Antepartum care (third trimester): Clinical sciences

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Introduction0:00–0:34

Third trimester antepartum care refers to pregnancy care from 28 weeks of gestation through the end of pregnancy. Care during this time is critical to monitor for high-risk conditions and prepare for delivery.
All patients in the third trimester warrant consideration of additional ultrasounds; screening tests; assessment of fetal well-being; counseling on birth plans; trimester-specific pregnancy education; and counseling on postpartum contraception.When assessing a patient presenting for a third trimester antepartum visit, your first step is to obtain a focused history and physical.

Focused H&P0:34–2:01

The history should include asking whether they’re experiencing contractions, possible leakage of fluid, vaginal bleeding, and appropriate fetal movements.
Additionally, patients may report common benign pregnancy symptoms, such as Braxton Hicks contractions, back aches, round ligament pain, edema, acid reflux, and mild shortness of breathHere's a clinical pearl!
Braxton Hicks contractions, often referred to as “false labor,” present with infrequent and minimally painful tightening of the abdomen.
On the flip side, contractions representing “true labor” are painful, regular, and increase in frequency over time. Typically, false labor is felt only in the front of the abdomen, while true labor is felt in the lower back as well as the abdomen.
Your physical exam should include a review of weight, since both insufficient and excessive weight gain can lead to complications.
Also, pay attention to blood pressure, as new elevations could indicate gestational hypertension or preeclampsia. Perform fetal Doppler assessment at each visit and follow up on any abnormality with prolonged monitoring.
With the focused history and physical complete, it’s time to initiate third trimester antepartum care. For patients with abnormal fundal heights or those with conditions that raise the risk of macrosomia or growth restriction, growth ultrasounds are done every 3 to 4 weeks.

Obstetric US2:01–3:45

Some patients may have had a prior ultrasound that showed an abnormality, such as placenta previa or a fetal anomaly, so reassess any previous abnormalities in the third trimester.
While uncommon, some patients with insufficient prenatal care get to the third trimester without having an ultrasound and require assessment of their due date.
Here's a clinical pearl! In the third trimester, the due date is assessed by comparing the gestational age calculated by the last menstrual period to fetal biometry, meaning an assessment of the fetal head, abdomen, and extremities.
For pregnancies at 28 weeks and beyond that have not previously had ultrasound confirmation of their due date, assign a new due date if the gestational age by ultrasound is more than 21 days off from menstrual dates.
Keep in mind that in cases where there is no ultrasound confirmation of dates before 22 weeks of gestation, the pregnancy would be considered suboptimally dated.
This means that timing for indicated deliveries, such as those with preeclampsia, should be based on the best clinical estimates.
Also, suboptimally dated pregnancies are not candidates for elective delivery after 39 weeks and 0/7 days.Next up, let’s talk about different screening assessments in the third trimester.

Screening3:45–5:24

If not already done in the second trimester, be sure to order a CBC around 28 weeks to reassess for anemia, as well as a glucose tolerance test to screen for gestational diabetes.
Patients at high-risk for infectious diseases need repeat screening for HIV, syphilis, gonorrhea, and chlamydia. Unless a patient is already known to be a carrier of group B streptococcus, collect a vaginal-rectal swab between 36 and 38 weeks.
Additionally, assess fetal presentation at approximately 36 weeks by palpating through the Leopold maneuvers, or by a limited ultrasound exam if the patient’s body habitus prevents adequate assessment.
If the fetus has a breech presentation or transverse lie at or after 36 weeks, counsel on the external cephalic version, or ECV.
Finally, repeat depression and intimate partner violence screening as well, usually at the 28-week visit.Here’s another clinical pearl!
ECV is a procedure performed after 37 weeks, where providers will attempt to move the fetus into a cephalic presentation by applying external pressure on the patient's abdomen.
ECV is elective, meaning that after you explain the risks and benefits, your patient can choose to have it performed in order to prevent a c-section.
If ECV fails, or if the patient declines, the next step for delivery would be a c-section Alright, let’s talk about minimizing stillbirth risk by assessing fetal well-being.

Assess Fetal Well Being5:24–6:29

Patients at low-risk for macrosomia and growth restriction should still be screened with a fundal height at each visit. Measure from the pubic bone to the uterine fundus, because the measurement in centimeters correlates with the patient’s week of gestation.
If the measurement is more than 2 centimeters different from their gestational age, order a growth ultrasound. For patients at high-risk for macrosomia or growth restriction, obtain growth ultrasounds regardless of the fundal height.
Also, counsel patients on fetal movement awareness. Explain that each fetus is different and they should reach out if movements seem atypical in their specific case.
Patients who are at high-risk for stillbirth should also undergo antenatal surveillance, such as nonstress tests or biophysical profiles starting at 32 weeks.
Alright, it is important to review the patient's desires and what they can expect during the birth itself. Talk to patients about options for pain management in labor.

Counsel on Birth Plan6:29–7:27

This may include things like IV narcotic medication, an epidural, or nitrous oxide; or nonpharmacologic options like massage.
Patients with a prior c-section need counseling on the mode of delivery, meaning whether they wish to pursue a vaginal birth after c-section, unless a contraindication is present; or have a repeat c-section.
It’s also important to discuss the patient's wishes for immediate postpartum care. This means reviewing the benefits of delayed cord clamping and the “golden hour,” which is uninterrupted skin-to-skin contact between the patient and infant immediately after delivery lasting at least an hour.Just like in other trimesters, you’ll need to provide trimester-specific education.

Patient Education7:27–9:12

The tetanus, diphtheria, pertussis, or Tdap vaccine, is recommended for all pregnant patients between 27 and 36 weeks of gestation.
This is done because maternal antibodies cross the placenta and protect the fetus until they can receive immunity. Now, education on breastfeeding benefits and mechanics is also helpful.
For patients with a history of struggling to breastfeed; an anatomic variation that may make breastfeeding difficult; or multiple gestation; offer referral to a lactation consultant prior to delivery.
Next, you’ll want to give the patient all the necessary information to help prepare for labor and birth. Talk to them about the risks and benefits of elective induction of labor that can be scheduled anytime after 39 weeks.
If the patient has no indication or desire for sooner delivery, discuss what they would like to do if they reach 41 weeks of gestation, which is called late term gestation.
Patients should be informed there’s an increased risk of complications beyond 41 weeks, and if they decline delivery, recommend antenatal fetal surveillance.
Delivery is indicated no later than 42 weeks, or post-term gestation, due to the risk of poor outcomes. It’s still important to give labor and delivery precautions in the third trimester to review signs and symptoms of preterm labor, term labor, and rupture of membranes, as well as preeclampsia warnings.
This education allows patients to know when to present for evaluation.Last, but not least, make sure to review prior to delivery options for postpartum contraception.

Counsel on Postpartum Contraception9:12–10:42

All options should be reviewed, including surgical, hormonal, and nonhormonal. For patients interested in permanent surgical sterilization, discuss tubal ligation at the time of c-section, immediate postpartum tubal ligation following vaginal delivery, delayed interval tubal ligation at least 6 weeks after delivery, and don’t forget partner vasectomy.
For patients not interested in surgical sterilization, discuss hormonal and nonhormonal coverage. Progesterone-only hormonal options can be started immediately postpartum.
The risk of venous thromboembolism is actually higher postpartum compared to during pregnancy, therefore contraception containing estrogen should be delayed at least 4 weeks in patients at low risk for venous thromboembolism, and 6 weeks in those with any risk factors.
While many breastfeeding patients are concerned about the impact of estrogen on milk supply, once the supply is established, estrogen tends to be well tolerated.
For patients seeking nonhormonal contraception, this can be utilized immediately after delivery. Remember, intrauterine devices either need to be placed immediately after delivery of the placenta, or after a 4 to 6 week wait, due to increased risk of perforation.Alright, as a quick recap… Third trimester antepartum care occurs any time after 28 weeks of gestation.

Review10:42–11:44

Ultrasound is commonly used to assess fetal growth, reevaluate prior abnormal findings, and even for dating if not done earlier in the pregnancy.
Screen all patients with a CBC and glucose tolerance test if not already done in the second trimester, and screen for group B streptococcus if their carrier status is unknown.
Screen for HIV, syphilis, gonorrhea, and chlamydia if at increased risk. Also, screen also for depression, intimate partner violence, and fetal malpresentation.
Assess fetal well-being with fundal heights and fetal movement awareness for low-risk patients, or perform antenatal surveillance and growth ultrasounds if high-risk.
Prepare the patient for delivery with a discussion on birth plans, and provide trimester-targeted education. Lastly, don’t forget to review with the patient options for postpartum