Pregnancy Dating and Antenatal Scheduler

Dates the pregnancy, applies the ACOG redating rule, and returns the antenatal plan · v2.1

  • Choose how the pregnancy is being dated, then enter the corresponding values.
  • Where both a last menstrual period and an early scan are entered, the ACOG redating rule is applied and the tool states which estimate it has adopted and why.
  • You get the estimated date of delivery and the current gestational age.
  • Plus a dated antenatal schedule showing what is due now, and the supplementation and prophylaxis plan.
  • The traditional calendar date for the delivery is printed alongside, for the antenatal card and the conversation.

  • Multiple pregnancy, where the scan schedule, the aspirin indication and the timing of delivery all differ.
  • The staging or management of hypertensive disease, anaemia, gestational diabetes and preterm labour, which it names as milestones and takes no further.
  • Foetal weight, growth centiles and Doppler indices.
  • A pregnancy conceived on hormonal contraception or during lactational amenorrhoea, where the last menstrual period is unreliable and an early scan should be used instead.
  • Gestations beyond 44+0 weeks, which are refused rather than extrapolated.

1. Gestational Dating

Dating rests on the last menstrual period alone. If the pregnancy reaches 22+0 weeks without a confirming scan it is, by ACOG definition, suboptimally dated.

Naegele's rule assumes 28 days. The tool corrects for a shorter or longer follicular phase, holding the luteal phase at 14 days.

Converted using the INTERGROWTH-21st crown-rump length standard, valid from 15 to 95 mm. Use the mean of three measurements in a true mid-sagittal plane.

ACOG assigns the estimated date of delivery from the embryo age and the date of the embryo transfer. An ART-derived date is not revised by a later scan.

The date already recorded in the antenatal card. Gestational age and every scheduled date are counted back 280 days from it. The tool adopts the date as entered and does not revise it.

The gestational age recorded for today in a referral letter or an antenatal card, where the dating itself was done elsewhere. The tool works back to a dating anchor and forward to an estimated date of delivery. It adopts the figure as given and cannot check how it was arrived at.

2. Optional

Udupi

Used only to convert the estimated date of delivery into the traditional calendar date shown at the foot of the result, which some families ask for. It has no effect on any clinical output.

1. How the Gestational Age Is Fixed

Gestational age is counted from the first day of the LMP, not from the date of conception. It decides when aneuploidy screening is worth doing, sets the legal window under the MTP Act, decides whether a woman in preterm labour is given steroids and magnesium, and settles when a post-term pregnancy is induced. One wrong number at booking moves all of them, in the same direction.

  • ACOG Committee Opinion 700: ultrasound of the embryo or foetus in the first trimester, up to and including 13+6 weeks, is the most accurate method of establishing or confirming gestational age, to 5 to 7 days by CRL.
  • Where the LMP is uncertain, dating rests on the earliest scan. Where both are available, the EDD is revised only if the discrepancy exceeds the threshold for the gestational age at which the scan was performed.
  • Once established, the EDD should be changed only in rare circumstances, discussed with the patient and documented.
  • A pregnancy that reaches 22+0 weeks with no ultrasound confirming or revising the EDD is suboptimally dated, which is ACOG's term for it.

2. The Dating Methods and Their Arithmetic

Basis Calculation Point to Note
LMP, 28-day cycle EDD = LMP + 280 days, that is LMP + 9 months + 7 days Naegele's rule.
LMP, irregular cycle EDD = LMP + 280 + (cycle length - 28) days Corrects the follicular phase and holds the luteal phase at a constant 14 days. A woman with a 35-day cycle ovulates around day 21, so her pregnancy is 7 days less advanced than her LMP suggests.
Crown-rump length GA in days = 40.9041 + 3.21585 √CRL + 0.348956 × CRL, CRL in millimetres, valid from 15 to 95 mm INTERGROWTH-21st first-trimester standard, which this tool uses. The standard deviation widens with CRL, from about 2.7 days at 15 mm to about 4.2 days at 95 mm. The older Robinson and Fleming chart, still printed on many Indian and UK reports, differs by under a day across the same range.
ART, day-5 blastocyst EDD = embryo transfer date + 261 days ACOG Committee Opinion 700. An ART-derived EDD is not revised on the strength of a later scan.
ART, day-3 embryo EDD = embryo transfer date + 263 days ACOG Committee Opinion 700.
ART, oocyte retrieval EDD = retrieval date + 266 days Follows arithmetically from the two figures above but is not stated in the Committee Opinion. Offered here as a derived value.

A CRL is only as good as the plane it was taken in, and the technique carries more weight than the choice of chart:

  • The mean of three discrete measurements, not a single one.
  • A true mid-sagittal plane, with the genital tubercle and foetal spine longitudinally in view.
  • The maximum length from cranium to caudal rump, as a straight line.
  • Above 84 mm the CRL no longer dates reliably and head circumference is used instead.

3. When to Redate, and When Not To

ACOG Committee Opinion 700, Table 1. The band is selected by the LMP-derived gestational age at the time of the scan, which is what the footnote to the published table specifies.

Gestational Age at Scan (by LMP) Measurement Discrepancy Requiring EDD Redating
Up to 8+6 Weeks Crown-Rump Length (CRL) More than 5 days
9+0 to 13+6 Weeks Crown-Rump Length (CRL) More than 7 days
14+0 to 15+6 Weeks BPD, HC, AC, FL More than 7 days
16+0 to 21+6 Weeks Composite Biometry More than 10 days
22+0 to 27+6 Weeks Composite Biometry More than 14 days
28+0 Weeks and Beyond Composite Biometry More than 21 days
Caution on third-trimester redating: ACOG attaches a footnote to the final row. A foetus that is small because of growth restriction will measure young, and redating it converts a growth problem into a dating problem, removing the very diagnosis that mattered. Management decisions based on third-trimester ultrasonography alone need the whole clinical picture and close surveillance.

Which is why a size and dates discrepancy is read as a growth question first and a dating question second:

Feature Symmetrical FGR (Early Onset) Asymmetrical FGR (Late Onset) Macrosomia (Large for Dates)
Pathology Intrinsic foetal insult reducing overall cell number (hypoplasia). Uteroplacental insufficiency causing glycogen depletion in liver (hypotrophy). Maternal hyperglycaemia causing foetal hyperinsulinaemia (hypertrophy).
Aetiology Chromosomal anomalies (Trisomy 18, 13), TORCH infections, severe malnutrition. Pre-eclampsia, chronic hypertension, severe anaemia, smoking. Gestational Diabetes Mellitus (GDM), maternal obesity, multiparity.
Onset First trimester (early, global insult). Third trimester (late, selective insult). Second to third trimester (metabolic-driven).
Biometry HC and AC proportionally reduced. Normal HC/AC ratio. Brain-sparing: HC normal, AC severely reduced. High HC/AC ratio. Accelerated AC growth (liver hypertrophy). EFW > 90th centile.
Effect on Dating A late scan measures young across all parameters and invites wrongful redating. AC lags while HC holds, so composite biometry underestimates less severely. A late scan measures old and can wrongly bring the EDD forward.
Prognosis Poor. Often associated with structural or genetic abnormalities. Better if detected early, and better again where uteroplacental blood flow can be improved. Good if glucose controlled. Risk: shoulder dystocia, birth injuries.

4. What Is Prescribed, and When

The timeline prints the doses against dates. These are the four points on which the prescription is most often got wrong.

  • The IFA tablet is 60 mg, not 100 mg. Under Anemia Mukt Bharat the prophylactic antenatal tablet is 60 mg elemental iron with 500 mcg folic acid, one daily from the second trimester, for a minimum of 180 days in pregnancy and a further 180 days postpartum. The 100 mg figure comes from the 2010 MoHFW antenatal guideline and has been superseded.
  • Anaemia in pregnancy is a haemoglobin below 11 g/dL (Anemia Mukt Bharat, MoHFW 2018): mild 10.0 to 10.9, moderate 7.0 to 9.9, severe below 7.0 g/dL, measured by digital haemoglobinometry rather than the Sahli method. For mild or moderate anaemia the therapeutic regimen is two tablets daily for three months, with haemoglobin rechecked after one month.
  • Folic acid alone comes first. 400 to 800 mcg daily from the periconceptional period through the first trimester, or 4 to 5 mg daily where a previous pregnancy was affected by a neural tube defect. Combined IFA starts only in the second trimester: first-trimester iron worsens nausea and adds no neural tube protection.
  • Calcium sits below the WHO figure. The MoHFW 2014 schedule is 500 mg elemental calcium with 250 IU vitamin D3 twice daily from 14 weeks, giving 1 g of calcium and 500 IU of vitamin D a day, continued for 6 months postpartum and not taken with the IFA tablet. WHO recommends 1.5 to 2.0 g daily where dietary calcium intake is low.
Aspirin: start between 12 and 16 weeks, and no later than 28. The USPSTF (2021, Grade B) and the ACOG and SMFM Practice Advisory (2021) recommend low-dose aspirin from 12 weeks for those at high risk of pre-eclampsia, continued daily until delivery. ASPRE used 150 mg at bedtime from 11 to 14 weeks until 36 weeks and reduced preterm pre-eclampsia by 62 per cent. American bodies specify 81 mg because that is the tablet strength marketed there; in India the marketed strengths are 75 mg and 150 mg, so the strength belongs on the prescription. The risk factors that qualify a woman are listed at the aspirin milestone in the timeline, and one high-risk factor alone is enough.

5. Programme and Statute

  • Td, not TT. Td has replaced tetanus toxoid in the Universal Immunisation Programme. Td-1 early in pregnancy, Td-2 at least 4 weeks after Td-1. Where the woman received two Td doses in a pregnancy within the last 3 years, a single booster replaces the two-dose course. Tdap at 27 to 36 weeks for neonatal pertussis protection is an ACOG and CDC recommendation and is not part of the Indian programme.
  • Deworming: a single 400 mg dose of albendazole after the first trimester, preferably in the second. No repeat dose is given in pregnancy.
  • PC-PNDT Act 1994: Form F and the signed declaration that sex determination will not be performed are required before every ultrasound performed on a pregnant woman, not only the anomaly scan. The sonologist must also declare on each report that the sex of the foetus was neither detected nor disclosed. Records are retained for two years, or until the final disposal of any legal proceeding, and a monthly return goes to the Appropriate Authority by the fifth of the following month. Non-compliance is a criminal offence.
MTP (Amendment) Act 2021, and why the anomaly scan date matters.
  • Up to 20 weeks: the opinion of one registered medical practitioner.
  • Between 20 and 24 weeks: two practitioners, and only for the categories set out in Rule 3B, which are survivors of sexual assault, rape or incest; minors; women whose marital status changed during the pregnancy; women with a major physical disability; mentally ill women; foetal malformation carrying a substantial risk of being incompatible with life or of serious handicap; and pregnancy in a humanitarian or disaster setting. The Supreme Court held in 2022 that the distinction Rule 3B draws on marital status is unconstitutional.
  • Beyond 24 weeks: no upper limit where a State Medical Board, comprising a gynaecologist, a paediatrician and a radiologist or sonologist, diagnoses substantial foetal abnormality.
Booking the TIFFA at 18 to 20 weeks rather than at 22 preserves the decision window.

6. GDM Screening and What a Negative DIPSI Means

The DIPSI test is 75 g of oral glucose in about 300 mL of water, given irrespective of fasting status, with a 2-hour plasma glucose of 140 mg/dL or above diagnostic of GDM. A value of 120 to 139 mg/dL is treated by FOGSI as gestational glucose intolerance requiring follow-up. The two schedules differ: MoHFW, which the timeline follows, tests at the first contact and again at 24 to 28 weeks, while FOGSI sets the second test at 24 to 26 weeks and adds a third at 32 to 34 weeks in high-risk women.

Know the limitation of the test you are using. Against IADPSG criteria, the non-fasting DIPSI test had a sensitivity of 22.6 per cent and a specificity of 97.8 per cent in 1031 women (Mohan et al, Acta Diabetologica 2014), and the authors concluded it could not be recommended for diagnosis. A negative DIPSI is therefore a weak negative. Where a fasting 75 g OGTT with IADPSG thresholds is feasible, particularly in a woman with risk factors, it is the better test. The figure of 27.7 per cent, often seen quoted for the same test, comes from the same paper: it is the sensitivity against the older WHO 1999 criteria rather than against IADPSG. Both numbers are Mohan 2014. Neither is from the WINGS study.

Once GDM is diagnosed, the MoHFW targets are fasting below 95 mg/dL and 2-hour post-prandial below 120 mg/dL. Medical nutrition therapy with physical exercise for 2 weeks comes first. If it fails, metformin 500 mg twice daily orally is started at 20 weeks, to a maximum of 2 g daily. Insulin may be started at any point in pregnancy, at an initial 4 to 8 units depending on the 2-hour value.

7. Three Milestones the Sources Do Not Agree On

The timeline prints all three. It does not settle any of them.

Milestone The Positions What This Tool Does
Thyroid screening The Indian Thyroid Society and FOGSI (2019) recommend TSH in every pregnant woman at the first antenatal visit, with trimester-specific upper limits of 2.5 mIU/L in the first trimester and 3.0 mIU/L in the second and third. The American Thyroid Association (2017) recommends against universal screening and sets the upper limit at 4.0 mIU/L where no population-specific range exists. Indian normative studies report first-trimester upper limits between 5.0 and 5.8 mIU/L, so a 2.5 mIU/L cut-off labels a large fraction of an Indian population as subclinically hypothyroid. Reports the ITS and FOGSI position, because it is the Indian professional recommendation, and flags the disagreement rather than resolving it. Treatment is clear-cut above 10 mIU/L and is a judgement between 2.5 and 10, informed by TPO antibody status.
Group B streptococcus Universal rectovaginal screening at 36+0 to 37+6 weeks is an ACOG and CDC recommendation. India has no national GBS screening programme, and Indian studies report colonisation prevalence of 7 to 13 per cent in tertiary centres. Prints the milestone, to be offered on institutional protocol rather than as a universal mandate. The window exists because a culture predicts colonisation at birth reliably for about 5 weeks, covering births to 41+0 weeks; beyond that, repeat screening is reasonable where the first culture was negative.
Foetal movement counting The AFFIRM trial, a stepped-wedge cluster randomised study of 409,175 pregnancies across 33 UK hospitals, found no reduction in stillbirth from a package of reduced-foetal-movement awareness and management (4.06 against 4.40 per 1000, adjusted odds ratio 0.90, 95 per cent CI 0.75 to 1.07), while caesarean birth rose from 25 to 28 per cent and neonatal unit admission rose. ACOG Practice Bulletin 229 (2021) states that not all patients need to perform a daily movement assessment, at Level C. Asks the woman to report a change in the pattern of movement promptly, rather than to count to a number.

8. ANC Visits: Three Frameworks in Use

All three are in current use in India, and which applies depends on the setting rather than on the evidence.

Source Schedule
MoHFW (2010) A minimum of 4 visits: the first within 12 weeks, the second between 14 and 26 weeks, the third between 28 and 34 weeks, the fourth between 36 weeks and term. This is the national minimum
WHO (2016) A minimum of 8 contacts, at up to 12 weeks and then at 20, 26, 30, 34, 36, 38 and 40 weeks
FOGSI and ICOG (2009) One visit in the first trimester, monthly to 30 weeks, fortnightly to 36 weeks and weekly to delivery, which comes to 12 to 14 visits
The 9th of every month is the PMSMA day. Under the Pradhan Mantri Surakshit Matritva Abhiyan (MoHFW, 2016) every government facility offers a free antenatal check on the 9th of the month, given by an obstetrician or a physician, to any woman in her second or third trimester. High-risk pregnancies identified there are line-listed and marked with a red sticker, and the extended scheme introduced in 2022 tracks them by name to 45 days after delivery.

9. Term, Late Term and Post-Term

Classification Gestational Age Clinical Significance
Early Term 37+0 to 38+6 weeks Higher neonatal unit admission risk than full term. Elective delivery is not recommended without an indication.
Full Term 39+0 to 40+6 weeks Optimal window. Lowest neonatal morbidity and mortality.
Late Term 41+0 to 41+6 weeks Induction can be considered from 41+0 (ACOG Practice Bulletin 146). NICE NG207 asks that induction from 41+0 be discussed. Antenatal surveillance may begin, typically twice-weekly biophysical or modified biophysical profile.
Post-Term 42+0 weeks and beyond Induction is recommended after 42+0 and by 42+6 weeks. Rising risk of meconium aspiration, macrosomia and placental insufficiency.
The 39-week question. The ARRIVE trial reported lower caesarean rates with elective induction at 39 weeks in low-risk nulliparous women. ACOG's 2018 advisory on it has been superseded by a 2025 Clinical Practice Update on full-term nulliparous individuals without a medical indication for delivery, and ACOG Committee Statement 17 (2025) asks that the risks and benefits of elective induction against expectant management be discussed collaboratively. What has not changed is that elective delivery before 39+0 without an indication remains inappropriate, and that a decision to induce at 39 weeks depends on confirmed dating, which is the reason this tool insists on the dating basis.

10. What This Tool Does Not Print

  • An aneuploidy risk figure. It prints the windows for combined screening, cell-free DNA, chorionic villus sampling and amniocentesis, and calculates no risk.
  • An estimated foetal weight or a growth centile.
  • A gestational age from symphysio-fundal height. Dating rests on the LMP, an early scan or the ART date.
  • A Bishop score or an induction protocol.
  • A choice between the three antenatal visit frameworks.
  • A single upper limit for the first-trimester TSH, because the sources do not agree on one.

Each is an absence stated on purpose rather than a gap filled with something plausible.

Abbreviations AC (Abdominal Circumference) · ACOG (American College of Obstetricians and Gynaecologists) · AFI (Amniotic Fluid Index) · AMB (Anemia Mukt Bharat) · ANC (Antenatal Care) · Anti-D (Anti-D Immunoglobulin) · ART (Assisted Reproductive Technology) · ATA (American Thyroid Association) · BMI (Body Mass Index) · BPD (Biparietal Diameter) · BPP (Biophysical Profile) · CDC (Centers for Disease Control and Prevention) · cfDNA (Cell-Free Deoxyribonucleic Acid) · CI (Confidence Interval) · CRL (Crown-Rump Length) · CVS (Chorionic Villus Sampling) · DIPSI (Diabetes in Pregnancy Study Group India) · DNA (Deoxyribonucleic Acid) · DVP (Deepest Vertical Pocket) · EDD (Estimated Date of Delivery) · EFW (Estimated Foetal Weight) · FGR (Foetal Growth Restriction) · FL (Femur Length) · FMF (Foetal Medicine Foundation) · FOGSI (Federation of Obstetric and Gynaecological Societies of India) · GBS (Group B Streptococcus) · GDM (Gestational Diabetes Mellitus) · Hb (Haemoglobin) · HBsAg (Hepatitis B Surface Antigen) · HC (Head Circumference) · hCG (Human Chorionic Gonadotropin) · HIV (Human Immunodeficiency Virus) · IADPSG (International Association of Diabetes and Pregnancy Study Groups) · ICOG (Indian College of Obstetricians and Gynaecologists) · IFA (Iron and Folic Acid) · IM (Intramuscular) · ITS (Indian Thyroid Society) · IV (Intravenous) · IVF (In Vitro Fertilisation) · LMP (Last Menstrual Period) · MgSO4 (Magnesium Sulphate) · MNT (Medical Nutrition Therapy) · MoHFW (Ministry of Health and Family Welfare) · MTP (Medical Termination of Pregnancy) · NICE (National Institute for Health and Care Excellence) · NIPT (Non-Invasive Prenatal Testing) · NT (Nuchal Translucency) · NTD (Neural Tube Defect) · OGTT (Oral Glucose Tolerance Test) · PAPP-A (Pregnancy-Associated Plasma Protein A) · PC-PNDT (Pre-Conception and Pre-Natal Diagnostic Techniques) · PMSMA (Pradhan Mantri Surakshit Matritva Abhiyan) · PPTCT (Prevention of Parent to Child Transmission) · RDT (Rapid Diagnostic Test) · Rh (Rhesus Factor) · RPR (Rapid Plasma Reagin) · SBAR (Situation, Background, Assessment, Recommendation) · SLE (Systemic Lupus Erythematosus) · SMFM (Society for Maternal-Fetal Medicine) · Td (Tetanus and adult Diphtheria) · Tdap (Tetanus, adult Diphtheria and acellular Pertussis) · TIFFA (Targeted Imaging for Foetal Anomalies) · TORCH (Toxoplasmosis, Other Agents, Rubella, Cytomegalovirus, Herpes Simplex) · TPO (Thyroid Peroxidase) · TSH (Thyroid Stimulating Hormone) · TT (Tetanus Toxoid) · UIP (Universal Immunisation Programme) · USPSTF (United States Preventive Services Task Force) · VDRL (Venereal Disease Research Laboratory) · WHO (World Health Organization)
References
  1. ACOG, AIUM and SMFM. Committee Opinion No. 700. Methods for Estimating the Due Date. Obstet Gynecol. 2017;129(5):e150-e154.
  2. Papageorghiou AT, Kennedy SH, Salomon LJ, et al. International standards for early fetal size and pregnancy dating based on ultrasound measurement of crown-rump length in the first trimester of pregnancy. Ultrasound Obstet Gynecol. 2014;44(6):641-648.
  3. Robinson HP, Fleming JE. A critical evaluation of sonar crown-rump length measurements. Br J Obstet Gynaecol. 1975;82(9):702-710.
  4. ACOG and SMFM. Committee Opinion No. 579. Definition of Term Pregnancy. Obstet Gynecol. 2013;122(5):1139-1140.
  5. ACOG Practice Bulletin No. 146. Management of Late-Term and Postterm Pregnancies. Obstet Gynecol. 2014;124(2):390-396.
  6. National Institute for Health and Care Excellence. Inducing Labour. NICE Guideline NG207. London: NICE; 2021.
  7. ACOG Committee Opinion No. 797. Prevention of Group B Streptococcal Early-Onset Disease in Newborns. Obstet Gynecol. 2020;135(2):e51-e72.
  8. ACOG Practice Bulletin No. 226. Screening for Fetal Chromosomal Abnormalities. Obstet Gynecol. 2020;136(4):e48-e69.
  9. ACOG Committee Opinion No. 713. Antenatal Corticosteroid Therapy for Fetal Maturation. Obstet Gynecol. 2017;130(2):e102-e109; and SMFM Consult Series No. 58. Use of antenatal corticosteroids for individuals at risk for late preterm delivery. Am J Obstet Gynecol. 2021;225(5):B36-B42.
  10. ACOG Committee Opinion No. 455. Magnesium Sulfate Before Anticipated Preterm Birth for Neuroprotection. Obstet Gynecol. 2010;115(3):669-671.
  11. 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; and ACOG and SMFM Practice Advisory, Low-Dose Aspirin Use for the Prevention of Preeclampsia and Related Morbidity and Mortality, December 2021.
  12. Rolnik DL, Wright D, Poon LC, et al. Aspirin versus Placebo in Pregnancies at High Risk for Preterm Preeclampsia (ASPRE). N Engl J Med. 2017;377(7):613-622.
  13. Ministry of Health and Family Welfare, Government of India. Anemia Mukt Bharat: Operational Guidelines and Training Modules. New Delhi; 2018 and 2019.
  14. Ministry of Health and Family Welfare, Government of India, Maternal Health Division. National Guidelines for Calcium Supplementation During Pregnancy and Lactation. New Delhi; December 2014.
  15. Ministry of Health and Family Welfare, Government of India, Maternal Health Division. National Guidelines for Deworming in Pregnancy. New Delhi; 2014.
  16. Ministry of Health and Family Welfare, Government of India, Immunization Division. Tetanus and Adult Diphtheria (Td) Vaccine: Operational Guidelines. New Delhi.
  17. Ministry of Health and Family Welfare, Government of India. Diagnosis and Management of Gestational Diabetes Mellitus: Technical and Operational Guidelines. New Delhi; 2018.
  18. Mohan V, Mahalakshmi MM, Bhavadharini B, et al. Comparison of screening for gestational diabetes mellitus by oral glucose tolerance tests done in the non-fasting (random) and fasting states. Acta Diabetol. 2014;51(6):1007-1013.
  19. Indian Thyroid Society and FOGSI. Recommendations for the Management of Thyroid Dysfunction in Pregnancy. Mumbai; 2019.
  20. FOGSI and ICOG. Good Clinical Practice Recommendations: Routine Antenatal Care for the Healthy Pregnant Woman. 2009; and FOGSI, Hyperglycemia in Pregnancy: Optimizing Pregnancy Outcome. 2024.
  21. ICOG and FOGSI. Recommendations for Good Clinical Practice: Use of Anti-D Immunoglobulin for Rh Prophylaxis. 2009; and FOGSI, Anti-D Immunoglobulin for Rh Prophylaxis: Key Practice Points. 2022.
  22. Government of India. The Medical Termination of Pregnancy (Amendment) Act, 2021 (No. 8 of 2021) and MTP (Amendment) Rules, 2021, Rule 3B.
  23. Government of India. Pre-Conception and Pre-Natal Diagnostic Techniques (Prohibition of Sex Selection) Act, 1994, and MoHFW, Technical Guidelines for Use of Ultrasonography in Pregnancy, 2014.
  24. World Health Organization. WHO Recommendations on Antenatal Care for a Positive Pregnancy Experience. Geneva: WHO; 2016.
  25. Norman JE, Heazell AEP, Rodriguez A, et al. Awareness of fetal movements and care package to reduce fetal mortality (AFFIRM): a stepped wedge, cluster-randomised trial. Lancet. 2018;392(10158):1629-1638.
  26. Doubilet PM, Benson CB, Bourne T, Blaivas M. Diagnostic criteria for nonviable pregnancy early in the first trimester. N Engl J Med. 2013;369(15):1443-1451. Reaffirmed by the Society of Radiologists in Ultrasound first-trimester lexicon, Radiology 2024;312(2).
How to Cite This Tool

DOIhttps://doi.org/10.5281/zenodo.22401628

AMA Style:Umakanth S. Pregnancy Dating and Antenatal Scheduler. Version 2.1. MEDiscuss Clinical Decision Support System. Published 2026. Accessed . https://mediscuss.org/cdss/pregnancy-timeline. doi:10.5281/zenodo.22401628

Vancouver Style:Umakanth S. Pregnancy Dating and Antenatal Scheduler [Internet]. Version 2.1. MEDiscuss.org; 2026 [cited ]. Available from: https://mediscuss.org/cdss/pregnancy-timeline. doi:10.5281/zenodo.22401628

Disclaimer and scope
Disclaimer: This decision-support system is written for healthcare professionals. It does not substitute clinical judgment, and the treating physician retains absolute responsibility for every diagnostic, dosing and therapeutic decision. The algorithms are built on the evidence as it stands, and the evidence moves. Verify the output against your current institutional protocol, and against the patient in front of you.
© 2026 MEDiscuss.org. All rights reserved. Provided free of charge for clinical use. Unauthorised reproduction or redistribution is strictly prohibited.
Category Therapeutic & Management PathwaysScheduler
Specialties Obstetrics & Gynaecology
Status Essential

Independently reviewed by

Dr Shashikala K Bhat

Reviewed 3 September 2026. Written by Dr Shashikiran Umakanth.

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