What is Pregnancy?

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It is called pregnancy, gestation or gravida to the period that goes from the implantation of the fertilised egg in the uterus to the time of partum/delivery.

A normal pregnancy period is a physiological state of the woman that begins with fertilisation and ends with the delivery and the birth of the baby.

Duration of the Pregnancy

Embryonic development

Human pregnancy lasts 40 weeks from the first day of the last menstruation/period, or 38 weeks from fertilisation (approximately 9 months).

Multiple pregnancy

A multiple pregnancy is one in which more than one foetus is developing. This comes about as a result of the fertilisation of two or more ovules, or when the ovule is divided, giving rise, in this case, to genetically identical twins

The double or twin pregnancy is the most common form of multiple pregnancy, although there are certain occasions in which triplet pregnancies occur.

Non-identical twins come from two different ovules, and have two placentas and two sacs. The babies can be of the same or a different gender.


On the other hand, identical twins are produced by the spontaneous division of a single embryo, generated from a single ovule. They are always the same gender and identical. They may share a single placenta, or have two different ones, and can share a single sac, or each one may have their own.

Normal pregnancy and risk pregnancy

normal pregnancy is that which occurs with no unfavourable factors (biological, psychological, socio-demographic, etc.) and/or previous maternal diseases or those acquired during the course of the pregnancy, which may interfere in its normal progression.

Pregnancy is classified into the following levels of risk: low, medium, high, or very high.

The risk assessment is updated in each visit as this can vary. For example, a low risk pregnancy may change to a high risk one if diabetes appears during gestation.

If the pregnancy is considered low or medium risk, a midwife will be your main contact.

high risk pregnancy is one that has more possibilities of developing complications during gestation. In these cases, the woman must be subjected to a more rigorous monitoring, in order to avoid possible risks.

It is estimated that 10% of pregnancies are high risk, and the causes can be very variable and may occur before, during, or after gestation.

If your pregnancy has a high or very high risk, your main contact will be a doctor (obstetric-gynaecologist) and all the specialists that are considered necessary.

Substantiated information by:

Anna Sandra Hernández Aguado
Isabel Benito Díaz
Maria Àngels Martínez Verdú

Published: 20 February 2018
Updated: 20 February 2018


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