Dynamics of belly size by weeks of pregnancy

The expanding belly becomes an obvious indicator of the new life growing inside during pregnancy. Many women are curious about what constitutes normal and how their belly size compares to others, so they track it eagerly week by week. Knowing about these changes can reassure expectant mothers that everything is going according to plan and help them feel more involved in their pregnancy.

There will be noticeable variations in the baby’s belly size from week to week as their body adjusts to the new life. But it’s crucial to keep in mind that each pregnancy is different. The way the belly grows depends on a number of factors, including body type, the baby’s position, and whether this is the first or second pregnancy.

This week-by-week guide offers a helpful reference for what to expect during the various stages of pregnancy by breaking down the typical changes in belly size. This guide gives you a clear understanding of the exciting growth occurring during this unique time, whether you’re curious about your own experience or just seeking general knowledge.

Physiological reasons for growth

The stomach during pregnancy does not grow on its own, this process is due to the rather rapid growth of the 2nd organ – uterus – uterus. As soon as the test showed two stripes, the uterus has very small dimensions with a volume of 5 ml and a weight of about 50-60 grams. But already in the second month of pregnancy, there is a gradual and systematic increase in the number of muscle fibers. This is necessary so that the female reproductive organ can grow and increase in size, and the uterus will have to stretch significantly – about 500 times compared to its size before pregnancy. By the 9th week of pregnancy, the uterus reaches the size of a goose egg. And while it fits within the small pelvis, there is no belly, it does not grow. As the reproductive organ grows and rises above the small pelvis higher into the abdominal cavity, the belly becomes noticeable. And already after the 14-15th week of pregnancy, such a size as the VDM – the height of the fundus of the uterus is easily determined. It is this part (wide) that the uterus rises into the abdominal cavity, and the growth of the VDM is growing with every week of pregnancy. The belly increases significantly after the 16th week of pregnancy, and for many it already becomes visible by this time. The rate of belly growth is very individual, and depends on the constitution, the size of the pelvis, the presence or absence of excess weight. The place of attachment of the placenta, the number of fetuses, and their estimated weight also play a role.

Because each woman’s abdominal circumference varies before becoming pregnant, the measurement during pregnancy is therefore very unique. On the other hand, the uterine fundus height provides a more average measure. As a result, the physician measures the OB and VDM at the same time, entering the results into the expectant mother’s exchange card following each visit.

Changes in size by time – norms

The uterus grows continuously, but gradually. It leaves the boundaries of the pelvis at about the 13th week of pregnancy, and before this time it is quite possible to lie on your stomach without fear of harming the child. From the same period, the VDM measureds – the height to which the reproductive organ rises above the bosom. And if for a woman observing the growth of the abdomen is more of an entertaining nature, then for a doctor, it is the VDM that shows whether the uterus is growing normally, whether there are prerequisites for polyhydramnios or oligohydramnios, a large fetus, whether there are grounds to suspect intrauterine growth retardation of the baby. The abdominal circumference is measured with an ordinary centimeter tape along the line of its most protruding part, and VDM – in a lying position from the pubis to the borders of the fundus of the uterus (the doctor feels them). To change it, you can use both a centimeter tape and a special obstetric pelvis meter.

Since each woman’s OB is unique, as was previously mentioned, what matters is not how many centimeters a woman gains in a given week but rather how her girth changes over time. However, there are standards for VDM.

Table VDM by weeks during pregnancy.

From the presented table it is clearly seen that the rate of growth of the height of the fundus of the uterus is observed only at the end of the last trimester, when the abdomen descends – the baby is pressed by the presenting part (head or pelvic end) to the internal os of the cervix, exerting additional pressure on it and leading to its gradual preparation for childbirth. With the lowering of the belly, the expectant mother finds it easier to breathe, heartburn decreases, the ribs hurt less, but the downward pressure increases, which leads to frequent urination. In thin and asthenic individuals, the belly becomes noticeable earlier, in overweight women the belly is sometimes not visible until the very latest stages. The girth of the abdomen relative to its initial size changes individually.

Why the belly grows slowly?

• The abdominal muscles are strong, trained, the woman regularly exercised before pregnancy and had a flat tummy. In this case, the abdominal wall stretches much longer.
• The woman has a wide pelvis and hips, due to which the space of the small pelvis is also larger, so the growing reproductive organ manages to occupy its usual place in the small pelvis longer.
• A small amount of water. The amount of amniotic fluid (their index) is significantly lower than normal. This condition is dangerous in itself, so the slow rate of growth of the tummy is not the main reason for concern.
• Excess weight. If a woman has extra pounds and fat deposits in the abdomen and hips, then the pregnancy will become noticeable to everyone much later.
• The expectant mother is about to give birth – not the first. The more births there were, the weaker the muscles, the more susceptible to stretching the anterior abdominal wall. Therefore, the belly always becomes noticeable much earlier during the third birth than during the first.

Additionally, there are requirements that are independent of the woman. Pregnancy-related small belly is frequently inherited by a girl from her mother and is linked to the features and composition of the musculoskeletal system. In this instance, you don’t need to worry.

Remain composed and unperturbed by the fact that your belly appears smaller than other women’s; in fact, it is hardly noticeable. It’s the VDM that matters much more. There is no need for concern if this size is typical. The girth, or circumference, of the abdomen in this instance, is meaningless.

Too fast growth

Some women bemoan the fact that their baby bulged out of nowhere at the start of the second trimester, making it hard to conceal from prying eyes.

You shouldn’t be alarmed because this phenomenon typically has very clear causes.

• The expectant mother has a narrow pelvis. This ensures an earlier exit of the fundus of the uterus from the pelvis into the abdominal cavity, so the growth of the tummy becomes obvious earlier. A narrow pelvis of 3-4 degrees can be a direct indication for delivery by cesarean section, but it is in no way dangerous for the baby during pregnancy, does not affect its development and well-being.
• Pregnancy is not the first. This circumstance is a fairly weighty argument in favor of early growth of the abdomen, since with each subsequent birth the abdominal muscles weaken – such is the inevitability, a kind of retribution of women for the happiness of motherhood.
• A pregnant woman has not one, but two or more babies growing under her heart, while the uterus grows somewhat faster, but the size of each of the fetuses is slightly below the average norms.
• High amniotic fluid index (polyhydramnios) also provokes faster growth of the uterus and an increase in the number of muscle fibers.

• A woman"s thinness makes the belly more noticeable.

If the VDM does not correspond to the term

Further testing is not necessary if the woman’s belly is not expanding at the rate she had anticipated and the pregnancy is progressing without causing the doctor any concerns. However, a change in the VDM is a more precise indication to take action. And the attending physician ought to take action.

Naturally, no one will diagnose anything if the uterine fundus’s height differs from the typical average statistical values. Only a few more tests are advised for the patient, the primary one being a Doppler ultrasound, which gives you an idea of the baby’s size and development as well as the quality and speed of blood flow through the placenta and umbilical cord.

A mistake in estimating the gestational age may have occurred if the VDM is less than the timing norms. The following circumstances may result in this: if a woman has an irregular cycle and is unable to recall the date of her last menstrual cycle following IVF during a pregnancy that happened while she was nursing her previous child. Meanwhile, the baby’s overall development is within normal limits, and the Doppler scan reveals no abnormalities in the flow of blood between the mother and the fetus.

When there is oligohydramniosis, the fetus is often positioned incorrectly in the uterine cavity (e.g., across, diagonally), which causes the VDM to decrease.

When the difference is two centimeters or greater, there may be a fetal growth delay. This illness can arise for a variety of reasons. This includes a Rh conflict, disruption of the placenta’s and the umbilical cord’s blood flow, and insufficient nourishment for the expectant mother. When the real cause of the problem is found and, if feasible, removed, the baby typically "catch up" with its terms.

The main suspicion in cases where the VDM is exceeded by two centimeters or more is a large fetus. To rule out diabetes in the mother, blood tests for sugar are advised at the same time.

These days, it doesn’t matter if a pregnancy is single or multiple based on the size of the VDM. Obstetricians used this indicator in the past, before ultrasounds, to suspect multiple pregnancies. Later, they felt two heads, and frequently made mistakes.

Today, ultrasound technology is ideal for diagnosing multiple pregnancies; a woman can find out if she is expecting one or more babies as early as 7-8 weeks into her pregnancy.

Monitoring your growing tummy during your pregnancy can be a thrilling and comforting experience. It gives you a sense of connection with your baby’s internal development as it is a visible indication of their growth and development.

Each pregnancy is different, and factors such as your body type, the baby’s position, and whether this is your first pregnancy will all affect how big your belly gets. Having routine check-ups with your doctor will guarantee that everything is developing according to plan.

Keep in mind that a larger or smaller belly does not always mean that there is an issue. To maintain your health and the health of your unborn child, trust your body and the advice of your healthcare provider.

Given that a woman’s belly grows each week during pregnancy, parents and medical professionals can better monitor the health and progress of the pregnancy by being aware of this normal progression.

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