How should pregnancies and births be classified in pregnant patients using standard obstetric terminology?

Standard Obstetric Classification System for Pregnancies and Births

Pregnancies should be classified as pregnancy events (counting each pregnancy as one event regardless of number of fetuses), while births should be classified as birth events, with explicit separate reporting of singleton, twin, and higher multiple gestations for both categories. 1

Core Classification Framework

Pregnancy Classification

Count pregnancies as events, not by number of fetuses:

• A twin pregnancy = 1 pregnancy event
• A singleton pregnancy = 1 pregnancy event
• Always report singleton, twin, and higher multiple pregnancies separately 1

Birth Classification

Count births as events, not by number of infants:

• Twin live birth = 1 live birth event
• Singleton live birth = 1 live birth event
• Always report singletons, twins, and higher multiples separately 1

This distinction is critical because it prevents treatments that increase multiple gestations from appearing artificially favorable in outcome reporting 1.

Essential Pregnancy Outcome Definitions

Viable Intrauterine Pregnancy

A pregnancy diagnosed by ultrasound examination showing at least one fetus with a discernible heartbeat. Always document the gestational age at which the ultrasound examination was performed 1.

Live Birth

The complete expulsion or extraction from a woman of a product of fertilization after 20 completed weeks of gestational age, which after separation breathes or shows any evidence of life (heartbeat, umbilical cord pulsation, or definite movement of voluntary muscles), regardless of whether the umbilical cord has been cut or placenta is attached 1.

• If gestational age is unknown, a birth weight of 350 g or more can be used 1
• Report as birth events (twin birth = 1 event)
• Separately document singleton, twin, and higher multiple births

Miscarriage

The spontaneous loss of an intrauterine pregnancy prior to 20 completed weeks of gestational age. Should only be reported after a viable pregnancy has been confirmed by ultrasound 1.

Stillbirth

The death of a fetus prior to complete expulsion or extraction from the mother after 20 completed weeks of gestational age, determined by the fact that after separation, the fetus does not breathe or show any evidence of life 1.

• When involving twins or higher multiples, report as a single event 1
• Document gestational age at diagnosis

Ectopic Pregnancy

A pregnancy outside the uterine cavity, diagnosed by ultrasound, surgical visualization, or histopathology 1.

Termination of Pregnancy

Intentional loss of an intrauterine pregnancy through medical, surgical, or unspecified intervention. Selective embryo or fetal reduction must be explicitly reported 1.

Gestational Age Determination

Calculate fetal age using the best obstetric estimate, which may include:

• Early ultrasound (most accurate)
• Last menstrual period date
• Perinatal details

For assisted reproductive techniques: add 14 days to the number of completed weeks since fertilization 1.

Report gestational age at birth as median and interquartile range; mean and standard deviation support future meta-analysis 1.

Critical Documentation Requirements

For Multiple Gestations

• Pregnancy loss in twins/higher multiples must be explicitly accounted for 1
• Report birthweight for each individual infant in the multiple birth set 1
• If a member of a multiple birth set dies in the neonatal period, explicitly report this 1
• If major congenital anomaly occurs in a member of a multiple set, explicitly report this 1

Birthweight Documentation

• Collect within 24 hours of birth using calibrated electronic scale with 10-g resolution 1
• Report separately for singletons, twins, and higher multiples 1
• Do not adjust for gestational age 1
• Include birthweight of stillbirths 1

Neonatal Mortality

Death of a live born baby within 28 days of birth:

• Early neonatal mortality: death in first 7 days after birth
• Late neonatal mortality: death between 8-28 days after birth 1

Obstetric History Documentation

Document using standardized terminology 2:

Gravidity: Total number of pregnancies (as pregnancy events)

Parity: Number of births (as birth events)

Previous pregnancy outcomes: Categorize as fetal death (including pregnancy loss and stillbirths) versus live birth, with documentation of:

• Number of fetal deaths and live births
• Gestational age for each outcome 2

Common Pitfalls to Avoid

1. Do not count twins as two pregnancy events or two birth events - this artificially inflates success rates of treatments that increase multiple gestations 1

2. Do not report miscarriage before ultrasound confirmation of viable pregnancy - this leads to inconsistent reporting 1

3. Do not use the 20-week threshold inconsistently - this is the critical dividing line between miscarriage and stillbirth 1

4. Do not fail to document gestational age at ultrasound diagnosis - timing of ultrasound varies significantly between countries (6-8 weeks in USA, 11-13 weeks in UK, after 16 weeks in Netherlands) 1

5. Do not adjust birthweight for gestational age - report raw measurements 1

This standardized classification system ensures consistent reporting across healthcare systems and research settings, facilitating accurate comparison of outcomes and appropriate clinical decision-making.