Introductory Chapter: About Multiple Pregnancies

1. Introduction

Twins are the commonest type of multiple pregnancies. It means that two offspring created by the same pregnancy can be identical and become (monozygotic). Twins usually develop from one zygote, which splits and forms two embryos, non-identical or (dizygotic), meaning that each twin sets from separate oocytes, fertilized by different sperm [1]. One in 250 natural pregnancies will result by chance in twins [2].

2. Types of twins

The first type is when two separate oocytes are fertilized by two different sperm. This is non-identical or (dizygotic twins), but the result of if one oocyte fertilized, this is identical twins (monozygotic). Rare type is conjoined twins. There are rare (unique) twins, mirror twins, conjoined twins (physically connected.), parasitic twins, semi-identical twins, and female and male identical twins [3].

3. The risk factors

Genetics, diet, previous pregnancies, and use of fertility drugs are risk factors for multiple pregnancies and raise the chances of having twins. Age is another essential factor, especially ages over 35 have a greater chance of multiple pregnancies. High parity and race are risk factors [4]. Igbo-Ora, southwestern Nigeria, Twin Capital of the World, has a large number of twin pregnancies. In Igbo-Ora, research has suggested that this is most likely related to the women’s eating habits in the area [5, 6]. Research has found no direct relationship between dietary intake and multiple pregnancies but has proven that a widely consumed tuber (yams) could be responsible [6, 7].

4. Multiple pregnancies are increasing

There has been about a 10-fold rise in twinning rates over the past two decades [8]. Around 30–50% of all twin pregnancies result from infertility treatments. The incidence of twins increased in the last four decades in developed countries. As women delayed childbearing and the age of the first pregnancy became late became an important factor, and wild use of medication for induction of ovulation and IVF increased the probability of multiple births [9].

5. Vanishing twin syndrome

About 10–15% of singleton births start as twins, and often, one is lost in the early pregnancy; this is called vanishing twin syndrome. In 1945, vanishing twin syndrome was first recognized [10, 11].

6. Cryptophasia

According to what is (published in the Journal Institute of General Linguistics), there are bizarre phenomena that twins can speak a unique language only they can understand. But it disappears with time as the twins grow and learn other languages [12].

7. Time of delivery

The percentage of twins that can make it to 37 weeks’ gestation is 49%, and 6% are preterm [13]. Care is required during the antenatal period twin pregnancy is more susceptible to anemia; thus, they need extra care for their health and different prenatal vitamins. Women pregnant with twins should take the same prenatal vitamins for any pregnancy, but recommending extra folic acid and iron. The additional folic acid and excess iron will help ward off iron-deficiency anemia, which is more common when pregnant with multiple pregnancies [14].

The meaning of twin, A, and B The twin developing closest to the cervix is called Baby A, and the other is called baby B [15].

8. ART and Multiple pregnancies

Multiple pregnancies are now more common as a result of fertility treatments [16]. In vitro fertilization (IVF) might cause multiple pregnancies due to more than one embryo transfer [17]. Induction of ovulation non-ART fertility treatments stimulates the development of multiple oocytes, which cannot be controlled, and may lead to multiple pregnancies [18].

We know that some infertility patients prefer to have twins. Still, as a fact, all multiple pregnancies have higher risks for both infant and mother [19]. It has been shown that in the last four decades, multiple pregnancies steadily increased, and twins nearly doubled [20]. The increasing trend of multiple pregnancies coincides with the introduction of fertility treatment [21]. After considering maternal age, more than one-third of twins and more than three-quarters of triplets and higher-order multiples resulted from conception assisted by fertility treatments [22]. Improving the practice of ART results in a decrease in multiple pregnancies due to fewer embryos being transferred during ART [23].

The maximum number of embryo transfers should not be more than four in women above the age of 39 years. In those older women with high-quality embryos, no more than three embryos should be transferred. If four embryos are transferred, the data suggest that the transfer of four or more embryos has a positive effect: increasing the pregnancy rates without significantly impacting the multiple pregnancy rates. This effect is only seen in women aged <45. Transferring three embryos may increase the chance of multiple pregnancies without increasing the overall pregnancy rate. The maximum number of embryo transfers should not be more than three embryos [24].

Fertility treatments can cause twins to have a higher risk of congenital disabilities than singletons; it questions the notion that fertility treatments contribute to those abnormalities [25]. The implantation of two fertilized oocytes leads to twins, and requesting to transfer more than one embryo may increase the chance of multiple pregnancies [26].

9. There are risks associated with IVF twins

9.1 Preeclampsia

It is one of the complications of multiple pregnancies edema, high blood pressure, and proteinuria. Premature labor is a significant and common complication of multiple pregnancies. Statistically, about 60% of twins are born before their due date [27]. The risk is about three times more than in the case of normal twin pregnancies [28].

9.2 Twin-twin transfusion syndrome (TTTS)

Another thing you should remember when it comes to twins with IVF is the risk of TTTS. When two identical twins share the placenta, the possibility of twin-twin transfusion can occur at about 5%. Life-threatening conditions might happen if one of the babies had more blood than the other twins [29].

9.3 Intrauterine growth restriction (IUGR)

IUGR is a complication that might occur in multiple pregnancies. It means that one of the babies is not developing at the pace it should. Due to this delayed growth, several health implications are imminent for either or both babies [30].

9.4 Cesarean section

Carrying twins might also mean that a cesarean section might be the method of delivering twins having a higher incidence of cesarean section. Compared with vaginal birth, recovering from a cesarean section requires more time, and looking after two babies after a cesarean section can be very difficult [19]. Low birth weight and premature delivery, depending on the time of the delivery, heart problems, problems with breathing, hearing, vision, and cerebral palsy are all issues that may occur [31].

10. Conclusion

Multiple pregnancies have high maternal and neonatal complications, especially preterm delivery, which increases the risk of significant neonatal morbidity and mortality. Promotion of the elective single embryo transfer strategy is needed to reduce multiple pregnancies following IVF technologies.

Disclosure

I state that this introduction has not been previously published, nor being considered for publication elsewhere. No conflict of interest.