Losing Weight in Early Pregnancy

When to report it

Weight loss in early pregnancy is common. Three versions of it should be raised rather than watched.

You cannot keep food or fluids down. The NHS: "If you are being sick frequently and cannot keep food down, tell your midwife or doctor, or contact the hospital as soon as possible. There is a risk you may become dehydrated, and your midwife or doctor can make sure you get the right treatment."

The weight is still going down. The NHS names weight loss as one of the three defining signs of hyperemesis gravidarum, alongside prolonged and severe nausea and vomiting, and dehydration. It advises seeing a GP or midwife with severe nausea and vomiting because "getting help early can help you avoid dehydration and weight loss".

You are losing weight without sickness. Weight loss with no nausea and no vomiting is a different question and is worth mentioning at your next appointment, because it has not been explained by the usual cause.

Signs of dehydration the NHS lists: feeling thirsty, tired, dizzy or light-headed, not peeing very much, and having dark yellow and strong-smelling pee.

Why early loss is less alarming than it feels

The single most useful fact here is about timing. The NHS: "Most pregnant women gain between 10kg and 12.5kg (22lb to 28lb), putting on most of the weight after week 20."

Most of pregnancy weight gain is not fat storage but the baby, the placenta, amniotic fluid, extra blood volume and breast tissue, and almost all of that accumulates in the second half. A first-trimester dip therefore comes out of your own reserves at a point when the baby's requirements are small.

The other reason it happens has nothing to do with sickness at all: a great many people change how they eat on getting a positive test. Alcohol goes, coffee often goes, certain foods go, and cooking becomes unappealing. That alone can shift the scales.

How common the sickness behind it is

The NHS: "Around 8 out of every 10 pregnant women feel sick (nausea), are sick (vomiting) or both during pregnancy. This does not just happen in the morning. For most women, this improves or stops completely by around weeks 12 to 20, although for some women it can last longer."

So the majority of pregnancies involve a period where eating is difficult. Losing a little weight during it is a predictable consequence rather than a complication.

Where hyperemesis gravidarum begins

The NHS describes HG as "much worse than the normal nausea and vomiting of pregnancy" and gives a prevalence figure with the honest caveat attached: "Exactly how many pregnant women get HG is not known as some cases may go unreported, but it's thought to be around 1 to 3 in every 100."

Its features:

• prolonged and severe nausea and vomiting
• dehydration
• weight loss

It adds a timing distinction that helps: "Unlike regular pregnancy sickness, HG may not get better by 16 to 20 weeks. It may not clear up completely until the baby is born, although some symptoms may improve at around 20 weeks."

Two risk factors it names: HG appears to run in families, so a mother or sister who had it raises your chance; and having had HG in a previous pregnancy makes it more likely next time, "so it's worth planning in advance."

Treatment exists

The NHS is clear that this is treatable rather than something to endure: "There are medicines that can be used in pregnancy, including the first 12 weeks, to help improve the symptoms of HG. These include anti-sickness (anti-emetic) drugs, steroids, or a combination of these. You may need to try different types of medicine until you find what works best for you."

Where symptoms cannot be controlled, admission for intravenous fluids may be needed. RCOG's patient information on pregnancy sickness and hyperemesis covers the same pathway from the specialist side.

Will it affect the baby?

The NHS answers this in one line: "HG can make you feel very unwell, but it's unlikely to harm your baby if treated effectively." It adds the caveat that matters: "However, if it causes you to lose weight during pregnancy, there is an increased risk that your baby may be born smaller than expected (have a low birthweight)."

That is the argument for asking early rather than proving you can cope. The risk attaches to sustained weight loss, and sustained weight loss is what treatment prevents.

What to do while it lasts

• Fluids before food. Dehydration causes more trouble than a few missed meals, and it is the thing that lands people in hospital.
• Eat whatever stays down. A week of dry toast is not a nutritional failure.
• Small and frequent beats waiting until you feel able to face a meal.
• Cold food over hot, because smell drives aversion more than taste.
• Keep taking your supplements if you can. Folic acid and vitamin D are recommended throughout, and NICE's antenatal care guideline builds supplement advice into routine care. If you cannot keep them down, say so rather than silently stopping.
• Do not try to make up the loss by eating more later. The NHS is clear pregnancy is not the time to diet in either direction.

What is not weight loss

Two things get counted as weight loss and are not. Day-to-day fluctuation of a kilogram or so is water and gut contents rather than tissue. And a scale reading that has not moved for six weeks in the first trimester is not loss; it is the normal picture at a stage where most gain has not started.

The number worth watching is the trend across several weeks, and the person to show it to is your midwife.