The vagina contains at least a billion microbial cells, dominated by lactobacilli. Here we perform metagenomic shotgun sequencing on cervical and fecal samples from a cohort of 516 Chinese women of reproductive age, as well as cervical, fecal, and salivary samples from a second cohort of 632 women. Factors such as pregnancyhistory, delivery history, cesarean section, and breastfeeding were all more important than menstrual cycle in shaping the microbiome, and such information would be necessary before trying to interpret differences between vagino-cervical microbiome data. Greater proportion of Bifidobacterium breve was seen with older age at sexual debut. The relative abundance of lactobacilli especially Lactobacillus crispatus was negatively associated with pregnancy history. Potential markers for lack of menstrual regularity, heavy flow, dysmenorrhea, and contraceptives were also identified. Lactobacilli were rare during breastfeeding or post-menopause. Other features such as mood fluctuations and facial speckles could potentially be predicted from the vagino-cervical microbiome. Gut and salivary microbiomes, plasma vitamins, metals, amino acids, and hormones showed associations with the vagino-cervical microbiome. Our results offer an unprecedented glimpse into the microbiota of the female reproductive tract and call for international collaborations to better understand its long-term health impact other than in the settings of infection or pre-term birth.

Five hundred thirty-four histologically confirmed incident cases of breast cancer in Chinese women of Shanghai and an equal number of age and sex-matched population controls were interviewed as part of an epidemiological study of breast cancer risk factors. Early age at menarche was positively associated with breast cancer risk whereas early age at first full term pregnancy, high parity, and long duration of nursing were each negatively associated. We found high average body weight to be a risk factor, especially among women over age 60. Use of oral contraceptives after age 45 also was a risk factor, but use in general was not. Personal history of benign breast disease and history of breast cancer in first degree female relatives both increased risk. Multivariate analysis showed that each of these risk (or protective) factors was independently related to breast cancer. In addition to confirming most of the breast cancer risk factors of Western populations in a low risk developing Asian country, this study demonstrates a clear beneficial effect on breast cancer risk of lactation in a population characterized by a long cumulative duration of nursing in the majority of women. Finally, this study supports several other recent reports of a residual and beneficial effect of parity on breast cancer risk after controlling for age at first full term pregnancy.