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OBSTETRICS > MULTIFETAL PREGNANCY > Flashcards

MULTIFETAL PREGNANCY Flashcards

1
Q

What is the mechanism of dizygotic or fraternal twin formation?

A

Dizygotic twins result from the fertilization of two separate ova.

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2
Q

What is the mechanism of monozygotic or identical twin formation?

A

Monozygotic twins result from the fertilization of a single ovum and are genetically identical.

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3
Q

What determines the outcome of monozygotic twinning?

A

The outcome depends on when the division of the zygote occurs.

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4
Q

When does diamniotic, dichorionic twinning occur?

A

It occurs when the zygote divides within the first 72 hours after fertilization.

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5
Q

When does diamniotic, monochorionic twinning occur?

A

It occurs if the division occurs between the 4th and 8th day after fertilization.

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6
Q

When does monoamniotic, monochorionic twinning occur?

A

It occurs approximately 8 days after fertilization when the chorion and amnion have already differentiated.

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7
Q

What usually results if division occurs beyond 8 days after fertilization?

A

Conjoined twins.

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8
Q

What is chorionicity?

A

Chorionicity refers to the type of placenta and determines the likelihood of twin-related complications.

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9
Q

What type of placenta is monozygotic until proven otherwise?

A

Monochorionic placenta.

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10
Q

What types of placenta can be either dizygotic or monozygotic?

A

Dichorionic placenta.

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11
Q

What factors influence twinning?

A

Race, maternal age, parity, heredity, nutrition, fertility treatment, and pituitary gonadotropins.

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12
Q

What increases the likelihood of twinning due to heredity?

A

A history of twins in first-degree relatives.

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13
Q

How can sonography help determine chorionicity early in pregnancy?

A

By assessing the number of gestational sacs and placental masses.

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14
Q

What sonographic feature indicates dichorionic twins?

A

Thick dividing membrane (≥2 mm) or the twin peak sign/lambda sign.

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15
Q

What sonographic feature indicates monochorionic twins?

A

Thin dividing membrane (<2 mm) or the T-sign.

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16
Q

What does the twin peak sign or lambda sign suggest?

A

Dichorionic twins.

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17
Q

What does the T-sign suggest?

A

Monochorionic twins.

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18
Q

What is the appearance of a dichorionic-diamniotic pregnancy on ultrasound?

A

Two separate compartments for the babies.

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19
Q

What is the appearance of a monochorionic-diamniotic pregnancy on ultrasound?

A

Two yolk sacs with a thin membrane dividing them.

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20
Q

What is the appearance of a monochorionic-monoamniotic pregnancy on ultrasound?

A

One yolk sac and a single amniotic cavity.

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21
Q

What is the relationship between chorionicity and gender in twins?

A

Different genders indicate dichorionic twins, while same genders could be dichorionic or monochorionic.

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22
Q

What clinical signs suggest multifetal gestation during the second trimester?

A

Uterine size larger than expected, palpable two fetal heads, and >1 fetal heart beats noted.

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23
Q

What sonographic technique confirms twin pregnancy?

A

Identifying two fetal heads or abdomens in the same image plane.

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24
Q

What imaging modality is preferred for conjoined twins?

A

MRI provides detailed assessment of pathology in conjoined twins.

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25
Q

How do B-hCG and maternal serum alpha-fetoprotein (MSAFP) levels differ in twin pregnancies?

A

Both are generally higher with twins compared to singletons.

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26
Q

What condition can also present with high levels of B-hCG?

A

Hydatidiform mole.

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27
Q

What imaging feature can differentiate dichorionic from monochorionic twins?

A

Membrane thickness: dichorionic membranes are thick (4 layers), while monochorionic membranes are thin (2 layers).

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28
Q

How should a pregnancy be managed if chorionicity is uncertain?

A

It should be managed as monochorionic until proven otherwise.

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29
Q

Why might MRI be used in twin pregnancies?

A

To assess pathology in twins, especially in cases of conjoined twins.

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30
Q

Why are fundic heights larger in multifetal pregnancies?

A

Between 20 and 30 weeks, fundic heights are approximately 5 cm greater than expected for singletons of the same fetal age.

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31
Q

What is the accuracy of sonographic determination of chorionicity based on gestational age?

A

It is most accurate in the first trimester and decreases with advancing gestational age.

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32
Q

What biochemical markers are unreliable for identifying multiple fetuses?

A

Serum and urine levels of B-hCG and maternal serum alpha-fetoprotein (MSAFP) are not reliable due to variability.

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33
Q

What are some maternal physiological burdens in multifetal pregnancy?

A

Increased risk of serious complications, hyperemesis gravidarum, hypervolemia, anemia, increased cardiac output, decreased vascular resistance, greater uterine growth, and compression of abdominal organs and lungs.

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34
Q

What is hyperemesis gravidarum?

A

Excessive nausea and vomiting during pregnancy.

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35
Q

Why is the iron supplement dose doubled in multifetal pregnancy?

A

Due to higher blood volume expansion and increased risk of anemia.

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36
Q

By what percentage does cardiac output increase in multifetal pregnancies compared to singletons?

A

Another 20% above singleton pregnancies.

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37
Q

Why is vascular resistance lower in twin gestations compared to singleton pregnancies?

A

Due to physiological adaptations to accommodate multifetal growth.

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38
Q

What is the risk of spontaneous abortion in singleton pregnancies?

A

0.009000000000000001

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39
Q

What is the risk of spontaneous abortion in multiple pregnancies?

A

0.073

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40
Q

Which type of placentation is more common in miscarriages involving multiple gestations?

A

Monochorionic placentation.

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41
Q

How does the incidence of congenital malformations in twins compare to singletons?

A

406 per 10,000 twins versus 238 per 10,000 singletons.

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42
Q

Which type of twin gestation has a higher malformation rate: monochorionic or dichorionic?

A

Monochorionic twins.

43
Q

Why do multifetal gestations often result in low birth weight?

A

Due to restricted fetal growth and preterm delivery.

44
Q

What factors contribute to growth restriction in monochorionic twins?

A

Unequal allocation of blastomeres, vascular anastomoses, and discordant structural anomalies.

45
Q

What is the relationship between pre-pregnancy BMI and hypertensive disorders in multifetal pregnancies?

A

BMI ≥30 kg/m² is an independent risk factor for preeclampsia.

46
Q

Why does multifetal pregnancy have a higher chance of preeclampsia?

A

Due to greater placental mass and abnormal remodeling of spiral arteries.

47
Q

Why do young primigravida and elderly primigravida patients have a higher risk of hypertension?

A

Their spiral arteries are either too immature or too aged, leading to higher vascular resistance.

48
Q

Why is preterm birth more common in multifetal pregnancies?

A

Uterus stretching increases with the number of fetuses, leading to higher chances of preterm labor.

49
Q

What are the cognitive outcomes of twins compared to singletons?

A

Generally similar, but cerebral palsy risk is higher in twins and higher-order multiples.

50
Q

What are some complications unique to monochorionic twins?

A

Twin-twin transfusion syndrome (TTTS), twin anemia-polycythemia sequence (TAPS), and conjoined twins.

51
Q

What is twin-twin transfusion syndrome (TTTS)?

A

A condition where blood is transfused from a donor twin to a recipient twin, leading to anemia and growth restriction in the donor and polycythemia and circulatory overload in the recipient.

52
Q

What are the diagnostic criteria for TTTS?

A
  1. Monochorionic diamniotic pregnancy. 2. Oligohydramnios (vertical pocket <2 cm) in the donor sac and polyhydramnios (vertical pocket >8 cm) in the recipient sac.
53
Q

What are the management options for TTTS?

A

Expectant management, amnioreduction, fetoscopic laser ablation, septostomy, and selective feticide (not practiced in the Philippines).

54
Q

What is the most common type of conjoined twins?

A

Thoracopagus twins (joined at the chest or thorax).

55
Q

What is an external parasitic twin?

A

A grossly defective fetus or merely fetal parts attached externally to a relatively normal twin.

56
Q

What is a fetus in fetu?

A

An internal parasitic twin where one embryo is enfolded within its twin, losing normal spatial arrangement and organ presence.

57
Q

What are the survival chances of twins with TTTS?

A

Survival is possible if the condition is diagnosed early and treated, especially in Stage I.

58
Q

Between the donor and recipient twin in TTTS, which is more likely to survive?

A

The recipient twin.

59
Q

What is Twin Anemia-Polycythemia Sequence (TAPS) characterized by?

A

Significant hemoglobin differences between donor and recipient twins without discrepancies in amniotic fluid volumes typical of twin-twin-transfusion syndrome.

60
Q

What are the neonatal criteria for diagnosing TAPS?

A

Intertwin hemoglobin difference >8.0 g/dL and intertwin reticulocyte count ratio >1.7.

61
Q

What is the antenatal diagnostic method for TAPS?

A

MCA-PSV (Middle Cerebral Artery - PSV) by Doppler.

62
Q

What is the MCA-PSV fetal criterion for anemia in TAPS?

A

MCA-PSV >1.50 MoM in the donor.

63
Q

What is the MCA-PSV fetal criterion for polycythemia in TAPS?

A

MCA-PSV <0.80 MoM in the recipient.

64
Q

Describe TAPS Stage 1.

A

MCA-PSV donor >1.5 MoM and MCA-PSV recipient <1.0 MoM with no signs of fetal compromise.

65
Q

Describe TAPS Stage 5.

A

Intrauterine demise of one or both fetuses preceded by TAPS.

66
Q

What is Twin-Reversed Arterial Perfusion (TRAP) also known as?

A

Acardiac twin.

67
Q

What is the key feature of TRAP sequence?

A

A recipient twin lacks a heart and other structures, while the donor twin shows features of heart failure.

68
Q

How does blood flow in TRAP sequence?

A

Reverse blood flow of deoxygenated arterial blood from the donor to the recipient twin through an artery-to-artery placental shunt.

69
Q

What is the treatment option for TRAP sequence?

A

Fetoscopic laser photocoagulation of placental vessels or intrauterine blood transfusion.

70
Q

What are the complications of complete hydatidiform mole with coexisting normal fetus?

A

Persistent trophoblastic disease requiring chemotherapy, heavy bleeding, preeclampsia, or preterm delivery.

71
Q

How is twin discordancy calculated?

A

(Larger twin weight - Smaller twin weight) / Larger twin weight.

72
Q

What percentage weight discordancy is significant in twins?

A

Greater than 20%.

73
Q

What is the most important determinant of discordant growth in monochorionic twins?

A

Unequal placental sharing.

74
Q

What is ‘vanishing twin syndrome’?

A

The early disappearance of one fetus in a twin pregnancy.

75
Q

What is ‘fetus papyraceous’?

A

A dead fetus flattened through desiccation.

76
Q

What is the recommended delivery time for monochorionic twins?

A

By 37 weeks’ AOG.

77
Q

What is the main risk to the surviving twin after the death of a monochorionic co-twin?

A

Exsanguination into the dead twin through vascular anastomoses, leading to hemodynamic changes and ischemic brain damage.

78
Q

What are the possible abnormalities in the surviving twin after co-twin death in monochorionic twins?

A

Neural tube defects, microcephaly, hydrocephalus, porencephaly, and multicystic encephalomalacia.

79
Q

What causes maternal DIC in single fetal death in twins?

A

Thromboplastins from the dead fetus and placenta entering maternal circulation, activating the extrinsic coagulation pathway.

80
Q

What is the role of platelet count and fibrinogen level monitoring in maternal DIC?

A

Used before delivery as maternal DIC is rare.

81
Q

Which type of twins has a higher risk of neurodevelopmental impairment after co-twin demise?

A

Monochorionic twins.

82
Q

What is the recommended weight gain for women with a normal BMI in a twin pregnancy according to the Institute of Medicine?

A

“37 to 54 lbs.”

83
Q

What is the daily recommended caloric intake for women with twins?

A

“40 to 45 kcal/kg/day (20% protein, 40% carbohydrates, 40% fat)

84
Q

What is the cornerstone of fetal assessment in twin pregnancy?

A

“Identification of abnormal fetal growth or discordancy.”

85
Q

What is the significance of SVP <2 cm in amniotic fluid assessment?

A

“It indicates oligohydramnios and may suggest uteroplacental pathology.”

86
Q

At what SVP value is polyhydramnios indicated?

A

“SVP ≥8 cm.”

87
Q

What ultrasound measurements define oligohydramnios and polyhydramnios in the four quadrants?

A

“Oligohydramnios: <5 cm; Polyhydramnios: >25 cm.”

88
Q

At what gestational age should ultrasound be done to assess viability, chorionicity, and Crown-Rump Length in twin pregnancies?

A

“10 to 13 weeks.”

89
Q

What is the significance of a thickened nuchal translucency?

A

“It is commonly seen in Down syndrome.”

90
Q

What is the recommended time frame for a Congenital Anomaly Scan (CAS) in twin pregnancies?

A

“18 to 22 weeks; optionally 24 to 26 (28) weeks for better fetal heart evaluation.”

91
Q

Why is monochorionic twin pregnancy monitored more frequently than dichorionic twins?

A

“Due to higher risk of complications like TTTS

92
Q

What is the recommended monitoring frequency for monochorionic twins starting at 16 weeks?

A

“Ultrasound every 2 weeks.”

93
Q

At what frequency should dichorionic twins be monitored for fetal growth after 20 weeks?

A

“Every 4 to 6 weeks.”

94
Q

What tests are commonly used to assess fetal well-being in twin pregnancies?

A

“Nonstress Test (NST) or Biophysical Profile (BPP).”

95
Q

When is pulmonary maturation usually synchronous in twins?

A

“By approximately 32 weeks.”

96
Q

What is the planned delivery time for uncomplicated dichorionic-diamniotic twins?

A

“38 + 0 to 38 + 6/7 weeks.”

97
Q

When should uncomplicated monochorionic-diamniotic twins be delivered?

A

“36 + 0 to 36 + 6/7 weeks.”

98
Q

What is the delivery recommendation for monochorionic-monoamniotic twins?

A

“Elective cesarean section between 32 + 0 and 34 + 0 weeks after corticosteroids.”

99
Q

What is the recommended route of delivery for cephalic-cephalic twin presentations?

A

“Vaginal delivery if there are no standard indications for cesarean.”

100
Q

What is the maximum allowable time interval between the delivery of twins to avoid fetal distress and acidosis?

A

“30 minutes.”

101
Q

In cases of TTTS, TAPS, or sFGR after 26 weeks, what is the management recommendation?

A

“Prompt delivery of both twins if impending death of one twin is suspected.”

102
Q

What is the oxytocin regimen for induction or augmentation of labor in twin pregnancies?

A

“The same as in singleton pregnancies.”

103
Q

What is the most common initial sign of uterine rupture during TOLAC in twin pregnancies?

A

“Fetal heart rate changes.”

104
Q

What is the primary approach for detecting fetal complications in monochorionic twins?

A

“Serial ultrasounds.”

OBSTETRICS (13 decks)

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