{'fraction_non_alphanumeric': 0.05150684931506849, 'fraction_numerical': 0.04219178082191781, 'mean_word_length': 4.308139534883721, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Regionalized perinatal care systems and very low-birth-weight and very preterm infants.

0.32; 95% CI, 0.08-1.20; HR, 0.56; 95% CI, 0.29-1.09; and HR, 0.53; 95% CI, 0.29-0.96), and nested case-control sets (odds ratio, 0.46; 95% CI, 0.32-0.65). Despite these differences in study design, the estimates of the association of RRSO with breast cancer risk have been generally similar. The 2 extreme estimates include those of Kauff et al (HR, 0.32; 95% CI, 0.08-1.20) and Domchek et al (HR, 0.36; 95% CI, 0.20-0.67). The former group did not match on start time while the latter group did. Although these data do not directly address the concerns that have been raised, they also do not support the hypothesis that matching on follow-up period necessarily results in biases away from the null hypothesis. The mean follow-up times by RRSO in our study are presented in the TABLE, which supplements Table 3 in our article. The only subgroup difference observed was a longer follow-up period in non-RRSO vs RRSO in BRCA2 mutation carriers without prior breast cancer (5.1 vs 3.3 years). For BRCA2 without prior breast cancer, the point estimate of the association with RRSO was stronger (HR, 0.36) than in other groups, which could be consistent with bias in the effect of longer follow-up among the non-RRSO group. Protection from bias should remain an important concern for all future studies of this type. Studies of cancer risk reduction with RRSO are likely to be undertaken only as observational studies (rather than randomized trials), which limits the ability to obtain accurate estimates of risk reduction needed for optimal cancer prevention strategies. It remains encouraging that all of the estimates of the effect of RRSO to date strongly support its use as an important cancer prevention tool in these highrisk women.