MFM Fellow Calculators

VBAC Success Calculator

Trial of Labor After Cesarean — induction success probability

Chronic hypertension

Tobacco use

Primary cesarean for labor dystocia

Prior NSVD (count)

Prior VBAC (count)

Years since last delivery

yr

Enter values to estimate
VBAC success probability

Bishop Score

Cervical favorability before induction of labor

Cervical dilation

Effacement

Fetal station

Cervical consistency

Cervical position

Bishop Score

0 / 13

Intrauterine Transfusion

Packed-RBC volume for fetal anemia (IVT / IUT)

Fetal parameters

Estimated fetal weight

g

Observed fetal hematocrit

Pre-transfusion fetal sample

%

Targets

Desired fetal hematocrit

%

Donor blood hematocrit

Packed RBCs, usually 75–85%

%

Enter fetal weight and
observed hematocrit

Cerebroplacental Ratio

CPR = MCA-PI ÷ UA-PI

MCA pulsatility index (PI)

UA pulsatility index (PI)

Enter MCA and UA
pulsatility indices

Fetal Analgesia during IUT / Procedures

Paralysis & analgesia by estimated fetal weight

Estimated fetal weight

g

Enter estimated fetal weight

sFlt-1 / PlGF Ratio

Preeclampsia interpretation & clinical implications

Gestational age

sFlt-1 / PlGF ratio

Enter ratio and
gestational age

Reference

≤ 38Any GA · Rule out PET for 1 week (NPV 99.3%)

39–84<34 wk · High risk of PET within 4 weeks (PPV 36.7%)

39–109≥34 wk · High risk of PET within 4 weeks (PPV 36.7%)

≥ 85<34 wk · PET / placental insufficiency likely

≥ 110≥34 wk · PET / placental insufficiency likely

Gestational Age & Due Date Calculator

Calculate from LMP, ultrasound date, or IVF transfer

Calendar

Calculation Method By :

Last Menstrual Period (LMP)

CCAM Volume Ratio (CVR) Calculator

Congenital Pulmonary Airway Malformation — Hydrops Risk Assessment

Lesion Measurements

Lesion Length

cm

Lesion Height

cm

Lesion Width

cm

Fetal Biometry

Head Circumference (HC)

Measured at same scan as the lesion

cm

Lesion Morphology

Dominant cyst present (≥2 cm macrocystic lesion)

Enter measurements to see results

Result

CVR Score

—

Lesion Volume (ellipsoid)—

Risk Thresholds

CVR	Dominant Cyst	Hydrops Risk
< 1.6	Absent	Low (<3%)
≥ 1.6	Absent	High (~75%)
< 1.6	Present	Intermediate
≥ 1.6	Present	High

Dominant cyst note: Stocker type I / macrocystic lesions (≥2 cm dominant cyst) may be amenable to thoracoamniotic shunting and carry a different natural history than solid/microcystic lesions even at the same CVR.

MCA Peak Systolic Velocity (PSV) Calculator

Middle Cerebral Artery Doppler — Fetal Anemia Assessment (Mari 2000)

Gestational Age

Weeks + Days

MCA Doppler Measurement

Measured MCA PSV

Angle of insonation must be <20° — preferably 0°

cm/s

Clinical Context

Red cell alloimmunization (e.g. anti-D, anti-Kell)

Hydrops fetalis already present

Enter gestational age and
MCA PSV to see results

Result

MoM (Multiples of Median)

—

Median MCA PSV for GA—

1.5 MoM threshold for GA—

Centile chart

Interpretation Thresholds

MoM	Interpretation	Action
< 1.29	Normal	Routine follow-up
1.29 – 1.49	Borderline	Repeat in 1–2 wk
≥ 1.50	Moderate–severe anemia	Consider FBS / IUT

Anti-Kell alloimmunization

Anti-Kell suppresses erythropoiesis. MCA PSV thresholds still apply, but anemia may occur at lower MoM. Lower threshold for FBS is appropriate. Standard MoM cutoffs may underestimate risk.

Technique note: Sample near the origin of the MCA from the circle of Willis. Angle of insonation <20° (ideally 0°). Avoid fetal breathing movements. Use the highest measurable PSV from at least three consecutive waveforms.

Fetal Head Circumference — Microcephaly & Macrocephaly Screening

SD-based assessment using Chervenak 1984 normative chart (20–42 weeks)

Gestational Age

Weeks + Days

Measurement

Head Circumference (HC)

Outer-to-outer, at the level of the thalami and cavum septi pellucidi

mm

Enter gestational age and
HC measurement to assess

Result

SD Score (z-score)

—

Mean HC for GA—

+2 SD threshold (macrocephaly)—

−2 SD threshold (microcephaly)—

−3 SD threshold (severe)—

−5 SD−3 SD−2 SD0+2 SD+3 SD

Extreme (<−5)

Severe (−3 to −5)

Microcephaly (−2 to −3)

Normal (−2 to +2)

Macrocephaly (>+2)

Centile chart

Classification Thresholds

SD Score	Classification	Action
> +2 SD	Macrocephaly	Detailed anatomy
−2 to +2 SD	Normal	Routine care
−2 to −3 SD	Microcephaly	Full workup
−3 to −5 SD	Severe microcephaly	Urgent MRI + genetics
< −5 SD	Extreme microcephaly	Multidisciplinary

Workup Checklist

When HC < −2 SD (Microcephaly), consider:
• Fetal MRI brain (best after 28–30 wks)
• TORCH serology (CMV, Toxo, Rubella, Zika)
• Chromosomal microarray / exome if indicated
• Detailed anatomy scan (associated anomalies)
• Serial growth scans q3–4 weeks
• Fetal neurology / genetics referral

When HC > +2 SD (Macrocephaly), consider:
• Detailed neurosonography (ventriculomegaly, arachnoid cyst)
• Fetal MRI brain (best after 28–30 wks)
• Rule out hydrocephalus, megalencephaly, storage disorders
• Chromosomal microarray
• Serial head growth monitoring
• Pediatric neurology consultation

Important caveat: HC must be interpreted with overall fetal growth context. Isolated mild reduction (−2 to −2.5 SD) with normal biometry and anatomy may represent a constitutional variant. Severe or progressive microcephaly (<−3 SD) warrants comprehensive workup regardless of associated findings.

Lung-to-Head Ratio (LHR) & O/E LHR Calculator

Congenital Diaphragmatic Hernia — Pulmonary Hypoplasia Severity (Jani 2007 / TOTAL Trial)

Gestational Age

Weeks + Days

CDH Side

Left CDHRight CDH

Measurement Method

Contralateral Lung

Measure at 4-chamber view — longest diameter and its perpendicular

Diameter 1 (longest)

mm

Diameter 2 (perpendicular)

mm

Fetal Head Circumference

mm

Liver Position (Left CDH)

Liver herniation into thorax (liver-up)

Enter GA, lung diameters &
HC to calculate O/E LHR

Result

O/E LHR

—

Lung area (D1 × D2)—

Observed LHR—

Expected LHR for GA—

0%25%35%45%100%

SevereModerateMildExpected

Severity & Survival (Left CDH, Liver-up)

O/E LHR	Severity	Survival
< 15%	Extreme	<5%
15–24.9%	Severe	~10–25%
25–34.9%	Moderate	~30–60%
35–44.9%	Mild	~60–80%
≥ 45%	Expected normal	>80%

TOTAL Trial — FETO Eligibility

Group	Criteria	FETO window
Severe	O/E LHR <25% + liver-up	22–24 wks
Moderate	O/E LHR 25–34.9% + liver-up	27–29 wks
Not eligible	Liver-down or O/E LHR ≥35%	—

Right CDH: Generally 10–15% worse survival at equivalent O/E LHR. Standard thresholds still applied but prognosis more guarded.

Technique: Measure the contralateral (unaffected) lung at the 4-chamber view. 2D method: longest diameter × perpendicular (Jani 2007). Tracing method: planimetry trace of the lung outline — more reproducible, ~45% smaller area than 2D (Peralta 2005). AP method: anteroposterior diameter × perpendicular at its midpoint. HC from standard biometry. O/E LHR corrects for gestational age; expected values differ by method (Jani 2007 / Peralta 2005).

Lethality Quick Reference

Condition	Key US Clues	Thorax	Lethality	Gene(s)
Thanatophoric dysplasia	Severe micromelia; telephone-receiver femurs; macrocephaly; ± cloverleaf	Narrow	Lethal	FGFR3
OI type II	Hypomineralization; fractures/callus; compressible skull; beaded ribs	Hypoplastic	Lethal	COL1A1/COL1A2
Achondrogenesis	Extreme micromelia; poor ossification; large head; hydrops	Very small	Lethal	COL2A1; SLC26A2
Hypophosphatasia	Hypomineralization; short/bowed bones; fractures	Small	Lethal	ALPL
Campomelic dysplasia	Bowed long bones esp. tibiae; ambiguous genitalia	Often small	Often lethal	SOX9
Short-rib polydactyly	Short ribs; narrow thorax; polydactyly; renal/cardiac	Severe restriction	Often lethal	DYNC2H1, IFT140…
Jeune (ATD)	Narrow thorax; short ribs; variable limb shortening	Variable	Variable	IFT140, DYNC2H1…
Achondroplasia (het.)	Rhizomelia 21–27w; macrocephaly; frontal bossing; trident hand	Adequate	Survivable	FGFR3
Achondroplasia (hom.)	Earlier rhizomelia; macrocephaly; severe chest narrowing	Severe	Lethal	FGFR3
Diastrophic dysplasia	Short limbs; hitchhiker thumbs; clubfeet; joint contractures	Adequate	Survivable	SLC26A2
Ellis-van Creveld	Short limbs; postaxial polydactyly; congenital heart disease	Adequate	Survivable	EVC, EVC2
Chondrodysplasia punctata	Epiphyseal stippling; limb shortening; variable features	Variable	Variable	ARSE, EBP, PEX7

Cardiothoracic Ratio (CTR)

Fetal cardiac size — normal CTR ≤ 0.50

Measurements

Cardiac Circumference

Trace the outer edge of the heart (epicardium)

mm

Thoracic Circumference

Trace the outer edge of the bony thorax (ribs only) — exclude skin and subcutaneous fat

mm

CTR Classification

CTR	Interpretation	Action
≤ 0.50	Normal	Routine
0.51–0.57	Borderline	Repeat + echo
> 0.57	Cardiomegaly	Echo + MFM

Causes of Elevated CTR

Structural

CHD — AVSD, Ebstein anomaly, HLHS, TOF

Functional

Cardiomyopathy, arrhythmia, SVT

Volume Overload

Fetal anemia, AVM, twin-to-twin transfusion

Extrinsic

CDH (mediastinal shift), pleural effusion

Other

Hydrops fetalis, pericardial effusion

Technique and Measurement
Should be performed on a four-chamber view of the heart at the end of diastole (just before contraction).

Obtain a transverse (axial) plane of the fetal chest that clearly shows a complete rib on each side.

Clear visualization of cardiac structures and thoracic boundaries is required.

Umbilical Artery Pulsatility Index

GA-specific percentiles — INTERGROWTH-21st (Drukker 2020)

Reference

INTERGROWTH-21st (Drukker 2020) · 24–40 weeks · Z-score & centile

Gestational Age

Weeks + Days

Measurement

Observed UA Pulsatility Index (PI)

Leave blank to see reference values only

Enter gestational age to view
UA PI reference values

Result

UA Pulsatility Index Percentile

—

Observed PI—

50th centile (median)—

95th centile (upper normal)—

050th75th95th>95th

Clinical Interpretation

Percentile	Interpretation	Action
< 95th	Normal	Routine surveillance
≥ 95th	Elevated — investigate	Repeat + growth scan

Clinical Notes

Normal trend: UA PI decreases progressively with advancing gestation as placental villous vascularity increases and resistance falls.

Elevated PI: Suggests increased placental resistance. In FGR, up to 25% show elevated UA PI. Progressive worsening indicates deterioration.

MFM Referral Criteria

NGH institutional criteria — Fetal & Medical Disorders Clinics

Direct MFM referral (stay in MFM)

Consult & may return to original MRP

Group A — Direct MFM Referral (Remain under MFM Care)

Multiple Fetal Anomalies

Documented multiple fetal anomalies on ultrasound

Fetal Arrhythmias

Any fetal arrhythmia requiring evaluation and monitoring

Rh Isoimmunization

Rh isoimmunization or fetuses at risk for isoimmunization with positive blood group antibodies

Fetal Hydrops

History of previous or current fetal hydrops (immune or non-immune)

Monochorionic Twin

All monochorionic (MCDA and MCMA) twin pregnancies — serial TTTS and TAPS surveillance

Triplet Gestation and Above

Higher-order multiples regardless of chorionicity

DCDA Twins with Complications

Dichorionic/Diamniotic twins with IUGR, OR oligohydramnios (largest amniotic pocket ≤2 cm), OR growth discordance >20%

Early-Onset IUGR (<24 weeks)

Fetal growth restriction identified before 24 weeks of gestation

Severe IUGR

AC or EFW <3rd percentile at <37 weeks — OR — AC or EFW <10th percentile + oligohydramnios and/or abnormal umbilical artery Doppler at <34 weeks

Abnormal Fetal Doppler ± IUGR (<37 weeks)

Any abnormal umbilical artery, MCA, or ductus venosus Doppler waveform with or without growth restriction before 37 weeks

Severe Amniotic Fluid Abnormality (<37 weeks)

Severe polyhydramnios (AFI >35 cm) OR oligohydramnios (AFI <3 cm) at gestational age <37 weeks

Dilated Fetal Renal Pelvis >15 mm

Renal pelviectasis >15 mm at any gestational age

Group B — MFM Consultation (May Return to Original MRP After Counselling)

Previous History of Fetal Anomalies

Prior pregnancy with fetal anomaly — counselling and risk assessment for current pregnancy

Family History of Genetic Disease

After counselling ± antenatal genetic testing if needed; may return if test result is normal

Teratogenic Medication Exposure

Pregnant patient who used teratogenic medication — after normal detailed scan and counselling

Isolated Fetal Anomalies (Selected)

Cleft lip/palate · Familial clubfoot · Mild renal pelvis dilatation 7–15 mm · Isolated cardiac anomalies (e.g., VSD, vascular ring)

DIDA Twins with One IUFD

Dichorionic/Diamniotic twin gestation with single intrauterine fetal demise

AC or EFW <10th Percentile (34–37 weeks)

Fetal growth at <10th percentile between 34 and 37 weeks of gestation

Non-Specific Positive Blood Group Antibodies

Positive antibodies not known to cause fetal/neonatal anemia

Mild–Moderate Amniotic Fluid Abnormality (<37 weeks)

Polyhydramnios (AFI 24–35 cm) OR oligohydramnios (AFI 3–10 cm) at <37 weeks

Antenatal Diabetic Clinic

Type I Diabetes Mellitus

All T1DM pregnancies

Type II DM with HbA1c ≥7%

HbA1c ≥7% done within 3 months of pregnancy

Note: Gestational diabetes and Type II DM with HbA1c <7% are not eligible for this clinic

Medical Disorders in Pregnancy (MDP) Clinic — For referrals outside these criteria, contact Dr. Feras Alkharouf or his delegate

Cardiac Diseases

Pulmonary Arterial Hypertension

Cardiomyopathy

Previous Peripartum Cardiomyopathy

Arrhythmias

Excluding PVCs and PACs

Ischemic Heart Disease / Coronary Artery Disease

Moderate–Severe Mitral Stenosis

Moderate–Severe Aortic Stenosis

LV Impairment — EF ≤45%

Tetralogy of Fallot

Aortic Dilatation ≥40 mm

Other Adult Congenital Heart Disease

Note: Exclude mWHO Class I (NYHA Class 1) — may follow up with general Ob/Gyn

Respiratory Diseases

Bronchiectasis

Restrictive Lung Disease

Endocrine Diseases

Hyperthyroidism / Graves Disease

With positive antibodies

Hyperparathyroidism

With abnormal calcium levels

Adrenal Insufficiency / Addison Disease

Renal Diseases

Chronic Kidney Disease

IgA nephropathy, nephrotic syndrome, nephritic syndrome

ESRD on Dialysis

Renal Transplant

Note: Exclude chronic proteinuria alone

Neurological Diseases

Refractory Epilepsy / Multiple AEDs

Or last seizure <1 year ago

Multiple Sclerosis on Medication

Myasthenia Gravis

Acute Stroke

Hemorrhagic or thrombotic

Rheumatological Diseases

SLE (Systemic Lupus Erythematosus)

Rheumatoid Arthritis

With positive Anti-Ro / Anti-La antibodies

Sjogren Syndrome

Mixed Connective Tissue Disease

Scleroderma / Systemic Sclerosis

Hematological Diseases

Sickle Cell Anemia

Exclude post stem cell transplant

Thalassemia Major

Alpha and beta thalassemia major

Immune Thrombocytopenic Purpura (ITP)

Platelet level below 50 × 10⁹/L

TTP (Thrombotic Thrombocytopenic Purpura)

Hematological Malignancies

Inflammatory Bowel Diseases

Crohn Disease

On biological medication

Ulcerative Colitis

On biological medication

Liver & GI Diseases

Autoimmune Hepatitis

Viral Hepatitis (Active Disease)

Liver Transplant

Cancer

Pre-pregnancy Cancer — Treated <1 Year Ago

Treated with radiotherapy and/or chemotherapy within 1 year before pregnancy

Cancer Diagnosed During Pregnancy

Any type of cancer first diagnosed during the current pregnancy

Mental Health

Complex Mental Health Disorder

e.g., Schizophrenia, Psychosis

Maternal Genetic Diseases

Ehlers-Danlos Syndrome

Marfan Syndrome

Phenylketonuria (PKU)

Other Significant Genetic Disease

With fetal and/or maternal implications

Infectious Diseases

HIV

Other Significant Infectious Disease

With fetal and/or maternal implications

For referrals outside the stated criteria, contact Dr. Feras Alkharouf or his delegate before referring.

CVS / Amniocentesis Timing

Next available Sunday or Tuesday at 12w (CVS) and 15w (Amnio)

Today's Gestational Age

Twins Calculators

EFW Discordance & TAPS (Mo/Di) assessment

Ultrasound EFW only

Estimated Fetal Weights

Twin 1

Larger

g

Twin 2

Smaller

g

(Larger EFW − Smaller EFW) ÷ Larger EFW × 100

Enter both EFW values above

VBAC Success Calculator

Bishop Score

Intrauterine Transfusion

Cerebroplacental Ratio

Fetal Analgesia during IUT / Procedures

sFlt-1 / PlGF Ratio

Gestational Age & Due Date Calculator

CCAM Volume Ratio (CVR) Calculator

MCA Peak Systolic Velocity (PSV) Calculator

Fetal Head Circumference — Microcephaly & Macrocephaly Screening

Lung-to-Head Ratio (LHR) & O/E LHR Calculator

Skeletal Survey

Cardiothoracic Ratio (CTR)

Umbilical Artery Pulsatility Index

MFM Referral Criteria

Twins Calculators