Antepartum Care in the Second and Third Trimester

Function

Frequency of Antepartum Visits

Traditionally, the American College of Obstetricians and Gynecologists (ACOG) and other US guidelines recommend 12 to 14 in-person visits for low-risk pregnancies.[6] Conversely, several other regions (eg, Canada and Europe) typically schedule fewer visits, approximately 7 to 11, for these patients. Despite having a higher frequency of visits, the maternal mortality rate remains higher in the US than in other countries.[7] The World Health Organization (WHO) has recommended a minimum of 8 visits for low-risk patients is needed to provide adequate prenatal care.[1] Clinicians most commonly evaluate patients in a 1-on-1 setting, though some areas in the US follow a group prenatal care model that is similarly effective.[8] The following visit schedule is followed by US institutions:

• Every 4 weeks from 10 to 28 weeks gestation
• Every 2 weeks from 28 to 36 weeks gestation
• Weekly from 36 weeks until delivery [1]

Pregnancies with conditions that increase the risk of antepartum fetal demise are classified as high-risk; in these patients, increased surveillance is indicated.[9] Conditions that determine whether a pregnancy is high-risk or not are not well-defined; however, obstetrical history or maternal, fetal, and placental factors can indicate an increased risk of stillbirth. See StatPearls' companion reference, "Initial Antepartum Care," for more information on high-risk pregnancies.

Prenatal Management in the Second Trimester

In the second trimester, antepartum care consists of updated histories at each visit, including reviewing current pregnancy-related issues and new concerns, including symptoms such as headaches, altered vision, pelvic cramping, abdominal pain, nausea or vomiting, vaginal bleeding, leakage of fluid, or dysuria. The clinical assessment also includes documentation of maternal blood pressure, maternal weight, and fetal heart rate.[10] The US Preventive Services Task Force (USPSTF) recommends obtaining a baseline blood pressure at the initial visit with reevaluation at each prenatal visit, as this is essential to identify hypertensive disorders in pregnancy. Furthermore, preexisting hypertensive disorders (eg, chronic hypertension) may only be discovered during a prenatal evaluation, as the antepartum visit may be the only encounter a patient has had with a health professional. An appropriately sized sphygmomanometer should be used with a larger cuff in patients with an arm circumference >33 cm. Obtaining an accurate blood pressure measurement is critical. Therefore, clinicians should ensure that patients are relaxed and in a seated position with back support and legs uncrossed while their blood pressure is measured with their arm at the level of the right atrium.[11] A positive screening result for hypertension during pregnancy is a systolic blood pressure of ≥140 mm Hg or diastolic blood pressure of ≥90 mm Hg measured twice at least 4 hours apart in a patient without chronic hypertension.[12] 

Fetal heart rates can be detected via Doppler ultrasound in nonobese patients at as early as 10 weeks gestation. At approximately 20 weeks gestation, patients may begin to perceive fetal movement, also referred to as "quickening". Clinicians should inquire about fetal movement at each visit after a patient reports feeling fetal movement.[10] During this trimester, patients are also counseled after fetal viability to be aware of fetal movement and to report perceived decreased fetal movement; some clinicians may use various "fetal kick count" methods to quantify fetal movement (eg, 10 movements within 2 hours), though the optimal protocol has not been defined.[13] Abdominal palpation to assess fundal height at each visit after 20 weeks gestation and fetal presentation at 36 weeks gestation should also be performed.[10] See StatPearls' companion reference, "Leopold Maneuvers," for more information on fetal presentation assessment through palpation. 

Second-Trimester Laboratory Studies

Several laboratory and aneuploid screening studies are performed during the second trimester also to provide optimal time for potential interventions. In patients who have elected to perform combined first- and second-trimester aneuploidy screening tests, an independent second-trimester serum screening (eg, quad screen) or amniocentesis for diagnostic aneuploidy testing, the specimen should be collected at the appropriate time.[14][15] See StatPearls' companion reference, "Prenatal Genetic Screening," for more information on various aneuploidy screening tests. ACOG and USPSTF also recommend screening laboratory studies for gestational diabetes and anemia be performed in all pregnant individuals between 24 to 28 weeks gestation. The most common method for gestational diabetes screening is the 1-hour 50-g glucose tolerance screening, though some institutions use a 75-g, 2-hour glucose tolerance diagnostic test. Different cut-off thresholds are used for the 50-g glucose tolerance screening to be considered an abnormal result, including ≥135 mg/dL (7.5 mmol/L), ≥130 mg/dL (7.22 mmol/L), and ≥140 mg/dL (7.8 mmol/L). Because studies have not demonstrated an optimal cut-off threshold, clinicians should determine which cut-off to implement based on the prevalence of community gestational diabetes risk factors and clinical preference for test sensitivity and specificity. In patients with a positive 50-g glucose screen, a diagnostic test is necessary with a 100-g, 3-hour oral glucose tolerance test.[16] The following values are used as parameters for abnormal results:

• Fasting: ≥95 mg/dL
• First hour: ≥180 mg/dL
• Second hour: ≥155 mg/dL
• Third hour: ≥140 mg/dL [16]

The presence of ≥2 abnormal results establishes the diagnosis of gestational diabetes.[16] See StatPearls' companion reference, "Gestational Diabetes," for more information. A repeat complete blood count should also be performed when the gestational diabetes screen specimen is collected to screen for anemia, which is prevalent in pregnant women due to increased iron and folate requirements. Because iron deficiency is a common underlying etiology for anemia, iron studies should be performed in patients with abnormal results (see Table. Recommended Initial Prenatal Serum Laboratory Studies).[17] In patients with known Rhesus (Rh)-negative status with a negative antibody screen on initial prenatal testing, an antibody screen should be repeated at 28 weeks gestation. Anti(D)-immune globulin should also be administered at 28 weeks in these patients.[18] 

Second- and Third-Trimester Imaging Studies and Antenatal Fetal Surveillance

Because the second trimester encompasses a vast majority of the rapid fetal growth period, ultrasound surveys and antenatal fetal surveillance are performed during this trimester to provide optimal time for potential interventions. A standard fetal anatomy transabdominal ultrasound examination is recommended at 18 to 20 weeks gestation, as this is the optimal time to visualize fetal anatomic structures. This fetal imaging provides a thorough assessment of the developing pregnancy, including placental location, amniotic fluid volume, fetal number, size, presentation, cardiac activity, and anatomy. The cervix should also be assessed during this ultrasound examination for any abnormalities (eg, shortening or funneling).[19] See StatPearls' companion references, "Cervical Insufficiency" and "Sonography 2nd Trimester Assessment, Protocols, and Interpretation," for more information.

Additionally, in patients who are identified as having high-risk pregnancies or clinical suspicion of a pregnancy complication (eg, fundal height less than gestational age or vaginal bleeding), ultrasound imaging may be performed for diagnostic evaluation or as part of antenatal surveillance. Indications for additional ultrasound evaluation in the second or third trimesters include a vast array of issues that necessitate assessment of fetal growth and well-being, amniotic fluid levels, and/or placental location and bleeding. Typically, fetal growth assessments require serial ultrasounds performed at 4-week intervals.[19] See StatPearls' companion references, "Fetal Growth Restriction" and "Sonography 3rd Trimester and Placenta Assessment, Protocols, and Interpretation," for further information.

Antenatal fetal surveillance is primarily indicated in high-risk pregnant patients or those with abnormal clinical findings (eg, decreased fetal movement) suggestive of an increased risk for fetal demise.[9] Antenatal fetal surveillance comprises several techniques, including kick counts, nonstress tests, contraction stress tests, biophysical profiles, and umbilical artery blood flow velocity. Clinicians must determine which testing strategy to employ, the testing frequency, and when to initiate antenatal fetal surveillance based on various clinical factors (eg, complication severity, survival prognosis, and gestational age). ACOG recommends antenatal fetal surveillance not be initiated until the patient reaches a gestational age at which fetal demise is more likely and the clinician is willing to deliver; typically suggesting 32 weeks gestation to be appropriate for most high-risk patients. Moreover, 32 weeks gestation is the age most fetuses become reactive on nonstress testing. However, clinicians may choose to initiate testing earlier due to clinical risk factors. Antenatal fetal surveillance is commonly performed at weekly to twice weekly intervals; however, the optimal frequency has not been defined, as this must be individualized according to the clinical picture.[9] See StatPearls' companion references, "Prenatal Nonstress Test," "Ultrasound Biophysical Profile," "Fetal Growth Restriction," and "Sonography 3rd Trimester and Placenta Assessment, Protocols, and Interpretation, for more detailed information regarding these evaluation studies.

Prenatal Management in the Third Trimester

The third trimester of antepartum care, spanning from approximately 28 weeks gestation to delivery, consists of the final preparations, screenings, necessary treatments, and counseling to facilitate safe and timely delivery and improved maternal and fetal outcomes. Generally, prenatal visits during this trimester increase in frequency, particularly around 36 weeks gestation, when visit intervals are commonly reduced from every 2 weeks to weekly. However, this visit schedule is individualized, adjusting as clinically indicated (eg, high-risk patients). Furthermore, patients often also require assessment outside the outpatient clinic setting for urgent concerns (eg, preeclampsia symptoms or signs of labor). Antepartum care in the third trimester involves the same clinical assessment as the second trimester, reviewing current pregnancy-related issues and reviewing newly occurring issues and documentation of maternal blood pressure, maternal weight, fundal height, fetal movement, and fetal heart rate. Further diagnostic testing should be performed in patients with abnormal clinical findings (eg, elevated blood pressure or significant peripheral edema). See StatPearls' companion reference, "Preeclampsia," for more information evaluation of hypertension in pregnancy. Additionally, in patients with labor symptoms or in whom labor induction is being considered, a cervical examination may be performed to assess for labor.[20] 

If emergent maternal-fetal-associated complications arise, patients may require induction of labor or imminent delivery depending on the circumstance and severity.[21][22] Additionally, as patients reach or approach their expected date of delivery, various issues may need to be discussed with shared decision-making, such as labor induction, post-term pregnancy, and delivery, as well as continued patient education regarding peripartum and postpartum topics, including labor signs, breastfeeding, and contraception.[23][24] 

Pregnancies that reach 37 weeks gestation are considered term pregnancies; however, up to 10% of pregnancies continue beyond 42 weeks gestation, referred to as post-term or postdate pregnancies. Post-term pregnancies are associated with a high risk of fetal death and growth restriction. However, labor induction in attempts to avoid post-term pregnancy complications also has risks, including cesarean delivery, prolonged labor, and postpartum hemorrhage. Balancing maternal and fetal risks when determining optimal delivery timing is complex. In patients with post-term pregnancies, several studies have demonstrated that labor induction at or beyond term has fewer fetal deaths, neonatal intensive care unit admissions, and Cesarean deliveries compared with expectant management, though more operative vaginal births. These considerations may be useful during discussions with patients to determine optimal management.[21] In patients with high-risk pregnancies or other potential delivery indications, management must also be individualized. See StatPearls' companion references, "Induction of Labor," "Bishop Score," and "Oxytocin," for more detailed information regarding labor induction. 

Third-Trimester Screening Tests and Vaccinations

In preparation for delivery, several laboratories are also recommended. In high-risk patients, the Centers for Disease Control and Prevention recommends testing for human immunodeficiency virus, syphilis, chlamydia, and gonorrhea in the third trimester using applicable serum or nucleic acid amplification tests between 28 and 36 weeks gestation.[25] ACOG guidelines also recommend screening for group B beta-hemolytic streptococcus (GBS) colonization between 36 0/7 and 37 6/7 weeks gestation with cultures from the lower vagina and rectum except in patients with documented GBS bacteriuria earlier in the current pregnancy or a history of a previous infant with GBS disease; in these patients, intrapartum antibiotic prophylaxis should always be administered as standard of care.[26] See StatPearls' companion reference, "Group B Streptococcus in Pregnancy," for more information. Additionally, tetanus, diphtheria, and acellular pertussis booster vaccine (Tdap) should be offered to patients between 27 and 36 weeks.[27]

Issues of Concern

Common Pregnancy Complaints

Clinicians will frequently encounter several conditions commonly associated with pregnancy. These conditions, including nausea and vomiting, lower back pain, and gastroesophageal reflux, may be exacerbated or caused by physiologic changes due to pregnancy. However, these symptoms may also indicate a more concerning underlying disease. Consequently, clinicians must carefully perform a thorough evaluation and recognize "red-flag" signs that should prompt further investigation to prevent misdiagnosis and adverse outcomes. Generally, the management approach recommended in pregnancy is to use conservative therapies first, reserving pharmacologic treatment for symptoms unresponsive to nonpharmacologic interventions.[28]

Nausea and vomiting

Nausea and vomiting occur in approximately half of pregnant patients, most commonly between 4 and 12 weeks gestation. Physiologic causes are multifactorial, including rapidly increasing levels of pregnancy-related hormones such as β-human chorionic gonadotropin, estrogen, progesterone, placental growth hormone, and leptin. In patients with severe nausea and vomiting or symptoms persisting beyond the first trimester, other obstetric (eg, molar pregnancy and hyperemesis gravidarum) and nonobstetric (eg, appendicitis and thyroid disease) etiologies should be considered.[28] 

Severe cases may require hospitalization and evaluation for more serious causes. Concerning clinical features that should prompt consideration of differential diagnoses include significant weight loss, severe headache, signs of dehydration, diarrhea, fever, abdominal pain, and vaginal bleeding. For instance, hyperemesis gravidarum, identified by severe dehydration, is accompanied by acid-base and electrolyte abnormalities. Patients experiencing typical nausea and vomiting may receive relief from nonpharmacologic and pharmacologic interventions. However, due to the potential risks of many medications in pregnancy, nonpharmacologic therapies are preferred for the initial treatment of nausea and vomiting in pregnancy, including smaller portions, more frequent meals, ginger, and vitamin B₆ supplementation. Medications commonly used during pregnancy include metoclopramide, promethazine, and ondansetron; however, clinicians should carefully inform patients of the risks and benefits of any medication before initiation.[29][30][28] See StatPearls' companion reference, "Hyperemesis Gravidarum," for more information[30]

Gastroesophageal reflux

Due to progesterone-mediated lower esophageal sphincter relaxation, gastroesophageal reflux disease is a common condition during pregnancy. However, in patients with atypical clinical features (eg, severe colicky abdominal pain, positive Murphy sign, leukocytosis, fever) or symptoms that are severe, unresponsive to therapy, or onset after 20 weeks gestation, differential diagnoses should be considered, including peptic ulcer disease, preeclampsia, cholecystitis, and acute fatty liver of pregnancy. Conservative therapies for gastroesophageal reflux during pregnancy include eating frequent small meals and limiting caffeine, peppermint, and chocolate intake. Preferred pharmacologic agents are over-the-counter non-salicylate antacids or famotidine. Proton pump inhibitors may be considered for persistent gastroesophageal reflux that is unresponsive to initial treatments.[28]

Musculoskeletal back pain

Patients during the antepartum course may also have significant lower back and pelvic pain complaints, most commonly in the third trimester of pregnancy, caused by the physiologic increase of lordosis, musculoskeletal laxity, increasing weight from the gravid uterus, and alignment distortion. Musculoskeletal pain is typically exacerbated by walking significant distances, bending forward, or lifting moderately weighted objects. Severe cases of back pain may warrant orthopedic evaluation. Back pain management includes rest, heating pads, back braces, and analgesics. Red flag symptoms occurring with acute low back pain that may indicate a more concerning underlying condition include saddle anesthesia, progressive weakness, numbness, renal colic, urinary retention, trauma, vaginal bleeding, severe abdominal pain, loss of fluid, uterine contractions, uterine tenderness, change in fetal movement, or dysuria. Patients with concerning features such as these should have further evaluation to exclude maternal-fetal complications, not dismissed as having a typical pregnancy complaint.[28]

Musculoskeletal back pain therapy during pregnancy primarily comprises exercises, physical therapy, support devices, and warm baths. Acetaminophen may also be considered.[28][31] Furthermore, a Cochrane review also demonstrated osteopathic manipulative treatment to be effective in improving function and reducing pelvic and lower back pain during and after pregnancy.[32] See StatPearls' companion reference, "Osteopathic Manipulative Treatment: Muscle Energy Procedure - Lumbar Vertebrae," for more information on osteopathic manipulative treatment techniques.

Clinical Significance

Antepartum care is the health care provided during pregnancy to optimize outcomes for both the mother and the fetus. The primary objectives are to identify high-risk pregnancies and to monitor the health of the mother and the development of the fetus. Prenatal visits are an intricate balance of maternal and fetal management aimed to prevent significant maternal and fetal morbidity and mortality and provide support throughout the prenatal course. Close follow-up with timely review of new complaints or issues, physical exam findings, sonography abnormalities, and laboratory results facilitate the necessary interventions. These may include escalation of care to more frequent antepartum care visits, close follow-up by maternal-fetal medicine specialists, antepartum fetal surveillance, and potential early delivery depending on the gestational age, clinical picture, and potential improvement of outcomes.

While many interventions can be performed with relative ease, multiple obstacles may prevent the implementation of these recommendations. Clinicians may have racial biases, insufficient knowledge of updated guidelines, or miss diagnoses that lead to suboptimal care. Furthermore, social determinants of health may frequently prevent patient compliance with visits or management recommendations, including reduced access to prenatal facilities, unreliable transportation, communication barriers, childcare needs, and medication costs, resulting in poor patient outcomes. Because of this, clinicians should strive to remain current on all obstetric guidelines, provide supportive, unbiased care, and identify any barriers to antepartum interventions to optimize maternal-fetal outcomes.[3][4][5]

Other Issues

Anticipatory Counseling in the Second and Third Trimester

Patient education and anticipatory counseling are essential components of antepartum care and often comprise a significant portion of each prenatal visit. Appropriate counseling can decrease patient anxiety, create a supportive maternal experience, and reduce adverse outcomes. Therefore, clinicians should thoroughly address general issues (eg, appropriate weight gain, nutrition, and physical activity) as well as individualized concerns that may arise.[33] During the second and third trimesters, anticipatory counseling primarily involves peripartum and postpartum issues, including birth plans or potential complications and newborn care. See StatPearls' companion reference, "Initial Antepartum Care," for additional information on anticipatory antepartum counseling.

Work accommodations

With more than half of pregnant women working from conception until delivery, employment during the antepartum course is another common area of concern for patients. According to the Family and Medical Leave Act, pregnant employees must be granted at least 12 weeks of unpaid leave from employment for delivery and newborn care. ACOG also states that pregnant women may continue employment until labor begins in the absence of obstetric complications. However, some types of work require accommodations during pregnancy. Especially in jobs with exposures to substances that may result in fetal anomaly, miscarriage, or other adverse effects (eg, lead, mercury, arsenic, pesticides, solvents, ionizing radiation, and specific chemotherapeutic agents), adequate ventilation and protective gear should be ensured. Clinicians should provide appropriate employer letters as needed to obtain work accommodations or maternity leave.[34]

Some types of employment may increase the risk of pregnancy complications, including employment that requires strenuous heavy lifting, prolonged standing, excessive repetition, or extended work hours. These demanding conditions may place additional stress on the patient as well as the pregnancy course, leading to complications such as gestational hypertension with an increased risk of developing preeclampsia, preterm premature rupture of membranes, preterm labor and delivery, and fetal growth restrictions. Exacerbation of musculoskeletal low back pain may be exacerbated in pregnancy with physically demanding work. The National Institute of Occupational Safety and Health recommends lifting restrictions for pregnant employees based on gestational age, lifting height, and lifting frequency. Generally, the recommended weight limit in pregnant women less than 20 weeks is 16 kg, and 12 kg in those 20 weeks or more gestation if performed infrequently. For those who lift more than 1 hour at a time, the recommended weight limit of 14 kg in pregnant women less than 20 weeks is 16 kg, and 10 kg in those 20 weeks gestation or more; for those who are required to lift for more extended periods, the weight limit is 8 and 6 kg for those gestational ages, respectively.[34]

Peripartum counseling

As patients reach or approach their expected delivery date, various issues may need to be discussed with shared decision-making, such as labor induction, post-term pregnancy, and delivery, as well as continued patient education regarding peripartum topics, including labor signs, patient birth plans, and available pain management options as this studies have demonstrated anticipatory counseling eg, childbirth education improves the pregnancy experience and reduces postpartum depression.[23][24] During this trimester, anticipatory counseling should include patient education regarding symptoms that are concerning and labor signs that should be reported or medical care sought. The Centers for Disease Control and Prevention recommends instructing patients to seek immediate medical care for maternal warning signs, including persistent headaches, dizziness, fever of 100.4 °F (38 °C) or higher, peripheral edema, vision changes, chest pain, severe nausea, abdominal pain or contractions, vaginal bleeding, leakage of vaginal fluid, or decreased fetal movement. Additionally, in low-risk individuals, clinicians should discuss a patient's labor expectations and desires, such as admission during latent labor versus expectant management, pain management techniques, emotional support individuals (eg, family members and doulas), and maternal labor positions to facilitate a supportive environment.[35] 

Postpartum issues

Several postpartum concerns should also be discussed before delivery to allow the patient time to consider each available option and the risk-benefit ratio of any decisions. Postpartum contraception is a significant issue that should be thoroughly discussed throughout the second and third trimesters and determined before a patient is discharged from the hospital. Contraceptive options include hormonal contraceptives, nonhormonal contraceptives, and permanent sterilization and counseling should be individualized, taking into consideration a patient's desires and clinical factors (eg, future pregnancy plans, pregnancy intervals, comorbid conditions, and breastfeeding status).[36] See StatPearls' companion references, "Oral Contraceptive Pills," "Intrauterine Device," "Tubal Sterilization," and "Vasectomy," for additional information on these contraceptive options. Clinicians should also encourage patients to participate in breastfeeding and childcare classes. A Cochrane review demonstrated that multiple discussions with clinicians were the most effective intervention in promoting breastfeeding.[37] Clinicians should also encourage patients to find a newborn care clinician before delivery to ensure that their concerns regarding vaccinations, circumcision, and clinician accessibility for emergencies can be discussed. See StatPearls' companion reference, "Breastfeeding," for additional information. Other peripartum issues that should be discussed before delivery include umbilical cord blood banking, circumcision in male neonates before hospital discharge, and neonatal administration of vitamin K and conjunctival antibiotics after delivery.

Enhancing Healthcare Team Outcomes

During the antepartum period, obstetric management involves significant challenges due to the complexity of caring for both the patient and the fetus. The dual focus on maternal and fetal well-being necessitates a team-directed approach involving an interprofessional team to enhance patient-centered care, outcomes, patient safety, and team performance. In high-risk pregnancies, increased surveillance and consultation with maternal-fetal medicine specialists are critical for managing risks and planning delivery. Antepartum care during the second and third trimesters involves ongoing assessments, supportive patient education with shared decision-making, and coordinated interventions from various interprofessional team members. These professionals conduct regular check-ups, laboratory studies, imaging, and antenatal fetal surveillance to monitor maternal and fetal health, addressing concerns such as fetal movement, maternal blood pressure, and weight gain.

Interprofessional communication is vital, ensuring seamless care coordination and timely response to pregnancy complications, involving collaboration between physicians, nurses, advanced practitioners, nutritionists, and pharmacists to monitor and adjust treatments. Patients with a high risk may require additional imaging and surveillance, with findings communicated promptly among the team to adjust care plans. Pharmacists play a crucial role in advising on medication safety during pregnancy, while nurses provide patient education and support, reinforcing the care plan and addressing patient concerns. Advanced practitioners often bridge gaps, offering specialized care and guidance on complex cases. By integrating the expertise of all team members and maintaining open lines of communication, clinicians can effectively manage the challenges of antepartum care, ensuring the safety and well-being of both mother and child throughout the pregnancy.