Multiple gestations refer to a pregnancy with more than one fetus.
A twin pregnancy is when two fetuses develop in the uterus simultaneously.
Multiple gestations are associated with a higher rate of almost every potential complication of pregnancy, excluding post-term delivery and macrosomia. The best outcome in multiple gestations is seen in diamniotic, dichorionic twinssince each fetus has their own nutrient supply.
70% of twins are dizygotic, and 30% are monozygotic.
36% of twin pregnancies and 77% of higher order pregnancies occur following infertility treatment, e.g., in vitro fertilisation or clomiphene.
Definition of terms
| Terms | Description |
|---|---|
| Monozygotic | Identical twins arising from a single zygote |
| Dizygotic | Non-identical twins from two different zygotes |
| Monoamniotic | A single amniotic sac |
| Diamniotic | Two separate amniotic sacs |
| Monochorionic | Shares a single placenta |
| Dichorionic | Two separate placentas |
| Superfecundation | Fertilization of two separate ova released in the same menstrual cycle resulting in dizygotic twins |
| Heteroplacental superfecundation | Dizygotic (dichorionic diamniotic) twins with two different fathers |
| Superfetation | Fertilization and implantation of a second embryo during an ongoing pregnancy resulting in two fetuses of different gestational age |
Summary of monozygotic twin gestation
| Dichorionic-diamniotic | Monochorionic-diamniotic | Monochorionic-monoamniotic | |
|---|---|---|---|
| Frequency | 25% | 60 – 70% | 1 – 2% |
| Time of separation | ≤ 72 hours | 4 – 8 days | 9 – 12 days |
| Stage of separation | Morula stage | Blastocyst stage | Embryonic stage |
| Stuctures | Separate chorion and amniotic sac | Shared chorion and separate amniotic sac | Shared chorion and shared amniotic sac |
| Ultrasound findings | Lambda sign (intertwin membrane + twin peak) | T-sign (intertwin membrane) | No intertwin membrane |
| Associated complications | Fewer rates of complications | Twin-to-twin transfusion syndrome (TTTS) | Twin-to-twin transfusion syndrome (TTTS), Cord accidents |
- Risk factors for multiple gestation
- Artificial reproductive technology
- Clomiphene
- Human menopausal gonadotropin
- African heritage
- Multiparity
- Family history of multiple gestation
- Obesity
- Tall mother (the taller the mother the higher the risk of twinning)
- Geography (South west nigeria has a 1 in 20 risk of twinning)
- Signs and symptoms
- Increased incidence of hyperemesis gravidarum
- Larger than expected symphysiofundal height
- Quantitafive hCG and AFP high relative to date
- Investigations
- Complete blood count to monitor for anaemia at first visit, 20 weeks and 28 weeks
- Ultrasound for diagnosis at first visit
- Lamda sign or twin peak sign – triangular appearance of membranes (dichorionic diamniotic)
- T-sign – membranes abruplty meet the chorion (monochorionic diamniotic)
- No membrane separating the twins in monochorionic monoamniotic twins
- Treatment
- Nutritional supplementation including folate and iron.
- 10-14 weeks
- Ultrasound to determine chorionicity or amnionicity
- 18-22 weeks
- Anatomy ultrasound
- Serial ultrasounds during the 2nd and 3rd trimester (frequency depends on chorionicity)
- 2 weekly from 16 weeks for monochorionic twins (have a high risk of twin-to-twin transfusion)
- 4 weekly from 20 weeks for dichorionic twins
- 4 – 6 weekly for dizygotic twins
- Cervical length measurements to predict preterm labour
- 28 weeks
- Antenatals steroids for monochorionic monoamniotic twins
- Delivery
- Prescribe antenatal steroids
- Elective caesarean delivery for:
- Monoamniotic twins (due to risk of cord prolapse in the second twin)
- Diamniotic twins when the presenting twin is not in cephalic presentation (possibility of locked twins)
- May be required for delivery of the second twin after successful birth of the first twin
- Vaginal delivery for:
- Diamniotic twins when the first twin is in cephalic presentation
Timing of delivery
| Timing | Twins |
|---|---|
| 32 – 34 weeks | Uncomplicated monochorionic monoamniotic twins |
| 36 – 37 weeks | Uncomplicated monochorionic diamniotic twins |
| 37 – 38 weeks | Uncomplicated dichorionic diamniotic twins |
| Before 35 + 6 weeks | For triplets. 75% of triplets deliver before 35 weeks |
| Induction at any time | Significant fetal growth retriction |
Complications of Multiple Gestation
| Classification | Complication |
|---|---|
| Maternal complications | Hyperemesis gravidarum, iron deficiency anaemia, intrahepatic cholestasis of pregnancy, venous thromboembolism |
| Fetal complications | Prematurity, cerebral palsy, discordant growth, congenital anomalies, stillbirth, fetal growth restriction, twin-twin transfusion syndrome, twin anaemia polycythaemia sequence |
| Obstetric complications | Pre-eclampsia and eclampsia, uterine atony and post-partum hemorrhage, postpartum depression, instrumental delivery or caesarean delivery |
| Complications affecting the 2nd twin | Low birth weight, malpresentation, cord prolapse, abruptio placentae |
| Complications with one intrauterine fetal demise (IUFD) | Disseminated intravascular coagulopathy, chorioamnionitis |