Tuesday, February 14, 2012

Pregnancy 101: Peas made me puke, but not just in the morning


Jeanne, would you like some...peeeaaasss?
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I was seven weeks deep when it hit me. Suddenly, I was in a chronic state of queasiness. Under most circumstances, I had it under control. Sure, I would gag every time I brushed my teeth, but (mostly) I could keep it all down. Then I went to my aunt Diane’s house for dinner.

Aunt Diane rolls with a crowd of self-made Italian chefs and, as a result, most of her cooking falls under the “rustic Italian” umbrella. It is not uncommon to see sitting in her cupboard a massive inventory of jarred plum tomatoes or for an entire section of her freezer to be dedicated to homemade vodka sauce, always frozen in those takeaway containers that originally brought us egg drop soup. Under normal circumstances, I’d be psyched to eat over.

I don’t recall the entire menu, but there is one side dish that has been forever burned into memory, and not in a good way. I remember starring at my plate, specifically at the heaping pile of sautéed peas. I kept rearranging the peas on my plate, sometimes spreading them out, sometimes piling them up. Then Diane looked at me and excitedly asked, “Jeanne, did you try my peas? I made them just for you!” I don’t know what compelled her to make these peas for me. Perhaps it was because I am a vegetarian and the rest of the meal involved meat? But, there they were, staring me down, and there Diane was, watching with anticipation, waiting for my approval.

Because I adore my aunt Diane and I wanted to make her happy (after all, she did just cook an entire meal for my small family), I scooped up a moderate amount of peas with my fork and deposited them in my mouth. I had to use every fiber of my being to chew them, and even more effort to actually swallow. My body was not cooperating and I had to implement a state of near meditation to keep them from coming back up. Luckily, I kept my cool and was able coerce my face into showing a smile while simultaneously telling my aunt and friend that her peas were delicious.

Credit: Jeanne Garbarino.
My husband picked up on my soaring level of discomfort and without missing a beat, ate all my peas when Diane wasn’t looking. We ended the evening with my stomach contents intact, but barely.

The next morning, as I was preparing my 18 month-old daughter’s daycare lunch, I remembered that we were provided with a parting gift of sautéed peas. I took them out of the fridge and proceeded to aliquot them into containers more suitable for a toddler. As I removed the lid, the onion-tinged aroma of Diane’s sautéed spring peas smacked me across my face. My body was clearly angry about what I had done to it the night before and, as if it were in a state of protest, I found myself sprinting to the bathroom where I began to puke.

From that day forth, I could not eat peas, let alone see or smell them, without eliciting extreme nausea. It didn’t matter what time of day, the mere presence of peas, although not necessary, was sufficient to make me toss my, well, peas.

That’s the funny thing about morning sickness – it isn’t just a morning thing.

What is morning sickness?

Tick-tock. Credit: Jeanne Garbarino
It has long been known that nausea and vomiting are common symptoms of pregnancy. In fact, documentation of this phenomenon goes as far back as 2000 BC. However, the term “morning sickness” is a complete misnomer. For one, pregnancy-related nausea and vomiting is not just a morning thing. It can happen at any time of day. Second, the term “sickness” suggests a state of unhealthiness. We know that perfectly healthy pregnant women who deliver perfectly healthy babies experience morning sickness, and this type of nausea and vomiting is not an indicator of maternal and/or fetal health.

But, that doesn’t change the fact that it sucks.

Morning sickness, more appropriately known as nausea and vomiting in pregnancy (NVP), affects approximately two-thirds of women in their first trimester of pregnancy. In many cases, morning sickness subsides at the end of the first trimester. In other cases, the symptoms of morning sickness can last for the entire pregnancy. For both my pregnancies, I experienced morning sickness for the first 5 months.

I feel so lucky.  

No one really knows the exact mechanisms responsible for the onset morning sickness. We do know that the drastic hormonal changes that occur during early pregnancy certainly play a role; however, these effects are likely indirect. For instance, estrogen levels do not differ between pregnant women with morning sickness and those who do not experience symptoms.  Furthermore, there is no causal relationship between human chorionic gonadotropin (hCG), the early pregnancy hormone detected by pregnancy tests, and morning sickness, despite the fact that peak hCG levels and peak severity of pregnancy-related nausea and vomiting occur at approximately the same time.

Based on these observations, scientists suggest that the hormonal fluctuations in pregnant women can elicit different responses in an individual, rendering some extremely susceptible and others remarkably resistant to the same stimulus (with regard to nausea and vomiting). This begs the question: Is there a genetic predisposition to morning sickness?

While a “morning sickness” gene has not been identified, a few lines of evidence point toward a potential for inheriting the tendency. For instance, identical twins, are fairly likely to share a tendency to morning sickness. Also, you are more likely to experience morning sickness if your mom experienced it, too. Even though genetics may be involved, the onset of morning sickness is probably what scientists call “multifactorial,” a result of a very complex interaction between genetics and environment, making it difficult to find a treatment that is effective and safe for everyone.

Until more is known, we are stuck eating saltines and sour candy. At least it’s something, right?

Right?

Food aversions and morning sickness

Make them if you dare. Credit: Jeanne Garbarino.
For my first pregnancy, it was smoked salmon, which I probably shouldn’t have been eating in the first place. For my second pregnancy, it was peas. (Interestingly, my aunt Diane initially provided both foods, which, after that initial consumption, was immediately followed by the onset of morning sickness.) The mere sight of either peas or smoked salmon elicited an uncomfortable queasiness that often culminated with a sprint to the porcelain throne. Apparently, this type of experience is pretty normal. 

Developing an aversion to a specific tastes and smells during pregnancy is an extremely common phenomenon. In fact, between 50–90% of pregnant women worldwide experience some level of food aversion, with the most common aversions being meat, fish, poultry, and eggs. Furthermore, research suggests that food aversions developed during pregnancy are actually novel as opposed to an exaggeration of a pre-existing dislike for a certain food.

Complementing the development of food aversions is the report that dietary changes in pregnant woman are often related to changes in olfaction, or sense of smell. More specifically, some pregnant women experience increased sensitivity to certain odors, and usually in an unpleasant way. This heightened sensitivity is thought to be protective against foods that could pose a problem for mother and baby, such as those that have become rancid.  

When I was pregnant, the self-perceived powerfully pungent scent of peas could have probably knocked me over if it was translated into some other physical force. I wish I had a gas mask.  

Is there some benefit to morning sickness?

In general, nausea and vomiting are a defense mechanism, acting to protect us from the accidental ingestion of toxins. While morning sickness is likely a very complicated condition that needs further study, a popular explanation suggests that morning sickness is beneficial to both mother and fetus.

Several lines of observations support this idea, formally called the “maternal and embryo protection hypothesis”: (a) peak sensitivity to morning sickness occurs at approximately the same time that embryo development is most susceptible to toxins and chemical agents; and (b) women who experience morning sickness during their pregnancy are less likely to miscarry compared to women who do not experience morning sickness.

In essence, the maternal and embryo protection hypothesis suggests that morning sickness is an adaptive process, contributing to evolutionary success (measured in terms of how many of your genes are present in later generations). However, morning sickness is not found in all societies. One possible explanation for this is that those societies that do not widely experience morning sickness are significantly more likely to have plant-based diets (meats spoil much faster than plants). Another argument against evolutionary adaptation is that morning sickness has been documented only in three other species: domestic dogs, captive rhesus macaques, and captive chimpanzees.  

It makes sense that the pregnancy-related nausea and vomiting widely known as morning sickness is a means to help protect mom and baby. It makes sense that women have a mechanism to detect and/or expel toxins and potentially harmful microorganisms if ingested. But the idea that morning sickness is actually a product of evolution is still under debate.

And even as a biologist, if I ever have to go through morning sickness again, the idea that it could be protective won’t really bring me comfort as I am puking up my guts. But, biology is biology and sometimes we just have to deal with it.

References
Andrews, P. and Whitehead, S. Pregnancy Sickness. American Physiological Society. 1990 February;5: 5-10.
Flaxman, S.M. and Sherman, P.W. Morning Sickness: A mechanism for protecting mother and baby. The Quarterly Review of Biology. 2000 June; 75(2):
Goodwin, TM. Nausea and vomiting of pregnancy: an obstetric syndrome. American Journal Obstetrics and Gynecology. 2002; 185(5): 184-189.
Kich, K.L. Gastrointestinal factors in nausea and vomiting of pregnancy. American Journal Obstetrics and Gynecology. 2002; 185(5): 198-203.
Nordin, S., Broman, D.A., Olofsson, J.K., Wulff, M. A Longitudinal Descriptive Study of Self-reported Abnormal Smell and Taste Perception in Pregnant Women. Chemical Senses. 2004; 29 (5): 391-402



1 comment:

  1. Interesting post. I'm wondering if morning sickness is seen cross culturally at the same levels? Do your references actually look at women from different cultures, or just American women?

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