What is the significance of determining gravida (number of times pregnant) and parity (number of births) in a woman pregnant with twins?

Significance of Gravida and Parity in Twin Pregnancy

Determining gravida and parity in twin pregnancies is crucial for risk stratification and management, as twin pregnancies have significantly higher risks of maternal and fetal complications compared to singleton pregnancies.

Definition and Clinical Significance

• Gravida refers to the number of times a woman has been pregnant, while parity refers to the number of births beyond the age of viability (typically ≥24 weeks gestation) 1
• There is inconsistency in how parity is calculated for multiple gestations, with 84% of healthcare providers counting a twin delivery as "para 2" while 8 professional sources define multiple births as a single parous event 1
• Twin pregnancies have approximately 5-fold increase in fetal death and 7-fold increase in neonatal death compared to singletons, primarily due to complications of prematurity 2

Risk Assessment Based on Gravida/Parity

• Primiparous women (first pregnancy) with twins have significantly higher risks compared to multiparous women with twins 3:

  • Higher rates of cesarean delivery (35% vs 6% in multiparas) 3
  • Higher rates of blood transfusion (11.6% vs 2.5% in multiparas) 3
  • Higher rates of composite adverse maternal outcomes (12.6% vs 3.2% in multiparas) 3
  • Earlier gestational age at delivery and higher rates of preterm birth before 34 weeks 3

• High parity (≥5 previous births) appears to serve as a protective factor rather than a risk factor for adverse outcomes in twin pregnancies 3

Chorionicity Determination

• Determining chorionicity (number of placentas) and amnionicity (number of amniotic sacs) is essential in twin pregnancy management and should be established as early as possible 2
• Monochorionic twins (single placenta) have significantly higher risks of intrauterine morbidity and mortality compared to dichorionic twins 4
• First trimester ultrasound has nearly 100% accuracy in determining chorionicity, while accuracy decreases in later pregnancy 2

Impact on Pregnancy Monitoring

• Women with twin pregnancies require more intensive monitoring than singleton pregnancies, including:

  • First trimester scan for dating and chorionicity determination 2
  • Nuchal translucency scan at 11-14 weeks 2
  • Detailed anatomic survey at 18-22 weeks 2
  • Regular growth scans in the third trimester 2

• Parity affects uterine artery blood flow in early second trimester, with nulliparous women showing significantly higher pulsatility index (indicating higher resistance) in both singleton and twin pregnancies 5

Specific Risks Based on Gravida/Parity

• Placenta previa is more common in twin pregnancies, especially dichorionic twins 2
• Velamentous cord insertion and vasa previa occur more frequently in twin pregnancies 6
• Congenital anomalies are more common in twin pregnancies, particularly monozygotic twins (estimated to be 2-3 times greater than singletons) 2
• Risk of major fetal anomaly affecting only one twin varies by chorionicity: 1 in 25 dichorionic twins, 1 in 15 monochorionic-diamniotic twins, and 1 in 6 monoamniotic twin pregnancies 2

Management Implications

• Referral to a tertiary center may be appropriate for high-risk twin pregnancies, particularly monochorionic-monoamniotic twins 2
• Mode of delivery considerations differ based on parity:
  • Primiparous women have higher rates of cesarean delivery for twins 3
  • At 32-37 weeks, planned vaginal delivery may be favorable, while after 37 weeks, planned cesarean delivery might be safer 7

Pitfalls to Avoid

• Failing to determine chorionicity in the first trimester when accuracy is highest 2
• Inconsistent documentation of parity in twin pregnancies can lead to confusion in risk assessment and management 1
• Not recognizing that primiparous women with twins require more intensive monitoring due to higher risks 3
• Overlooking the need for specialized care for monochorionic twins, which have unique complications like twin-to-twin transfusion syndrome 2