliest ultrasound display or pregnancy detection. It appears as an echogenic ring surrounding a clear center. Even with an ectopic pregnancy, the gestational sac can be identified by ultrasound, even if the pregnancy is not in the uterine cavity.

The gestational sac first appears at about 4 weeks gestational age and grows at a rate of about 1 mm per day until the 9th week of pregnancy. It can be detected on ultrasound towards the end of the 5th week of pregnancy.

Yolk

As pregnancy progresses, the next structure to become visible on ultrasound is the yolk sac. It is a round structure with a bright edge.

The yolk first appears in the 5th week of pregnancy and grows to a maximum of 6 mm. A yolk larger than 6 mm usually indicates an abnormal pregnancy. 

When the size of the gestational sac is 12 mm or more, the absence of yolk usually indicates a failed pregnancy.

Fetal heartbeat

With a transvaginal ultrasound examination, the heart activity of the fetus is often detected even before the cell mass, the mass of the fetus, can be determined. The fetal heart muscle begins its rhythmic contraction very early, and this rhythmic movement can be seen at the edge of the yolk. At first, the heart rate of the fetus is slower (60-90 beats/minute) and increases with the further development of the fetus. For early pregnancy, the value of the heartbeat is less important than its presence or absence. 

Sometimes, during a normal pregnancy, the fetal pulse is not detected until the fetus is at least 4 mm long. If cardiac activity is not detected in a fetus greater than 4 mm in length, the prognosis is not good. 

Echoes of the fetus

Fetal echoes represent a mass, a collection of fetal cells separated from the yolk and first appear on a transvaginal ultrasound immediately after the 6th week of pregnancy. This mass of cells is known as the fetal echo and indicates the development of the embryo. 

From the 6th week of gestation, the fetus grows at a rate of about 1 mm per day. Based on this, in early pregnancy, the gestational age can be determined with a simple calculation – the measured length of the fetal echo is added or adds 6 weeks of pregnancy. Thus, a fetal echo measuring 5 mm represents a gestational age of 6 weeks and approximately 5 days.

Fetal Length (CRL)

In early pregnancy, the fetus is in a coiled position, so measuring its length from head to toe is impossible. Instead, the length from head to rump (CRL = crown-rump length) is measured. 

The CRL measurement is a reproducible and most accurate measure of gestational age. After 12 weeks, the accuracy of CRL in predicting gestational age decreases and is replaced by biparietal measurement of fetal diameter.

In the first weeks of pregnancy, depending on earlier or later fertilization or earlier or later implantation of the embryo, deviations of only a few days show very different pictures. In case of unfavorable signs, a follow-up ultrasound examination is always necessary in about a week to determine the actual situation and the direction in which the pregnancy is leading.

Indicative values ​​that indicate a healthy pregnancy development: