Prenatal Care Schedule and Screening: What to Order and When

Clinical Practice Update — Visit Timing, Routine Laboratory Tests, Ultrasound, and Risk-Based Screening in Pregnancy

This is an original clinical education article informed by current guidelines and evidence. See References below for source documents.

MDA-PNS-2026 · 14 min read

Clinical Focus

Prenatal care schedule, routine and risk-based screening tests, ultrasound timing, and laboratory monitoring across all three trimesters

Target Audience

Obstetricians, family medicine physicians, midwives, OB/GYN residents, prenatal care nurses

Setting

Outpatient prenatal clinics, maternal-fetal medicine, primary care

Source Evidence

•ACOG Practice Bulletins and Committee Opinions on Prenatal Care (2018–2024)
•ACOG Clinical Consensus No. 8 — Tailored Prenatal Care Delivery (2025)
•SMFM Consult Series #74 — Cell-Free DNA Screening for Aneuploidies: Updated Guidance (2025)
•USPSTF Screening Recommendations — Preeclampsia, Gestational Diabetes, Rh(D), Folic Acid (2021–2023)
•NICE Antenatal Care Guideline [NG201] (2021, updated 2024)
•WHO Recommendations on Antenatal Care for a Positive Pregnancy Experience (2016)

Key Clinical Takeaways

The most important actionable points from this prenatal care schedule and screening Practice Update. Each links to the full discussion below.

Prenatal care schedule and screening timeline showing recommended tests and visit frequency across all three trimesters of pregnancy — Overview of the prenatal care schedule and screening approach across trimesters.

1Book the first prenatal visit ideally before 10 weeks — earlier visits improve dating accuracy and allow timely screening → First Visit
2Order a comprehensive first-trimester lab panel at the initial visit — blood type, CBC, infectious disease serology, and urine culture → First-Trimester Labs
3Offer aneuploidy screening to every patient regardless of age — cfDNA is now recommended as the most sensitive and specific screening test for common aneuploidies → Aneuploidy Screening
4Start low-dose aspirin (81 mg daily) after 12 weeks of gestation for patients with preeclampsia risk factors, optimally before 16 weeks → Preeclampsia Prevention
5Screen universally for gestational diabetes at 24–28 weeks using either one-step or two-step glucose testing → GDM Screening
6Perform the anatomy ultrasound between 18 and 22 weeks — this is the single most comprehensive fetal structural assessment → Ultrasound Timing
7Screen for Group B Streptococcus between 36 0/7 and 37 6/7 weeks to guide intrapartum antibiotic prophylaxis → Third-Trimester Screening
8Consider tailored visit schedules based on patient risk — ACOG 2025 guidance supports 6–10 targeted visits for average-risk patients as equivalent to 12–14 visits → Visit Schedule
9Administer Rh immunoglobulin at 28 weeks for Rh-negative patients — cfDNA fetal Rh typing can now identify pregnancies where RhIg is unnecessary → Rh Management
10Guidelines differ on the optimal GDM screening method and whether the traditional visit schedule should be maintained or tailored — know your institutional approach → Where Guidelines Differ

What Should Happen at the First Prenatal Visit?

The first prenatal visit is the most information-dense encounter of the entire pregnancy. It sets the foundation for risk stratification, establishes gestational dating, and initiates all first-trimester screening. ACOG recommends this comprehensive assessment take place ideally before 10 weeks of gestation.

Perform a comprehensive initial prenatal needs assessment ideally before 10 weeks of gestation, including detailed medical, surgical, obstetric, and family history; current medication review; screening for social determinants of health; and documentation of the last menstrual period for dating.

Strong Rec High Evidence ACOG 2025 NICE 2021

Order first-trimester routine laboratory tests at the initial visit: blood type and Rh factor, antibody screen, complete blood count, rubella immunity, hepatitis B surface antigen, HIV, syphilis serology, urine culture, and urine protein assessment.

Strong Rec High Evidence ACOG 2018 USPSTF 2019

Prescribe folic acid supplementation of 0.4 to 0.8 mg (400–800 mcg) daily, ideally started at least one month before conception and continued through the first 2–3 months of pregnancy. Increase to 4 mg daily for patients with a history of neural tube defects.

Strong Rec High Evidence USPSTF 2023

Evaluate for preeclampsia risk factors at the first visit. Start low-dose aspirin (81 mg daily) after 12 weeks of gestation, optimally before 16 weeks, for patients with one or more high-risk factors (prior preeclampsia, multifetal gestation, chronic hypertension, pregestational diabetes, renal disease, autoimmune disease) or two or more moderate-risk factors (nulliparity, obesity, age ≥35, family history, >10-year pregnancy interval). Continue until delivery.

Strong Rec Moderate Evidence USPSTF 2021 ACOG/SMFM 2021

Consider screening for thyroid dysfunction with TSH only in patients with symptoms or risk factors. Universal thyroid screening in pregnancy is not currently recommended.

Conditional Rec Low Evidence ACOG 2020

Clinical Pearl: The first visit is your one opportunity to catch everything. Build a standardised first-visit order set in your EHR that includes all routine labs, dating ultrasound request, and an aspirin risk-factor checklist. Forgetting the urine culture is one of the most common first-visit omissions — asymptomatic bacteriuria occurs in roughly 2–10% of pregnancies and is associated with pyelonephritis and preterm birth if untreated.

First-Visit Laboratory Panel: Test-by-Test Guide

Test	Clinical Reason	What to Do With an Abnormal Result	Common Pitfalls
Blood type + Rh + antibody screen	Identifies Rh-negative patients and alloantibodies that may cause haemolytic disease	Rh-negative: plan RhIg at 28 weeks (unless fetal Rh is known negative by cfDNA or paternal testing). Positive antibody screen: refer to MFM for serial titres	Forgetting to repeat antibody screen at 28 weeks before giving RhIg
CBC	Baseline haemoglobin; identifies anaemia and thrombocytopenia early	Hb <11 g/dL: start iron, recheck at 28 weeks. Platelets <100: investigate cause	Not repeating CBC at 28 weeks to catch third-trimester anaemia
Hepatitis B surface antigen	Prevents vertical transmission through neonatal immunoprophylaxis	Positive: check viral load, refer hepatology, arrange neonatal HBIg + vaccine at birth	Not communicating the result to the delivery team and nursery
HIV	Enables antiretroviral therapy to reduce vertical transmission to <1%	Positive: urgent referral to HIV medicine; start ART promptly	Not retesting in the third trimester for patients with ongoing risk factors
Syphilis (RPR/VDRL)	Congenital syphilis rates are rising sharply; early detection allows curative treatment	Positive: confirm with treponemal test, stage, and treat with penicillin per CDC guidelines	Not retesting at 28 weeks and at delivery in high-prevalence areas as now recommended by CDC
Rubella IgG	Non-immune patients need postpartum MMR vaccination	Non-immune: counsel on avoidance, vaccinate postpartum before discharge	Forgetting the postpartum MMR order at discharge
Urine culture	Detects asymptomatic bacteriuria, which is linked to pyelonephritis and preterm birth	Positive (≥10⁵ CFU/mL): treat with appropriate antibiotic and confirm clearance	Ordering a urinalysis instead of a culture — dipstick alone misses asymptomatic bacteriuria

Consider adding hepatitis C screening (now recommended universally per USPSTF 2020), Pap smear (if due), and varicella IgG based on patient history.
Chlamydia and gonorrhoea screening is recommended for all patients under 25 and for those with risk factors at any age.

How Should You Approach Aneuploidy Screening?

Aneuploidy screening should be offered to every pregnant patient through shared decision-making. The landscape changed significantly in 2025 with SMFM Consult Series #74 (endorsed by ACOG), which now recommends cfDNA screening for common aneuploidies be routinely available to all patients and recognises it as the most sensitive and specific screening option. Traditional serum screening remains a valid alternative when cfDNA is unavailable, not covered, or when the patient prefers it after counselling.

Counsel every pregnant patient about the availability of aneuploidy screening and diagnostic testing, regardless of maternal age. Ensure the patient understands the difference between screening (risk estimation) and diagnostic testing (definitive answer). After pretest counselling, every patient has the right to pursue or decline screening.

Strong Rec High Evidence SMFM 2025 ACOG 2025

Ensure that cfDNA screening for common aneuploidies (trisomies 21, 18, and 13) is routinely available to all obstetric patients. It is the most sensitive and specific screening test for these conditions in any patient population. However, it remains a screening test — positive results still require diagnostic confirmation with CVS or amniocentesis.

Strong Rec High Evidence SMFM 2025 (GRADE 1B) ACOG 2025

Perform first-trimester combined screening (nuchal translucency ultrasound plus serum PAPP-A and free beta-hCG) between 11 and 14 weeks as an alternative when cfDNA cannot be offered (e.g., insurance non-coverage, vanishing twin, maternal organ transplant) or when the patient prefers serum-based screening after counselling.

Strong Rec High Evidence SMFM 2025

Do not use cfDNA screening for routine general population screening for microdeletion syndromes or large genome-wide copy number variants. Patients interested in information about fetal copy number variants should be offered diagnostic testing (CVS or amniocentesis) rather than cfDNA-based microdeletion panels. The exception is 22q11.2 deletion, which may be offered with appropriate pretest counselling.

Against Moderate Evidence SMFM 2025 (GRADE 1C)

Clinical Pearl: A common source of patient confusion is the belief that cfDNA is a diagnostic test. When counselling, frame it simply: “This blood test tells us whether the risk is higher or lower than average. If it comes back high-risk, we would then offer a procedure to know for certain.” This prevents the distress of patients who assume a positive cfDNA result means a definitive diagnosis.

How Often Should Patients Be Seen?

The traditional prenatal care schedule of 12–14 visits has been largely unchanged since 1930. In April 2025, ACOG released Clinical Consensus No. 8 recommending a paradigm shift: tailored visit schedules of 6–10 targeted visits for average-risk patients have been shown to produce equivalent outcomes with improved accessibility. Higher-risk patients still require individualised, often more frequent, monitoring.

Consider tailoring prenatal visit frequency and modality based on the patient’s medical and social needs. For average-risk patients, evidence supports 6–10 targeted visits (incorporating telehealth where appropriate) as producing outcomes equivalent to the traditional 12–14 visit schedule. The traditional pattern (every 4 weeks until 28 weeks, every 2 weeks until 36 weeks, then weekly) remains appropriate where tailored scheduling has not been implemented.

Moderate Rec Moderate Evidence ACOG 2025 WHO 2016

Perform a dating ultrasound in the first trimester (ideally 8–13 weeks) to confirm viability, establish gestational age, and identify multiple pregnancies. First-trimester dating is the most accurate method for estimating the due date.

Strong Rec High Evidence ACOG 2017

Perform the detailed fetal anatomy ultrasound between 18 and 22 weeks to assess fetal structures, placental position, amniotic fluid volume, and cervical length when indicated. An anatomy survey is recommended for all patients regardless of the aneuploidy screening method chosen.

Strong Rec High Evidence ACOG 2023 SMFM 2025

Avoid routine third-trimester ultrasound in low-risk pregnancies. It has not been shown to improve perinatal outcomes and increases healthcare costs without clear benefit.

Against Moderate Evidence ACOG 2023

Clinical Pearl: If the placenta is noted to be low-lying or covering the cervical os at the 18–22 week scan, do not alarm the patient. The vast majority of low placental positions at mid-trimester will resolve by 32 weeks as the lower uterine segment grows. Schedule a follow-up scan at 32 weeks and counsel the patient to present for any vaginal bleeding.

What Screening Should You Order in the Second and Third Trimesters?

Screen all pregnant patients for gestational diabetes between 24 and 28 weeks using either the one-step 75 g OGTT (IADPSG criteria) or the two-step approach (50 g GCT followed by 100 g OGTT if positive).

Strong Rec High Evidence ACOG 2018 USPSTF 2021

Consider early glucose screening in the first trimester for patients with significant risk factors for type 2 diabetes (BMI ≥30, prior GDM, PCOS, first-degree relative with diabetes). If the initial screen is normal, rescreen at 24–28 weeks.

Moderate Rec Low Evidence ACOG 2018

Repeat the complete blood count at 28 weeks to screen for third-trimester anaemia. Administer Rh immunoglobulin (300 mcg IM) at 28 weeks for all Rh-negative patients who are not alloimmunised and whose fetus is not confirmed to be Rh-negative by cfDNA or paternal testing.

Strong Rec High Evidence ACOG 2018

Screen for Group B Streptococcus colonisation with a combined vaginal-rectal swab between 36 0/7 and 37 6/7 weeks of gestation. This window ensures culture results remain valid for up to 5 weeks, covering births through at least 41 weeks. Positive results guide intrapartum antibiotic prophylaxis.

Strong Rec High Evidence ACOG 2020

Administer Tdap vaccine between 27 and 36 weeks of every pregnancy to maximise neonatal pertussis antibody levels. Earlier timing within the window produces higher cord blood antibody titres.

Strong Rec High Evidence ACIP/CDC 2023

Monitor blood pressure and urine protein at every visit from the second trimester onward. New-onset hypertension after 20 weeks requires urgent evaluation for preeclampsia with laboratory work including liver enzymes, platelets, and creatinine.

Strong Rec High Evidence ACOG 2020 NICE 2021

Info

Syphilis screening guidelines have changed. Given the sharp increase in congenital syphilis cases in recent years, CDC now recommends repeat syphilis testing at 28 weeks and again at delivery in many jurisdictions, especially in areas with higher prevalence. Check your state or regional guidance.

Clinical Decision Pathway

A practical, question-based approach to prenatal screening decisions. Follow the questions at each stage of pregnancy.

Prenatal Care Schedule and Screening: 5 Decision Points

Decision 1: Patient presents for first prenatal visit. What do you order?

Comprehensive lab panel (blood type, Rh, antibody screen, CBC, rubella, HBsAg, HIV, syphilis, urine culture). Dating ultrasound if not already performed. Review medication list and start prenatal vitamins with folic acid 0.4–0.8 mg daily.

Assess preeclampsia risk factors and initiate low-dose aspirin 81 mg daily after 12 weeks if indicated, optimally before 16 weeks.

Decision 2: Patient wants to know about genetic screening. How do you counsel?

Explain the difference between screening (risk estimate) and diagnostic testing (CVS/amniocentesis).

If patient wants screening → cfDNA is recommended as the most sensitive and specific option (available from ~10 weeks). First-trimester combined screening (11–14 weeks) remains a valid alternative.

If patient wants a definitive answer → offer CVS (10–13 weeks) or amniocentesis (15–20 weeks).

If patient declines all screening → document discussion, continue routine care.

Decision 3: Patient reaches 18–22 weeks. What imaging is needed?

Anatomy ultrasound for all patients, regardless of aneuploidy screening method chosen. Review for structural anomalies, placental location, amniotic fluid, and cervical length if at risk for preterm birth.

Decision 4: Patient reaches 24–28 weeks. What tests are due?

GDM screening (50 g GCT or 75 g OGTT per local protocol). Repeat CBC. Administer RhIg if Rh-negative and fetal Rh not confirmed negative. Repeat antibody screen. Consider repeating syphilis and HIV in high-risk patients.

Decision 5: Patient reaches 36 weeks. What needs to happen before delivery?

GBS vaginal-rectal swab at 36 0/7 to 37 6/7 weeks (results valid for 5 weeks). Tdap vaccine if not yet given. Confirm fetal presentation. Discuss birth plan and labour signs. Increase visit frequency if not already weekly.

Prenatal Screening Timeline: When to Order What

This table organises screening by gestational age windows, with practical reminders to help prevent missed tests.

Gestational Age Window	Tests and Actions	Who Gets It	Don’t Forget
Before 10 weeks	Full lab panel, dating ultrasound, preeclampsia risk assessment, SDoH screening, medication review, folic acid	All patients	Urine culture (not just dipstick). Chlamydia/gonorrhoea if <25 or risk factors. Hep C (universal per USPSTF 2020)
10–14 weeks	cfDNA screening (from ~10 weeks) or first-trimester combined screening (11–14 weeks); start aspirin 81 mg if indicated; CVS if desired	All patients offered screening; aspirin for those at risk	NT scan must be done before 13+6 weeks. Aspirin should start by 16 weeks at latest
15–20 weeks	Quad screen (if no first-trimester screening); amniocentesis if desired	Patients who missed first-trimester screening; those wanting diagnostic testing	AFP can also screen for open neural tube defects
18–22 weeks	Anatomy ultrasound	All patients regardless of screening method	Note placental location. If low-lying, repeat scan at 32 weeks
24–28 weeks	GDM screening (GCT or OGTT), repeat CBC, RhIg for Rh-negative patients (if fetal Rh not known negative), repeat antibody screen	All patients (GDM); Rh-negative patients (RhIg)	Repeat syphilis in high-prevalence areas. Iron supplementation if Hb <11
27–36 weeks	Tdap vaccination	All patients, every pregnancy	Earlier in the 27–36 window gives higher cord blood titres
36 0/7–37 6/7 weeks	GBS vaginal-rectal swab, confirm fetal presentation, repeat syphilis/HIV if indicated	All patients (GBS); high-risk patients (repeat STI screen)	GBS results are valid for 5 weeks. Swab too early and you may need to repeat

Clinical Pearl: Build the 28-week visit as a “checkpoint” in your workflow. It should trigger four actions simultaneously: GDM screen, repeat CBC, RhIg for Rh-negative patients, and repeat antibody screen. Batching these prevents missed items.

Evidence in Context

Where the major guidelines agree, where they diverge, and what remains uncertain in prenatal screening.

Where ACOG, USPSTF, and NICE Agree

All three frameworks agree that universal GDM screening at 24–28 weeks is essential, that aneuploidy screening should be offered to all pregnant patients regardless of age, that GBS screening before delivery guides intrapartum prophylaxis, and that a mid-trimester anatomy scan is standard of care. They also broadly agree on the first-visit lab panel.

Where Guidelines Differ: GDM Screening Method

The single largest area of disagreement in prenatal screening is how to test for gestational diabetes. ACOG continues to recommend the two-step approach (50 g GCT followed by 100 g OGTT), citing fewer diagnoses and less medicalisation. The WHO and IADPSG recommend the one-step 75 g OGTT, which diagnoses more cases and may improve outcomes. NICE uses a 75 g OGTT but with different thresholds. In practice, your institution’s chosen protocol matters more than which guideline you cite.

Cell-Free DNA Screening: The 2025 Paradigm Shift

SMFM Consult Series #74 (2025), endorsed by ACOG, represents a significant shift. cfDNA screening is now recommended to be routinely available to all obstetric patients (GRADE 1B) and is recognised as the most sensitive and specific screening test for trisomies 21, 18, and 13 in any population. This replaces the earlier cautious “may be offered” language. NICE takes a different approach, using a contingent model where cfDNA is offered only to those with elevated combined-screening risk. Traditional serum screening remains relevant when cfDNA cannot be offered or when the patient prefers it. Importantly, cfDNA does not replace the anatomy ultrasound, which detects structural abnormalities that cfDNA cannot.

Visit Frequency: ACOG’s 2025 Tailored Prenatal Care Model

ACOG Clinical Consensus No. 8 (April 2025), endorsed by SMFM and multiple nursing and midwifery organisations, recommends moving away from the rigid 12–14 visit model that has been unchanged since 1930. Three systematic reviews have demonstrated equivalent maternal and neonatal outcomes with 6–10 targeted visits for average-risk patients. The new model emphasises screening for social determinants of health, shared decision-making about visit frequency and modality, and incorporation of telehealth. For higher-risk patients, visit frequency should still be individualised based on clinical needs.

What We Still Don’t Know

Optimal GDM screening thresholds: The thresholds used in the one-step and two-step approaches were derived from different outcome data. A definitive trial comparing long-term maternal and neonatal outcomes across thresholds is still lacking.

cfDNA for microdeletions in average-risk populations: SMFM 2025 recommends against routine screening for microdeletions but allows opt-in 22q11.2 screening with counselling. The clinical utility of broader microdeletion panels in low-risk pregnancies remains uncertain.

First-trimester preeclampsia prediction models: Algorithms combining uterine artery Doppler, PlGF, PAPP-A, and maternal factors show promise for identifying preeclampsia risk earlier and more accurately than clinical risk factors alone, but they are not yet standard practice in most settings.

Optimal implementation of tailored prenatal care: ACOG 2025 endorses flexible visit schedules, but the best way to implement these in diverse practice settings — particularly regarding health equity, patient satisfaction, and detection of late-onset complications — is still being studied.

References

1.Rink BD, Dugoff L, Kuller JA; SMFM Publications Committee. Society for Maternal-Fetal Medicine Consult Series #74: Cell-free DNA screening for aneuploidies: Updated guidance. Pregnancy. 2025;1:e70139. doi:10.1002/pmf2.70139
2.Jones E, Peahl AF, Turrentine M, et al. Tailored Prenatal Care Delivery for Pregnant Individuals. ACOG Clinical Consensus No. 8. Obstet Gynecol. 2025;145(5):565–577. doi:10.1097/AOG.0000000000005889
3.US Preventive Services Task Force. Aspirin Use to Prevent Preeclampsia and Related Morbidity and Mortality: US Preventive Services Task Force Recommendation Statement. JAMA. 2021;326(12):1186–1191. doi:10.1001/jama.2021.14781
4.US Preventive Services Task Force. Screening for Gestational Diabetes: US Preventive Services Task Force Recommendation Statement. JAMA. 2021;326(6):531–538. doi:10.1001/jama.2021.11922
5.US Preventive Services Task Force. Folic Acid Supplementation to Prevent Neural Tube Defects: US Preventive Services Task Force Reaffirmation Recommendation Statement. JAMA. 2023;330(5):454–459. doi:10.1001/jama.2023.12876
6.ACOG Committee Opinion No. 797. Prevention of Group B Streptococcal Early-Onset Disease in Newborns. Obstet Gynecol. 2020;135(2):e51–e72. doi:10.1097/AOG.0000000000003668
7.NICE Guideline [NG201]. Antenatal care. 2021, updated 2024. nice.org.uk/guidance/ng201
8.WHO. WHO recommendations on antenatal care for a positive pregnancy experience. Geneva: World Health Organization; 2016. who.int/publications/i/item/9789241549912

How to Read the Evidence Tags

Every recommendation in this article carries two tags indicating how strong the recommendation is and how robust the supporting evidence is. These are Medaptly’s own simplified interpretations for educational clarity.

Recommendation Strength

Tag	What It Means	In Practice
Strong Rec	High-quality evidence broadly supports this action. The benefits clearly outweigh the risks for most patients.	This should be standard practice.
Moderate Rec	The weight of evidence favours this action, though some uncertainty remains.	Most patients should receive this, but clinical context may reasonably lead to a different decision.
Conditional Rec	The benefit is less certain. The right choice depends on the individual patient.	Discuss with the patient. Use shared decision-making.
Against	Evidence shows no benefit, or the risks outweigh potential benefits.	Avoid this intervention.

Evidence Quality

Tag	What It Means	How Confident Can You Be?
High Evidence	Based on multiple well-designed RCTs or high-quality meta-analyses.	Very confident. Unlikely to change substantially.
Moderate Evidence	Based on a single RCT, large observational studies, or meta-analyses with limitations.	Reasonably confident. Direction likely correct.
Low Evidence	Based on expert consensus, small studies, or extrapolated evidence.	Less certain. May change as better evidence emerges.

These are Medaptly’s simplified interpretations for educational clarity. For the full classification systems used by each source guideline, consult the original documents listed in References.

Article Information

For Educational Purposes Only. This is original clinical education content informed by current published guidelines and clinical evidence. It does not constitute medical advice, is not endorsed by any guideline body (ACOG, USPSTF, SMFM, NICE, WHO, or any other organisation), and does not replace individualised clinical judgement, institutional protocols, or local formulary guidance. Drug dosages and screening thresholds should always be verified against current prescribing information and institutional protocols before clinical use. Readers are encouraged to consult the original source guidelines listed in the References section for the full evidence review and complete recommendation sets.