第四代试管婴儿是通过第四代试管婴儿技术，即通过人工辅助生殖技术，将和卵子在体外进行受精，然后将受精卵移植到母体子宫内发育而成的婴儿。目前，第四代试管婴儿在许多国家都是合法的，但也有一些国家对此进行了限制。接下来，我们将详细介绍第四代试管婴儿在哪些国家是合法的。

1. 美国

美国是第四代试管婴儿合法的国家之一。在美国，许多州都允许进行试管婴儿技术，而且美国拥有许多世界一流的生殖医学专家和设施。许多来自世界各地的夫妇都选择前往美国进行第四代试管婴儿。

In the United States, many states allow for the use of IVF technology, and the country is home to many world-class reproductive medicine experts and facilities. Therefore, many couples from around the world choose to travel to the United States for fourth-generation IVF.

2. 英国

英国也是允许进行第四代试管婴儿的国家之一。英国拥有严格的生殖医学法律和监管体系，保障了试管婴儿技术的安全和合法性。许多英国的生殖医学中心拥有先进的设备和技术，为需要进行第四代试管婴儿的夫妇提供了良好的选择。

The UK is also one of the countries that allow for fourth-generation IVF. The UK has strict reproductive medicine laws and regulatory systems, ensuring the safety and legality of IVF technology. Many reproductive medicine centers in the UK have advanced equipment and technology, providing a good choice for couples in need of fourth-generation IVF.

3. 加拿大

加拿大也是一个允许进行第四代试管婴儿的国家。加拿大的生殖医学技术水平较高，许多医疗机构提供专业的第四代试管婴儿服务。加拿大的生殖医学法律也比较宽松，为需要进行第四代试管婴儿的夫妇提供了良好的选择。

Canada is also a country that allows for fourth-generation IVF. Canada has a high level of reproductive medicine technology, and many medical institutions provide professional fourth-generation IVF services. In addition, Canada's reproductive medicine laws are relatively lenient, providing a good choice for couples in need of fourth-generation IVF.

4. 澳大利亚

澳大利亚是允许进行第四代试管婴儿的国家之一。澳大利亚拥有先进的生殖医学技术和设施，许多专业的生殖医学中心为需要进行第四代试管婴儿的夫妇提供了全方位的支持和服务。澳大利亚的生殖医学法律也比较宽松，为夫妇提供了合法、安全的第四代试管婴儿选择。

Australia is one of the countries that allow for fourth-generation IVF. Australia has advanced reproductive medicine technology and facilities, and many professional reproductive medicine centers provide comprehensive support and services for couples in need of fourth-generation IVF. Australia's reproductive medicine laws are also relatively lenient, providing a legal and safe choice for couples.

5. 西班牙

西班牙是欧洲国家中允许进行第四代试管婴儿的国家之一。西班牙拥有世界领先的生殖医学专家和设施，许多国际夫妇选择前往西班牙进行第四代试管婴儿。西班牙的生殖医学法律和监管体系也比较健全，为需要进行第四代试管婴儿的夫妇提供了良好的选择。

Spain is one of the European countries that allow for fourth-generation IVF. Spain has world-leading reproductive medicine experts and facilities, and many international couples choose to travel to Spain for fourth-generation IVF. Spain's reproductive medicine laws and regulatory systems are also relatively sound, providing a good choice for couples in need of fourth-generation IVF.

6. 中国

中国是亚洲国家中允许进行第四代试管婴儿的国家之一。中国拥有先进的生殖医学技术和设施，许多专业的生殖医学中心为需要进行第四代试管婴儿的夫妇提供了全方位的支持和服务。中国的生殖医学法律和监管体系也比较健全，为夫妇提供了合法、安全的第四代试管婴儿选择。

China is one of the Asian countries that allow for fourth-generation IVF. China has advanced reproductive medicine technology and facilities, and many professional reproductive medicine centers provide comprehensive support and services for couples in need of fourth-generation IVF. China's reproductive medicine laws and regulatory systems are also relatively sound, providing a legal and safe choice for couples.

通过以上介绍，我们可以看到第四代试管婴儿在许多国家是合法的，而且许多国家拥有世界一流的生殖医学专家和设施，为需要进行第四代试管婴儿的夫妇提供了良好的选择。希望本文对您有所帮助。