Gray R H
Contraception. 1984 Oct;30(4):297-309. doi: 10.1016/s0010-7824(84)80022-0.
Unconfirmed epidemiologic studies suggest a possible increased risk of birth defects associated with Natural Family Planning (NFP) use, and an increased incidence of spontaneous abortion or frequency of chromosomal abnormalities in abortuses associated with conceptions outside the most "fertile period". The risk is approximately two- to four-fold, but the evidence is by no means conclusive. The implication for NFP depends on the frequency of method failures in user populations, but is not likely to constitute a major hazard. Further research could utilize a data bank of NFP charts.
未经证实的流行病学研究表明，使用自然计划生育法（NFP）可能会增加出生缺陷的风险，并且在最“易孕期”之外受孕导致的自然流产发生率增加或流产胎儿中染色体异常的频率增加。风险大约是两到四倍，但证据绝非确凿。对自然计划生育法的影响取决于使用人群中该方法失败的频率，但不太可能构成重大危害。进一步的研究可以利用自然计划生育法图表的数据库。
