OECD categorises educational levels as:
Low levels of education attained refers to individuals not having attained ISCED level 3 (graded at levels 0-2, that is, not achieving beyond lower secondary education)
Middle levels of education attained refers to individuals having attained ISCED levels 3 and/or 4 (upper secondary and/or post secondary non-tertiary education)
High levels of education attained refers to individuals having attained ISCED levels 5 and/or 6 (short-cycle tertiary education and/or Bachelor's or equivalent level)
Source: Education at a Glance 2012: OECD Indicators
I recommend using low levels of education for inclusion in an academic paper. You will note that the term low-educated women is also used in the OECD paper, above.
With regard to your sample sentence, I suggest referring first to the wider group of women being studied, then to the sub-groups within.
'Among women with low levels of education living in low-fertility countries, those in employment are more likely to decide against a second childbirth than those who are not.'