Type of  Multiples	Average gestation multiples confirmed	Range (in weeks)
Twins	9.8 weeks	4 - 20
Triplets	7.2 weeks	1 - 35
Quadruplets	6.3 weeks	2 - 25
Quintuplets	5.9 weeks	2 - 15
Sextuplets	4.9 weeks	4 - 6

 

Type of Multiples	% Conceived Spontaneously
Twins	53.9%
Triplets	14.4%
Quadruplets	4.2%
Quintuplets+	0%

For more information about the use of fertility treatments in the conception of higher order multiple, see MOST FAQ #4 and the MOST Recommendations on the Responsible Use of Fertility Treatments (PDF).

0.94% did not respond to questions about fertility treatments

12.82% were not treated for infertility (spontaneous pregnancies)

40.62% were treated for infertility but did not use Assisted Reproductive Technology (includes medications and insemination procedures)

45.62% underwent one or more Assisted Reproductive Technology procedures (see table below for details)

a total of 86.24% of all survey respondents took fertility medications as part of their treatment for infertility.

Fertility Procedure Counts
Procedure	# of Respondents
In-vitro fertilization (IVF fresh cycle)	724
Intrauterine insemination (IUI)	371
Intracytoplasmic sperm injection (ICSI)	211
Gamete transfer (GIFT)	68
Artificial insemination (AI)	65
Blastocyst transfer (ZIFT)	37
Donor eggs	35
Donor sperm	29
In-vitro fertilization (IVF frozen cycle)	28
Assisted hatching	28
Other (not specified)	9
Surrogate	5
Donor embyros	1

(Note: some respondents underwent more than one type of procedure.)

For information on how a higher order multiple pregnancy is diagnosed, see MOST FAQ #3.

Observations:

Due to recent improvements in many ART procedures, the percentage of respondents indicating their higher order multiples were conceived as a result of one or more ART procedures has declined. Since 2003, more respondents to the MOST birth survey have indicated conceiving their higher order multiples following the use of ovulatory stimulating medications alone than following the use of ART procedures.