Impact on the maternal body
Carrying multiple fetuses forces the cardiovascular system, lungs, liver, and kidneys to work at maximum capacity. Maternal morbidity and mortality increase by 3–7 times compared to singleton pregnancy, and concomitant somatic pathologies are exacerbated in almost 100% of cases.
One of the most formidable complications is preeclampsia. It occurs in 45% of patients. The pathogenesis is associated with an excessive volume of placental tissue (hyperplacentosis). It is important to distinguish true preeclampsia from edema and hypertension caused by a routine increase in intravascular volume. With hypervolemia, the glomerular filtration rate is increased, proteinuria is absent, and hematocrit is decreased. Such patients benefit greatly from conventional bed rest.
Also typical for multiple pregnancy is anemia. It comes in two types:
- Physiological (hydremia) — occurs due to the outpaced growth of plasma volume, leading to a drop in hematocrit and hemoglobin (especially in the II trimester).
- Iron deficiency — develops due to the depletion of iron stores against the background of enhanced erythropoiesis.
Blood smear analysis helps differentiate these conditions.
Ultrasound diagnostics and monitoring
Ultrasound is the main control tool. When assessing anatomy, attention is paid to the nuchal translucency. In monochorionic twins, this is a marker of high risk for chromosomal abnormalities or a prognostic sign of severe twin-to-twin transfusion syndrome (TTTS). In monochorionic monoamniotic twins, conjoined twins must be ruled out.
According to ultrasound fetometry, fetal development is divided into three types:
- Physiological development of both fetuses.
- Dissociated (discordant) development — the weight difference is 20% or more.
- Growth restriction of both fetuses.
The ultrasound doctor also evaluates the structure and maturity of the placentas, the volume of amniotic fluid in each amnion, and the site of umbilical cord insertion. Velamentous insertion of the umbilical cord is common in twins.
To assess the functional state, CTG (with two sensors simultaneously) and Dopplerometry are used. In monochorionic twins, maximum blood flow velocity in the middle cerebral artery must be measured. This allows timely detection of anemia-polycythemia sequence (if both fetuses are alive) or diagnosing anemia in the surviving fetus if the second one has died and blood transfusion has occurred.
Specific complications
In addition to maternal risks, multiple pregnancy threatens the fetuses themselves.
- Fetal growth restriction (FGR) is diagnosed 10 times more often. Monochorionic twins are characterized by selective FGR (weight difference > 25%), which sharply increases the risk of intrauterine death of the low-weight fetus.
- Preterm birth is one of the most frequent complications, arising due to uterine overdistension. Delivery timing directly depends on the multiplicity order.
Pregnancy management and delivery tactics
Patients require frequent monitoring: up to 28 weeks, antenatal clinic visits are scheduled twice a month, then every 7–10 days. Sick leave is issued already at 28 weeks. Three consultations with a general practitioner are mandatory during pregnancy.
Balanced nutrition is of great importance. The total weight gain should be at least 18–20 kg, of which the woman must gain a minimum of 10 kg in the first half of pregnancy.
Prevention of complications:
- Anemia: from the 16th–20th week, iron preparations (60–100 mg/day) and folic acid (1 mg/day) are prescribed.
- Preterm birth: the optimal time for prediction is 18–21 weeks. Transvaginal cervicography is performed. If the cervical length is ≤ 25 mm, the risk of spontaneous birth before 32 weeks reaches 50%. In such cases, restriction of physical activity, daytime rest, and in twins, the insertion of an obstetric pessary and vaginal progesterone are indicated.
The choice of delivery method depends on fetal presentation by the end of pregnancy. In 80% of cases, both fetuses lie longitudinally (cephalic-cephalic, cephalic-breech, or breech-breech). Combinations of longitudinal and transverse presentations or transverse presentation of both fetuses are less common.
Briefly: answers to topical questions
What ultrasound signs allow determining twin chorionicity in the first trimester of pregnancy?
To determine twin chorionicity in the first trimester of pregnancy, specific ultrasound markers formed at the base of the inter-twin septum are used.
- λ-sign (lambda sign) — reliably indicates a dichorionic type of placentation.
- T-sign — reliably indicates monochorionicity.
- Two separately located placentas — a criterion for dichorionic twins.
- Thick inter-twin septum (more than 2 mm) — a criterion for dichorionic twins.
What specific complications are characteristic exclusively of the monochorionic type of multiple pregnancy?
Exclusively for the monochorionic type of multiple pregnancy, a number of specific complications associated with the presence of vascular anastomoses in the placenta are characteristic.
- Twin-to-twin transfusion syndrome (TTTS) — occurs due to arteriovenous anastomoses in the thickness of the placenta.
- Reversed arterial perfusion — the most pronounced manifestation of TTTS, in which one fetus develops at the expense of the other.
- Selective fetal growth restriction (sIUGR) — accompanied by a high risk of intrauterine death of the fetus with lower body weight.
- Anemia-polycythemia sequence (TAPS) — diagnosed by evaluating the maximum blood flow velocity in the middle cerebral artery.
What indications determine the choice of cesarean section in a twin pregnancy?
The choice of cesarean section in a twin pregnancy is determined by a number of absolute and relative fetal indications.
- Monochorionic monoamniotic twins — an absolute indication.
- Conjoined twins — an indication at any gestational age.
- Non-cephalic presentation of the first fetus — breech (especially in nulliparous women) or transverse position.
- Transverse position of the second fetus — considered by many obstetricians as an indication for surgery on the second fetus.
- Estimated fetal weight less than 1500 g — in case of preterm delivery.
- Death of one of the fetuses — in monochorionic twins at a viable gestational age, emergency intervention is required.
What are the features of preventing hypotonic bleeding in the third stage of labor in multiple pregnancy?
Prevention of hypotonic bleeding in multiple pregnancy is mandatory in the placental and postpartum periods. This is due to the high risk of hypotonic bleeding caused by uterine overdistension.
Class and exam questions
How to distinguish true preeclampsia from edema due to hypervolemia?
With hypervolemia, the glomerular filtration rate is increased, there is no significant proteinuria, and hematocrit decreases dynamically. The pregnant woman's condition significantly improves with bed rest.
Why measure middle cerebral artery blood flow in monochorionic twins?
This is necessary to detect anemia-polycythemia sequence if both fetuses are alive, or to diagnose severe anemia in the surviving fetus in case of intrauterine death of the second.
What difference in fetal weight is considered critical?
In dissociated development, the difference is 20% or more. For selective growth restriction in monochorionic twins, the criterion is a difference of more than 25%.
How to prevent preterm birth in asymptomatic cervical shortening?
With a cervical length of 25 mm or less, restriction of activity, increased daytime rest, as well as the insertion of an obstetric pessary and the use of vaginal progesterone are indicated.
What else to study on this topic
- Pathogenesis and stages of twin-to-twin transfusion syndrome (TTTS)
- Twin anemia-polycythemia sequence: diagnostic criteria
- Velamentous cord insertion: intrapartum risks and management
- Biomechanism of labor in various twin presentation variants
- Technique of transvaginal cervicography
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