By Dr Georgiana Tang, Medical Director, City Fertility Centre Sydney.
It can be a confusing and heartbreaking time if you are experiencing problems falling pregnant with your second child when first time around it was relatively easy.
This issue is often called “secondary infertility” and is defined as a couple who, despite having achieved a pregnancy in the past (which may or may not have resulted in the birth of a child), are unable to do so again after a year or more of regular unprotected intercourse.
While there are few official statistics on the prevalence of secondary infertility in Australia, it is thought that it affects 1 in 10 couples.
Sometimes an answer cannot be found for the cause of a couple’s secondary infertility, but it is thought that the following are the most common factors affecting success:
Maternal Age
- Maternal age is a significant factor and often the most important indicator of a woman’s chance of conceiving. Conception rates for normal, healthy couples are, at best, 20-25 per cent per menstrual cycle. Once a woman reaches the age of 35, her fertility begins to decline. By age 40, it is estimated that her conception rate is in the range of 8-10 per cent a month and at age 43, the pregnancy rate is thought to be as low as 1-3 per cent a month.
Female Factor
- Irregular menstrual cycles may suggest a problem with ovulation and result in difficulty conceiving. The average length of the menstrual cycle is 28 days, but can range between 25 and 35 days. The female menstrual cycle is determined by a complex interaction of hormones, so any hormone imbalance can make your period irregular. While in most cases irregular cycles are not dangerous, it is important to determine what is causing the irregularity.
- Blocked fallopian tubes are more common in secondary than primary infertility. If the egg can’t meet the sperm normally due to a blockage, conception will be very difficult.
Male Factor
- Poor sperm function resulting in the man not having enough normal moving sperm per ejaculate can impact on conception. Unfortunately, having a previous pregnancy is not proof that this is the case. Developing and transporting mature, healthy, functional sperm depend on a specific sequence of events occurring in the male reproductive tract. Many disturbances can occur along that path, preventing cells from maturing into sperm or reaching the woman’s fallopian tube, where fertilisation occurs. Read male infertility causes for more information.
Lifestyle
- Weight is a common factor affecting fertility success. For women, ovulation can be negatively impacted on by being either underweight or overweight, and studies have shown that bringing your body mass index (BMI) within the normal range can help ovulation occur normally, thus increasing chances of pregnancy. It’s also important for men to ensure a healthy BMI, and studies have consistently linked obesity to a lower sperm count among overweight men because testosterone levels drop while estrogen levels rise.
Unknown
- Unfortunately, it is estimated that about 10 per cent of infertility remains unexplained even after complete medical evaluation.
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