The main findings of this study were as follows: the SSR of ART babies in Jilin Province was 50.64%; SSR was associated with fertilization methods. And comparing to IVF, ICSI might decrease the percentage of male babies.
SSR is often used as an important indicator of population health and fertility. As far we know, the normal value of SSR is 51.22% [1]. Different from those of large sample studies, an analysis from the UK showed that the SSR of babies born through ART was 50.98% [11]. It was lower than the normal value and approximated to ours. A study specifically on single embryo transfer revealed that the SSR of New Zealand and Australia were 51.3% and 51.5%, respectively [4]. They were all higher than the normal value. A Chinese large sample research [12] from 18 reproductive centers showed an SSR of 51.8%, it was beyond the normal level. From our data result and the national, we could preliminarily conclude that ART might influence the SSR in China. Due to some factors such as large sample size gaps, research time, geographical differences or social demography structure, our result was different from the above studies. Whether the relatively lower SSR of babies born through ART in Jilin Province will balance the total SSR of the province, including through natural pregnancy, remains to be studied.
Although our results only showed an association between fertilization methods and SSR, this result was consistent with the results of other similar studies [4, 5, 13, 14]. The development of ICSI was facilitated when researchers focused on male infertility by considering sperm factors at the beginning of treatment for infertility [15]. As second-generation IVF technology, ICSI has been widely used worldwide. But researchers have never stopped discussing the safety of ICSI [16]. In the China’s first large sample study [12] about SSR of ART babies, a preliminary analysis was conducted on the reasons why ICSI might reduce SSR. They thought that the patient’s spermatogenic function was impaired, normally functioning sperm with Y chromosome was also reduced. However, other studies had shown that patients with normal spermatogenesis had reduced SSR after ICSI [4]. We analyzed the possible reason was although the best indication for ICSI targeted male factors such as azoospermia, some patients had ICSI because of non-male factors [15]. For example, those patients who had previously experienced failed fertilization with IVF. Therefore, the above different research results might have different conclusions, depending on what the indications for ART were. In this study, male factors accounted for the largest proportion of infertility factors. The number of patients undergoing ART for both male and female factors also accounted for a significant proportion. And we separated patients who had ICSI from rescue-ICSI. Rescue-ICSI were all performed after unsuccessful IVF that were for non-male factors. Unlike with ICSI alone, no effect on SSR was shown when compared to IVF. Most infertile men in our centre were patients with azoospermia or chromosomal abnormalities. Therefore, we tentatively concluded that the proportion of male babies born to ART patients who were solely due to male factors was lower than that of other factors.
There are some limitations in our study. Firstly, our sample size is relatively small. As a newly developed technology in Jilin Province in recent years, the sample size was limited when the gender of the offspring was excluded as one male and one female. What’s more, the information we have collected is not comprehensive. We should collect information such as the test results of some reports from the parents, etc. This is the incomplete information caused by the incomplete electronic medical record system in the early stage. We think that in the future, with the gradual improvement of our system, we will analyse the impact on SSR from a more comprehensive perspective.
