美国女性不孕率下降 男性不育率不变

美国国立卫生统计中心的全国家庭成长调查(NSFG)报告显示，15~44岁已婚女性的不孕率从1982年的8.5%(对应240万人)降至2006~2010年的6%(150万人) (Natl. Health Stat. Report. 2013;67:1-19)。

该报告的数据基于2006年6月~2010年6月对15~44岁男性和女性进行的22,682次访问。在所有接受调查的女性中，生殖力受损女性的比例在2006~2010年稳定在11%。在这之前，该比例从1982年的8.4%显著增至1995年的10%和2002年的12%。在已婚女性中观察到相似模式，但受累比例更高：在1982年和1988年，生殖力受损的已婚女性比例为11%，2002年增至15%，2006年~2010年降至12%。

从男性采集的数据显示，在2006~2010年间，9.4%的15~44岁男性和12%的25~44岁男性报告存在某种形式的不育，这与2002年(男性在该年首次被纳入调查)报告的比例相似。

在女性中，从1982年起开始使用的2个不孕指标是不孕(定义为调查前12个月内未妊娠，不管这12个月的每个月内是否与丈夫或同一伴侣进行无防护性交)和生殖力受损(在妊娠或活胎妊娠方面存在身体障碍)。不孕指标仅限于已婚或同居的夫妻，原因是其不区分男性或女性伴侣之间的不育(不孕)。由于样本量方面的问题，研究者仅报告了已婚女性亚组的不育估计值，但指出在2006年~2010年期间不孕的已婚和同居女性比例相似，分别为6%和4.9%。

研究者指出，在未生育过的女性中，不孕和生殖力受损与年龄密切相关：在35~44岁的未生育过的已婚女性中，不孕比例从1982年的44%降至2006~2010年的27%。

研究者还将本调查数据与1965年的全国不育研究数据进行了比较：在不孕的已婚女性中，原发性不孕率(在生第一个孩子方面存在困难的女性比例)从1965年的17%增至1982~2010年的41%~46%，这与这些年来推迟生育的模式和趋势一致。

虽然贫困水平与教育程度无明确关联，但教育程度较低且处于贫困收入水平的女性进行绝育手术的比例更高。例如，在2006~2010年间，在25~44岁女性中，未完成高中教育的女性因避孕原因进行绝育手术的比例为44%，而具有学士学位的女性和具有硕士或以上学位的女性的这一比例分别为21%和16%。教育程度较高的女性具有生殖力的比例(65%~71%)也高于具有高中或高中以下教育程度的女性(42%~43%)，这可能是因为后者在较年轻时就开始和完成生育并进行绝育手术。

NSFG自1982年起就一直采集所有25~44岁女性的生殖力受损相关数据，并自1973年起采集已婚女性的12个月不孕数据。这些数据概括了推迟生育等社会趋势的影响，并显示了对不孕相关医疗服务的潜在需求。

研究者声明无经济利益冲突。美国国立卫生统计中心隶属于美国疾病预防控制中心。

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By: ELIZABETH MECHCATIE, Internal Medicine News Digital Network

Recent trends in fertility problems in the United States include a drop in the proportion of married women aged 15-44 who were infertile from 8.5% in 1982 to 6% between 2006 and 2010, according to a report from the National Center for Health Statistics.

The corresponding number of women affected dropped from 2.4 million in 1982 to 1.5 million in the later period.

Among all the women surveyed, the proportion of women with impaired fecundity stabilized at 11% in 2006-2010. Prior to this period, the proportion had increased significantly from 8.4% in 1982 to 10% in 1995 and 12% in 2002. There was a similar pattern observed among married women, although the proportion affected was higher: In 1982 and 1988, 11% of married women had impaired fecundity, increasing to 15% in 2002 and dropping to 12% in 2006-2010, according to Anjanai Chandra, Ph.D., of the NCHS, and her coauthors.

The data are from the National Survey of Family Growth (NSFG), which provides nationally representative measures of fertility, based on 22,682 interviews with men and women aged 15-44, from June 2006 through June 2010. The report was published on Aug. 14 (Natl. Health Stat. Report. 2013;67:1-19). Data are also collected for men: Between 2006 and 2010, 9.4% of men aged 15-44 and 12% of men aged 25-44 reported having some form of infertility, which was similar to the proportion reported in 2002, when men were first included in the survey,

In women, the two infertility measures used since 1982 are infertility (defined as "a lack of pregnancy in the 12 months prior to the survey, despite having unprotected sexual intercourse in each of those months with the same husband or partner") and impaired fecundity ("physical difficulty in either getting pregnant or carrying a pregnancy to live birth"). The infertility measure has been limited to couples who are married or living together, because it does not distinguish between infertility in the male or female partner. Because of issues with the size of the sample, the authors reported infertility estimates in subgroups in married women only, but noted that in 2006-2010, the proportions of married and cohabiting women who were infertile were similar, at 6% and 4.9%, respectively.

The authors pointed out that among nulliparous women, infertility and impaired fecundity were closely associated with age: Among married nulliparous women aged 35-44, the proportion who were infertile dropped from 44% in 1982 to 27% in 2006-2010.

They also compared some data to data from the National Fertility Study in 1965: Among married women who were infertile, the rate of primary infertility – the proportion who were having problems having their first child – increased from 17% in 1965 to 41%-46% in 1982-2010, "which is consistent with patterns and trends in delayed childbearing over these years," the authors pointed out.

While there was no "clear association" between poverty level and education, women who were less educated and at poverty income levels were more likely to be surgically sterilized. For example, between 2006 and 2010, among women aged 25-44 years, 44% of those who had not completed high school had undergone surgical sterilization for contraceptive reasons, compared with 21% of those with a bachelor’s degree and 16% of those with a master’s degree or higher degree. The women with more education also were more likely to be fecund (65%-71%), compared with those with a high school education or less (42%-43%), "presumably because these latter women started and completed their fertility at younger ages and opted for surgical sterilization," the authors wrote.

The NSFG has been collecting data on impaired fecundity in all women aged 25-44 years since 1982 and 12-month infertility data in married women since 1973. The data provide "demographic ‘snapshots’ of the impact of societal trends such as delayed childbearing, and tracks the potential demand for infertility-related medical services," said Dr. Chandra and her associates.

There are no disclosures. The National Center for Health Statistics is part of the Centers for Disease Control and Prevention.