Maternity - Pregnancy, part 2: Prenatal Care: 1st, 2nd, and 3rd Trimester Visits
by Meris Shuwarger BSN, RN, CEN, TCRN August 30, 2021 Updated: August 09, 2023 6 min read
Pregnancy involves a lot of OB/GYN visits! This article gives an overview of all the appointments that need to happen during pregnancy—this article is an overview, and later on in this series, we cover some of these exams more in depth.
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.
First Trimester Visit(s)
The first trimester of pregnancy is the first 12 weeks (months 1, 2, and 3) and the first prenatal visit will take place during this time. A patient may have more than one visit in their first trimester, but it depends on when they realize that they may be pregnant.
During the first trimester visit, the provider will obtain the pregnant patient's obstetric history, calculate the estimated date of delivery, run important laboratory tests, perform a transvaginal ultrasound, and give the patient some initial maternal teaching.
Until approximately 28 weeks, the pregnant patient will have monthly visits.
During the first trimester visit(s), the care team will gather the patient's obstetric history, meaning how many pregnancies and of what type. There is a special acronym for this, GTPAL. Check out our next video to learn more!
Calculating estimated date of delivery
During the first trimester visit(s), the provider or care team will calculate the patient's estimated date of delivery—when baby is expected to arrive! One useful way of calculating this is with Naegele's rule.
First trimester visit labs and diagnostics
During the first trimester visit(s), the patient will have some important labs and diagnostic testing done, including the following:
- Complete blood count
- STI & HIV testing
- Pap test
- Blood typing, including Rh factor
- Rubella titer
- Hepatitis B
- HCG (for high risk patients).
A transvaginal ultrasound is a test that gives a view of the patient's uterus, ovaries, fallopian tubes, cervix, and the surrounding area. During the first trimester visit(s), the patient may get a transvaginal ultrasound to confirm pregnancy, site of implantation (to ensure it's a safe pregnancy, not ectopic). Transvaginal means across or through the vagina, so the ultrasound device is placed inside the vagina, as opposed to an abdominal ultrasound wherein the device is against the abdomen.
A transvaginal ultrasound makes it much easier to get detailed imagery of the uterus and fallopian tubes than an abdominal ultrasound. Catching an ectopic pregnancy in the earliest stage of pregnancy is crucial to prevent harm to the patient.
First trimester maternal patient teaching
During the first trimester visit(s), you will give the pregnant patient some patient teaching about what to expect during their pregnancy. This includes nutritional guidance, weight gain, warning signs of complications, and expected side effects. In our Maternity Nursing Flashcards we cover patient teaching in detail. You can check out Part 4: Maternal Teaching: Nutrition/Weight Gain, Warning Signs, Unpleasant Side Effects which follows along with our flashcards.
Second Trimester Visits
The second trimester of pregnancy is from week 13 - 24 (months 4, 5, and 6) and there will be some important visits during this time.
Starting in the second trimester, the fetal heart rate will be assessed via doppler and fetal vital signs and weight will be obtained at each visit.
14 - 18 weeks (month 4)
During 14 - 18 weeks of pregnancy, the patient will get MSAFP testing done, followed up with amniocentesis if anything abnormal is found, and a gestational diabetes screening.
During 14 - 18 weeks of pregnancy, the patient may get a maternal serum alpha-fetoprotein (MSAFP) test, which is a test for genetic abnormalities like neural tube defects and Down syndrome.
During 14 - 18 weeks of pregnancy, if a patient has an abnormal result on their MSAFP test, they may require an amniocentesis, which is an invasive procedure wherein some amniotic fluid is removed from the uterus with a long needle and tested for genetic abnormalities.
Gestational diabetes test
If a patient is at high risk for gestational diabetes, they may be tested during 14 - 18 weeks of pregnancy with an oral glucose tolerance test. If a patient does not have higher risk, this test happens later.
18 - 22 weeks (month 5)
During 18 - 22 weeks of pregnancy, the patient will have an ultrasound to assess for any fetal abnormalities, and the fundal height will start to be measured during this time.
During 18 - 22 weeks of pregnancy, a patient will have an ultrasound as a standard part of prenatal care and to check for abnormalities that may require additional testing. By the time the patient has reached the second trimester of pregnancy, their ultrasounds will usually be abdominal rather than transvaginal.
Fundal height measurement
During 18 - 22 weeks of pregnancy, the patient will begin to need a fundal height assessment. Beginning at 18 weeks of pregnancy, the gestational age of the pregnancy should correlate to the fundal height in centimeters plus or minus two weeks
What is the fundus?
The fundus is not just a word that some nursing students and nurses find hilarious; it's the topmost part of the uterus. Fundal height is measured from the fundus to the pubic symphysis (middle anterior pelvis, above the vulva).
22 - 24 weeks (month 6)
During 22 - 24 weeks of pregnancy, the patient will need a glucose tolerance test, and for first pregnancies and those at risk for preterm labor, cervical length will start to be measured during this time.
Glucose tolerance tests
While it was only high-risk patients who were tested in month 4, in month 6 (22 - 24 weeks) of pregnancy, all patients will be given a 1-hour glucose tolerance test to test for gestational diabetes. If it is needed, it will be followed up with a 3-hour glucose tolerance test.
During 22 - 24 weeks of pregnancy, patients who are on their first pregnancy may have a transvaginal ultrasound done to have the length of the cervix assessed. This can help to identify risk factors for preterm labor. As long as the result of this test is normal, and the patient does not have preterm labor on their first pregnancy, this exam won't be repeated in the future.
Third Trimester Visits
The third trimester of pregnancy is from week 25 - 40 (months 7, 8 and 9) and there will be some important prenatal visits that take place during this time. After approximately 36 weeks, prenatal visits will be weekly until delivery.
At 28 weeks of pregnancy, Rhogam will be administered to Rh-negative patients, and visits will begin to happen every 2 weeks.
In the first trimester, patients were tested for Rh factor, which checks for maternal-fetal blood type incompatibility. If a pregnant patient is Rh negative (blood type incompatible), they will be administered Rhogam at 28 weeks and within 72 hours of delivery.
30 - 32 weeks
During 30 - 32 weeks of pregnancy, patients will need to begin kick counts, receive a TDaP, and undergo non-stress tests if they have a high-risk pregnancy.
Third trimester maternal patient teaching
At 30 weeks, patients should be taught to perform kick counts, which is exactly what it sounds like—How many times does the baby kick? This is important knowledge as it helps to assess the fetal well-being.
At 30 weeks, patients can be given the tetanus, diphtheria, and acellular pertussis (TDaP) vaccine. If it is given in the third trimester, it can impart some protection to the baby. If not given then, it will be given after delivery.
A nonstress test is a non-invasive test done in the third trimester to measure fetal heart rate response to fetal movement.
35 - 37 weeks
During 35 - 37 weeks of pregnancy, patients may need to have a vaginal/rectal Group B Strep swab obtained, and at approximately 36 weeks, their visits will need to occur weekly until delivery.
Group B strep swab
Group B streptococcus beta-hemolytic (GBS) is a bacterial infection that can be passed to a child during the birthing process that can cause life-threatening newborn infections. During 35-37 weeks, a patient should have a rectal and vaginal swab for this bacteria. If the patient has Group B strep, they can be treated at the time of delivery.
Hi, I'm Meris, and in this video, I'm going to be talking about what happens at OB/GYN visits in the first, second, and third trimesters. I'm going to be following along using our maternity flashcards. These are available on our website leveluprn.com. 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 jump right in with what happens at the first-trimester visit.
So I say visit because typically there's only one. However, it just depends on when a patient realizes that they may be pregnant. So the first visit, the initial visit, should be done before 12 weeks of gestation. However, if that patient does come in and they're very early, let's say six weeks, they'll probably come back again four weeks later. But for most people, they have just the one.
Now, this is a really big visit for a lot of reasons.
First is, baby is too small for us to use a Doppler to assess the heart rate. So instead, we have to do an ultrasound. That's the only way to confirm cardiac activity at this point. So there will be an ultrasound to assess that the fetus has a heartbeat and what that rate is.
And then going forward, the heart rate will be assessed with a Doppler from the outside.
The other thing is that this is where a lot of labs and diagnostic testing is performed. So on this card, you can see that there is a heading called labs. And on here, we have a lot of big ones.
I want to call your attention to CBC [complete blood count]. Do we already have a problem with anemia? Do we already have an infection? We want to know that.
STI testing. In a lot of states, this is mandatory. So be familiar with your state's laws.
A Pap test. If my patient has not had a Pap test recently or is due for one, then we're going to do it at this visit.
Blood typing. Blood typing, including Rh factor. This is very important. And we will talk about that in a little bit.
And then we're going to be testing for hepatitis B, or hepatitis B immunity, for HIV.
And then if your patient is high risk, as in they may have had multiple miscarriages or something along those lines, they may also have serial, meaning in a row, a few HCG, which is the pregnancy hormone levels drawn to be sure that the pregnancy seems to be developing appropriately.
Also, maternal teaching will be done, and we'll talk about that in a later video.
And then, until 28 weeks - we have a line on here - but until 28 weeks, these visits will be monthly, so every four weeks. There's not a lot to see or do at these visits in the early days because baby is very little.
So let's move on to the second trimester. Now, when you look at the second-trimester card, whoo-hoo-hoo, there is a lot of bold red text on here. And to me, that means I should really know this card, and probably want to star and highlight this card because it might be really important for me to know.
So, from 14 to 18 weeks, anywhere in that time, MSASP, maternal serum alpha-fetoprotein testing will be done. We'll talk about that in a later video. But that is when that will occur.
If there is an abnormal MSASP, then we can progress to an amniocentesis. Again, we'll talk about that later.
And then gestational diabetes screening happens at this early time for patients who are high risk, as in they had gestational diabetes in a prior pregnancy. Maybe they were prediabetic before getting pregnant. Maybe they have a strong family history. We're going to test them much earlier than everybody else.
Now, from 18 to 22 weeks, we have a lot.
We will have an ultrasound. This is commonly called an anatomy scan because it is looking for abnormalities in the fetal anatomy. So we're going to check everything out with baby, see if we have any sort of congenital heart defects, neurological defects, anything that can be seen on the ultrasound.
Fundal height assessment will begin at this point. This is very important. Fundus height means I'm measuring from the pubic symphysis all the way up to the fundus. The fundus is the topmost part of the uterus.
And we're going to measure this in centimeters. The gestational age of the pregnancy should correlate to the fundal height in centimeters plus or minus two weeks, beginning around 18 weeks, so from 18 to 32 weeks. Let's say I'm 24 weeks pregnant. My fundal measurement should be about 24 centimeters. Anything drastically less or more is cause for further investigation.
And then, from 22 to 24 weeks, this is where a routine gestational diabetes screening will happen. This is going to be a one-hour oral glucose tolerance test. And then follow up with a three-hour if needed. We'll talk about that in a later video.
And for first-time pregnancy, it's very commonly there will be an ultrasound done, a transvaginal ultrasound, to assess the length of the cervix. This can help us to identify risk factors for preterm labor. But as long as that is normal and the patient does not have preterm labor this pregnancy, that won't be repeated in the future.
Now, let's talk about the third trimester. Again, we can see a lot of bold red text on here. So let's go through it.
If the patient is Rh-negative, which we know because we did the blood type at the first visit, if our patient is Rh-negative, they will receive RhoGAM, or the RhoGAM is the anti-D antibody. So this is going to help to suppress that. That will be administered to Rh-negative patients at 28 weeks.
From this point on, all visits are going to be every two weeks. So now, 28 weeks. We're going to be seen at 30 weeks, and then 32 and 35.
So then, 30 to 32 weeks, this is going to be huge education for your patients. At 30 weeks, your patient should be performing kick counts. They are what they sound like. It's counting how many times the baby kicks. This is important. It helps us to assess the fetal well-being. So that's going to be something that we want to start at 30 weeks.
Also, at thirty weeks, we can give TDaP vaccine to the pregnant patient. So that's the tetanus, diphtheria, and acellular pertussis vaccine. If given in the third trimester, it does impart some protection to the baby.
And then, NSTs. Nonstress test may be performed at this time if they are indicated from 35 to 37 weeks.
Really, really important. Listen to me. 35 to 37 weeks, we are going to do a vaginal and rectal swab for group B, beta hemolytic strep. So you will hear this just called group B strep. And it's a swab of the vagina and rectum. This is a bacteria that some people just carry. But if the patient has it, we need to treat them at the time of delivery.
And then starting at 36 weeks, visits with the provider will be weekly. So 36, 37, 38, 39, 40, and beyond until the patient delivers, just depending on when that baby comes.
So I hope that review kind of comprehensively of what happens throughout the three trimesters of prenatal care was helpful. We're going to talk a lot more about what all of those things are and what they mean in future videos. So be sure that you subscribe so that you're the first to know when they are alive on our channel. If this review was helpful for you, I would love it if you could like this video so that I know. And if you have a great way to remember something or a really good story, I would love to hear it below. Please leave us a comment so we know. All right. Thanks so much, and happy studying.
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