How Does a Twin Pregnancy Differ From a Single Child Pregnancy?

Written by amber keefer
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Twins can now be identified fairly early in pregnancy. But the only way to determine for certain if a woman is pregnant with twins is by an obstetric ultrasound, which by the 6th week usually can detect two embryos, two placentas, and two heartbeats. A Doppler test also may be used at about 12 weeks of pregnancy to identify the presence of two separate fetal heartbeats, but is not always reliable, as background noise mistaken for a second heartbeat may actually be the mother's heartbeat.

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Common Signs of Multiples

More than half of all pregnant women surveyed report some degree of morning sickness, which includes nausea and/or vomiting. Yet only a small percentage of women pregnant with twins say they experience worse morning sickness. Exhaustion and extreme fatigue, particularly during the first trimester, are the most frequent complaints by women who are pregnant with multiples. Although unusual tiredness may indicate a twin pregnancy, factors such as work, stress, and caring for other children can contribute to fatigue. Women pregnant with twins often report feeling the babies move early on in pregnancy.

Other Indicators

Elevated levels of HCG, a hormone that stimulates the production of progesterone, can help to confirm that a woman is pregnant with twins. Many physicians choose not to rely on HCG levels alone, as conditions other than a twin pregnancy can cause high levels. In addition, women who are pregnant with twins tend to have elevated levels of AFP, a protein released by the foetus that is excreted into the mother's blood. Women also tend to retain more water. Even though swelling of the hands, feet, and ankles is a common symptom of pregnancy in general, the rise in hormone levels normal with a twin pregnancy causes a woman to retain even more fluid.


While some women consider rapid weight gain in the first months, as a sign of being pregnant with twins, increased appetite during pregnancy is more likely the cause. Then again, two foetuses need to be supplied with more nutrients. Yet research shows that women pregnant with twins usually gain only about 4.54 Kilogram more than women carrying a single baby. How much weight a woman gains throughout pregnancy depends on her height, body type and weight before she became pregnant. Although doctors measure the height of a woman's uterus to help determine gestational age of the foetus, some physicians use it as a way to predict whether a woman might be pregnant with twins. The common belief is that a woman's uterus expands beyond the normal range of a single pregnancy if she is pregnant with multiples. However, it is not uncommon for a woman to measure larger and begin to show sooner than she did in a previous pregnancy.


Women pregnant with twins are at increased risk for common complications of pregnancy. They are more than twice as likely as other pregnant women to suffer gestational diabetes during pregnancy. The increase in hormones produced by a second foetus interferes with the body's ability to produce insulin. Usually controlled by diet, gestational diabetes is not a risk to the developing babies. A twin pregnancy also puts a woman at greater risk for problems affecting the placenta, which could cause haemorrhage during pregnancy or following delivery. Fortunately, most problems can be detected well before they present a serious risk. Pregnancy-Induced Hypertension (PIH) and preeclampsia are other potential risks. Because blood volume increases during pregnancy, carrying more than one baby can raise blood pressure even more. High blood pressure is one symptom of preeclampsia, which affects one in three women pregnant with multiples. If not monitored closely, preeclampsia can cause serious complications including seizures, stroke, or kidney failure. In addition, recent studies indicate that women who carry two or more foetuses are at greater risk for heart attack or heart failure. This may be due to an increase in physiological stress caused by a multiple pregnancy, which causes the heart to work harder.

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