A rose by any other name is still a rose. However, an article that doesn't really inform its readers is just an empty headline.
The article Long Time to Conception Tied to Birthing Problems reports the results of a Dutch-National Institutes of Health (NIH) study. From the article's lede, you'd expect the study to show that a history of infertility puts you at an increased risk of experiencing delivery problems.
While increasingly sophisticated techniques for treating infertility now bring hope to couples, Danish researchers caution that infertile women who do eventually conceive may face a higher risk of birthing problems.
Researchers at the University of Aarhus, in conjunction with colleagues at the U.S. National Institutes of Health, found in a study of Danish births that women who had tried to conceive for more than one year -- a generally accepted definition of infertility -- were at greater risk for premature birth, low birth weight or Caesarean section.
Right from the start you begin to see that this study might not meet your expectations.
The definition of infertility--it's not only the time it takes you to become pregnant, it's also the quality of intercourse. For example, if you only have sex twice in one year, or if you have sex only during the infertile period of your cycle, you're not infertile, you're just not doing it right, so to speak.
Between 10 percent and 20 percent of women report their time to conception over one year long, the study says, and it was not only those women who had undergone fertility treatment that were at risk, but also those who eventually conceived naturally.
The causes of infertility--the study apparently doesn't differentiate between female and male factors. Because what causes infertility in women is very different from what causes infertility in men, it would be very difficult for a study to establish a cause-and-effect relationship between infertility, in general, and birthing risks. For example, let's say a woman is infertile because of female factors--she has an anatomical problem with her uterus, like myomas (fibroids) which are mostly benign uterine muscle growths inside the uterine cavity. Once she becomes pregnant, she has a high likelihood of having a Caesarian section (C/S) delivery related to her infertility. In contrast, if the woman is infertile because of male factors--her partner's sperm is of poor quality--once she becomes pregnant, her likelihood of having an infertility-related C/S delivery is zero.
Her team analyzed nearly 56,000 births from the Danish National Birth Cohort study, where women were asked to report the length of time they took to conceive.
The method used to determine infertility--the researchers didn't look at the women's medical records (a fairly reliable way to establish infertility). Instead, they just asked the women to remember how long they thought it took them to become pregnant. This is not a very reliable method to establish true infertility. (Our recollections are subject to recall bias.)
So, the "long time to conception" part of the study is problematic: infertility is poorly defined, and it's not clear if the study subjects were really infertile, or just thought they were. Unfortunately, the "birthing problems" part is also problematic.
A lot of factors can cause premature and low weight births: age, smoking, medical problems (e.g. diabetes), anatomical problems (e.g. incompetent cervix), etc. Also, unless we know what type of C/S we're talking about, an increased C/S rate in previously infertile women means nothing. In other words, if infertile women have a higher number of elective C/S, it doesn't mean their C/S risk is increased. It simply means that, understandably, women who take a bit longer to become pregnant (or who have to undergo infertility treatments) are more inclined to opt for a C/S delivery.
This means the study has to control for all these other factors. Otherwise, even if an increased risk of these birthing problems is seen, it's not possible to say that the higher risk is related to infertility.
"The raw data showed high risks -- approximately 30 percent to over twice the risk," says lead researcher Olga Basso, a research associate professor at the University of Aarhus Epidemiology Science Center. "But when we adjusted the figures to account for such factors as age and obesity and smoking, the increase we saw was lower, but a still statistically significant association."
In other words, the high risks-- approximately 30 percent to over twice the risk were not connected to infertility, but rather to other known causative factors (age, obesity, etc.). Once these confounding (or rather, confusing) factors are corrected for, the increase is lower. Notice how the article gives you the high, yet meaningless in this context, 30% increase in risk. However, the article makes no mention of the % of the actual increased risk in birthing problems related to infertility. It only tells you that there's a lower, but still statistically significant association.
But let's not get tangled up in percentages. Let's look at what the researchers tell us, in plain English, about these risks (emphasis mine):
"I think women should be concerned, but alarmed is too strong a term," says Christopher Ford, a senior research fellow in reproductive medicine at the University of Bristol. "The biggest risk, it seems, is a mild increase in prematurity between 34 and 37 weeks; that is not an enormous problem. If they were at higher risk for being born before 34 weeks, it would present a real problem, but I don't see that here."
The risk of adverse birth is a relatively small risk and something you have to bear in mind, but not catastrophic," Ford adds. "It can sound quite bad that there is a 50 percent change in the odds, but that is different than change in the risk, and that's important."
Crystal clear, no?
The bottom line for what this study found: in infertile women who eventually conceive, an association with a relatively small increase in birthing problems was noted. Since an association doesn't establish a cause-effect relationship, infertility may, or may not, cause the birthing problems.