Table 4.

Live Births per 100 Couples at 24 months of Natural Procreative Technology Treatment by Characteristics of Couples Beginning Treatment

Couple Category	Couples (n)	Live Births (n)	Crude Proportion	Adjusted Proportion^*
All couples	1072	273	25.5	52.8
Woman's age (years)
≤30	86	29	33.7	59.1
>30–35	412	134	32.5	58.6
>35–40	423	89	21.0	46.1
>40	151	21	13.9	50.9
Time spent attempting to conceive (years)
1–3	246	90	36.6	66.0
>3–6	468	129	27.6	55.4
>6–9	210	39	18.6	44.9
>9	118	14	11.9	42.8
Previous live birth
Yes	257	92	35.8	73.9
No	785	181	23.1	48.5
Previous ART attempts (n)^†
0	702	216	30.8	61.5
1	128	29	22.7	41.9
2	125	18	14.4	34.9
≥3	97	10	10.3	19.8

* Adjusted by life-table analysis, where withdrawal or continuing treatment at the end of study follow-up are censoring events. Adjusted proportions should be interpreted with caution because of small numbers in subgroups.
† Assisted Reproductive Technology (ART) includes in vitro fertilization (IVF) with or without intracytoplasmic sperm injection (ICSI).