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.

Written and verified by the psychologist Cristina Roda Rivera.

Last update: 21 December, 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

Hormonal changes begin early in pregnancy and are due to the placenta secreting hormones into the mother’s bloodstream.

The following hormones play an important role during pregnancy:

• Human chorionic gonadotropin (hCG). It occurs only in pregnancy and almost exclusively in the placenta. The levels of hCG in the mother’s blood and urine increase greatly during the first trimester. Also, this hormone may explain the nausea many women experience in the first two to three months.
• Human placental lactogen (hPL). It’s a hormone made by the placenta that nourishes the fetus and stimulates the mammary glands in the breasts for nursing.
• Estrogens. This group of hormones help develop female sexual traits and is normally found in the ovaries. Also, the placenta produces them to help maintain a healthy pregnancy.
• Progesterone. The ovaries and placenta produce it during pregnancy. It stimulates the thickening of the uterine lining to implant a fertilized egg.

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

Increase in body temperature

During pregnancy, it’s normal for body temperature to increase and to sweat more. This is because pregnant women have a higher metabolic rate and increased sweat gland activity.

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.

Changes in the kidneys and urinary system

Kidneys receive more blood, so they have to filter more as well. On the other hand, since the uterus is bigger, the ureters have to take a more sinuous path to the bladder, with urinary infections being more frequent.

The gastrointestinal tract

Pregnancy has little or no effect on gastrointestinal secretion or absorption, but it does have a significant effect on gastrointestinal motility. Pregnancy-related motility changes are present throughout the gastrointestinal tract and are related to elevated levels of progesterone.

Also, the enlarged uterus displaces the intestine, which can affect the presentation of different conditions, such as appendicitis. Knowing about the gastrointestinal changes in pregnancy is important to accurately interpret laboratory tests, as well as imaging studies for pregnant patients.

Glucose levels in pregnancy

A fetus’s organs, such as the brain, heart, kidneys and lungs, begin to form during the first 8 weeks of pregnancy. High blood glucose levels can be harmful during this early stage. In fact, it can increase the fetus’s chance of having birth defects such as heart, brain or spinal defects.

On the other hand, high blood glucose levels during pregnancy can also increase the chance that the baby will be born early, weigh too much, have trouble breathing, or have low blood glucose immediately after birth.

Breathing (and gasping) more deeply than normal

One of the many smart changes in pregnancy is that women exhale more deeply with each breath towards the end of the pregnancy. Progesterone contributes to it.

This helps women ventilate both additional heat and residual gases well, protecting her and the fetus from health issues.

Smart adaptations for the fetus to develop

Cholesterol increases by about 50%, while triglycerides can increase by up to 200-300%. 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.

The placenta

During pregnancy, the body accumulates more water than it would otherwise. 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.