Scientific answers to 3 typical questions of pregnancy

Nature does not stitch without thread. Those seemingly illogical behaviors that women have in pregnancy and postpartum have a scientific explanation that guarantees that the mother "has not gone crazy" even though her hormanas are far from the usual levels.

The unstoppable desire to prepare the cradle

You know you have enough baby clothes, but for some reason you come home with a couple more sets ... just in case. The crib is ready with its sheets washed with neutral soap. The fridge is not neat enough and it's about time someone cleaned the shelves in the living room. Since we are, maybe it would be better to fill the food pantry, clean the cabinets, sweep the floor for the third time today, wash the sheets again or, please, stop the world that the stain in the window is killing me.


The nesting instinct It refers to the trend in animals that expect offspring to overeat and prepare the nest. This behavior can be observed in a variety of mammals and birds. Thus, the imperative need to eat, store food and prepare the nest for the arrival of new members of the pack is regulated by the hormones progesterone, estradiol and prolactin. Because the survival of a baby is highly correlated with the home in which it will be received, it is natural that evolutionarily we have developed a biological system in response to this event.

The segregation of progesterone, estradiol and prolactin that trigger the preparation of a home for the arrival of the baby, also play a major role in the maternal bond. So much so that, in studies with rats and rabbits, it can be observed that when the nests they prepare are altered or when they are not allowed to build their nests, they suffer from a prolactin deficiency. Rats mothers and rabbits in this situation do not form a bond with their offspring, even come to step on them and not offer attachment.


In humans, the nesting instinct comes from both a hormonal and cultural trigger. The instinct of nesting helps us psychologically to prepare ourselves for the great change that involves welcoming a new member of the family. Culturally, it promotes a certain image of how parents should be, what is the image of a perfect home and it is normal that we want the best for our children. In this way, we are motivated to make everything shine, have everything ready for the arrival of the baby, or suffer the possible criticism of our environment about the house in which our baby will live.

The segregation of prolactin not only prepares the physiology of women to be able to breastfeed, but also acts as a neuromodulator. Prolactin during and after pregnancy decreases libido and promotes maternal behavior. It is because of this combination that we may have a lower tendency to be affectionate with our husbands but to put immense love in folding a blanket.


On the other hand, the segregation of progesterone and estradiol modulates neuronal membrane receptors such as serotonergic, noradrenergic and dopaminergic receptors. These receptors are highly associated with the processes of anxiety and depression. Progesterone modulates these membrane receptors by regulating them in the same way that antidepressants work. Thus, progesterone plays an important role in affective disorders and exercises its actions on the limbic system. It is from this emotional state of calm and happiness that we are born having everything ready for the arrival of our baby.

Why now my labor does not seem as painful as before?

Never more. This has been worse than I expected. How did people do a century ago, and does it mean? How awful. I do not go through this again.

Five years later: "I want another baby, pregnancy was not so bad and childbirth was not, I want a baby that sleeps like a little angel and curls up and fits in my arms."

From an evolutionary point of view, the memory of pain plays an important role. Pain indicates a threat to our health and avoiding it is often key to our survival. In spite of this, the pains of childbirth are an indicator that something wonderful is about to happen, and the more contractions hurt, the closer the event is. Historically, giving birth has been associated with pain and a high risk of maternal death. This being the case, evolutionarily our predisposition should be to avoid having more children, if we survive the delivery of the first. However, this is not the case.

Although we never completely forget a delivery, we usually remember the pain and discomfort less objectively. This is due to a combination of factors. The first is due to a "halo effect". The euphoria, the relief, the happiness and the anxieties of holding our baby in our arms for the first time, seeing him open his little eyes, holding a finger, and seeing him sleeping peacefully creates a mnemic footprint much more powerful than the discomfort and the pain.It does not mean that you have forgotten the birth, it means that the reward and love of the arrival of the baby has diminished relevance to everything else.

Following this line, it can be observed that, over time, many women remember childbirth and its pains and discomforts as less severe than how they were originally remembered. This relationship is observed mainly in women who reported moderate levels of pain after delivery. In cases of extreme pain, the memories are more consistent. Those women who say that childbirth carries the worst pain imaginable, claim exactly the same one year later. This same correlation is observed in women who assert their delivery as free of pain.

It has been scientifically discovered that women do not forget to have experienced pain during childbirth, but their level and valence can vary. Many women talk about their pain positively, using it as evidence of how well they delivered. Most women remember their births as less painful after five years.

On the other hand, at the beginning of labor, the uterus becomes hypersensitive to oxytocin. When the end approaches, our body produces more oxytocin. By the time the delivery is over, our body has a substantial increase in oxytocin. This hormone, also known as "the hormone of love", plays a role in the recognition and establishment of social relationships and in the formation of bonds of trust and generosity. In addition, it also intensifies positive social memories and increases the sense of well-being. This effect added to the halo effect explains why the pain of childbirth is not always remembered accurately and can be remembered differently over time.

I'm happy, but why do I sometimes feel like crying?

You can be talking about the nurse who gave you an ibuprofen that morning and a few seconds find you crying for the love you feel when, immediately, you start to laugh out loud thinking about how ridiculous you should see crying, which reminds you to your physical image with those kilos that now clash without a baby inside and return to mourn. All in less than two minutes of clock.

Although levels of oxytocin reach a maximum at the end and after delivery, they begin to fall progressively in the following hours. In the first 24 hours after delivery, hormone secretion decreases almost to its prepartum level. This abrupt change always brings emotional consequences.

To this are added drastic changes to our life, customs and body. If it is normal to find yourself overwhelmed from time to time in normal life, if you add new responsibilities, the pressure to be a good mother, the grief of your previous life It is a cosmic recipe to suffer what Americans callbaby blues, which is not a postpartum depression as such, but an extremely volatile emotional state.

It is common to have mood swings after childbirth, especially after four or five days. Many women find themselves confused in the face of this struggle between sadness and happiness. They feel that before such a beautiful event they can not complain or talk about other more negative aspects that they may be experiencing, which only increases the baby blues.

On the other hand, the few hours of sleep and the abnormal sleep pattern do not help these disorders, but rather aggravate them. The areas of the brain that deal with emotional responses are approximately 60 percent more reactive in people who have not slept than in those who have fallen asleep properly. Several scientific studies have shown that lack of sleep affects the mechanisms of emotional regulation and generates emotional instability. With the lack of hours of sleep, the amygdala, the emotional center, is set in motion and becomes relevant above the prefrontal cortex (responsible for rational and logical judgment). In this way, the lack of sleep, the eminent responsibility, the overwhelming changes and hormonal transformations are the main causes of suffering this roller coaster of emotions.

Dr. Maite J. Balda. Psychologist and Master in Cognitive Neurosciences

Pregnancy calendar week by week

Click on each petal or circle to see the content of your week or trimester of pregnancy respectively.

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