The Invisible Changes of Pregnancy

Pregnancy is a revolution for a woman's body. During the nine months of gestation, her body adapts to various changes, many of which aren't obvious to an outside observer.
The Invisible Changes of Pregnancy

Last update: 21 June, 2022

Pregnancy generates many changes in the woman’s body. We can classify these transformations as visible and invisible. In both cases, they involve adaptations of the body that guarantee the normal development of the fetus.

The female body also prepares for childbirth and lactation by influencing the woman’s attitude and behavior. In fact, everything is geared toward the arrival of the baby in order for it to be fed and protected.

However, what are the invisible changes of pregnancy? They’re the kinds of transformations that can’t be seen, but that play an extremely important role if the pregnancy is to come to term successfully.

The invisible changes of pregnancy: hormones

It doesn’t take long for most pregnant women to realize that hormones have a mind of their own. Indeed, hormonal changes begin early in pregnancy and are due to the placenta secreting hormones into the mother’s bloodstream.

One example is the secretion of the hormone, human chorionic gonadotropin (hCG) in early pregnancy. This hormone may explain the nausea many women experience in the first two to three months. It’s usually the first symptom of pregnancy and occurs long before there are any visible changes in the body.

Pregnancy tests are based on this hormone, which is found in the blood and urine a few days after conception.

Pregnant woman
Hormones affect almost every organ in the body. They’re responsible for how the placenta largely controls what happens in the mother’s body during pregnancy.

In addition, large amounts of the hormones progesterone and estrogen are secreted during pregnancy. These have effects on organs and tissues that grow or adapt to the pregnancy, such as the uterus, breasts, and blood vessels, and aim to help a woman’s body prepare to have a child. In fact, there’s only one other time when our bodies produce equally large amounts of these hormones: puberty.

A few extra liters of blood

After a few weeks of pregnancy, changes occur in the cardiovascular system. A woman’s blood volume increases, and about a quarter of it drains through the growing uterus to the placenta. There, oxygen and nutrients are exchanged from the mother to the fetus. This is absolutely crucial for the fetus to grow and develop normally.

Therefore, the woman’s heart must pump a little harder and faster. That’s why many women feel an increased pulse rate during pregnancy. As a matter of fact, the blood supply through the uterine vessels increases about tenfold toward the end of pregnancy. Therefore, the blood vessels are required to expand and adapt, which is called remodeling.

A lack of remodeling can be seen in pregnancy complications such as pre-eclampsia and a failure in the fetus to gain weight.

The gastrointestinal tract

The gastrointestinal tract is lined with a layer of muscle that’s also affected during pregnancy. The sphincter between the esophagus and the stomach loosens up a bit and makes it easier for the acidic contents of the stomach to pass into the esophagus.

This causes acid reflux, which is common, especially towards the end of pregnancy. Constipation is also common, due to slower than usual bowel movements.

Pregnant women breathe more deeply

Pregnancy, with the growing fetus and placenta, produces a great deal of heat and residual carbon dioxide gas that the woman has to get rid of. One of the many smart changes of pregnancy is that the woman exhales a little deeper with each breath as she approaches full term.

Hormones secreted by the placenta (progesterone) contribute to this, as the brain’s center for breathing reacts to a slightly lower than normal level of carbon dioxide. This helps her to ventilate both additional heat and residual gases well, thus protecting her and the fetus from health damage.

Smart adaptations for the fetus to develop

Another important change is that the woman develops resistance to absorbing sugar on her own. Her altered metabolism helps to prioritize the supply of sugar to the fetus so that it grows well. For this reason, she’ll need to use other nutrients, such as fats, to a greater extent.

Cholesterol increases by about 50 percent, while triglycerides can increase by up to 200-300 percent. This is because cholesterol is included as a basic component for the growth of both the placenta and the fetus.

The increase in lipids is a normal adaptation for the placenta and the fetus to develop normally, in part because the fetus has received a lot of sugar that the woman herself uses when she isn’t pregnant.

Pregnant woman
In addition to physical changes, there are also psychological changes in pregnant women.

The placenta

During pregnancy, the body accumulates more water than it would otherwise. Also, fluid is excreted from the blood vessels into the tissues. This swelling is called edema and it normally accumulates in the legs, especially at night, and even more so during pregnancy.

Edema is most often seen as part of the normal changes of pregnancy. However, the rapid development of pronounced edema is present in pre-eclampsia.

Changes in the brain until after childbirth

In 2016, a team of researchers from the Netherlands and Spain used magnetic resonance imaging (MRI) to study what happens in the brain during pregnancy. By comparing MRI images taken before the women became pregnant with images taken after they gave birth, the researchers found that pregnancy reduces the brain’s gray matter.

Gray matter is the tissue that contains the cell bodies and synapses of nerve cells. The results of this study showed that their loss of volume persisted for at least two years after delivery. It’s thought that this remodeling may play a role in helping women make the transition to motherhood.

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