OBGYN

• Fertilization

  Occurs in Ampulla of Fallopian tube
• Total duration of pregnancy

  9 months + 7 days /40 weeks/280 days
• POG (Period of gestation)/ PO (Period of) amenorrhoea/ PO pregnancy


  Calculated from the first day of LMP
• ACOG recommendation: Termination of pregnancy done at ≥ 41 wks (Induction of labour is done)
• Obstetrical score


  • GTPAL system
  • Gravidity and parity represented by one number
• Gravidity


  Total no times a female has conceived → Past + present
• Parity


  Total of no of past-pregnancies which crossed period of viability (India : 28 wks)
• Twins and triplets counted as 1 pregnancy
• Parity represented by two numbers

  • First number is parity
  • Second number is no. of abortions : Pregnancy loss at < 20 wks (includes ectopic and molar pregnancy)
• Grand multipara


  4 or more previous births
• Multipara


  2 or more previous births
• GTPAL system


  • G : Gravida, Total no of times a female has conceived (twin considered as single conception)
  • T : No. of term deliveries (≥ 37 wks)
  • P : No. of preterm deliveries (20–36 wks + 6 days) (Not parity)
  • A : No. of abortion (pregnancy ending < 20 wks → ectopic, molar, abortion)
  • L : No. of living children at present (here twins taken as 2)
• Type of pregnancy by weeks of gestation

  • Pre-term pregnancy < 37 wks
  • Early-term pregnancy 37-38 wks + 6 days
  • Full-term pregnancy 39-40 wks + 6 days
  • Late-term pregnancy 41-41 wks + 6 days
  • Post-term pregnancy ≥ 42 wks
• Events by day after fertilization


  1. Day 1- Day3: 8-16 celled zygote is called as Morula

  2. Day 4: 16 celled Morula enters uterine cavity

  3. Day 5: Zona pellucida lost, Blastocyst formation begins

  4. Day 6-10: Implantation window

  5. Day 11: Implantation ends (Day 25 of cycle)
• EDD (Estimated Date of Delivery)

  • For regular cycles: Presumptive EDD (Naegele's formula) - 1st day of LMP + 9 months & 7 days
  • If cycle length is not 28 days: Expected EDD = Presumptive EDD + (Cycle length - 28)
  • For IVF cycles: For fresh cycles - Day of oocyte retrival/fertilization + 266 days, For frozen cycle with D3 transfer - Date of D3 transfer + 263 days, For frozen cycle with D5 transfer - Date of D5 transfer + 261 days
  • If cycles are irregular or patient is lactating/on OCP/unsure about LMP: Best method for dating pregnancy is USG using Crown-Rump Length (CRL)
• Early pregnancy signs


  • Goodell's sign: Softening of cervix
  • Chadwick/Jacquemier sign: Bluish discoloration of cervix/vagina
  • Osiander sign: Lateral vaginal wall pulsation
  • Palmer's sign: Rhythmic uterine contraction
  • Piskacek sign: Unequal growth of uterus
  • Hegar sign: Softening of isthmus such that on bimanual palpation, vaginal & abdominal fingers touch each other
• Height of uterus


  • At 12 weeks: At pubic symphysis
  • At 22 weeks: At the level of umbilicus
  • Immediately after delivery: Just below umbilicus (corresponds to 20 weeks)
  • 24 hrs after delivery (D2 after delivery): Decreases by 1 finger breath / day
• Quickening


  Mother feels fetal movement for the first time in that pregnancy - In primi-gravida: 18-20 weeks, In multi-gravida: 16-18 weeks
• Lightening/welcome sign


  At 36 weeks: Uterus at xiphisternum (mother → Respiratory discomfort), At 40 weeks: Height of uterus↓ to the level of 32 weeks (Head of fetus enter pelvis) → mother relieved of discomfort
• Absolute signs of pregnancy

  • Fetal Heart Sounds (FHS): By Doppler at 10 weeks, stethoscope at 20 weeks
  • Fetal parts: Palpated or movements felt
  • USG evidence of pregnancy
  • Fetal skeleton on X-ray at 16 weeks (C/I in pregnancy)
• Signs of pregnancy on USG


  • Double decidual sac sign and double bubble sign: Intra-uterine pregnancy
  • Decidua capsularis + decidua parietalis = Decidua vera (Fuse at 14-16 weeks)
• Scans during pregnancy


  • Dating/viability scan: 6-8 weeks
  • Nuchal translucency scan: 11-13 weeks + 6 days
  • Anomaly scan/target scan: 18-20 weeks (extend till 22 weeks)
  • Growth scan: 32-34 weeks
  • Placental localization: Best time is 3rd trimester
• In all pregnant females: Target or anomaly scan should be done
• Gestational sac


  • 1st sign: Intradecidual Sign (Interstitial implantation)
  • 1st structure seen: Gestational sac
  • Double Decidual Sac Sign: Inner ring - Decidua capsularis, Outer ring - Desidua parietalis
  • Double Bleb Sign: 2 Bubbles - Yolk sac and amniotic sac
• Fetal Echo: Only done if fetal congenital heart defect is suspected (TTTS, Rubella infection, pre-gestational DM), time → 22-24 weeks
• Causes of NT ≥ 3 mm

  • Most common cause is Aneuploidy (Downs syndrome > Turners syndrome), Others: Trisomy 18 and 13, Congenital heart disease, Early marker for TTTS (Twin to twin transfusion syndrome)
• Next step after increased NT

  1. Karyotyping/FISH

  2. Fetal Echo
• Cystic hygroma


  More generalised fluid collection with presence of septa, Better marker of aneuploidy than increased NT
• Parameters used to estimate gestational age by USG

  • T1: Before CRL can be measure → MSD (mean sac diameter) used, CRL: Best parameter over all, Used till 11 weeks + 6 days (till CRL < 84 mm), Most accurate gestational age determined between: 7-9 weeks, CRL in mm + 42 = Gestational age in days, Smallest CRl measured: 5 mm
  • T2/CRL>84mm: BPD > HC
  • T3: Best - FL + BPD + HC, single best: FL
• Estimation of fetal growth by USG

  Single best USG parameter for fetal growth: AC (Abdominal circumference), Fetal kidney and cord insertion should not be visible
• Estimation of weight of fetus

  Best clinical formula: Johnson formula, On USG best way: Hadlock formula/Shepard formula, Single best parameter: AC
• Macrosomia


  Definition: weight of the fetus ≥ 4 kgs, Risk factors: Post-term pregnancy, Diabetic mother, Male fetus, Maternal obesity, Diagnosis: Abdominal circumference ≥ 35 cm on USG, Mode of delivery: Vaginal delivery
• Indications of c-section


  • In diabetic female if weight of fetus ≥ 4.5 kg or in non-diabetic patient if weight of fetus is ≥ 5 kgs
  • If patient has macrosomic baby in this pregnancy and H/O c-section: VBAC is a relative contraindication
• Structures seen on TVS in early pregnancy

  • Gestational sac: 4 1/2-5 weeks (4 weeks + 3 days)
  • Yolk sac: 5 weeks
  • Fetal pole: 5-5 1/2 weeks (CRL)
  • Cardiac activity: 5 1/2-6 weeks (M mode)
• All these structures are seen on TAS (Trans abdominal sonography) only 1 week after when it's seen on TVS (Transvaginal sonography)
• True gestational sac vs Pseudo-gestational sac

  In Intra uterine (IU) pregnancy: Eccentric, Grows, Yolk sac forms inside later

  In ectopic pregnancy: Central, Does not grow, No yolk sac formed
• Important cut-off's


  • MSD to measure CRL: 25 mm
  • CRL to get cardiac activity: 7 mm
  • Critical HCG titre at which gestational sac is seen on TVS: 1500 IU
  • Minimum value of HCG at which gestational sac is seen: 1000 IU
• Important scenarios


  • If MSD is ≥ 25 mm and CRL cannot be measured /fetal pole not seen → missed abortion (anembryonic pregnancy loss /blighted ovum), MTP (medical abortion)

  2. If MSD < 25 mm and CRL not seen → Wait and watch, Repeat USG after 1 week

  3. If CRL is ≥ 7 mm and cardiac activity not seen → Missed abortion, MTP

  4. If CRL is < 7 mm and cardiac activity not seen → Repeat USG after 1 week
• Congenital anomalies seen on Ultrasound

  • Anencephaly: Earliest anomaly detected: 10 week (T1), Best time to detect: 14 weeks (T2), IOC: TVs, ↑ AFP, Best biochemical marker in NTD: Acetylcholine esterase, Shower cap sign: Brain tissue exposed

  2. Spina bifida: Meningocoele: Protrusion of meninges, Meningomyelocoele: Protrution of meninges + Spinal cord

  3. Duodenal atresia: On USG: Double bubble sign, Leads to polyhydramnios, Associated with Trisomy 21

  4. Posterior urethral valve: On USG: Key hole sign, Associated with: Oligohydramnios
• Congenital anomalies seen on Ultrasound (cont.)

  • Lemon sign: Bossing of frontal bones

  Banana sign: Downward displacement of cerebellum

  Mickey mouse sign

  Frog eye sign