Selective abortion of one or more embryos or fetuses in a multiple gestation pregnancy. The usual goal is to improve the outcome for the remaining embryos or fetuses.

The condition of carrying two or more FETUSES simultaneously.

The status during which female mammals carry their developing young (EMBRYOS or FETUSES) in utero before birth, beginning from FERTILIZATION to BIRTH.

Four individuals derived from four FETUSES that were fertilized at or about the same time, developed in the UTERUS simultaneously, and born to the same mother.

Three individuals derived from three FETUSES that were fertilized at or about the same time, developed in the UTERUS simultaneously, and born to the same mother.

The condition of carrying TRIPLETS simultaneously.

Results of conception and ensuing pregnancy, including LIVE BIRTH; STILLBIRTH; SPONTANEOUS ABORTION; INDUCED ABORTION. The outcome may follow natural or artificial insemination or any of the various ASSISTED REPRODUCTIVE TECHNIQUES, such as EMBRYO TRANSFER or FERTILIZATION IN VITRO.

Two individuals derived from two FETUSES that were fertilized at or about the same time, developed in the UTERUS simultaneously, and born to the same mother. Twins are either monozygotic (TWINS, MONOZYGOTIC) or dizygotic (TWINS, DIZYGOTIC).

Five individuals derived from five FETUSES that were fertilized at or about the same time, developed in the UTERUS simultaneously, and born to the same mother.

The age of the conceptus, beginning from the time of FERTILIZATION. In clinical obstetrics, the gestational age is often estimated as the time from the last day of the last MENSTRUATION which is about 2 weeks before OVULATION and fertilization.

In utero measurement corresponding to the sitting height (crown to rump) of the fetus. Length is considered a more accurate criterion of the age of the fetus than is the weight. The average crown-rump length of the fetus at term is 36 cm. (From Williams Obstetrics, 18th ed, p91)

Conditions or pathological processes associated with pregnancy. They can occur during or after pregnancy, and range from minor discomforts to serious diseases that require medical interventions. They include diseases in pregnant females, and pregnancies in females with diseases.