Dating calculator
Exam pearl
Naegele's rule (LMP + 280 days) assumes a regular 28-day cycle with ovulation on day 14. First-trimester CRL is the single most accurate dating method and should generally take precedence over LMP-based dating when the discrepancy exceeds guideline thresholds (ACOG Committee Opinion 700 / SMFM 2017).
WHO 8-contact ANC schedule
Why 8 contacts, not 4?
The 2016 WHO model replaced the older 4-visit Focused ANC package after evidence linked more contacts to fewer stillbirths and greater maternal satisfaction, without proven harm. "Contact" is used deliberately instead of "visit" to emphasize active clinician–woman engagement.
Supplementation & prevention
| Intervention | Dose / regimen | Timing | Guideline |
|---|---|---|---|
| Iron + folic acid (IFA) | 30–60 mg elemental iron + 0.4 mg folic acid, daily | Start at booking, continue through pregnancy; intermittent (weekly) IFA is an alternative where daily adherence/anemia prevalence is low | WHO ANC 2016 |
| Calcium | 1.5–2 g elemental calcium/day (divided doses, separate from iron) | From 20 weeks in populations with low dietary calcium intake | WHO 2018 update (pre-eclampsia prevention) |
| Low-dose aspirin | 75–162 mg once daily (evening dosing favored) | Start 12–16 weeks (before 16w ideally) if ≥1 high-risk or ≥2 moderate-risk factor for pre-eclampsia; continue to delivery | ACOG / USPSTF 2021 |
| Tetanus toxoid (TT) | TT1 at first contact if unimmunized → TT2 ≥4 weeks later → TT3 ≥6 months → TT4 ≥1 yr → TT5 ≥1 yr (lifelong protection after TT5) | Per national EPI schedule | WHO EPI |
| Deworming | Albendazole 400 mg or Mebendazole 500 mg, single dose | After the 1st trimester, in endemic areas | WHO |
| IPTp-SP (malaria) | Sulfadoxine-pyrimethamine, single clearance dose | Starting 13 weeks, doses ≥4 weeks apart, at each scheduled contact, in moderate–high transmission areas | WHO malaria in pregnancy policy |
| Insecticide-treated net (ITN) | Provide/reinforce use | At booking, malaria-endemic areas | WHO |
| Anti-D immunoglobulin | 300 mcg (1500 IU) IM | ~28 weeks routinely if Rh(D)-negative & unsensitized; repeat after any sensitizing event and postpartum if baby is Rh-positive | ACOG Practice Bulletin 181 |
High-yield distinction
Folic acid dose for routine ANC prophylaxis is 0.4 mg/day — this is different from the 4–5 mg/day high dose used for women with a prior neural-tube-defect-affected pregnancy or on antiepileptics, which should start ≥1 month pre-conception and continue through the first trimester.
Danger signs & screening
Danger signs in pregnancy — seek care immediately
- Vaginal bleeding, any amount
- Severe headache with blurred vision
- Convulsions / fits
- Severe abdominal or epigastric pain
- Fast or difficult breathing
- Fever
- Severe or persistent vomiting
- Reduced or absent fetal movements
- Watery vaginal leakage (possible ruptured membranes)
- Sudden swelling of face, hands, or legs
Source: WHO ANC 2016 recommendations; adapted to Ethiopian FMOH ANC protocol patient-education materials.
Booking-visit laboratory panel
- CBC / Hb (anemia screen)
- Blood group & Rh(D)
- Urinalysis: protein, glucose, nitrites
- HIV testing (opt-out, per national policy)
- Syphilis: RPR/VDRL or point-of-care treponemal test
- HBsAg per national policy
- 75 g OGTT for GDM — universal or risk-based, 24–28 weeks
- Recto-vaginal GBS swab — 36–37 weeks (where resources allow)
- Repeat Hb — 3rd trimester
- Malaria RDT/microscopy if febrile, endemic area
- Urine culture if symptomatic or recurrent bacteriuria
Gestational diabetes — diagnostic thresholds
| Timepoint | IADPSG / WHO 2013 one-step (75 g OGTT) |
|---|---|
| Fasting | ≥ 92 mg/dL (5.1 mmol/L) |
| 1 hour | ≥ 180 mg/dL (10.0 mmol/L) |
| 2 hour | ≥ 153 mg/dL (8.5 mmol/L) |
Any one abnormal value is diagnostic. The two-step approach (50 g screen → 100 g diagnostic, Carpenter–Coustan criteria) remains an accepted alternative in some settings, including much of US practice (ACOG).
Fetal development timeline
- ACOG. How Your Fetus Grows During Pregnancy, FAQ156.
- WHO. Recommendations on antenatal care for a positive pregnancy experience (2016).
- RCOG. Fetal Awareness: Updated Review of Research and Recommendations for Practice (2022).
Hypertensive disorders of pregnancy
Definitions (ACOG 2020 / ISSHP 2018)
Gestational hypertension
Pre-eclampsia
- Proteinuria ≥300 mg/24h, protein/creatinine ratio ≥0.3, or dipstick 2+ if quantitative testing unavailable
- or, in the absence of proteinuria: thrombocytopenia (platelets <100×10&sup9;/L), renal insufficiency (creatinine >1.1 mg/dL or doubling of baseline), impaired liver function (transaminases ≥2× normal), pulmonary edema, or new-onset headache/visual symptoms unresponsive to medication and not explained by an alternative diagnosis
Pre-eclampsia with severe features
Eclampsia & HELLP
Common pitfall
Hypertension alone (without proteinuria or another severe feature) is gestational hypertension, not pre-eclampsia. Conversely, severe features (e.g., BP ≥160/110 or thrombocytopenia) upgrade the diagnosis to severe pre-eclampsia even if the urine dipstick is negative.
Bedside classification engine
Educational decision support only — always correlate with the full clinical picture; this is not a substitute for clinical judgment.
MgSO4 toxicity — know the antidote
Loss of patellar reflex is usually the earliest sign of magnesium toxicity, followed by respiratory depression (RR <12/min) and, at higher levels, cardiac arrest. Antidote: calcium gluconate 1 g (10 mL of 10%) IV over 10 minutes. Hold/reduce the dose if urine output <25–30 mL/h, since magnesium is renally cleared.