研究開発・学会発表

Ninety percent of couples want a second child, according to surveys in Japan. However, previous studies suggest that the fertility rate decreases when the second pregnancy is not started within 3 years after the first birth. The pregnancy rate also diminishes in women aged over 40, even for those who have given birth previously. Therefore, the interval between the first and second conceptions is considered important for a second pregnancy.

This was a qualitative, cross-sectional, paper-based questionnaire study. The respondents were 246 women planning to have a second child after having received infertility treatment before the first pregnancy. The study was conducted in Hanabusa Women’s clinic in Kobe, Japan, from July 2015 to January 2016.

The questionnaire included the woman’s age, first child’s age, number of years from the first birth to the start of the second fertility treatment, previous experience of infertility treatment or ART, and the cause of infertility at the first conception. The questionnaire was given to patients after they provided informed consent. The women were assured that they would experience no invasion of privacy and no disadvantages if they did not wish to respond.

The response rate was 81.5%. The average age of respondents was 36.7 years. The average age of the first child was 1.8 years and the most frequent age was between 1 and 2 years old. The average interval between the first birth and the start of the second fertility treatment was 1.6 years and the most frequent interval was 1 to 2 years (45.1%). Older women tended to start the second fertility treatment earlier than younger women: those aged under 29 waited an average of 1.9 years, whereas women over 40 waited only 1.1 years. The causes of infertility at the first child included fallopian tube abnormality, male factors, uterus factors, and unknown factors. The most frequent cause of infertility in women who started second fertility activity within three years after the first birth was fallopian tube abnormality (27.5%), whereas in women who waited longer than three years it was unknown cause (26.1%).

The study was based on a questionnaire with a limited sample size. Future studies should increase the number of patients recruited from multiple facilities to confirm this preliminary conception. Clinical outcomes should also be examined.

Unknown cause of infertility at first conception and having a first baby at a young age delay the start of second fertility treatment. Analyzing these factors may encourage women to start fertility treatment for the second child early as possible.