Antepartum care (third trimester): clinical approach

Third trimester antepartum care encompasses pregnancy management from 28 weeks until delivery. This period is crucial for monitoring high-risk conditions and preparing for childbirth. Considerations during this phase include additional ultrasounds, screening tests, assessment of fetal health, birth plan discussions, education specific to this trimester, and counseling on postpartum birth control.

During a third trimester antepartum visit, begin with a focused history and physical examination. Inquire about symptoms such as contractions, potential fluid leakage, vaginal bleeding, and adequate fetal movements.

Patients might also experience typical benign pregnancy-related symptoms, including Braxton Hicks contractions, back pain, round ligament discomfort, swelling, acid reflux, and slight breathlessness.

A clinical insight: Braxton Hicks contractions, also known as “false labor,” are characterized by sporadic, mildly painful abdominal tightening. Conversely, “true labor” contractions are consistently painful, increase in regularity and intensity, and are felt in both the abdomen and lower back.

The physical examination should check weight changes, as both excessive and inadequate weight gain can lead to complications. Monitor blood pressure closely to detect any new increases that might suggest gestational hypertension or preeclampsia. Each visit should include a fetal Doppler assessment, with extended monitoring for any irregularities.

Once the focused history and physical are complete, initiate third trimester care.

For patients showing abnormal fundal heights or at risk of macrosomia or growth restriction, perform growth ultrasounds every 3 to 4 weeks. Reevaluate any previously noted issues such as placenta previa or fetal abnormalities during this trimester. In rare cases, patients may reach the third trimester without an ultrasound, necessitating a due date assessment.

Here’s another clinical pearl: In the third trimester, if the due date has not been confirmed by ultrasound before 28 weeks, and there is a discrepancy of over 21 days between the menstrual and ultrasound gestational age, a new due date should be assigned.

For pregnancies without ultrasound confirmation of gestational age before 22 weeks, consider them suboptimally dated. This impacts the timing of medically indicated deliveries, such as in cases of preeclampsia, and excludes these pregnancies from elective deliveries after 39 weeks and 0/7 days.

Lastly, discuss additional screening in the third trimester. If not conducted in the second trimester, order a complete blood count (CBC) at around 28 weeks to check for anemia, along with a glucose tolerance test for gestational diabetes screening. High-risk patients should be retested for HIV, syphilis, gonorrhea, and chlamydia. Collect a vaginal-rectal swab for group B streptococcus between 36 and 38 weeks unless previously identified as a carrier.

Additionally, it's essential to evaluate fetal presentation around 36 weeks through Leopold maneuvers or a limited ultrasound if the patient's body habitus complicates palpation. If a breech presentation or transverse lie is detected at or beyond 36 weeks, discuss the possibility of an external cephalic version (ECV). Also, conduct screenings for depression and intimate partner violence, typically around the 28-week visit.

Here’s a clinical pearl: ECV, performed after 37 weeks, involves externally manipulating the fetus into a head-down position to potentially avoid a cesarean delivery. This procedure is elective, allowing patients to choose after understanding its risks and benefits. If ECV is unsuccessful, or if declined, a cesarean delivery would be the next step.

To minimize the risk of stillbirth, assess fetal well-being even in patients at low risk for macrosomia or growth restriction. Regular fundal height measurements should be taken from the pubic bone to the uterine fundus, correlating in centimeters to the gestational week. If this measurement differs by more than 2 centimeters from the expected gestational age, a growth ultrasound is warranted. High-risk patients should undergo regular growth ultrasounds regardless of fundal height measurements.

Educate patients on monitoring fetal movements, emphasizing the individual variability of fetal activity and urging them to report any unusual changes. High-risk patients should start antenatal surveillance, such as nonstress tests or biophysical profiles, from 32 weeks onward.

Discuss childbirth expectations and pain management options, including IV narcotics, epidurals, nitrous oxide, or non-pharmacological methods like massage. For those with a previous cesarean, review delivery options, whether attempting a vaginal birth after cesarean (unless contraindicated) or opting for a repeat cesarean.

Important discussions about immediate postpartum care should include the benefits of delayed cord clamping and the "golden hour" of skin-to-skin contact post-delivery.

Provide trimester-specific education, such as recommending the Tdap vaccine between 27 and 36 weeks to transfer maternal antibodies to the fetus. Also, offer guidance on breastfeeding, possibly referring patients with breastfeeding concerns to a lactation consultant before delivery.

Prepare the patient for labor and delivery by discussing the timing and potential risks of elective labor induction after 39 weeks. If the patient reaches 41 weeks (late-term gestation), inform them of the increased risk of complications and the need for antenatal fetal surveillance, with delivery advised by 42 weeks (post-term gestation).

Ensure the patient is aware of the signs and symptoms of preterm labor, term labor, ruptured membranes, and preeclampsia. This knowledge will help them recognize when to seek medical evaluation.

Finally, review postpartum contraception options thoroughly, including surgical, hormonal, and nonhormonal methods. Discuss the timing of hormonal contraception post-delivery, especially considering the higher postpartum risk of venous thromboembolism. For nonhormonal options like intrauterine devices, discuss the timing of insertion post-delivery to minimize risks.

Here's the key aspects of third trimester antepartum care comprehensively. After 28 weeks of gestation, essential practices include using ultrasound to monitor fetal growth, check for abnormalities, and establish or confirm the due date if previously undetermined. It's also standard to perform a complete blood count (CBC) and a glucose tolerance test if these were not completed in the second trimester, along with screening for group B streptococcus if the patient's carrier status is unknown.

Additionally, assessing risk through screenings for HIV, syphilis, gonorrhea, chlamydia, depression, intimate partner violence, and fetal malpresentation is crucial.

For fetal well-being, regular monitoring through fundal height measurements and fostering fetal movement awareness are recommended for low-risk patients. In contrast, high-risk patients should undergo more intensive antenatal surveillance and growth ultrasounds.

Preparing the patient for delivery involves discussing birth plans and providing education tailored to this trimester's specific needs. Finally, reviewing postpartum contraception options ensures the patient is well-informed about their choices following delivery. This comprehensive approach supports both maternal and fetal health during the critical final phase of pregnancy.

Ref:

"Guidelines for perinatal care, 8th ed. 2017. " acog

"Committee Opinion No. 700: Methods for estimating the due date" Obstet Gynecol (2017;129:e150–4)

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