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Sunday 20 October 2019

Nesting (Things We Don’t Know about Pregnancy Series #5)

I’ve been experiencing some severe nesting symptoms. But is it because nesting’s a real thing, or because of my personal desire to organise and structure life (especially in the wake of impending chaos)?

Women have long been observed to clean more in the spring. But is “spring cleaning” driven by their desire to go out in the weather, or cast off the stuffiness of winter?

What is Nesting?

Nesting in preparation for a baby includes anything from cleaning to organising, decorating to stockpiling. I have done all this – from emptying and restructuring drawers to buying baby bits, to sewing, stewing, and sticking in a frenzy of creative energy.

Making © TWDK.

The nesting instinct is supposed to peak shortly before delivery, leading to the anecdote that it’s a sign of impending labour, and the scientific suggestion that boredom (when movement is limited) and excitement may be driving factors. But not all women get nesting urges: 20% do not. And for others it comes and goes. For me, it struck in the first trimester – and has remained headstrong.

But are environmental factors enough to explain nesting? Various scientists who have studied animals think that the behaviour is rooted in evolution.

Nesting Animals

Baking © TWDK.
Nesting behaviours are seen in animals from birds to fish, rodents, cats, dogs, and pigs, predominantly in pregnant females. Pregnant dogs will steal blankets, cats will climb into haylofts, rabbits pluck out their own fur to line the burrow, sows leave the herd to travel up to 6.5km[1], and broody birds will insist on constant nest sitting.

Building a nest serves a purpose: it protects offspring. It might also serve a social purpose by creating a family “home”. Marsupials don’t nest. They carry their young with them in a pouch, and scientists think this might be why.

But these behaviours aren’t completely inexplicable: they are hormonally driven. When a pregnant female animal starts to nest, her oestradiol, prolactin and progesterone levels soar. When she stops, her oxytocin is high – the hormone responsible for contractions in labour. Shortly after the birth, progesterone levels drop, oestradiol stays steady, and prolactin keeps going up. The exact timings vary from species to species[2].

Not all Nesters are Pregnant Females

Stockpiling © TWDK.
Male and non-pregnant female animals sometimes nest. Scientists think this behaviour is performed to regulate temperature or endear themselves to a potential mate.

In one experiment on castrated doves injected with testosterone, males either courted females or nest-built, depending only on the female’s behaviour, showing the instinct to be social[3].


Human men also nest, with up to 90% in a relationship with a pregnant woman showing some kind of symptom.

This is called sympathetic pregnancy, or sometimes couvade syndrome – although couvade syndrome is not recognised as a “real” condition by many doctors. Some think that it’s psychosomatic, whilst others think there may be stress hormones behind it – such as cortisol[4]. Symptoms can include weight gain, morning sickness, mood swings, fatigue, and disturbed sleep. Some men even get sympathetic labour pains!

Marketing Nesting

Decorating © TWDK.
Big shops love to do market research on their customers, gathering anything and everything they know about their lives, homes, and purchase history. They then use this knowledge to send targeted vouchers and offers. But this can occasionally run into problems, Target discovered when they identified a teenager was pregnant before her father did.

Pregnancy is a key thing for companies to predict: once a parent sets a habit of buying in one place, they tend to stick to it, and babies are resource-intensive. As such, marketers put a lot of effort into calculating due dates and imprinting their brand.

Of course, they sometimes get it wrong. When I got married, Facebook spammed me with baby products – and my husband with dating sites. However, they can often be uncannily accurate.

But what do they use? Whilst prenatal vitamins may be a giveaway, there may be other patterns such as intense nesting purchases that factor into the algorithms (or fewer purchases as the parents are saving up).

Buying © TWDK.

There are many unknowns when it comes to pregnancy, and over the next few months, I’ll be exploring more of them with you. Look out for my next blog post, which will be about toxoplasmosis.

To read our full article on the things we don't know about pregnancy, check out our site. This article will be updated as we add posts across the coming months.

why don't all references have links?

[1] Wischner, D. Kemper, N. Krieter, J. (2009). Nest-building behvaiour in sows and consequences for pig husbandry. Livestock Science. 124 (1–3): 1–8. doi: 10.1016/j.livsci.2009.01.015.
[2] Woodside, B., and Leon, M. (1980). Thermoendocrine influences on maternal nesting behavior in rats. Journal of Comparative and Physiological Psychology, 94(1), 41-60. doi: 10.1037/h0077652.
[3] Silver, Rae (1978). The Parental Behavior of Ring Doves: The intricately coordinated behavior of the male and female is based on distinct physiological mechanisms in the sexes. American Scientist. Sigma Xi. 66 (2): 209–15. Bibcode: 1978 AmSci. 66.209S. JSTOR 27848517.
[4] Klein, Hilary (1991). Couvade syndrome: Male counterpart to pregnancy. International Journal of Psychiatry in Medicine. 21 (1): 57–69. doi:10.2190/FLE0-92JM-C4CN-J83T. PMID 2066258.

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