Obstetrics Marrow Pg 295-304 (Fundamentals of Reproduction)

Antepartum Fetal Monitoring

• Weekly Non-Stress Test (NST) is recommended for pregnancies with moderate and severe oligo/polyhydramnios starting from 28 weeks
• Weekly Biophysical Score (BPS) is advised for moderate and severe oligo/polyhydramnios starting at 28 weeks
• Ultrasound for fetal growth should be performed every 3 weeks for moderate and severe oligo/polyhydramnios starting at 28 weeks

Treatment of Oligo/Polyhydramnios

• Uncomplicated oligo/polyhydramnios: Termination of pregnancy by induction of labor at 39 weeks
• Complicated oligo/polyhydramnios: Termination of pregnancy by induction of labor at 37 weeks

Complications of Oligohydramnios

• Early pregnancy complications include:
  • Limited uterine distension
  • Restricted space for fetal development
  • Pulmonary hypoplasia (most common)
  • Limb reduction defects
• Late pregnancy complications include:
  • Cord compression leading to decreased fetal blood supply and fetal distress
  • Meconium staining of amniotic fluid which can be swallowed by the fetus causing meconium aspiration syndrome
  • Club foot/Congenital talipes equinovarus (CTEV)

Cardiotocography (CTG) Findings in Oligohydramnios

• Variable decelerations
• Late decelerations with or without decreased variability due to Uteroplacental Insufficiency (UPI)

Normal Pregnancy and Antenatal Care

• Fresh In Vitro Fertilization (IVF) cycle:
  • Day 14 of the cycle = Day of fertilization = Day of oocyte retrieval
  • Estimated Date of Delivery (EDD) = Day of fertilization + 266 days
• Frozen IVF cycle:
  • Day of fertilization doesn't coincide with the day of oocyte retrieval
  • Day 3 transfer (D 17 of the cycle) + 263 days = EDD
  • Day 5 transfer (D 19 of the cycle) + 261 days = EDD

Important Terminologies and Intrauterine Death

• Preterm Pregnancy: < 37 weeks
• Early Term: 37 weeks to 38 weeks + 6 days
• Full Term: 39 weeks to 40 weeks + 6 days
• Late Term: 40 weeks to 41 weeks + 6 days
• Post-term Pregnancy: ≥ 42 weeks (≥ 294 days)
• Abortion: Pregnancy loss at < 20 weeks
• Intrauterine Death (IUD)/Stillbirth: Pregnancy loss at ≥ 20 weeks

Classification of Preterm Birth

• American College of Obstetricians and Gynecologists (ACOG) classification:
  • Early preterm: < 34 weeks
  • Late preterm: 34 weeks to 36 weeks + 6 days
• World Health Organization (WHO) classification:
  • Late preterm birth: 34 weeks to 36 weeks + 6 days
  • Moderate preterm birth: 32 weeks to 33 weeks + 6 days
  • Very preterm birth: < 32 weeks
  • Extreme preterm birth: < 28 weeks

Basics of Pregnancy: Part 1

• Fetal growth period is calculated from the day of fertilization:
  • Period of fertilized ova: Up to 2 weeks after fertilization
  • Embryonic period: 3rd - 8th week after fertilization
  • Fetal period: 9th week after fertilization until delivery
• Fetal growth period is the only pregnancy event not calculated from the 1st day of the Last Menstrual Period (LMP)

Calculation of Estimated Day of Delivery (EDD)

• Natural conception:
  • Regular 28-day cycle: EDD using Naegele's formula: 1st day of LMP + 7 days + 9 months (add 7 days first)
  • Exception: LMP in February: Add 9 months first, then 7 days
• Cycle length < or > 28 days:
  • Calculate approximate EDD using Naegele's formula
  • Calculate the difference between given cycle length and 28 days
  • If cycle length > 28 days: Add the difference to approximate EDD
  • If cycle length < 28 days: Subtract the difference from approximate EDD
• Naegele's formula is not applicable for:
  • Pregnancy due to oral contraceptive failure
  • Lactational amenorrhea
  • Irregular cycles
  • Unsure about LMP

Amniotic Fluid

• Features:
  • Specific gravity: 1.008-1.010
  • pH: 7-7.5 (7.2)
  • Osmolarity: 260 osmol/L
  • Volume:
    • Maximum at 32-34 weeks: 1 L
    • At 40 weeks: 800 mL
    • At 42 weeks: 200 mL
• Applied aspect: Oligohydramnios in post-term pregnancy
• Source:
  • 1st Trimester: Ultrafiltration of maternal plasma across placenta
  • Up to 20 weeks: Transudation across fetal skin
  • ≥ 20 weeks: Fetal urine
• Maintenance of Amniotic Fluid Volume: Depends on fetal swallowing
• Notes:
  • Fetal urine production at term: 1000 mL/day
  • Keratinization of fetal skin: 22-25 weeks of pregnancy

Amniotic Fluid Disorders

• Polyhydramnios vs Oligohydramnios:

PolyhydramniosOligohydramniosAmniotic Fluid Index (AFI)≥ 25 cm< 5 cmSingle Deepest Pocket (SDP)≥ 8 cm< 2 cmMost Common (m/c)IdiopathicIdiopathicMildCauseIdiopathic Gross congenital anomalies (GCA): 1.Large placenta: Twin pregnancy Rh -ve pregnancy Diabetics 2.Increased urine output: Twin pregnancy Maternal diabetes: maternal hyperglycemia → Fetal hyperglycemia → Fetal polyuria → Polyhydramnios Bartter syndrome: Polyuria Fetal anemia: D/t a.Rh incompatibility b.Parvovirus B19 infection c.ThalassemiaIdiopathic Gross congenital anomalies (GCA): m/c: Renal anomalies 1.Small placenta PIH UPI (uteroplacental insufficiency) IUGR 3.Decreased urine output: Renal anomalies in fetus Posterior urethral valve Drugs: Indomethacin, ACE inhibitors 4.Decreased volume: Leaking after amniocentesis PPROM 5.Chromosomal anomalies: Triploidy 6.Abruptio: Rare (D/t ↓ in functional size of placenta)SevereGIT anomalies > NTD

• Notes:
  • AFI: Amniotic Fluid Index
  • SDP: Single Deepest Pocket

Polyhydramnios and Oligohydramnios

• Document outlines causes, investigations, and treatment of polyhydramnios and oligohydramnios.
• Polyhydramnios:
  • Other causes:
    • Increased transudation from skin
    • Abdominal wall defects (omphalocele, gastroschisis)
    • Swallowing defects (esophageal atresia, tracheo-esophageal fistula, duodenal atresia, cleft lip/palate)
    • Congenital diaphragmatic hernia
    • Chromosomal anomalies (trisomy)
    • Chorangioma of placenta
    • Sacrococcygeal teratoma
    • TORCH infections
    • Twin-to-twin transfusion syndrome
  • Note:
    • Most common cause (m/c) of polyhydramnios is a renal anomaly of the fetus
    • Other possible causes include UPI/PROM
    • In all cases of oligohydramnios, a sterile P/S examination is performed to rule out PROM.
• Oligohydramnios:
  • Note:
    • A common cause of oligohydramnios is a renal anomaly of the fetus.
    • Possible causes include UPI/PROM.

Investigations for Oligo/Polyhydramnios

• First Step: Transabdominal ultrasound (TVS)
• Next Steps:
  • Level 2/Anomaly scan: To rule out Generalized Congenital Anomaly (GCA)
  • If GCA is suspected, karyotyping should be done.
  • Sterile P/S examination: To rule out premature rupture of the membranes (PROM)
  • Umbilical artery Doppler: To rule out umbilical cord problems, IUGR (intrauterine growth restriction), or PIH (pre-eclampsia)
  • In polyhydramnios cases, DIPSI check is performed to check for diabetes and MCA Doppler check to evaluate for anemia
• Additional Information:
  • Indomethacin: Used for treatment of polyhydramnios beyond 32 weeks, and for premature closure of ductus arteriosus
  • P/A Height: Uterine height does not correspond to the gestational age for oligo/polyhydramnios
• Important Note: The document uses arrows (→\rightarrow→) to indicate potential causes.

BASICS OF PREGNANCY: Part 1

• Presumptions in a pregnant woman:

  • Prior to pregnancy:
    • Regular cycles:
      • Cycle length: 28 days
      • Day 14 of cycle: Day of ovulation
      • Total duration of pregnancy: 9 months + 7 days / 40 weeks / 280 days

• Timeline of pregnancy:

DayEvent1st day1st day of LMP (Last menstrual period)14th dayOvulation/Fertilization28th dayMissed period (corresponds to 4th week of pregnancy; Fertilization occurs a week prior)

• Period of pregnancy & fetal age:

ParameterDay of calculationPeriod of pregnancy/Gestation1st day of LMPFetal ageDay of fertilization

• Notes:
  • Difference between gestational age & fetal age = Fetal age + 2 weeks
  • Example: Cardiac activity starts at 5th week of pregnancy, 3 weeks after fertilization.
• Trimesters & Fetal growth period:

TrimesterCalculationT11st day of LMP → 13 weeks + 6 daysT214 weeks → 27 weeks + 6 daysT328 weeks → Delivery

Amniotic Fluid Assessment

• Color of Amniotic Fluid:

ColorConditionStraw colorNormal at termColorlessNormal at termGreenMeconium +, Fetal distress, Transverse lie/breech, Listeria infectionTobacco juiceSaffron/yellowish greenGoldenBilirubinDark redBlood

• Amniotic Fluid Index (AFI):
  • Method:
    • Sum the largest vertical length of amniotic fluid pockets in all four quadrants of the abdomen
  • Formula:
    • AFI = a + b + c + d
  • Interpretation:

Fundamentals of Reproduction

• Management of Oligo/Polyhydramnios:
  • Conservative management:
    • Maintain current management
    • Bed rest: Left lateral position
    • Improve hydration
  • Amnio-infusion:
    • Indication: Persistent variable deceleration
    • Timing: At labour
    • Fluid: Normal saline
• Associations of Oligohydramnios:

  • UPI (Uteroplacental Insufficiency):

    • Effect on blood supply to the fetus: reduced blood supply to the fetus
    • Effect on IUGR (↓ growth): brain sparing effect (Blood supply from peripheral organs directed towards the brain)
    • Effect on renal blood flow: reduced renal blood flow; reduced GFR
    • Effect on Oliguria: oliguria
    • Effect on Oligohydramnios: oligohydramnios

  • Syndromes:

    SyndromeDescriptionPotter's syndromeBilateral renal agenesis + Pulmonary hypoplasia + Typical flat facies.Potter's sequence: Above feature occurring due to any other reason.Amniotic Band syndromeAKA Streeter's syndrome/constriction band.Preterm Premature Rupture of Membranes (PPROM) before 37 weeks.Severe oligohydramnios.Membrane wraps tightly around the baby's digit in the form of a band.Digital amputation.

Polyhydramnios Management

• Management of Polyhydramnios:
  • Asymptomatic/mild symptoms: No intervention is required
  • Severe polyhydramnios (SVP ≥ 16/AFI ≥ 35cm): Respiratory discomfort, uterine irritability
• Additional Points:
  • Serial amniocentesis: Maximum amount: 2-2.5 L
  • Tocolytics:
    • < 32 weeks: Indomethacin
    • 32-34 weeks: Nifedipine
    • ≥ 34 weeks: Not given
  • Complications of polyhydramnios:
    • Preterm labor (due to uterine overdistension)
    • Premature rupture of membranes(PPROM)
    • Cord prolapse
    • Malpresentation/unstable lie (head of baby not fixed)
    • Abruption of placenta
    • Postpartum hemorrhage (PPH)
    • Subinvolution of uterus
  • Artificial rupture of membrane (C/1): In polyhydramnios
• Imaging Related to Amniotic Fluid Disorders: Displays ultrasound images showing specific conditions
  • Conditions:
    • Posterior urethral valve
  • Associations:
    • Polyhydramnios
    • Down syndrome
    • Oligohydramnios (late in pregnancy)
• Other Related Conditions:
  • Phocomelia (D/t Thalidomide)
  • Amniotic band syndrome