Secondary infertility: trouble conceiving after a pregnancy

Secondary infertility is defined by an earlier pregnancy, not only an earlier birth

The World Health Organization (WHO) defines infertility as the failure to achieve a pregnancy after 12 months or more of regular unprotected intercourse, and calls it secondary when at least one earlier pregnancy has been achieved (WHO, 2025). The NHS draws the same line: secondary infertility applies to someone who has had one or more pregnancies in the past and is having difficulty conceiving again (NHS, 2023). Neither definition requires the earlier pregnancy to have ended in a birth.

Population studies often use a narrower measure. The global estimate below counts a woman as having secondary infertility if she has had a live birth and has been unable to have another over 5 years, based on household survey answers about partnership, contraception and the wish for a child rather than on medical records (Mascarenhas and colleagues, PLOS Medicine, 2012).

About 1 in 10 women with a child were unable to have another in global survey data

An analysis of 277 health surveys, used to estimate infertility in 190 countries and territories, found that in 2010, among women aged 20 to 44 who had at least one live birth and were exposed to the chance of pregnancy, about 10.5 in 100 were unable to have another child. The figure for primary infertility was 1.9 in 100 (Mascarenhas and colleagues, 2012). The two figures are measured against different groups, so each describes how common the condition is within its own group, and they are not a ratio of one to the other.

We found no comparable current figure for secondary infertility in the US. The headline figure from the Centers for Disease Control and Prevention (CDC), that about 1 in 5 married women aged 15 to 49 with no previous births are unable to get pregnant after a year of trying, covers primary infertility only (CDC, 2024).

The time taken to conceive a first pregnancy is a weak guide to the second

In a reader survey run by the economist Emily Oster at ParentData, later pregnancies took slightly less time on average: among people with at least two planned pregnancies, the first took an average of 4.2 months to conceive and the second 3.3 months. The time taken for the first pregnancy explained only about 11 percent of the variation in the time taken for the second (ParentData, 2022). The survey was a convenience sample of 18,638 readers and excluded IVF, so these figures describe its respondents rather than the population.

Age and health can change between pregnancies

Fertility declines with age in women and, less predictably, in men (American College of Obstetricians and Gynecologists, ACOG, 2023), so the years between pregnancies matter in themselves. The guide to age and fertility gives the figures.

The NHS lists the same common causes for all infertility, without separating primary from secondary: problems with ovulation, poor semen quality, blocked or damaged fallopian tubes, and endometriosis. Fertility problems can affect either partner, and in about a quarter of cases no cause is found. Weight, smoking, alcohol and sexually transmitted infections such as chlamydia are among the risk factors it lists (NHS, 2023). StatPearls, a peer-reviewed clinical reference, notes that a history of earlier pregnancies, miscarriages or ectopic pregnancies can point to problems in the uterus or fallopian tubes, and lists intrauterine adhesions (Asherman syndrome) among the uterine causes of infertility (StatPearls, 2026).

The evaluation timetable is the same as before a first pregnancy

Neither US nor UK guidance sets a separate timetable for people who have been pregnant before. In the US, an evaluation is recommended after 12 months of trying, or after 6 months from age 35 (American Society for Reproductive Medicine, ASRM, 2023). In the UK, NICE recommends assessment after 1 year, referral to a specialist at the first appointment from age 36, and assessment of both partners (National Institute for Health and Care Excellence, NICE, 2026). The guide on when to see a doctor about fertility gives the details.