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In this article:
Key takeaways at week 13
Baby's development at week 13
3D anatomy views
Pregnancy symptoms this week
Your body at 13 weeks
Tips for week 13
Checklist for week 13
The end of week 13 is the end of the first trimester! We’re not just talking about getting through those work meetings without falling asleep (or puking), we’re talking about how you’re now 1/3rd of the way through your pregnancy! At 13 weeks pregnant, you’ve grown a fetus that has vocal cords, teeth and even fingerprints (wow!), and you’ve probably kept this incredible news (mostly) secret while wishing you could shout it from the rooftops—or, at the very least, use it as an excuse for getting to work late.
Watch Week 13 Highlights
That little cutie of yours is growing fast as you approach the second trimester. Here’s what you can expect.
At 13 weeks, baby is as big as a lemon. Your 13-week fetus is about 2.9 inches long and weighs about .81 ounces, and proportion-wise, their head is now about 1/3 the size of the body instead of 1/2.
At 13 weeks pregnant, you're three months pregnant, although doctors track pregnancy by week, not month. This is the last week of the first trimester. (We can’t say it enough because it’s so great to be here!)
A 13-week ultrasound could detect baby’s sex, but since it can be pretty tough to make out little boy or girl parts, your doctor will probably wait until the mid-pregnancy ultrasound (around 18 to 22 weeks), when it will be much more obvious, to look and see whether you’re having a girl or a boy.
If you’ve chosen to have prenatal cell-free DNA testing, also known as non-invasive prenatal testing (NIPT), to screen for chromosomal abnormalities, you’ll be able to find out the sex when you get your results. Hey, at 13 weeks, you may already know! Oh boy! (Or girl!)
You might notice that around 13 weeks pregnant, your symptoms change a bit. You might actually be able to get through the day without nausea (if not now, soon) or feeling the need to nap. But you may be experiencing a few of these 13 weeks pregnant symptoms too:
You can see all those blue streaks and spider veins under your skin because you have increased blood flow.
The second trimester is known as the least symptomatic and the most energetic. As you start to feel more like yourself and get that energy surge, you’re going to want to knock a bunch of to-dos off your list. Also, if you’ve found yourself too sick and tired to exercise lately, now’s the time to get back to a fitness routine.
Exercise will only benefit you and baby and can even make labor easier. Worth it!
If you’re one of those lucky pregnant women who feels up for a roll in the hay at 13 weeks, enjoy! You may notice a bit of post-coital spotting during pregnancy at 13 weeks. A little spotting is normal simply because your cervix is more sensitive. But heavy bleeding (like a period) isn’t, so call your doctor if it’s more like a flow. Otherwise, you and your partner can use your increased sex drive to enjoy some together time before baby arrives!
Sorry, twin moms-to-be. If you’re 13 weeks pregnant with twins, you might still be experiencing some morning sickness and fatigue. That’s because twin moms can have more of the pregnancy hormone hCG in their systems. If your nausea and vomiting is super severe, definitely bring it up to your OB. If you’re able to hold down food and liquids but you’re still feeling ill, just wait it out a little longer.
At 13 weeks pregnant, you’re turning the corner and may even feel like a new woman after a first trimester of morning sickness, fatigue and other issues.
You may experience 13 weeks pregnant symptoms, as well as some indigestion, achiness and tiredness that’s typical in the first trimester. Expect to feel a lot more at ease in the second trimester!
Your uterus is now big enough that it’s growing up and out of your pelvis. That means you’re starting to actually look pregnant. Finally, right? Expect to look more and more pregnant from here on out, because carrying a 13-week fetus calls for a weight gain increase. OBs recommend you gain weight in the healthiest way possible—that means slowly and steadily throughout your pregnancy. Here are the weight gain guidelines outlined by the American College of Obstetricians and Gynecologists (ACOG):
If you’re underweight (BMI under 18.5):
If you’re normal weight (BMI of 18.
5 to 24.9):
If you’re overweight (BMI of 25 to 29.9):
If you’re obese (BMI of 30 and above):
If you’re 13 weeks pregnant with twins:
Of course, you don’t want to stress yourself out about these numbers. What’s important is that you’re eating a healthy diet full of a variety of different foods, eating about 300 extra (nutritious) calories per day more than you did pre-pregnancy and getting plenty of exercise.
You’re probably feeling great in terms of nausea and morning sickness! However, to make room for your fast-growing 13-week fetus, your uterus is moving upward and outward. This expansion can cause stretch marks and itchy belly skin. Don’t forget to moisturize and eat well to keep skin soft and supple!
Possibly! It’s different for everyone, but some women (particularly those who have been pregnant before) may start to feel those telltale movements when baby’s at 13 weeks. If you haven’t felt the first flutters yet, don’t worry—it can take up to 25 weeks along to feel what’s called “the quickening.
”
It's debatable how much one's calorie needs actually increase during pregnancy, because the data shows that it varies widely between women (though usually in the ballpark of 300 to 500 calories extra). One researcher suggests that the adage of ‘eating for two’ be replaced with ‘eating for 1.1’ to better reflect the moderate increase in calories per day. Focus on nutrient-dense foods, so every bite is as packed with nutrition as possible.
Lily Nichols
RDN, CDE, registered dietitian, nutritionist and certified diabetes educator
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Left untreated, a urinary tract infection can potentially travel to the kidneys and pose a health risk for Mom and baby. If you need to use the bathroom more often than usual, feel burning during urination or it looks or smells unusual, visit your doctor, who can test for bacteria and prescribe antibiotics.
When you’re carrying a baby at 13 weeks, your body needs all the support it can get. Your pelvic floor can weaken from pregnancy and labor, but you can do Kegel exercises to strengthen the area. They don't take a lot of time or effort, and a regular routine during pregnancy can pay off with less urinary leakage after you give birth and enhanced sexual sensations. Sounds good!
You and your partner may be hot and heavy between the sheets right now, but have some fun outside the bedroom too, so you can spend quality time with each other before baby makes three.
No more morning sickness? Breakfast is served! It’s the perfect time to get calcium, protein and the powerful nutrients that come from produce and whole grains. A healthy morning meal can also help you set the tone for nutritious eating for the rest of the day.
Reminders for the week:
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At 13 weeks pregnant, you’re about to begin what is sometimes called the honeymoon period of pregnancy—the second trimester.
Your baby bump might start to show at 13 weeks and morning sickness may begin to ease. Keep reading to discover more about what happens at 13 weeks pregnant, including insights on your baby’s growth and development and the signs and symptoms you may experience.
Here are a few things to know and look forward to when you’re 13 weeks pregnant:
Your little one is growing fast now, and their organs are fully formed.
Your baby is starting to move and flex their arms and legs.
Pregnancy symptoms such as morning sickness and fatigue may begin to ease at 13 weeks.
You might notice some colostrum leaking from your breasts during this time. This thick, yellow fluid is considered your baby’s first milk in the first few days after birth.
Your baby bump might be showing now or will be visible very soon, so you could consider snapping some pictures of your belly at 13 weeks pregnant and over the coming weeks to see those changes in action!
Can you tell your baby’s gender at 13 weeks? This is still too early to find out your little one’s gender via ultrasound, but why not have some unscientific fun with our Chinese Gender Predictor:
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13 Weeks Pregnant: Your Baby’s DevelopmentKeep up with your baby’s progress and find out what happens at 13 weeks pregnant:
This week, your little one’s organs are fully formed and are hard at work!
The kidneys are starting to produce urine and release it into the amniotic fluid, and the spleen is busy producing red blood cells, which carry oxygen throughout the body.
Your baby's intestines have moved back into the abdomen from the umbilical cord, now that there’s enough room to accommodate them.
Some of the larger bones, including those of the skull, are beginning to harden.
Even though you won’t hear those coos and cries until after you give birth, your baby’s vocal cords have already started to develop.
If you’re 13 weeks pregnant with twins, read more about your babies’ development in our weekly twin pregnancy overview.
You’re 13 weeks pregnant, but how many months is that? At 13 weeks pregnant, you’re at the end of your third month of pregnancy.
Baby's Size at 13 Weeks PregnantAt 13 weeks, your baby is about the size of a large plum or small peach. Your little one could weigh more than 2 ounces.
Your Baby: What Does 13 Weeks Pregnant Look Like?It can be hard to picture what’s going on inside your belly at 13 weeks pregnant. Check out the visual below for an idea of what your little one might look like.
Your Body at 13 Weeks PregnantYou’ve just about made it to your second trimester, which many moms-to-be describe as the honeymoon period of pregnancy.
The discomforts you may have experienced in the first trimester—fatigue, nausea, and frequent urination—often ease up, and you may even feel a surge of energy during this trimester.
By this stage, your blood supply and flow are fully linked to the placenta, which will continue to grow as your pregnancy progresses. By the time you give birth, the placenta may weigh about one and a half pounds.
In a few weeks, your healthcare provider may begin monitoring your fundal height—the distance from your pubic bone to the top of your uterus (the fundus). Measuring the size of your growing uterus helps your provider determine how your baby is doing.
Breast tenderness may continue on and off, and other issues like constipation, bloating, and heartburn are normal at this stage, too, as your increased hormone levels can slow down digestion.
Learn more about prenatal health, fitness, nutrition, and more in our downloadable Pregnancy Guide.
13 Weeks Pregnant: Your SymptomsEvery pregnancy is unique.
It’s difficult to predict what to expect at 13 weeks pregnant, but here are some of the symptoms you may be experiencing now or in the coming weeks:
Vaginal discharge. A clear to milky-colored discharge known as leukorrhea may increase around this point in your pregnancy. You might be surprised to learn that this discharge has a unique purpose: It helps keep your vagina and birth canal clear of infection and irritation. If it gets a little messy, panty liners can be a big help. If your discharge is brown or foul-smelling, or if you notice spotting or bleeding at 13 weeks pregnant, contact your healthcare provider for advice.
Changing sex drive. It's perfectly normal for you and your partner to feel an increase or a decrease in sexual desire at various times during pregnancy. If your pregnancy is normal and both of you feel the urge, go ahead and enjoy the intimacy. Don't worry—your baby will be safe! Your uterus and the amniotic sac provide protection for your baby.
Talk to your healthcare provider if you’re worried or have questions about this or anything else. Note that your provider might advise you to abstain from sex if you have complications including a history of miscarriage or if you are at risk of preterm labor. Read more about sex during pregnancy.
Heartburn. Heartburn and indigestion can come and go throughout your pregnancy as your baby moves from one position to the next, and as your growing uterus puts pressure on your stomach. Pregnancy hormones also cause the muscle at the top of your stomach to relax, allowing stomach acid to travel up into the esophagus, which causes heartburn; this is more likely to happen if you lie down after having just eaten a large meal. You can reduce the discomfort by sitting upright after eating and avoiding potential triggers such as chocolate, citrus fruits, and fried or spicy foods.
Constipation. Hormones strike again! Progesterone and estrogen play an important role in pregnancy, but right now they might be causing your digestive system to work more slowly than usual.
This means that you may be feeling somewhat backed up at 13 weeks pregnant and have some cramping. Adding more fruits, vegetables, and whole-grain foods to your diet increases your fiber intake and helps keep things moving along. Drinking prune juice might also help, as can drinking lots of water and doing regular exercise.
Leaking colostrum. You may start to notice a thick, yellow fluid leaking from your breasts right about now. This is called colostrum, and it’s the milk that appears for the first few days after you give birth. It is completely normal, but you may want to try using disposable or cotton breast pads (without plastic liners) to help absorb any leaking fluid.
At 13 weeks pregnant, your baby is growing quickly and the changes in your body may be accelerating, meaning your pregnancy bump might start to show and become more obvious to others during this time.
At 13 weeks pregnant, your uterus may be moving up higher and forward, as well as increasing in size. Your expanding uterus might cause some aches and pains in the muscles and ligaments surrounding it.
You may be wondering if you can feel the baby move at 13 weeks pregnant. Though your little one is moving around inside your uterus and starting to flex their arms and legs, they’re probably still too small for you to feel those movements. If you’re wondering, when can you feel your baby move, this tends to happen around 16 to 20 weeks and is called quickening.
What Does 13 Weeks Pregnant Look Like?To get a better idea of what your belly might look like around thirteen weeks pregnant, when you’re reaching the end of your third month of pregnancy, check out the image below.
13 Weeks Pregnant: Things to ConsiderAt 13 weeks pregnant, you have a lot to think about, from sharing the good news to getting regular exercise.
Read on for some things to consider:
Have you shared the good news with your family and friends? The beginning of your second trimester is a great time to do this, because the risk of miscarriage is lower after the first three months. Of course, the decision about when to start spreading the wordis totally up to you! Get inspired with our creative pregnancy announcement ideas.
If you work, plan when you'll let your boss know that you’re expecting. Start to think about how you will share the news, and when. You’ll want to keep your employer and colleagues in the loop so they can make plans for accommodating your absence during your maternity leave. You might even like to have a little fun with announcing your pregnancy to co-workers.
Working out? If yes, keep it up! If not, consider consulting your healthcare provider about starting a basic fitness routine. If your provider gives you the all-clear, it could include things like walking, swimming, and maybe yoga.
Your body and mind will thank you—both during the last six months of your pregnancy and during your new baby’s first few months when increased levels of energy and fitness will help you deal with all the extra stress that’s placed on your body.
If you are doing abdominal exercises that have you lying flat on your back, you may want to look for alternatives during pregnancy, since the weight from your uterus can cause less blood to return to your heart when you're in that position. Ask your healthcare provider for advice.
It’s also worthwhile to pay attention to the pelvic floor muscles. The benefits of strengthening these muscles include improved bladder control and increased pelvic organ support. (The pelvic organs include the bladder, uterus, small intestine, and rectum.) You can strengthen the pelvic floor by doing small exercises as Kegels. Basically, these involve squeezing and relaxing the muscles in the pelvic and genital area.
Now that you’re pregnant, you may be feeling forgetful or struggling to concentrate; you may also be more intense dreams that you did before.
You’re not alone! Read up on the so-called “pregnancy brain” and learn why you may be experiencing more vivid dreams.
Why do I sometimes feel pain in my pelvic area? (Some lower back or pelvic pain at 13 weeks pregnant may be associated with round ligament pain resulting from things like your growing uterus, but consult with your healthcare provider about what’s normal and what isn’t.)
Am I gaining the right amount of weight? If not, what changes can I make to get on the right track?
Is chorionic villus sampling recommended?
Check out some to-dos to help you along during your pregnancy journey:
□ Start doing research into your child care options. You can ask friends, neighbors, or coworkers for recommendations for in-home care or child care centers.
□ If you work, find out about your maternity leave rights and options, including how many weeks you may have, and how much of that time might be paid. You can also ask if your employer offers any additional benefits.
□ Plan how to share your big news with your wider circle of family and friends.
□ Start making a shortlist of possible names for your little one with the help of our Baby Name Generator.
□ As you enter the second trimester, read up on the trimesters of pregnancy for an overview of what’s to come.
Week by week
13th - 16th week of pregnancy
Elena Gevorkova
Obstetrician-gynecologist, Moscow
BABY
The length of the fetus is 6-7 cm at the beginning of the week, reaching 10 cm by its end. The fetus weighs about 20-30 g at this time.
The countdown of the second trimester of pregnancy begins from the 13th week. From this period, intensive growth of the fetus occurs due to the lengthening of the arms and legs. The proportions of the body change, and the head is no longer as large in relation to the body as before. The formation of fingers and toes continues. The baby is already reaching out with his finger to his mouth, and often on ultrasound you can see that the thumb of the crumbs is in the mouth. This is how a very important reflex is manifested - sucking, which will be necessary for the child after birth.
Intensive growth of muscle tissue begins, especially in the limbs of the fetus. The activity of the fetus increases significantly, it makes smoother movements, but the woman still feels them, since the fetus is in the uterine cavity in a free position and practically does not come into contact with its walls.
A notable fact is the completion of the formation of all 20 milk teeth. They are located under the dense mucous membrane of the upper and lower jaws of the fetus.
The gastrointestinal tract develops intensively, the intestines fit into loops, completely filling the abdominal cavity. The inner surface of the intestine (mucosa) forms special villi that line the entire area of the intestine. After the baby is born, these villi will play a very important role in digestion, absorbing nutrients from the intestinal cavity. The intestine makes wave-like (peristaltic) movements, as a result of which the amniotic fluid swallowed by the fetus passes through it. They do not contain any nutrients, and their transport through the intestines is only a stimulus for the formation of a muscular intestinal wall, preparation for postpartum life.
Future MOTHER
The beginning of the 13th week is marked by the fact that pregnant women feel much better and finally there is an opportunity to feel the whole range of positive emotions associated with the period of bearing a baby. Toxicosis, malaise, drowsiness recede. The emotional background changes, the woman becomes more calm, less irritable.
This is due to a more stable hormonal background and the fact that the critical periods of pregnancy are experienced safely.
At this time, most expectant mothers begin to change the shape of the abdomen. As a rule, the changes are invisible to others, but pregnant women clearly notice the appearance of a rounded tummy, discomfort when wearing previously familiar things. This requires an update of the wardrobe, the selection of more comfortable clothes.
BABY
The fetus has a length of up to 13 cm, its weight is 40-45 g.
The appearance of the fetus changes due to the distinct formation of the face. The cheeks are rounded, the eyebrows are outlined, the bridge of the nose becomes more pronounced. The baby makes distinct movements - holds on to the umbilical cord, feels his face, tummy. The head and body are covered with an embryonic fluff, which is tightly attached to the skin of the fetus. It performs a protective function, retaining a special lubricant located on the entire surface of the skin, which during childbirth will allow the child to slide smoothly along the mother's birth canal.
Later, the thin, almost transparent germinal down will be replaced by thicker hairs.
During this period, important events occur regarding the respiratory organs of the fetus. The intensive development of the muscular system concerns not only the motor muscles of the arms and legs, but also the muscles of the respiratory system. The fetus makes rhythmic and intense movements that mimic breathing. Such "training" is very important, because immediately after birth, the child must take the first breath, which requires muscle effort and the ability of the muscles to obey the signals that come from the brain. The glottis is partially closed, which allows a small amount of amniotic fluid to enter the lungs during "inhalation", but during the subsequent intense "exhalation" it is pushed back. This washing promotes optimal maturation of the lung tissue.
Noticeable changes are noted in the structure of the genital organs of the fetus. In girls, the ovaries move from the abdominal cavity to the pelvic cavity.
In boys, the prostate gland (prostate) is intensively formed. The structure of the external genitalia is clearly differentiated into male and female genitalia, however, with ultrasound at this time, it is not always possible to reliably determine the sex of the fetus.
Important events take place in the organs of the endocrine system. The intensive functioning of the pancreas begins, the production of insulin, the hormone responsible for the metabolism of glucose in the body, occurs. From the 14th week, the functioning of the pituitary gland begins - the "chief" of all other glands, which controls their interaction and is responsible for growth processes. The pituitary gland is tiny and is located in the most protected part of the body - in the thickness of the brain, surrounded by the bones of the skull.
Expectant MOM
The intensive growth of the uterus continues, and from this period it becomes possible to independently feel the bottom of the uterus - its uppermost part - through the anterior abdominal wall; its upper edge is 10-15 cm above the pubis.
From this period, the use of special skin care products for pregnant women is recommended. The skin of the abdomen is not yet stretched, but certain changes are already taking place in it, and it is important to use cosmetics - creams, lotions, oils that moisturize the skin.
Stretch marks during pregnancy (stretch marks) appear due to ruptures of connective tissue fibers (microcracks). A change in the hormonal background in expectant mothers reduces the elasticity and firmness of the skin, and even a slight weight gain, as well as redistribution of the subcutaneous layer of fat and swelling, lead to the fact that the natural stretching of the skin occurs with its damage and the appearance of stretch marks.
The use of special cosmetics increases the elasticity of tissues and fills the cells with moisture; in this case, when the skin is stretched, microtrauma will occur less frequently.
BABY
By the end of the 15th week, the length of the fetus is 14-15 cm, and the weight is about 50-70 g.
legs. Fetal movements are very active; he manages to repeatedly change his position in the uterus in a few minutes. The fingers and toes are fully formed. The fetus often bends the arms at the elbows and wrists, actively clenching the fingers into a fist. The skin of the fingertips acquires a unique striation - a unique skin pattern. The formation of nails begins.
At this stage of pregnancy, the cardiovascular system of the fetus is improving. The fetal heart rate is twice as fast as the mother's pulse (its norm is 140-160 beats per minute). The tiny heart works very intensively, pumping up to 20 liters of blood per day. The circulatory system of the fetus is being improved: arteries and veins are actively growing, connecting into complexes. At this time, every organ - heart, brain, lungs, intestines, etc. - acquires its own vascular systems (arteries and veins). A dense network of blood vessels shines through the thin skin of the fetus, and therefore the fetus does not have the usual pink color, but red.
The formation of the nervous system goes through very important stages. The brain increases in mass, its convolutions and furrows deepen. Bones, muscles and all internal organs are intertwined with nerve fibers. A stable connection is formed between the brain (central nervous system) and the periphery. Impulses pass not only from the brain to the organs, but also in the opposite direction - this is how a very important “reverse response” system is born.
By week 15, the source of blood cell production changes. If up to this point, erythrocytes (red blood cells) were produced by the liver and the yolk sac, then from the 15th week this function is taken over by the red bone marrow, which is located inside the bones.
From this period it becomes possible to determine the blood type and Rh factor of the fetus. Of course, the group and Rh are predetermined at the moment of conception, when the parents' chromosomes merge, but the realization of this information (the formation of special antigen proteins on the surface of red blood cells) occurs at this stage.
Future MOM
The belly of a pregnant woman continues to increase in size, at this time its growth is quite gradual. The uterus has a rounded shape, its bottom can be felt 15-20 cm above the pubis.
Skin pigmentation may appear both on the abdomen and on any other part of the body - arms, legs, face, chest, back of the expectant mother. As a rule, on the abdomen, this is manifested by a brown line stretching from the pubis to the navel, or separately located irregularly shaped spots. Skin pigmentation is associated with intensive production of melanin pigment and its deposition in the skin due to changes in hormonal levels, and occasionally, a lack of vitamins. The appearance of age spots should not be accompanied by discomfort, redness, swelling of the skin. If something like this occurs, it is necessary to inform the doctor about this, since such phenomena may be signs of an allergic reaction or a skin disease (dermatosis of pregnancy). The color of the line or spots can vary from light beige to dark brown.
As a rule, these phenomena disappear on their own after childbirth. Do not use whitening creams without consulting your doctor: it may be unsafe for your baby.
BABY
Mimic muscles are formed in the fetus, and he starts their training – he frowns his eyebrows, opens and closes his mouth. The baby opens its eyes for the first time, which were previously tightly closed, learns to blink. Eyebrows and cilia are represented by fine fluffy hairs. The auricles are already in their usual place, while before this period they were located quite low - at the level of the neck. At this time, the inner ear is not yet able to hear, but the reaction of the fetus to loud sounds is clearly visible. This is due to a special type of sound perception - bone conduction, the fetus, as it were, "hears" with the dense parts of its body - the bones.
The fetus has already formed all the bones and joints. But the bones are still very soft, and the process of strengthening (ossification) will continue not only throughout pregnancy, but also after the birth of the child until puberty.
At 16 weeks, the external genitalia are already clearly visualized, and during an ultrasound examination, the sex of the baby can be determined almost unmistakably.
There is an intensive work of the kidneys of the fetus. From this period, the kidneys take over part of the excretory function, somewhat reducing the load on the placenta. During the day, the fetus swallows about 300-500 ml of amniotic fluid, they pass through the kidneys and are converted into urine. The fetus excretes urine every hour in small portions into the amniotic fluid through the formed urethra.
Expectant MOM
The general well-being of pregnant women usually improves significantly. Appetite normalizes, gradual weight gain begins; by this time it should not exceed 2.5-3 kg.
The growth of the abdomen at this stage of pregnancy is associated both with the development of the fetus and with a more intense accumulation of amniotic fluid. The tummy protrudes quite noticeably, but does not constrain the movements of the pregnant woman and does not give her a feeling of discomfort.
And although the size of the abdomen is small, nevertheless, it is time to change some of your habits in connection with its growth. This applies to the choice of body position during sleep. It is not recommended to sleep on the stomach and on the back. In the first case, it can be uncomfortable for the baby and disrupt the blood flow in the uterus. In the second case, the uterus presses on large veins, which worsens the outflow of blood, can provoke cramps, swelling of the legs and aggravate varicose veins. It is optimal to sleep on your side: this position is most convenient for both mom and baby.
The earliest period at which a fetal egg in the uterine cavity can be seen using transvaginal ultrasound is the 30th day of gestation, or 4-5 obstetric weeks of pregnancy. The level of hCG blood in this case should be at least 1000 mU / ml.
At this time, neither the embryo nor the yolk sac is visible. When visualizing two fetal eggs, it can be argued that this is a dichorionic multiple pregnancy. When visualizing one fetal egg, it can be argued that this is a monochorionic pregnancy. But at this time, we still cannot say how many embryos are in each fetal egg. In addition, during a single ultrasound, we still cannot tell if this pregnancy is progressing, since the embryo does not yet have a heartbeat. The average inner diameter (SID) of the fetal egg at this time is 2-10 mm.
The conclusion will indicate: Uterine pregnancy of a short term.
Learn more about ultrasound in early pregnancy
At this time, a white ring appears inside the fetal egg - this is the yolk sac.
Foci of erythropoiesis are formed in the wall of the yolk sac, which form a capillary network, supplying erythroblasts (nuclear erythrocytes) to the primary circulatory system of the fetus.
The yolk sac is a source of primary germ cells that migrate from its wall to the anlage of the gonads of the embryo. Until the 6th week after fertilization, the yolk sac, playing the role of the "primary liver", produces many important proteins for the embryo - alpha-fetoprotein, transferrins, alpha2-microglobulin. By the end of the first trimester of pregnancy, this provisional organ ceases to function and is reduced.
The normal size of the yolk sac is 2-6 mm. If two yolk sacs are visualized in the fetal egg, then this is a monochorionic multiple pregnancy. But if one yolk sac is visible inside the fetal egg, and the embryo is not yet clearly visualized, then this may still be monochorionic monoamniotic twins.
At the beginning of the 5th week, the embryo is practically indistinguishable on the wall of the yolk sac, but by the end of the week, the coccyx-parietal size (CTE) of the embryo reaches 3 mm.
SVD of the ovum 11-16 mm.
Read also: Is ultrasound harmful during pregnancy? Is ultrasound dangerous? How often can an ultrasound be done?
Inside the fetal egg, we see a "ringlet with a precious stone" :) - this is the yolk sac and the already clearly visible embryo, located nearby.
The heart of the embryo begins to beat at the beginning of the 6th obstetric week of pregnancy. It is the presence of a heart pulsation that is a reliable ultrasound sign of a progressing pregnancy. With CTE ≥6 mm and the absence of heart pulsation, a conclusion is made about stopping the development of this embryo. Normal heart rate (HR) of the embryo at the very beginning of the 6th week 70-90 beats per minute, but by the end of the week it becomes more than 100 beats. in min. In the early stages of pregnancy, it is not the heart rate that matters, but the presence or absence of heart contractions as such. Sometimes, with a non-developing pregnancy, you can see the reflection of the pulsation of the mother's vessels inside the embryo and take them for the baby's heartbeat. But in this case, the pulsation frequency will be identical to the mother's heart rate.
The presence of one yolk sac, one embryo and one pulsating heart in the vast majority of cases indicates a singleton pregnancy.
But in very rare cases, it may later turn out to be unseparated twins.
SVD of the ovum 13-23 mm. Embryo KTR 4-9 mm.
Read also: "I don't want an ultrasound, I want a baby!". Why is ultrasound during pregnancy necessary?
The distance between the embryo and the yolk sac gradually increases and the yolk duct (ductus vitellinus), which connects the yolk sac and the intestines of the embryo, becomes clearly visible. Just like the yolk sac, the duct becomes empty and resolves at a later date, but if this does not happen for some reason, then a blind protrusion of the ileum wall is formed in a person - Meckel's diverticulum.
Until this time, the chorion has an annular shape, surrounds the fetal egg from all sides, and it is still impossible to say which wall of the uterus the embryo has attached to.
In the case of monochorionic twins, the amniotic membranes are not yet visible, and in the presence of two yolk sacs, it is still impossible to tell whether this pregnancy is mono or diamniotic.
If the gestational sac contains two yolk sacs and two fetuses with cardiac activity, the subsequent number of amniotic cavities may be greater than the number of placentas (monochorial diamniotic) or the same (monochorial monoamniotic). In this case, it is possible to accurately determine amnionality after 8 weeks, when the amniotic membranes begin to be clearly visualized.
Embryo heart rate 130-160 beats per minute.
SVD of the ovum 24-30 mm, CTE of the embryo 9-15 mm.
During the ultrasound of the embryo, it is already possible to clearly distinguish individual segments - the head, trunk, limbs. The first movement appears. The amniotic membranes become clearly visible and we can already talk about the number of amniotic sacs in multiple pregnancies. The chorion is differentiated into a smooth one, facing the uterine cavity, and a branched one, from which the placenta will subsequently form, so that we can already talk about the predominant location of the chorion along the anterior or posterior wall of the uterus.
