Miscarriage and Obesity: Confusing Causality and Correlation Once Again

"Since you are overweight, I don't want you to get excited about this pregnancy because you'll probably miscarry."  -OB to mother at first prenatal appointment, documented on myobsaidwhat?!?

Can you believe some doctor told this to a woman at her first prenatal appointment? Gees, way to ruin this poor woman's joy and excitement over her pregnancy!

This is yet another example of a doctor mentally inflating the risks around obesity and pregnancy.  This is a common occurrence these days because of the obesity hysteridemic.  Women are not being given realistic summaries about risks associated with obesity and pregnancy, but instead are being given shaming tactics and doom-and-gloom predictions that greatly exaggerate their risks.

Miscarriage is one of the many things fat women are being scared with. I am hearing about more and more fat women being told that they are very likely to miscarry, or that if they did miscarry, their miscarriage was caused by their obesity.

Here are several more entries over at My OB Said WHAT!?! showing how fat women are often blamed for their miscarriages. Assumptions are often made about how the fat woman MUST be eating in order to be fat, and the woman is shamed and blamed, right at the time when she most needs love and support.

The first entry:

“New studies are showing that obesity causes miscarriage.” -Midwife to larger sized mother at prenatal who had previously had a miscarriage and was now pregnant again.

The second entry:

“You’re so fat, what did you expect? Obese women have no business getting pregnant anyway.” – Nurse at OB’s office, following a miscarriage at 14 weeks

Yet another entry:

“Stop trying so hard to get pregnant and focus that energy on eating healthy- your chance of miscarrying is higher anyway because you’re obese” — Midwife to mother at 15 pounds overweight three weeks after miscarrying with a blighted ovum.

The next entry is from a vegetarian who does not eat fast food. She was told:

“The reason you had a miscarriage is because you are fat. You will never carry a pregnancy to term unless you stop eating Big Macs.” – Midwife

Once again, fatness is blamed for anything bad that happens and fat women are not believed about their habits, just assumed to be eating constant junk food.  After all, that's the only reason why anyone might be fat, right?

Examining the Argument

Women are being blamed for their miscarriages and being told half-truths about it.  Once again, some care providers are confusing correlation and causality.

Yes, some research shows a higher miscarriage rate in women of size, although not all research has found this to be true.

But if there is an association, is it their obesity that is causing these miscarriages, or is something associated with obesity resulting in miscarriage?

The fact is, no one really understands what causes some miscarriages. Most miscarriages are due to chromosomal abnormalities and the embryo is miscarried early.  Sometimes, though, the answer is not clear-cut and no one knows why a miscarriage occurs.

But consider ─ if obesity caused miscarriage, then no fat woman would likely carry a pregnancy to term, and yet many of us do.  Furthermore, many of us who are fat have never had a miscarriage at all.  The association has to be more complex.

Yes, there is a higher rate of miscarriage in "obese" women. HOWEVER, there's a giant confounding factor there with PolyCystic Ovarian Syndrome (PCOS).

Many women of size have PCOS, and the hormone imbalances of PCOS can result in an increased rate of miscarriage.  Does the obesity cause the miscarriage or does the PCOS? This is an important confounding factor, and rarely is it controlled for in these obesity and miscarriage studies.

A few studies discuss the possibility of PCOS influencing miscarriage rates in obese women, but regularly discount its importance. However, many women with PCOS have great difficulty getting diagnosed (especially those with milder or atypical cases) and so the role of PCOS is probably underestimated in these studies.

Might there still be an independent effect of obesity (or something else associated with obesity) even after PCOS is accounted for?  Yes, it's possible.  But since not every study finds an increased risk for miscarriage among obese women, and since many obese women carry to term without any problems, you cannot conclude the obesity causes miscarriage.

To tell a fat woman that her obesity caused her miscarriage is just cruel.  And furthermore, it may well be that her miscarriage was due to chromosomal abnormality, just like most other miscarriages.  There's no way to know for sure why this particular pregnancy miscarried.  To pretend otherwise is just trying to shame and blame the mother.

Unfortunately, many doctors just see a risk associated with weight, mentally inflate that risk tremendously because of all the hysteria over obesity and pregnancy, start assuming the risk is far greater than it actually is, and conflate correlation with causation while they're at it.

In other words, if something bad happens to a fat person, many care providers conclude it MUST have been because of their fatness and nothing else.

Amazing how all that obesity got passed down over the generations if fat women were truly unable to carry to term.

My Story

As a side note, I should pass on that in my first pregnancy, I experienced a lot of spotting/bleeding in the first trimester.  We saw the heartbeat and everything, but the doctor still told me I had a very high chance for miscarriage. Obviously, there was some basis for concern, giving the frequent spotting, but the doctor told me I had a 50/50 chance of miscarriage, and her tone seemed to imply that it was almost a sure thing.

Yet once the heartbeat is seen, the odds for miscarriage drop considerably.  One site says that the risk drops to about 13% in women with vaginal bleeding but in whom the heartbeat has been documented.

My chances for miscarriage were probably a lot less than 50/50, but she told me 50/50.  I think she inflated it, given my weight, even though she didn't mention weight specifically.  Her tone implied that miscarriage was practically inevitable.  She scared me out of my wits, but despite all the dire predictions, I carried the pregnancy to term, no problem.

Oh, how I wish I had known then that the risk for miscarriage dropped considerably once a heartbeat has been documented.  It's not a guarantee, and there is still room for concern...but neither is it as chancy as many doctors think it is, even in fat women.

Although my doctor never specifically tied her prediction to my weight out loud, I think it influenced her prediction.  And her prediction certainly caused me a great deal of anxiety.  Fortunately, all was well, and that "50/50 chance of miscarriage" is learning to drive now.

The Fall-Out from the Blame Game

Few things are more gut-wrenching than when a woman loses her baby. Even when the baby is "just" a few weeks' gestation, miscarriage can be an absolutely devastating experience, and it leaves the woman feeling particularly vulnerable emotionally.

How incredibly heinous it is, then, for care providers to be telling fat women that their obesity caused their miscarriage when we don't in fact know whether that is true.

And of course, how heartless and disingenuous to tell women that unless they lose weight, they'll never carry a pregnancy to term.  Somehow, other fat women have carried a pregnancy to term without losing weight first. This is just another way to try and medically bully a woman into drastic weight loss.

To focus on a woman's weight in the middle or aftermath of a miscarriage is just cruel, yet many providers do just that, like in this woman's story:

“Oh my goodness! Do you know you’re overweight? Have you tried to diet and exercise??" – OB immediately upon entering the room and meeting a mother for the first time. The mother was in the process of miscarrying a 16 week pregnancy.

Care providers must start realizing the power of their words during tragic losses like these.  Cruel or insensitive words during difficult times can leave particularly deep and scarring emotional wounds.

And care providers need to recognize that careless or harsh comments about weight often lead to disordered eating and compulsive exercise behaviors in patients, like in this mother:

About eighteen months ago, I got pregnant. In a move that surprised both my boyfriend and me, we decided we wanted to keep the baby. Though the pregnancy was unplanned, we were really excited to become parents and the child was very much loved and wanted. When I was six and a half months pregnant, I miscarried. Since then, I’ve struggled to get out of bed. 

Not a day has gone by when I haven’t thought about who that child would have been. It was a girl. She had a name. Everyday I wake up and think, “My daughter would be six months old,” or “My daughter would maybe have started crawling today.” Sometimes, all I can think is the word daughter over and over and over. 

Of course, it seems that everyone around me is having a baby and everywhere I go all I see are babies, so I have to force myself to be happy for them and swallow how empty I feel. The truth is, I don’t feel much of anything anymore and yet, everything hurts. Most of the people in my life expect me to be over my sorrow by now. As one person pointed out, “It was only a miscarriage.” So I also feel guilty about being so stuck, grieving for a child that never was when I should just walk it off or something. 

I don’t talk very much about it. I pretend it never happened. I go to work and hang out and smile and act like everything is fine. My boyfriend has been fantastic and supportive, though I don’t think he understands how badly I’m actually doing. He wants us to get married and try for another child. He thinks this should cheer me up. It doesn’t. It makes me want to punch him in the head for not feeling the way I do. 

Then there is the reason I lost the baby. In the hospital, my doctor said he wasn’t surprised I lost the baby because my pregnancy was high risk because I was overweight. It was not an easy thing to hear that the miscarriage was my fault. Part of me thinks the doctor was a real asshole but another part of me thinks, “Maybe he was right.” It kills me to think that this was my fault, that I brought the miscarriage on myself. I can’t even breathe sometimes, I feel so guilty. When I got out of the hospital, I got a personal trainer and went on a diet and started losing weight but I’m totally out of control now. Sometimes, I don’t eat for days and then sometimes, I eat everything in sight and throw it all up. I spend hours at the gym, walking on the treadmill until I can’t lift my legs.

Or this mother (the full story from one of the entries above):

My 2nd pregnancy was a surprise and ended in miscarriage at 7 weeks. I was devastated. Somehow the loss is what triggered my husband’s readiness to officially start trying for the next baby...Thus my 3rd pregnancy began, with severe ovarian pain for many weeks. In the time before my scheduled first prenatal appointment, the midwife told me on the phone it could be an ectopic pregnancy...at the first prenatal appt...the midwife (who is also an ultrasound tech) said to me...“New studies are showing that obesity causes miscarriage.” She knew I’d just lost a baby to miscarriage a few months prior and took the opportunity while I’m laying there vulnerable with my shirt up and pants down and cold goop on my belly waiting to see if I was about to lose another baby to say this to me. I asked if she was saying that my fat killed my baby and she looked half-smug and half-sheepish as she replied that she ‘wouldn't say it didn't.’

After FINALLY confirming my baby was alive and not ectopic, the midwife launched into a 20 minute long lecture in which she told me, “I forbid you to gain any weight during this pregnancy! You know what can happen…” or she would “make” me go to the hospital to have my baby...I was so devastated and cowed by her horrible comment and constant bullying that for the duration of the pregnancy I swung wildly back and forth between binging and starving, a true eating disorder for the first time in my life. I was very depressed, constantly in a state of nervous panic, and too scared to call and ask for help when I developed a bladder infection- also the first and only bladder infection of my life.

Pregnancy #4, living baby #3, is due in 6 weeks. My current pregnancy at my first prenatal appointment, this midwife told me that she would refuse me as a client and send me to the hospital if I didn't LOSE 10 POUNDS IN A MONTH – yes while pregnant and severely sick with hyperemisis gravidarium she told me to purposely drop 10 pounds. I had just gotten my emotional eating and depression from the damage she caused last time under control and decided that for the health of my baby I would run like the wind if she treated me like that again, so when she did I dropped her – walked out before the appointment was finished and have never been back. I am now with a new birthing center, the midwives of which are supportive and praise me for my healthy eating habits and do not try to blackmail me into starving myself or losing weight during pregnancy...

I can still barely think about the things she said without crying. That was 2 1/2 years go and I’m still scarred to my soul from what she said about it being my fault for being too fat that my baby died. The pain of the loss dulls a little, but the sting of that comment still brings me to tears. No matter how many times other friends and healthcare providers tell me that most miscarriages, especially those in the first trimester, are unexplainable and happen to fat, skinny, tall, short, black, white, educated, and uneducated alike, I still cannot get the haunting pain and guilt of that comment out of my mind.

A thoughtless or blaming comment from a care provider can easily set a woman on the slippery slope to unhealthy behaviors and even an eating disorder.  Instead of helping, that is just going to add another layer of challenge for achieving a healthy pregnancy and baby someday.

Providers: When a woman loses a baby, give her sympathy and a listening ear.  That's ALL. No blaming, no shaming, no jumping to conclusions about causes.  Just LISTEN.

If she comes to you at another time and wants to explore possible causes for the miscarriage or ways to improve her chances for a term pregnancy next time, by all means discuss healthy eating and regular exercise as well as other possible factors. Promoting healthy habits is always a good idea. But don't assume that she has poor habits by virtue of her size alone, don't assume weight is the only culprit, and don't promise her that healthy habits or weight loss will result in a term pregnancy and a healthy baby.  It's just not that simple.

Concluding Thoughts

Women who experience miscarriage or stillbirth spend so much time in an agony of "what ifs" ─ did I miscarry because I had that cup of coffee, did I miscarry because I had a glass of wine before I knew I was pregnant, did I miscarry because I didn't eliminate enough stress in my life, did I miscarry because I was too fat/too skinny/too old/too young, etc.  They don't need anyone else adding to their own wildly unrealistic self-blame.

The truth is that miscarriages happen.  They happen all the time.  And no one knows why some pregnancies end in miscarriage.

If multiple repeat miscarriages happen, it can be helpful to look for possible causes (like low progesterone, PCOS, weak ovulation, high blood sugar, hormonal imbalances, a blood clotting disorder, etc.) but most of the time, there's no discernible cause.

It's true that some research suggests that obese women have a higher miscarriage rate; however, it is likely that this relationship is muddled by correlated issues like PCOS and the associated insulin resistance and hormonal differences. It is one thing to note a higher rate of miscarriage among women of size, and completely another to conclude that obesity is causing a miscarriage.

Remember, miscarriages happen all the time to women of ALL sizes and body types. To conclude that any one miscarriage happens to someone because of their certain body type or size is nonsense.

I can promise you, many other women with that particular body type or size have carried pregnancies to term before.  Why does one woman of that size or body type carry to term with no problems and others of that same size lose the pregnancy?  If the two were linked causally, that diversity of outcome would not happen...yet it does. The picture is obviously more complicated than that.

There is no rhyme or reason for pregnancy loss so much of the time.  To simplistically blame a woman's weight for her miscarriage is a care provider looking for simple answers that absolve them of having to look deeper, or from having to tell a woman that they simply don't know why this bad thing happened to her.

It's human nature to want answers because it gives us a sense of control over things. Sometimes providers jump to conclusions because they are human beings and they want to have a feeling of control over the uncontrollable.  When faced with tragic outcomes, the idea that if this woman just did "X" or "Y" then they could prevent bad things from happening to her ─ that's a very seductive idea.

But the hard truth is that we just don't know why most women miscarry.  And we really don't know how to prevent most miscarriages.  There is some research to suggest that weight could be a factor, but there's also research to suggest that it might not be a factor.  And there's no way to to know whether it's a factor in any one woman's situation.

So, please, providers, stop blaming fat women for their miscarriages, and try to be more sensitive when supporting a woman through a difficult experience like this.

All women ─ fat or thin, tall or short, old or young ─ deserve compassionate, gentle and loving support during a miscarriage. The last thing they need to hear is shaming and blaming at such a vulnerable time.

I'll say it again: When a woman loses a baby, give her sympathy and a listening ear.  That's ALL.  


References

Studies Finding That Obesity is Associated with Miscarriage

Fertil Steril. 2008 Sep;90(3):714-26. Epub 2008 Feb 6. Does high body mass index increase the risk of miscarriage after spontaneous and assisted conception? A meta-analysis of the evidence. Metwally M, et al.   PMID: 18068166 

Sixteen studies were included in the meta-analysis. Patients with a body mass index of > or =25 kg/m(2) had significantly higher odds of miscarriage, regardless of the method of conception (odds ratio, 1.67; 95% confidence interval, 1.25-2.25). Subgroup analysis from a limited number of studies suggested that this group of women may also have significantly higher odds of miscarriage after oocyte donation (odds ratio, 1.52; 95% confidence interval, 1.10-2.09) and ovulation induction (odds ratio, 5.11; 95% confidence interval, 1.76-14.83). There was no evidence for increased odds of miscarriage after IVF-intracytoplasmic sperm injection. CONCLUSION(S): There is evidence that obesity may increase the general risk of miscarriage. However, there is insufficient evidence to describe the effect of obesity on miscarriage in specific groups such as those conceiving after assisted conception.

Hum Reprod. 2004 Jul;19(7):1644-6. Epub 2004 May 13. Obesity is associated with increased risk of first trimester and recurrent miscarriage: matched case-control study. Lashen H, Fear K, Sturdee DW.  PMID: 15142995 

This was a nested case-control study. The study population was identified from a maternity database. Obese [body mass index (BMI) >30 kg/m2] women were compared with an age-matched control group with normal BMI (19-24.9 kg/m2). Only primiparous women were included in the study to avoid including the subject more than once, and to be able to correctly identify recurrent miscarriages. The prevalence of a previous history of early (6-12 weeks gestation), late (12-24 weeks gestation) and recurrent early miscarriages (REM) (more than three successive miscarriages <12 weeks) was compared between the two groups. RESULTS: A total of 1644 obese and 3288 age-matched normal weight controls with a mean age of 26.6 years [95% confidence interval (CI) 26.5-26.7] were included in the study. The risks of early miscarriage and REM were significantly higher among the obese patients (odds ratios 1.2 and 3.5, 95% CI 1.01-1.46 and 1.03-12.01, respectively; P = 0.04, for both]. CONCLUSIONS: Obesity is associated with increased risk of first trimester and recurrent miscarriage.

Studies Finding That Obesity is NOT Associated with Miscarriage

Eur J Obstet Gynecol Reprod Biol. 2010 Aug;151(2):168-70. Body Mass Index and spontaneous miscarriage. Turner MJ, et al.  PMID: 20488611

In a prospective observational study conducted in a university teaching hospital, women were enrolled at their convenience in the first trimester after a sonogram confirmed an ongoing singleton pregnancy with fetal heart activity present. Maternal height and weight were measured digitally and BMI calculated. Maternal body composition was measured by advanced bioelectrical impedance analysis. RESULTS: In 1200 women, the overall miscarriage rate was 2.8% (n=33). The mean gestational age at enrolment was 9.9 weeks. In the obese category (n=217), the miscarriage rate was 2.3% compared with 3.3% in the overweight category (n=329), and 2.3% in the normal BMI group (n=621). There was no difference in the mean body composition parameters, particularly fat mass parameters, between those women who miscarried and those who did not. CONCLUSIONS: In women with sonographic evidence of fetal heart activity in the first trimester, the rate of spontaneous miscarriage is low and is not increased in women with BMI>29.9 kg/m(2) compared to women in the normal BMI category.

Am J Epidemiol. 1988 Aug;128(2):420-30. Risk factors for spontaneous abortion and its recurrence. Risch HA, et al.    PMID: 3273482

Pregnancy histories of women interviewed as normal population controls during 1974-1981 in four case-control studies in the US and Canada were examined to identify risk factors for the occurrence of miscarriage. In total, 2,068 ever-gravid women aged 20-79 years at interview (mean age, 50.3 years) described 6,282 pregnancies, including 805 miscarriages. The roles of previous pregnancy history, age at pregnancy, and other factors were evaluated using relative risk binomial regression methods (similar to logistic regression)...Risk of miscarriage did not appear to be associated with years since previous pregnancy, height, weight or obesity, use of oral contraceptives within one year before pregnancy, or duration of oral contraceptive use. 

PCOS and Miscarriage

Best Pract Res Clin Obstet Gynaecol. 2004 Oct;18(5):755-71. The pathogenesis of infertility and early pregnancy loss in polycystic ovary syndrome. van der Spuy ZM, Dyer SJ. PMID: 15380145

Women with polycystic ovary syndrome (PCOS) frequently present with reproductive dysfunction. Ovarian function might be disturbed, with resultant abnormal folliculogenesis and steroidogenesis and, although it is difficult to define the exact pathogenesis of anovulation, many possible mechanisms have been postulated. Folliculogenesis in anovulatory women with PCOS is characterized by failure of dominance and the ovary has multiple small follicles, which are arrested but capable of steroidogenesis. Abnormalities in gonadotrophin and insulin secretion and disordered paracrine function have been identified. Women with PCOS have an increased prevalence of miscarriage, both after spontaneous and induced ovulation. Hypersecretion of LH, hyperandrogenaemia and hyperinsulinaemia have all been investigated as possible causes of PCOS. It is likely that these factors are interlinked and together might result in disordered ovarian and endometrial function. Multiple other possible abnormalities have been postulated as contributory factors in the reproductive failure. These include decreased plasminogen activator inhibitor activity, endothelial dysfunction and obesity. Ideally, therapy should target the underlying disorders but at present data are inadequate and further investigations are essential before therapeutic recommendations are truly based on an understanding of the pathophysiology.

Miscarriage After First Trimester Bleeding

J Clin Ultrasound. 1991 May;19(4):221-3. Fetal loss rate after ultrasonically documented cardiac activity between 6 and 14 weeks, menstrual age. Hill LM, et al.    PMID: 1646226

The pregnancy outcome of 347 patients with a confirmed, viable intrauterine pregnancy between 6.0 and 14.0 weeks, menstrual age, was determined. The miscarriage rate was 4.2% in a subgroup of patients without vaginal bleeding, as compared with 12.7% in a subgroup with bleeding (chi 2 = 7.4, p less than 0.006). First trimester vaginal bleeding was a significant covariate in the determination of the spontaneous miscarriage rate after fetal cardiac activity has been confirmed.

J Obstet Gynaecol. 2006 Nov;26(8):782-4. Probability of early pregnancy loss in women with vaginal bleeding and a singleton live fetus at ultrasound scan. Poulose T, et al.   PMID: 17130030 

Bleeding is a common feature of early pregnancy affecting about one-fifth of pregnant women in the first trimester...A prospective study was performed on 370 women with a singleton live fetus who had presented to the early pregnancy assessment clinic (EPAC) with vaginal bleeding. Women were grouped into light, moderate and heavy loss according to the self-assessed degree of vaginal bleeding. The women were also categorised according to the presence or absence of an intrauterine haematoma. The overall spontaneous miscarriage rate in the study was 11.1%; almost 90% of pregnancies continued to viability. Women with moderate or heavy bleeding had more than twice the rate of miscarriage compared with those with light bleeding. A total of 14% of the women had an intrauterine haematoma and those women were 2.6 times more likely to miscarry than those without (23% vs 9%). This relationship appeared to hold true even after controlling for blood loss. The data presented can be used to guide women with a live fetus about the chance of miscarriage after an episode of vaginal bleeding....