Maternity - Pregnancy, part 1: Signs and Physiologic Changes of Pregnancy

by Meris Shuwarger BSN, RN, CEN, TCRN August 30, 2021 Updated: August 09, 2023 6 min read

Why can blood pressure drop when a pregnant person lays down? Why can pregnancy make some people clumsy? Why isn't a pregnancy test a positive sign of pregnancy?! In this article, we'll answer all of these and more. Read on and we'll explain the signs of pregnancy, and changes that occur in each body system during pregnancy

This series follows along with our Maternity Nursing Flashcards which are intended to help RN and PN nursing students study for nursing school exams, including the ATI, HESI, and NCLEX.

Cool Chicken When you see this Cool Chicken, that indicates one of Cathy's silly mnemonics to help you remember. The Cool Chicken hints in these articles are just a taste of what's available across our Level Up RN Flashcards for nursing students!

Signs of pregnancy

Signs of pregnancy are classified into three different groups: presumptive signs, probable signs, and positive signs. These go from least to most certain.

Presumptive signs of pregnancy

Presumptive means presuming; so with presumptive signs, we can presume the patient is pregnant. But when you presume, you don't actually know for sure!

Presumptive signs of pregnancy are things that may (or usually) occur in pregnancy, but there are many other explanations for them. Patients exhibiting presumptive signs of pregnancy may experience:

  • Fatigue
  • Nausea
  • Amenorrhea (no menstrual period)
  • Breast changes
  • Urinary frequency
  • Quickening (the sensation of fetal movement)

However, a patient could be tired from lack of sleep, nauseated from anxiety, have amenorrhea from malnutrition or hypopituitarism, have breast changes due to medication, urinary frequency from diabetes insipidus, and the quickening could be gas. This is why the above are only presumptive signs!

Probable signs of pregnancy

Probable signs of pregnancy means the patient is probably pregnant, and can include Chadwick's, Gooddell's, or Hegar's sign, ballottement, or a positive pregnancy test.

Cool Chicken The signs are all the probable signs.

Chadwick's sign

Chadwick's sign is a probable sign of pregnancy, when the uterus softens and becomes blue or purple in color.

Gooddell's sign

Gooddell's sign is a probable sign of pregnancy which is a significant softening of the vaginal portion of the cervix.

Hegar's sign

Hegar's sign is a probable sign of pregnancy which is the softening of the lower part of the uterus.


Ballottement has to do with how the uterus feels to a healthcare provider when examined; it may feel like there is fluid inside or feel movable.

Positive pregnancy test

A positive pregnancy test definitely means you're pregnant, right? Wrong! It seems like it should be a positive sign of pregnancy, but it's not— a positive pregnancy test is actually only a probable sign of pregnancy. How can this be?!

A positive pregnancy test indicates the presence of human chorionic gonadotropin (HCG), which is colloquially referred to as the pregnancy hormone. However, there are other explanations for having HCG in one's system besides being pregnant, like a recent miscarriage, or rare tumors. This means there can be false positives! That's why a positive pregnancy test is only a probable sign.

Positive signs of pregnancy

Positive signs of pregnancy indicate that without a doubt, this patient is pregnant.

Fetal heart sounds are a positive sign of pregnancy. If a provider hears fetal heart sounds during an exam, there is no other explanation.

Seeing the fetus on an ultrasound is a positive sign of pregnancy. If a patient gets an ultrasound and a fetus is seen, there really is no explanation for that besides pregnancy!

If the healthcare provider feels fetal movement, that is considered a positive sign. Reports from the patient that they feel fetal movement are not reliable, because they are not trained to know what that feels like and it could be gas. But if the healthcare provider feels it, that's considered positive.

Cool Chicken Baby can be heard, felt, or seen!

Physiologic changes during pregnancy

Many, many changes happen to the body during pregnancy. The patient's body is creating another body, so it needs all systems firing! We've broken down the physiologic changes during pregnancy into body systems here. There are respiratory, cardiovascular, musculoskeletal, endocrine, gastrointestinal, renal, reproductive, and integumentary changes to know about.

Respiratory changes during pregnancy

The respiratory changes that may occur during pregnancy include increased oxygen requirements and respiratory rate as well as decreased lung capacity.

Cardiovascular changes during pregnancy

There are some important cardiovascular changes during pregnancy to be aware of. The pregnant patient's blood volume will increase by almost 50%, which can result in edema (fluid retention/swelling). This means that cardiac output is also increased, because more blood is being pumped. And for cardiac output to increase, the heart rate must increase, which can result in tachycardia. Tachycardia in pregnant patients is normal and expected.

Because blood plasma volume increases, the blood is more dilute, so concentrations of substances in the blood become lower. Thus, hemoglobin (Hgb) and hematocrit (Hct) levels drop slightly. Normally, when Hgb and Hct are low, this can mean anemia. Because the diluted blood is expected in pregnant patients, they are given a different threshold for anemia to be diagnosed.

Pregnancy anemia threshold

A patient who is pregnant is not considered to have true anemia unless the Hgb is less than 11 g/dL in the first and third trimesters, or less than 10.5 g/dL in the second trimester.

Musculoskeletal changes during pregnancy

During pregnancy, the body produces the hormone relaxin to relax the pelvic joint, and the patient may experience lordosis, a curvature of the spine


During pregnancy, the body creates a hormone called relaxin, which thankfully, does what it sounds like. It helps to relax the pelvic joint and ligaments so they are flexible enough to accommodate the exiting baby during labor.

Excess relaxin hormone, along with a changing body shape and weight distribution, may lead to a feeling of incoordination and clumsiness in the pregnant patient. Meris shares in the video that when she was pregnant, she fell down the stairs three times!


During pregnancy, a patient may experience lordosis, which is an increased inward curvature of the lumbar spine as the spine adjusts to the changing weight distribution and center of gravity as the belly sticks out. This can result in lower back pain.

Endocrine changes during pregnancy

During pregnancy, the endocrine system produces and secretes hormones from the placenta, like hCG, progesterone, and estrogen.

Gastrointestinal changes during pregnancy

During pregnancy, the gastrointestinal change to be aware of is lowered peristalsis. Peristalsis is the contraction of the stomach muscles and other muscles in the GI tract that move food along, which allows for digestion. Less peristalsis means less gastric emptying, and this can contribute to nausea and vomiting, constipation, and heartburn.

Renal changes during pregnancy

The renal changes to be aware of during pregnancy are increased blood flow to the kidneys, and urinary frequency.

Reproductive changes during pregnancy

Now, you might have been able to predict this one, but there are important reproductive changes happening during pregnancy. This is when the reproductive system takes center stage—it's its time to shine!

During pregnancy, the reproductive changes to be aware of are that the uterus and breasts increase in size, Chadwick's sign, and the areolas darken.

Supine hypotension

The uterus increases in size and weight (the baby's weight). If a pregnant patient is laying on their back, and their uterus is extra heavy, it can compress the inferior vena cava, block the blood flow in that vein and cause a drop in blood pressure, which is called supine hypotensive syndrome.

The easiest fix for this is for a pregnant patient to rest in a side-lying position, or with a pillow under one hip to shift the uterus to the side so they can maintain good blood flow.

Integumentary changes during pregnancy

The integumentary changes to be aware of during pregnancy are chloasma, striae gravidarum, and linea nigra.


Chloasma is a skin condition sometimes called the mask of pregnancy, and it can look like brown patches or discoloration on the face.

Striae gravidarum

Striae gravidarum are stretch marks. Striae means stripes and gravidarum means related to pregnancy. Stretch marks occur when the skin has to grow to accommodate a body that changes shape in a short period of time (as opposed to over the course of many years). The quick stretching causes the collagen and elastin in the skin to rupture, which causes miniature scars as the skin heals.

Stretch marks may start dark and become lighter over time when they have healed. Stretch marks are a normal part of human development; many kids, preteens, or teens get them as part of growth spurts.

Linea nigra

Linea nigra is Latin for black line. During pregnancy, linea nigra is a darkening of the abdomen that can appear as a vertical line, usually running vertically down the pregnant belly. Some patients get it, some don't. Oftentimes the line disappears after pregnancy.

It's important to note that skin changes, unlike changes in other body systems, can feel quite noticeable for patients when they look in the mirror. It's important to be able to educate your patients that these are not good or bad things, they're just normal changes during pregnancy!

Full Transcript

Hi, I'm Meris, and in this video, I'm going to be talking to you about the signs of pregnancy and the physiologic changes of pregnancy. I'm going to be following along using our maternity flashcards. These are available on our website, And if you already have a set of your own, I would absolutely invite you to follow along with me. So let's go ahead and get started.

First up, we're talking about the signs of pregnancy. So you'll see here that we have three different ones. We have presumptive. We have probable. And we have positive. Presumptive means presuming. I can maybe kind of presume you're pregnant. Probable means you're probably pregnant. And positive means without a doubt, you are pregnant.

So presumptive, these are going to be more like symptoms. I'm tired. I'm nauseated. I haven't had my period. That's called amenorrhea, amenorrhea without menstruation, breast changes, all of those sorts of things. They're presumptive because, yes, all of those may occur in pregnancy, but there are many other explanations for them. So they are just presumptive.

Now, you'll see here on probable signs, we have some bold red tags and a cool chicken to help you to remember. So we have a few things here.

Ballottement. Ballottement has to do with how the uterus feels to a healthcare provider. So ballottement is like moving, like it feels like fluid inside.

A positive pregnancy test. You might think that's a positive sign, but it's not. A positive pregnancy test only indicates the presence of human chorionic gonadotropin, or the pregnancy hormone. There are actually other explanations for having HCG in one's system. So, although it is suggestive, although it is probable that a patient with a positive pregnancy test is pregnant, it's not guaranteed.

Then you'll see we have Chadwick, Goodell, and Hegar's signs, three different signs. If your school makes you learn them, review them, but I'm not going to go into them. Three different signs that a healthcare provider may see, like the color of the cervix or the soft the softening of the cervix. All of the signs are probable signs. So all three of those, Chadwick, Goodell, and Hegar, all three of those you'll see here, our cool chicken that says that all of the signs are probable signs.

Okay. Now, positive signs. Positive signs means without a doubt, this patient is pregnant. So here they are.

Fetal heart sounds. There's no other explanation.

Seeing the fetus on ultrasound. No other explanation.

If the healthcare provider feels fetal movement, that is considered a positive sign. Not if the patient does, because that could be gas or flutters in the belly or whatever from many other things. So if the healthcare provider feels it.

So all of these are going to be definitive, meaning no other explanation. And you can see here we have a cool chicken that says baby can be heard, felt, or seen. If I can hear, feel,or see your baby, I am positive that you are pregnant.

Okay. So let's move on to physiologic changes in pregnancy. There's a lot, so we have two cards devoted to this. I'm not going to go super in-depth. I'm just going to point out a few things here.

Cardiovascular status. The patient's blood volume is going to increase by almost 50%. So things that can come along with that are going to be things like edema. Right? We have more fluid. We can have swelling. A little bit of tachycardia is normal and expected because it's hard for that heart to pump fast enough to keep up with the cardiac output of all of this fluid. Right? I got to keep it moving. So that's where we're going to have that tachycardia.

Now, because I have dilution of my red blood cells from the plasma volume, you're going to see dilutionally low levels in the lab work. So hemoglobin and hematocrit are going to drop slightly. That's normal. We don't consider a patient who is pregnant to have true anemia unless the hemoglobin is less than 11 grams per deciliter in the first and third trimesters, or less than 10.5 in the second. But point being, it is lower than a nonpregnant patient. And you'll see a lot of different things on this card.

Musculoskeletal. The body is creating a hormone called relaxin, which thankfully, does what it sounds like. It helps to relax the ligaments and everything like that that are holding everything tightly so that when labor happens, there's enough relaxation in these joints to allow for this movement.

But it can lead to things like clumsiness in coordination, which would be why when I was pregnant, I fell down the stairs three times because my body was very uncoordinated, thanks to all of that relaxin.

So then on the second card here, are a few things that I want to point out. And there's a really, really big one here [in reproductive]. It's that because this uterus is so big and so heavy, if I lay on my back, supine, what is underneath all of that? Think about it. It's going to be the inferior vena cava. And the inferior vena cava is where all of the blood from my lower extremities and everything is being returned back to my heart. If I lay on my back with a really heavy uterus, a gravid uterus, and put pressure on that vena cava, I'm going to cause a traffic jam, right, first of all. So that blood is not going to be getting back appropriately.

But then, what else is going to happen? I'm going to have hypotension. My blood pressure is going to drop because I'm not getting enough blood back to my heart, and so I end up with this hypotension. This is called supine hypotension syndrome. And a very easy way to combat it is don't lay on your back when you're pregnant or, if you need to, put a pillow under one hip so that we are just slightly rotating to move that uterus to the side and make sure that we are getting that good blood return.

[Gastrointestinal] Other things on here are going to be things like constipation, nausea, and vomiting, right. All of those things are going to be very common in pregnancy.

And then under the integumentary heading, we have a few things here. Chloasma. This is oftentimes called the mask of pregnancy, and it's kind of a little discoloration of the face. Then we have striae gravidarum. Striae are stretch marks, and gravidarum means related to pregnancy. So those are just pregnancy-related stretch marks. And then, we have the linea nigra, literally means black line. So this is going to be a darkening of the abdomen and it's a vertical line, usually running down the pregnant belly. Some people get it, some people don't. Same for all of these. It's not a good or a bad thing. It's just a thing that can happen. So it's good to be able to educate your patients.

Okay. That is it for the different physiologic changes in pregnancy and the signs of pregnancy. I hope that review was helpful. If it was, it would mean the world to me if you could like this video so that I know. If you have a really great way to remember something that I said in this video, I absolutely want to hear it. So please leave it in the comments below. And I know that somebody watching this video wants to hear it, too. Definitely be sure that you have subscribed to the channel because we have a lot more coming, and you want to be the first to know when the next video drops. This next video is actually a really great one, I think. It's going to be a comprehensive view of what happens in OB/GYN visits in the first, second, and third trimesters. It really helps you to get the timeline of prenatal care down. So I hope I will see you there. Thanks so much, and happy studying.

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