70-80% of women will experience some degree of nausea and/or sickness during the first trimester of pregnancy. (2, 4) There has been a lot of debate and conflicting research around what (if anything) the occurrence, frequency and severity can tell us. Plus of course a lot of ‘old wives tales’. So, as usual we turn to the latest science and research to get some answers. Specifically we look at: why we get morning sickness, what causes it. Why some women get it worse than others. We also consider whether it is actually a positive sign for a developing pregnancy? Plus, the ultimate old wives tale: will it be worse if you’re pregnant with a girl/more than one baby?!  

Ok, so why do we get morning sickness in the first place? 

The reality is the exact cause(s) are not totally clear at this stage. However, it looks to be driven by a combination of genetics, hormone fluctuations and metabolic factors. (2,3) 

Interestingly, some have theorised it is even a protective mechanism. The nausea, food aversions and preference for carbs have been linked to stopping us eating potentially harmful foods. Particularly as organs are developing in the first trimester (also known as organogenesis). Other theories relate to it potentially playing a role stimulating placental growth which is fundamental for a successful pregnancy. (1, 6) 

When shall I expect it to start/how long does it go on for? 

Symptoms usually begin 2 – 4 weeks after fertilisation ie. week 4-8 of your pregnancy. They typically peak between weeks 9-16 and generally fully resolve by 22 weeks. As most women can also attest, the label ‘morning sickness’ is also misleading. The reality is that 98% of the time symptoms persist through the day and are not (sadly) confined to the morning. (2) 

How bad is bad morning sickness? 

Of course feeling nauseous and sick and the extent varies from person to person. It is quite a broad spectrum. Researchers have come up with a universal system to assess how severe this is. It is known as a PUQUE score. (2)  Pregnancy-Unique Quantification of Emesis scoring system. This is easy to access on the internet and there are a variety of tools you can use to calculate your own situation. Here is an example below. 

Is it in your genes? 

Yes, it appears to play a part. When it comes to genetic factors, research looking at identical twins has shown that typically they experience similar pregnancy symptoms. Indicating some genetic component to how badly you get it. Similarly if your mother has experienced Hyperemesis Gravidarum (severe nausea and vomiting during pregnancy – click here for more) then you are three times more likely to experience it yourself. (2) 

However, it appears genetics are not the only factor at play when it comes to morning sickness… 

Your hormones go through immense change when you become pregnant. Obviously! The hormone that is most closely researched and linked with morning sickness is Human Chorionic Gonadotropin aka hCG. This is a pregnancy specific hormone that is produced by the outer cells of a fertilised embryo from the time it implants (4). It is also the hormone that pregnancy tests look out for. 

How hCG plays a role in how severely we experience morning sickness: 

Whilst other hormones are on the rise during pregnancy (progesterone and estrogen) the hormone that has been linked most closely to morning sickness is hCG. One of the reasons for this link is because typically it peaks at between 9-12 weeks, which is usually when most women feel at their worst. It has also been linked in higher concentration in women with molar pregnancies, with more than one fetus or while pregnant with a girl. All incidences where nausea and sickness have statistically been shown to be higher. (2, 3) 

That being said, this is not super clear-cut either. There is a lot of conflicting data and we don’t at this point have a clear correlation. One theory however is that it is the type of hCG (known as the isoform) of which there are many can be the contributing factor. (2) 

Interestingly hCG is key for development of the placenta. The size of which has also been linked to how badly we experience morning sickness. (1, 2, 3, 4, 6) 

Does pregnancy with twins/multiples make us more likely to experience morning sickness? 

‘hCG levels are known to be higher in multiple-fetal gestations’ (1)

We also know that compared to women carrying just one baby, women with twin pregnancies had ‘significantly higher odds for the presence of nausea and vomiting during pregnancy’. It also relates to severity (3). The important caveat here is that it is not a direct relationship. Meaning it will not automatically mean that if you are having twins for example you will experience severe sickness. It simply increases the odds that you might. 

What about if I’m having a girl?

It’s is a well known old wives tale that if you’re sick as a dog during pregnancy you’re having a girl. But is there any truth to this? 

Once again, the science isn’t totally clear cut. There is some conflicting evidence. However, one study conducted last year (3) looking at nearly 100,000 women (so a decent enough sample size to make it worth paying attention to) DID find a link. 

This study concluded once again that although it did not mean that being pregnant with a girl would automatically give you morning sickness, it concludes that it could increase the odds that you experience it. It also backed up the conclusions that carrying more than one baby, especially if one is a girl would increase the chances of morning sickness: 

‘We found that pregnant women carrying a female fetus or twin foetuses are at higher risk for the presence of nausea and vomiting during pregnancy compared to those carrying a male or singleton fetus.’ (3)

Although once again, the study acknowledges that we still do not fully understand the exact mechanisms behind this. Conflicting information remains. 

Is morning sickness a good sign for my pregnancy? 

Another ‘old wives tale’ which may have some degree of truth to it…

In one study of women who had experienced one of two prior miscarriages and a hCG confirmed pregnancy; nausea and nausea with vomiting during pregnancy were associated with a substantial reduction in the risk of pregnancy loss. (1) 

In fact, this study published in the highly respected Journal of the American Medical Association found that ‘nausea and vomiting were associated with a 50-75% reduction in the risk for pregnancy loss’ in women who had suffered a prior loss. 

What about those without prior pregnancy loss? 

As usual, it appears Goldilocks prevails: not too much, not too little… 

There have been a number of studies that have concluded that mild morning sickness is associated with favourable outcomes. Plus, reduced odds for a low birth weight, risk of preterm delivery and reduce chances of miscarriage. (2) 

Of course this is not (as usual) entirely conclusive. But, it can be a reassuring thought/compensation that if you’re experiencing mild nausea and sickness, its a sign that key elements like hCG and placental development are underway. Once again, extreme sickness is another thing which may well need help with. Click here to learn more about what Hyperemesis Gravidarum is and what to discuss with your doctor. 

So, how can we manage it?

So far, we have ascertained that there is some evidence that being pregnant with more than one baby and/or a girl can increase the chances and severity of your morning sickness. Similarly a healthy pregnancy with just one baby and/or a boy can be signalled by mild nausea and vomiting in the first 12-16 weeks. That being said, it can be really tough both physically and mentally…

What does the science suggest actually works to alleviate some of the symptoms? 

First and foremost if your symptoms are severe the absolute first port of call is your doctor. Click here for more. For everyone else, there is some evidence that both managing the portions and frequencies of your meals as well as the content can help. 

Looking at how and what you’re eating is the first line of defence: 

Eating small amounts of food several times a day instead of large meals is commonly recommended. Another feature of the hormonal shifts is that your digestion is likely to be more sluggish than usual so this helps ease the load. It can also help regulate blood sugar which can improve how you feel. (2) 

Bland foods low in fat can also help (fatty foods delay gastric emptying).  Similarly you’re probably unlikely to want to reach for spicy foods. Small volumes of liquid frequently with electrolytes can also be helpful for keeping you hydrated. Coconut water is a great example of this. 

Does ginger really work for morning sickness? 

The American College of Obstetrics and Gynaecology recommends ginger as a non-pharmacological intervention. In fact, a recent review and meta-analysis of randomised trials found that ginger did help with nausea compared to placebo. Although alas no real impact on vomiting. (2,7) 

How does it work? 

Ginger contains gingerols and shogaols which essentially act on the gastrointestinal tract as a dopamine and serotonin antagonist. What does that mean? In a nutshell: it gives a sluggish digestive tract a helping hand.

One word of caution however is that anyone who is taking anticoagulants should speak to their doctor before having ginger as it can potentially inhibit platelet function. As always, if in doubt ask your doctor. 

Ok so what is the bottom line with all of this? 

Whilst there is not a slam dunk answer or clear cut conclusion to a lot of these questions it does appear that there is some evidence that mild morning sickness can be a sign that your pregnancy is developing well. There is also evidence that if you’re pregnant with more than one baby and/or you’re having a girl the chances are higher that you’ll experience some (or more severe) symptoms. Once again, this is not conclusive, more likely it increases the odds. Still, for most people it won’t last for more than the first trimester. If in doubt, or you’re experiencing severe symptoms please speak to your doctor. Don’t worry, the second trimester should welcome in that boost of energy and pregnancy glow!  

References: 

1) Hinkle S, Mumford S, Schisterman EF: Association of Nausea and Vomiting during pregnancy with pregnancy loss: JAMA internal medicine: 2016 Nov 1: 176(11): 1621-1627

2) Bustos M, Venkataramanan R, Caritis S: Nausea and Vomiting of Pregnancy – What’s new? Autonomic Neuroscience: basic and clinical: 2017 Jan: 202 62-67

3) Mitsuda N, Eitoku M, Suganuma N: Severity of Nausea and Vomiting in Singleton and Twin Pregnancies in Relation to Fetal Sex: The Japan Environment and Children’s Study (JECS): Journal of Epidemiology: 2019; 29(9): 340-346

4) Barjaktarovic M, Korevaar T, Steegers E: Human Chorionic Gonadotrophin (hCG) concentrations during the late first trimester are associated with fetal growth in a fetal sex-specific manner: European Journal of Epidemiology: 2017; 32(2): 135-144

5) Whitehouse A, Alvares G, Maybery M: Symptom severity in autism spectrum disorder is related to the frequency and severity of nausea and vomiting during pregnancy: a retrospective case-control study: Molecular Autism: 2018: 9: 37

6) Sapra KJm Joseph KS, Ananth CV: Signs and Symptoms of Early Pregnancy Loss: Reproductive Sciences: 2017 April: 24(4) 502-513

7) Hu Y, Amoah A, Zheng H, Fu R: Effect of ginger in the treatment of nausea and vomiting compared with vitamin B6 and placebo during pregnancy: a meta-analysis: The Journal of Maternal-Fetal and Neonatal Medicine: Jan 2020

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