The baby's waiting time is magical. Parents are preparing for his appearance, dreaming that the child was born healthy. During pregnancy, a woman needs to do numerous examinations to monitor the development of the baby. One such study is screening.
Many mothers, not understanding the essence of this analysis, relate to it with apprehension and distrust. They ask questions - what kind of analysis is it when they do screening during pregnancy, does it hurt? Answers to these questions can be given by the attending physician, explaining in detail all the nuances of the procedure. But it is important for each mother to remember that the prescribed procedures should not be neglected. So what is pregnancy screening?
Screening Definition
Pregnancy screening, called perinatal, is a set of diagnostic procedures that can indicate possible abnormalities in the fetal development. This procedure prevents the development of certain diseases and helps to diagnose them early, when treatment is most effective.
The first screenings during pregnancy are free of charge strictly for a period of 11-13 weeks. If the study was conducted for a period of 14 weeks, then the results may be inaccurate. In the second and third trimester, the analysis is assigned according to the results of the first screening. In the event that the tests did not reveal malformations, repeated tests can be taken on their own on a paid basis.
If during screening the risks of such dangerous pathologies as
- Down syndrome
- Edwards syndrome
- neural tube defects - anencephaly (complete or partial absence of the brain), hydrocephalus, etc.,
- Patau syndrome
- triploidy
- abnormalities in the development of the spine, digestive tract, kidneys, etc.,
a pregnant woman is referred to a geneticist who will decide on a further examination of the expectant mother.
Indications for the study
Screening is mandatory for women who are at risk. Indications include:
- age from 35 years
- hereditary diseases
- alcohol and / or drug abuse
- the use of drugs prohibited during pregnancy,
- viral infections
- miscarriages and / or missed pregnancies in the past,
- if fetal malformations were found during past pregnancies,
- work in hazardous industries,
- close family ties between parents.
Screening Methods
Perinatal screening includes ultrasound diagnosis, a biochemical blood test. If the two previous methods have identified high risks of abnormalities, then the invasive method (amniocentesis, chorionic biopsy) can be used.
Ultrasound screening during pregnancy reveals the external features of the fetus and chromosomal abnormalities. Includes, in addition to the main study, Doppler ultrasound and cardiotocography.
A biochemical analysis is done to identify certain proteins in the mother’s blood, which may indicate pathologies.
First screening
The timing of the first screening during pregnancy falls at the end of the first trimester. It is usually performed from 11 weeks to 13 weeks and 6 days. It is recommended that this examination be carried out in the middle of this range.
The examination includes ultrasound diagnostics and analysis of venous blood for the presence of specific markers in the blood. The first screening is the most significant and informative for identifying risks. Such important indicators as the size of the collar zone, the coccygeal-parietal size of the fetus and the level of certain hormones in the blood serum allow the most accurate and reliable determination only at this stage of pregnancy.
Ultrasound of the first screening is a diagnosis of fetal development pathologies. The physical development of the fetus, its blood flow, is established. You can already see the bones of the skull, facial bones, brain and the development of internal organs. The doctor also looks at the condition of the uterus, placenta, umbilical cord, the amount of amniotic fluid.
Screening Standards for Pregnancy in the First Trimester
Norms of ultrasound examination| Index | 10 weeks | 11 weeks | 12 weeks | 13 weeks |
| KTR, mm | 33 - 41 | 42 - 50 | 51 - 59 | 62 - 73 |
| TVP, mm | 1.5 - 2.2 | 1.6 - 2.4 | 1.6 - 2.5 | 1.7 - 2.7 |
| BPR, mm | 14 | 17 | twenty | 26 |
| Heart rate, beats / min | 161 - 179 | 153 - 177 | 150 - 174 | 147 - 171 |
| Nasal bone, mm | determined by the bones of the nose | determined by the bones of the nose | no more than 3 | no more than 3 |
Definition of values:
KTR - coccygeal-parietal size of the fetus. Allows you to determine the correspondence of the size of the baby with the gestational age and set the estimated date of birth. Normally, KTR should coincide with the obstetric gestational age. But it is worth remembering that due to some possible nuances (for example, late ovulation), the obstetric period is not always calculated absolutely accurately. It is necessary to consider all screening indications in general.
TVP - the thickness of the collar space. The fetus at these times on the back of the neck has a skin fold in which fluid accumulates. The study measures the thickest part of the collar space. This is a very important indicator, which can be used to judge the presence or absence of genetic diseases, such as Down syndrome.
BDP - measured the distance between the temples. An increase in normal values may indicate brain diseases (hydrocephalus, brain hernia).
The size of the nasal bone is a very important indicator by which it is possible to detect the presence of Down syndrome.
Heart rate - heart rate.
The second type of study used in the first trimester screening is a biochemical blood test. It is usually performed after an ultrasound scan. The analysis reveals the values of two indicators in the blood serum of a pregnant woman - this is human chorionic gonadotropin (hCG) and PAPP-A - plasma protein A.
The norms of biochemical blood tests at the first screening| Index | 10 weeks | 11 weeks | 12 weeks | 13 weeks |
| HCG, honey / ml | 20000 - 95000 | 20000 - 95000 | 20,000 - 90,000 | 15,000 - 60,000 |
| PAPP-A, honey / ml | 0.45 - 3.73 | 0.78 - 4.77 | 1.03 - 6.02 | 1.47 - 8.55 |
Definition of values:
HCG is lowered - it can be a threat of miscarriage.
HCG is greatly increased - the risk of Down syndrome. But this indicator will also be increased with multiple pregnancy.
PAPP-A lowered - may indicate a genetic disease of the fetus.
PAPP-A is elevated - does not indicate pathology.
Important! In a multiple pregnancy, a biochemical blood test at the first screening is not so accurate for identifying the risks of malformations than in a single pregnancy. In this case, the results are evaluated only by a competent specialist, together with the results of ultrasound.
Actions for poor first screening rates
It is important to understand that screening is a study that indicates the likelihood of any pathology. If his results indicate this, you should contact a qualified geneticist as soon as possible for further examination. In such cases, additional studies are recommended - amniocentesis or choriocentesis. But first, you need to discuss all the risks with your doctor. Especially if these tests are recommended for multiple pregnancies, because in this case the possibility of a miscarriage from this intervention is higher than with a single pregnancy.
Also, the result of a blood test can be affected by diabetes in the mother, obesity, pregnancy with the help of IVF, etc.
An additional way to recheck the results is screening of the second trimester.
Remember that even with poor forecasts, there is a chance to give birth to a healthy baby.
Second screening
The second screening during pregnancy is carried out in the second trimester. This analysis is not mandatory, but it is necessary if there were deviations in the results of the first. The timing of screening during pregnancy varies slightly during this period. A biochemical blood test is recommended for periods of 16-20 weeks, preferably at 17-18 weeks. Ultrasound examination is a little later, the period of 22-24 weeks is considered the optimal time. Second-trimester screening is also performed for women who have been infected with infectious diseases during pregnancy. All other indications are similar to the indications for analysis in the first trimester.
Sometimes an ultrasound scan is enough. In this case, a biochemical blood test is not performed.
Ultrasound in the second trimester is very informative. The baby has grown, most organs are well visualized. During this period, much attention is paid to:
- The volume of the head, abdomen, chest. Based on these indications, fetal development and pregnancy maturity are determined.
- The brain (cerebellum, ventricles). The diameter of the large brain cistern should not exceed 10 mm, as this indicator may indicate hydrocephalus.
- Face (special attention is paid to the nasolabial triangle and the orbits).
- Spine (check for the presence of hernias, other neoplasms, as well as for non-closure).
- The kidneys, bladder, and other internal organs.
A biochemical test of venous blood in a second screening during pregnancy is called a “triple test”, since an analysis is made of the amount of three hormones in the blood serum:
- HCG.
- Free estriol is a hormone that is first produced by the placenta, and then by the baby’s liver. This is one of the main hormones during pregnancy. It plays an important role in the development of blood flow in the vessels of the uterus. If its value is reduced, this may indicate malformations of the child.
- Alpha-fetoprotein (AFP). The main function of this hormone is to protect the fetus from the mother’s immune system. It also helps your baby get certain fats and proteins.
- A study of the level of inhibin A in the blood is required if the picture is unclear from the results of other parameters. It is considered only in conjunction with the values of other hormones. May indicate chromosomal abnormalities.
Second Screening Standards
Norms of ultrasound examination| Index | 16 weeks | 17 weeks | 18 weeks | 19 weeks | 20 weeks | 21 weeks |
| abdominal circumference, mm | 88 - 116 | 93 - 131 | 104 - 144 | 114 - 154 | 124 - 164 | 137 - 177 |
| head circumference, mm | 112 - 136 | 121 - 149 | 131 - 161 | 142 - 174 | 154 - 186 | 166 - 200 |
| femur length, mm | 17 - 23 | 20 - 28 | 23 - 31 | 26 - 34 | 29 - 37 | 32 - 40 |
| fronto-occipital size, mm | 41 - 49 | 46 - 54 | 49 - 59 | 53 - 63 | 56 - 68 | 62 - 71 |
| BPR, mm | 31 - 37 | 34 - 42 | 37 - 47 | 41 - 43 | 43 - 53 | 46 - 56 |
| humerus length, mm | 15-21 | 17 - 25 | 20 - 28 | 23 - 31 | 26 - 34 | 28 - 35 |
At this stage of fetometry, much attention is paid. By measuring the lengths and sizes of parts of the baby’s body, one can judge the correct development in accordance with the gestational age. There is also the possibility of eliminating dysplasia, which at these dates is already possible to detect.
Very carefully considered
- the brain - for the presence of formations and tumors,
- heart - the structure and presence of abnormalities in the development of the entire cardiovascular system,
- internal organs - their presence, structure, location.
In addition to examining the fetus, the doctor carefully examines:
- The placenta - its location (in the future may affect the method of delivery), thickness (a very important indicator that can talk about intrauterine infection), maturity and structure (heterogeneity may be a sign of infection).
- The umbilical cord is the number of vessels in it. Normally, there should be three vessels - two arteries and one vein. A decrease in their number is the likelihood of fetal hypoxia and the presence of chromosomal diseases.
- Amniotic fluid volume. Their index is normally 10-20 cm.
- The condition of the uterus. Tone is detected, the neck length is measured (if it is short, there is a risk of premature birth).
Norms of biochemical analysis in the second screening| Index | 16 weeks | 17 weeks | 18 weeks | 19 weeks | 20 weeks |
HCG, honey / ml | 10000 - 58000 | 8000 - 57000 | 8000 - 57000 | 7000 - 49000 | 1600 - 49000 |
| AFP, units / ml | 15 - 95 | 15 - 95 | 15 - 95 | 15 - 95 | 27 - 125 |
| Estriol, nmol / L | 5,4 - 21 | 6.6 - 25 | 6.6 - 25 | 7.5 - 28 | 7.5 - 28 |
AFP increased - may indicate a violation of the development of the neural tube, abnormalities in the development of the liver and digestive system, etc.
AFP is reduced - there is a risk of fetal chromosomal diseases. Sometimes this indicator happens when the pregnancy is incorrectly determined.
HCG increased - multiple pregnancy, diabetes mellitus, Down syndrome.
HCG is lowered - the threat of interruption, an undeveloped pregnancy.
Estradiol is elevated - multiple pregnancy or large fetus.
Estradiol is lowered - chromosomal diseases, pathology of the adrenal glands, placental insufficiency, intrauterine infections, impaired brain development.
Note that the results of hCG and AFP levels are very difficult to correctly decipher during multiple pregnancy .
Third screening
The third screening during pregnancy falls in the third trimester. It is recommended for all pregnant women, especially if there were deviations in the results of the first and second screening. This study includes ultrasound diagnostics, dopplerometry and cardiotocography. Pregnancy screening dates in the third trimester for 32-34 weeks. Based on its results, a decision is made on the most likely method of delivery.
Dopplerometry allows you to check blood flow in the blood vessels of the baby, uterus and placenta. Based on the results of this examination, it is possible to judge the presence of hypoxia in the fetus.
Cardiotocography - records the heart rate. It can also diagnose hypoxia in the baby.
Ultrasound examination includes the measurement of the parameters of the child, the development of its internal organs, the position in the uterus, the presence of cord entanglement. The condition of the placenta, appendages, uterus, amniotic fluid volume is also checked.
Third Screening Standards
Ultrasound norms for 32 - 34 weeks of pregnancy| BPR, mm | LZR, mm | Exhaust gas mm | Coolant mm | Shin bone length, mm | Shoulder length mm | Forearm length, mm | Thigh length mm | Body weight, gr | Norm CTG, points |
| 85-89 | 102-107 | 309 -323 | 266-285 | 52-57 | 55-59 | 46 - 55 | 62-66 | 1790-2390 | 8-12 |
- The thickness of the placenta: at 32 weeks - from 25.3 mm to 41.6 mm; at 34 weeks - from 26.8 mm to 43.8 mm.
- The length of the cervix is at least 3 cm.
- Placenta of the first or second degree of maturity.
- The amniotic fluid index is 81-278 mm.
If the estimated body weight of the baby is more than normal, the doctor may advise you to make the ultrasound again closer to the birth. Based on its results, a decision will be made on natural childbirth or Caesarean section.
With abnormalities in Doppler ultrasonography, drugs are prescribed to improve blood circulation or the issue of delivery is raised.
A strong increase in amniotic fluid may indicate intrauterine infection or diabetes in the baby.
Screening Preparation
Before screening, it is necessary to fulfill a number of conditions in order to exclude unreliable results:
- Come on an empty stomach for a blood test. Or at least not earlier than 4 hours after eating.
- In a couple of days, introduce a diet that excludes carbonated drinks, seafood, fatty, smoked foods, chocolate, or limit their use.
- Refrain from sexual intercourse.
- Mom’s positive attitude is very important.
- It is worth moving the screening to another day if the mother is sick or if there is even a slight increase in body temperature. This can distort the test results.
Often women ask themselves which screenings during pregnancy are free and which ones will have to be paid for. The first screening is free, ultrasound, Dopplerography in the second and third trimester are also free, but you will have to pay for a biochemical blood test, even if there are indications.
There are always some errors in the form of individual characteristics of mom and dad. In this case, some deviations from the norm in the results will not talk about any deviations in the development of the baby. It happens that with poor forecasts, an absolutely healthy baby is born.
If a congenital defect is detected, thanks to the development of medicine, pathologies can be minimized, and sometimes even cured, of the baby. The main thing is not to forget how many weeks screening during pregnancy is carried out in each of the trimesters, so that the results are as true as possible. And at the slightest deviation from the norms, immediately contact a geneticist who will prescribe a further examination.
In conclusion, I want to say that screening results are not a sentence. The analysis only helps to identify possible risks in order to take action in time. To conduct it or not is up to you. In any case, you need to hope for the best.