By Cristina Mestre Ferrer BSc, MSc (embryologist), Manuel Aparicio Caballero MD, MSc (gynecologist) and Manuel Fernández MD, PhD (gynecologist).
Last Update: 11/17/2014

Multiple pregnancies are quite common due to several factors such as the delay in maternity or assisted reproduction techniques. However, in this last case their amount is trying to be reduced by explaining to the patient that the ideal is the transference of just one embryo.

Dangers multiple pregnancies

Twin pregnancies are dangerous and involve risks for the mother and the babies, during pregnancy as well as at the moment of delivery.

Most common complications

Multiple pregnancies are the most complicated, due to the increase in volume that involves carrying more than one baby. The uterus bears an excessive weight and may expand itself exerting more pressure on the rest of the organs. Carrying two or more babies means also a bigger placenta and raises the hormonal levels in blood.

Multiple pregnancies involve a higher demand for the body of pregnant women and might increase the complications suffered when compared to a normal pregnancy. These complications may be:

Vanishing twin

During the first analysis of pregnancy (5 – 6 weeks) two twins are observed, however in the following examinations only one foetus appears. In 60% of the cases one twin doesn’t develop and it’s reabsorbed. The foetus that survives develops normally and without complications.

Weight increase

Logically the weight increase in multiple pregnancies is higher than when the woman carries just one baby. An increase between 12 and 18 Kg is recommended in twin pregnancies.

Weight increase multiple pregnancies

Chromosome alterations

In this kind of pregnancies it’s more common for chromosome alterations to take place. Furthermore, if the pregnant woman is advanced in age the risk to suffer any kind of chromosome disorder doubles.

Twin-to-twin transfusion syndrome

It takes place when the blood vessels of the foetuses are linked. One foetus may receive too much blood and the other too little. It can even lead to foetus death; however, there are several ways of solving it. The premature diagnosis is of vital importance.

Delay in growth

If the conditions of the placenta are not appropriate the babies may not grow enough. The risk of presenting low weight is of 20% with one placenta (monochorial twins) and 30% with two placentas (fraternal twins). It is also possible that one twin grows more than the other.

Smaller babies

Placenta praevia

Due to the presence of more than one placenta or a bigger placenta, it is possible that it lies very low in the uterus and blocks the cervix, which may provoke vaginal bleedings and increase the risk of premature deliveries.

Premature deliveries

The estimated risk of premature deliveries in multiple pregnancies is 25% to 45% depending on the source you get the information from. It’s been proved that numerous twin pregnancies last less than 37 weeks. The premature delivery can produce complications for the foetus, since it hasn’t developed fully and the mother can suffer from anaemia among other complications.

Some other risks of the twin pregnancies are:

  • High blood pressure.
  • Eclampsia and pre-eclampsia.
  • Hypermesis gravidarium (excessive vomiting).
  • Digestive disorders.
  • Postpartum bleeding.

FAQs from users

Is a preterm birth more likely with twins?

By Manuel Aparicio Caballero MD, MSc (gynecologist).

According to the World Health Organization (WHO), a preterm birth occurs when the child is born before the week 37 of pregnancy. Some of the most common causes of preterm birth are:

  • Overdistention of the uterus: loss of tone in the uterine musculature that prevents this organ to recover its normal size.
  • Infection or uterine inflammation: certain bacteria can damage fetal membranes by causing its rupture and triggering a preterm birth. An infection that affects the uterus directly may lead to preterm birth as well.
  • Decidual bleeding: a type of vaginal bleeding that may occur while a woman is pregnant.

There exist many risk factors that can lead to premature birth, including obesity, high blood pressure, etc. A multiple pregnancy is one of these factors.

Which specific risks or dangers are involved in a multiple pregnancy?

By Manuel Fernández MD, PhD (gynecologist).

Although the potential risks for the fetuses and the mother are becoming increasingly controlled and less frequent, it is precisely in cases of multiple births where problems for the mother may raise, such as high blood pressure, diabetes, prematurity, problems at the time of delivery, etc. As for the baby, the potential dangers are those related to prematurity, most of them considered as mild and transitional, although some may become a serious health issue.

Authors and contributors

 Cristina Mestre Ferrer
BSc, MSc
Embryologist
Bachelor's Degree in Biological Sciences, Genetics & Human Reproduction from the University of Valencia (UV). Master's Degree in Biotechnology of Human Assisted Reproduction from the UV and the Valencian Infertility Institute (IVI). Embryologist at IVI Barcelona. More information
 Manuel Aparicio Caballero
MD, MSc
Gynecologist
Bachelor's Degree in Medicine from the University of Murcia. Specialist in Obstetrics & Gynecology. Master's Degree in Human Reproduction from the King Juan Carlos University and the IVI. Currently, he is part of the team of Tahe Fertilidad (Murcia, Spain). More information
License: 303008030
 Manuel Fernández
MD, PhD
Gynecologist
Graduate in Medicine and Surgery from the University of Seville. Specialist in Obstetrics and Gynecology from the University Hospital Virgen Macarena de Seville. Master's Degree in Assisted Reproduction from the Rey Juan Carlos University of Madrid. Gynecologist at IVI Seville since 2003 and Director since 2005. More information
License: 4114231