Table 3.

Risk for Spontaneous Abortion Among Childhood Cancer Survivors by Type of Cancer and Radiotherapy, With Sisters As Referent

Stratification Criteria	No. of Women	Women Who Became Pregnant		No. of Pregnancies	Spontaneous Abortions		PR*	95% CI
		No.	%		No. of Abortions	No. of Women
Sisters	2,737	1,944	71	5,092	304	261	1	Referent
Population comparisons	16,700	11,257	67	27,989	1,718	1,454	0.98	0.87 to 1.11
Survivors of childhood cancer	1,688	649	38	1,479	109	99	1.23	1.00 to 1.52
Type of cancer
Leukemias	292	72	25	158	10	10	1.2	0.7 to 2.0
Lymphomas	222	93	42	205	15	14	1.2	0.8 to 2.0
CNS neoplasms	434	148	34	323	25	23	1.3	0.9 to 1.9
Sympathetic nervous system tumors	53	17	32	41	4	4	1.7	0.8 to 4.0
Retinoblastoma	58	36	62	101	8	7	1.3	0.7 to 2.4
Wilms’ and other renal tumors	76	25	33	58	10	7	3.0	1.6 to 5.5
Malignant bone tumors	82	25	30	56	2	2	0.6	0.2 to 2.2
Soft-tissue sarcomas	107	50	47	121	8	8	1.1	0.6 to 2.0
Germ-cell, trophoblastic, and other gonadal neoplasms	83	25	30	48	8	7†	2.7	1.4 to 5.2
Carcinomas and other malignant epithelial neoplasms	252	149	59	346	16	15	0.8	0.5 to 1.2
Other and unspecified malignant neoplasms	24	9	38	22	3	2	2.4	0.9 to 6.6
Radiotherapy‡
No	1,082	448	41	1,006	63	60	1.06	0.82 to 1.36
Yes	578	192	33	457	44	37	1.58	1.15 to 2.17

Abbreviation: PR, proportion ratio.

^*Adjusted for age of mother at pregnancy (linear spline) and calendar time (linear).

^†One survivor with an uterine choriocarcinoma, one with ovarian cystadenocarcinoma, and five with ovarian germ-cell tumors.

^‡Information on radiotherapy was not available for 28 survivors.