Table II.

Standardized definitions for the core outcome set for infertility.

Viable intrauterine pregnancy confirmed by ultrasound	A pregnancy diagnosed by ultrasonographic examination of at least one fetus with a discernible heartbeat.	Researchers should report at which gestation the ultrasound examination was performed. Pregnancies are counted as pregnancy events, for example, a twin pregnancy is counted as one pregnancy event. Effect size estimates and 95% confidence interval should be reported for pregnancy events. The denominator should be per participant randomized. Singleton, twin and higher multiple pregnancy should be reported separately.
Pregnancy loss		When considering twin and higher multiple pregnancies, pregnancy loss should be explicitly accounted for.
Ectopic pregnancy	A pregnancy outside the uterine cavity, diagnosed by ultrasound, surgical visualization or histopathology.
Miscarriage	The spontaneous loss of an intrauterine pregnancy prior to 20 completed weeks of gestational age.	Miscarriage should be reported after a viable pregnancy has been confirmed by ultrasound.
Stillbirth	The death of a fetus prior to the complete expulsion or extraction from its mother after 20 completed weeks of gestational age. The death is determined by the fact that, after such separation, the fetus does not breathe or show any other evidence of life, such as heartbeat, umbilical cord pulsation or definite movement of voluntary muscles.	When considering stillbirth involving twins and higher multiple births they should be reported as a single event.
Termination of pregnancy	Intentional loss of an intrauterine pregnancy, through intervention by medical, surgical or unspecified means.	Selective embryo or fetal reduction should be reported.
Live birth	The complete expulsion or extraction from a woman of a product of fertilization, after 20 completed weeks of gestational age; which, after such separation, breathes or shows any other evidence of life, such as heart beat, umbilical cord pulsation or definite movement of voluntary muscles, irrespective of whether the umbilical cord has been cut or the placenta is attached. A birth weight of 350 g or more can be used if gestational age is unknown.	Live births are counted as birth events, for example, twin live birth is counted as one live birth event. Effect size estimates and 95% confidence interval should be reported for live birth events. The denominator should be per participant randomized. Singletons, twin and higher multiple births should be reported separately.
Gestational age at birth	The age of a fetus is calculated by the best obstetric estimate determined by assessments which may include early ultrasound, and the date of the last menstrual period, and/or perinatal details. In the case of assisted reproductive techniques, it is calculated by adding 14 days to the number of completed weeks since fertilization.	The gestational age of both live births and stillbirths should be reported. Gestational age at birth should be reported as a median and interquartile range. Reporting the mean and standard deviation in addition would support future meta-analysis.
Birthweight	Birth weight should be collected within 24 h of birth and assessed using a calibrated electronic scale with 10-g resolution.	The birthweight of singletons, twins and higher multiples should be reported separately. Birthweight for each newborn infant of the multiple birth set should be reported. Birthweight should not be adjusted for gestational age. The birthweight of stillbirths should be reported.
Neonatal mortality	Death of a live born baby within 28 days of birth. This can be sub-divided into early neonatal mortality, if death occurs in the first 7 days after birth and late neonatal, if death occurs between 8 and 28 days after birth.	Mortality related to preterm infants should be collected up to 28 days beyond their estimated due date. If a member of a multiple birth set dies in the neonatal period this should be explicitly reported.
Major congenital anomaly	Structural, functional and genetic anomalies, that occur during pregnancy, and identified antenatally, at birth, or later in life, and require surgical repair of a defect, or are visually evident, or are life-threatening, or cause death.	Major congenital anomalies should be classified using a standardized taxonomy. Major congenital anomaly should be reported as an infant with at least one major congenital anomaly detected. If a major congenital anomaly is identified in a member of a multiple set this should be explicitly reported.