Home pregnancy tests are accurate in almost all cases, but exceptions may exist. A twin pregnancy is a quite different and harder experience than a singleton in several ways. Specific risks and complications are highly likely when it comes to twin pregnancies or multiple pregnancies such as triplets and quadruplets.
In this write-up, we are going to look at whether twin pregnancy can produce false negative results on a pregnancy test, elaborate on how pregnancy test kits work, discuss the types of twins and their differences, and state complications that may be more intensified or are unique to twin and multiple pregnancies. Remember, this is just an overview; therefore, it is best not to depend on only written accounts regarding medical conditions. Consult a doctor for the most authentic advice regarding your conditions or complications.
1. Can twins cause false negative pregnancy test results? Why?
It is possible to get a false negative pregnancy test result in case of multiple pregnancies (twins, triplets, quadruplets, and so on). This is known as the ‘hook effect’ and is a rare phenomenon.
Pregnancy tests work by detecting the presence of Human Chorionic Gonadotropin (HCG) in a woman’s urine. The hormone HCG is produced after the embryo’s implantation in the uterine wall, which happens about 6 to 10 days after conception. The presence of this hormone in urine gives positive results, while the absence of it produces negative results.
Multiple pregnancies produce very high levels of HCG, which can cause an improper ratio of this hormone and the antibodies in the pregnancy test. This can interfere with the results and cause a false negative test result.
2. What are the types of twins?
There are two main types of twins. They are:
2.1. Fraternal Twins or Dizygotic Twins
Fraternal twins, also known as dizygotic twins, result when two separate eggs or ova are fertilised by two sperm during the same pregnancy. About 2 in 3 sets of twins are fraternal. Fraternal twins may be of the same or different genders. The birth of fraternal twins runs in families as genetic factors influence it.
2.2. Identical Twins or Monozygotic Twins
Identical twins, also known as monozygotic twins, are formed when a single fertilised egg cell or zygote splits into two and results in two conceptions simultaneously. The exact cause or biological mechanism behind the split is unknown, though there are several theories surrounding this. Identical twins share the same genomes and are always of the same sex. Identical twins do not run in families and have identical DNA.
Conjoined twins, also known as Siamese Twins, are rare sets of identical twins that are physically connected to each other and may share one or more internal organs. Such twins occur in every 50,000 to 60,000 births and are the result of embryos that did not split completely. About 70 percent of conjoined twins are born females as they are 3 times more likely to be born alive compared to males, but, unfortunately, most conjoined twins are stillborn. If the conjoined twins have separate organs, the chances for surgical separation and survival are greater than if they share the same organs; as per rules, conjoined twins that share a heart cannot be separated.
3. What are the chances of a twin pregnancy?
About 16 sets of twins are born per 1000 births in the US. Approximately 1 in 250 natural pregnancies results in the birth of twins.
4. What are the factors that increase the likelihood of twin pregnancy?
Women over 30, especially in their late 30s, are more likely to conceive twins. This is because as people get over, the levels of follicle-stimulating hormone (FSH) rise, which makes the woman likely to release and fertilize multiple eggs at a time.
4.2. Family History
Usually, an ovary releases only a single egg at a time. The biological process of ovulation is determined by our genes and some women have alleles of this gene that make them more likely to hyper ovulate or release multiple eggs from the ovary at a time. These eggs, if fertilized, will cause multiple pregnancies with fraternal twins. This is how having a family history of fraternal twins makes you more likely to birth fraternal twins.
Women with higher BMI are more likely to conceive twins than those with lower body weight. This is because obese women produce more oestrogen in the body; excess secretion of this hormone causes overstimulation in the ovaries, making them likely to release multiple eggs at once. This increases their chance of multiple pregnancies. However, other factors associated with being overweight generally makes it difficult for obese women to conceive.
4.4. Fertility Treatments
Fertility treatments such as IVF (which stands for in-vitro fertilisation) or ovulation induction therapies involve the use of fertility drugs, which may overstimulate the ovaries, leading to hyper ovulation or release of multiple eggs at the same time. This, in turn, increases the chances of multiple pregnancies.
4.5. Personal History
Women who have given birth to twins are more likely to conceive twins again. Such women often hyper ovulate (releasing more than one egg at a time), and this is the factor that increases their chances of conceiving fraternal twins.
5. What are the risks or complications related to twin pregnancy?
Multiple pregnancies are more likely to develop complications than single pregnancies. It is important to have proper knowledge about the risks or complications that may come with multiple pregnancies. Here is a list of complications and risks related to twin or multiple pregnancies.
5.1. Preterm Birth and Low Birth Weight
Around 60 percent of twins and almost all higher-order multiple births are premature. The more the number of fetuses in the woman’s womb, the higher the risk of complications and premature labour and birth. These babies are often small and have low birth weight (less than 5.5 pounds or 2,500 grams). Many such babies need care in an NICU, which stands for Neonatal Intensive Care Unit.
5.2. Gestational Hypertension & Gestational Diabetes
Gestational hypertension is a form of high blood pressure during pregnancy. Though the exact cause of gestational hypertension is unknown, some conditions such as pre-existing hypertension or high blood pressure, or kidney problems, may increase the risks of hypertension or high blood pressure during pregnancy.
Similarly, gestational diabetes is a kind of diabetes that can develop in a non-diabetic woman during pregnancy. Carrying multiple fetuses puts additional pressure on the body, increasing the demand for insulin. This is why the risk of developing gestational diabetes is also higher in women carrying twins or multiple babies than it is in case of a singleton pregnancy.
5.3. Twin-to-Twin Transfusion Syndrome (TTTS)
This extremely rare condition occurs when identical twins or other multiples share a single placenta. Twin-to-Twin Transfusion Syndrome happens in pregnancies where twins share a placenta as well as a network of blood vessels that supply oxygen and essential nutrients to the fetuses in the womb.
In certain cases, these blood vessels are not evenly distributed between the twins, causing an imbalance in their blood exchange. In such cases, one twin (called the donor twin) gives away more blood than it receives and has a huge risk of malnourishment and organ failure;. In contrast, the other twin (called the recipient twin) receives excess blood and runs the risk of overwork of the heart as well as other cardiac conditions. These pregnancies are also called monochorionic pregnancies.
This condition is characterized by low hemoglobin in the blood and is twice more common in multiple pregnancies than in single ones.
Early miscarriages in the first trimester are not unusual in cases of both single and multiple pregnancies. In cases of twin pregnancies, sometimes one baby may be lost due to miscarriage; if this happens during the first trimester, the surviving baby isn’t usually affected. The dead embryo is very small, and thus it is often reabsorbed into the lining of the uterus without causing any symptoms. This phenomenon is known as the Vanishing Twin Syndrome.
Preeclampsia is a complication in pregnancy that occurs due to problems in the way the blood vessels in the placenta grow in the early stages of pregnancy. This complication is more common in twin or multiple pregnancies due to the presence of a larger placenta or more than one placenta. Moreover, a single placenta that is shared by multiple foetuses has to work harder. These factors also increase the risk of miscarriage when it comes to twin pregnancies or multiple pregnancies.
5.6. Birth defects
Birth defects are twice as common in the case of multiple pregnancies as they are in the case of singleton pregnancies. Such congenital abnormalities include neural tube defects (such as spina bifida), gastrointestinal abnormalities and heart abnormalities.
5.7. Abnormal amount of Amniotic Fluid
Polyhydramnios is a condition characterized by excess amniotic fluid around the baby during pregnancy. Most women with this condition do not face many problems with their pregnancy, but they may have to go to a few extra check-ups.
Many women with polyhydramnios do not have any noticeable symptoms but some women with this complication may have symptoms like breathlessness, heartburn, constipation, swollen ankles and feet.
Though the reason behind this condition is often unclear, polyhydramnios could be caused by twin or multiple pregnancies, diabetes in the mother (including gestational diabetes), blockage in the baby’s gut (known as gut atresia), infection during pregnancy, the mother’s blood cells attacking the baby’s blood cells, and if your baby has a genetic condition.
5.8. Caesarean Delivery
A cesarean delivery, also called a cesarean section or C-section, is a surgical procedure of delivering babies (single or multiple) through an incision in the mother’s abdomen. In the case of twin or multiple deliveries, a woman has twice the chance of cesarean pregnancy than in the case of a single baby delivery. A C-section isn’t painful, but one may sometimes feel sensations of pulling and pressure; regional anesthesia is used to numb a patient from the waist down so that the mother can stay awake to see her baby being born and hold it in her arms after delivery.
5.9. Postpartum Haemorrhage
In simple words, Postpartum Haemorrhage refers to excessive bleeding of the mother after childbirth. The chances of experiencing postpartum hemorrhage or PPH is significantly higher in the case of twin pregnancies as compared to singleton pregnancies. A cohort study showed that more than 1 in 4 twin pregnancies had postpartum hemorrhage; therefore, the chances of PPH in twin pregnancy are about 27.8%. In the case of singleton pregnancies, only about 1 in 20 experienced it; therefore, the chances of PPH are only about 5.7%. This shows that the risks of PPH are about 5 times higher in the case of twin pregnancies than in the case of a singleton pregnancy.
Though it may not be possible to prevent multiple pregnancy complications, there are ways to minimize the chances of it. Twin pregnancy requires more care and medical check-ups than a singleton pregnancy. You must keep a few things in mind to manage multiple pregnancies effectively. If you are a mother carrying two or more babies, you need more calories, iron, protein and other essential nutrients. Adequate nutrition is necessary for the proper growth and development of fetuses.
Also, as multiple pregnancies run a higher risk of developing complications, frequent prenatal visits to a doctor are necessary for effective treatment and management. You will also need more rest if you are carrying multiple babies, and ensure there is enough maternal and fetal testing throughout your pregnancy. Take medications prescribed by your doctor or healthcare provider and properly follow the suggestions and instructions provided by them to minimize problems regarding your twin pregnancy.