The childbirth in the human species , as in all mammals, can be defined as “ the expulsion of the fetus from the maternal genital organs at the end of pregnancy ” (Treccani, Dictionary of Medicine). It can occur due to a series of natural processes or through obstetric operations and, depending on the time of pregnancy in which it occurs, is considered a term, preterm (premature or early) or post-term (late).
Calculating the date of birth at the beginning of pregnancy is therefore very important because, when the long awaited moment arrives, it is possible to immediately understand if the child is punctual, early or late and to intervene in the most appropriate way.
But how is the estimated date of birth calculated? And how do we proceed in the event of a term delivery, premature or late because mother and child are not at risk?
Pregnancy and gestation: what’s the difference?
The dating of the pregnancy , therefore the calculation of the presumed date of birth, is based on a precise parameter, or the first day of the last menstruation : it would be complex to rely on the moment of conception (spermatozoa can survive inside the uterus until to five days), too uncertain to define.
Gestation and pregnancy , commonly used as synonyms, refer to two different concepts :
The gestation period is the period from conception to birth of the child.
The pregnancy is the period from the first day of your last period until delivery.
The waste is in the two weeks from the first day of the last menstrual cycle, which coincides with the beginning of pregnancy, to the 14th day (ovulation phase in which conception takes place), from which the calculation is started of the weeks of gestation.
Expected date of birth: how is it calculated?
The calculation of the weeks of pregnancy is therefore based on the gestational age (calculated on the basis of the last menstruation) , not on the conceptional age (calculated on the basis of the moment of conception, which is assumed to be two weeks later). It is an important element to monitor the development of the embryo and to understand if the growth parameters are in the norm . It also allows the estimated date of birth to be calculated.
To do this it is necessary to count 280 days (40 weeks) from the first day of the last menstruation, with an extra margin or in less than 15 days . A pregnancy is “normal” if it ends 3 weeks before or two weeks after the fortieth. In this case, we talk about term delivery.
If, on the other hand, the pregnancy lasts less, or continues far beyond the term, the birth will be preterm or post-term. We must also specify that, especially when the woman has normally irregular cycles, it is important to perform a date with an ultrasound scan at the beginning of pregnancy: measuring the length of the embryo is, in fact, the most reliable means of dating pregnancy.
The management of the different types of childbirth is often multidisciplinary and specific for each woman, with actions and interventions to be evaluated in relation to the state of health of the mother and fetus. Let’s see which ones.
FOR TERMS,PRETERM AND POST~TERM
I’m leaving at term:
occurs between 37 and
41 weeks of pregnancy
Preterm birth (or premature birth):
37 Weeks of Pregnancy
happens at 42 weeks
ii pregnancy or beyond
I’m leaving soon
The term birth is what happens in “regular” times, that is between 37 and 41 weeks of pregnancy , to be precise between the beginning of the 37th and the end of the 41st week (41 + 6 days), that is between 259 and 294 days after the last menstruation . This is the situation that, unless complications arise, however rarer than in preterm and post-term delivery, involves less concern for women because it is considered more natural and normal.
I’m leaving for the future: the factors that favor it
A careful control and monitoring of symptoms by the gynecologist , for the entire duration of the pregnancy, allows optimal management of the various problems, with the aim of trying to favor term delivery. Furthermore a correct lifestyle, characterized by a balanced diet and the elimination of smoke , contributes to a better control of pregnancy.
Childbirth: cesarean or natural?
When the pregnancy has a regular course and the woman is in good health , it is possible to proceed with a natural birth . In this case, at the first signs of the beginning of labor (rupture of the amniotic sac, loss of the mucous plug or contractions that become more intense, generally every 10 minutes), the future mother will have to go to the hospital to give birth to her baby .
Natural childbirth is not recommended if the woman has already had a cesarean in the past or if the child is in a transverse or breech position . In that case, we will proceed with a caesarean section . In general, in the case of a previous cesarean or an abnormal position, the cesarean is scheduled , usually between the 38th and the 39th week. The cesarean can also be performed urgently , ie decided during labor, for example when abnormalities in the heartbeat of the fetus occur.
Compared to a natural birth, the caesarean section involves a greater post-partum suffering and a longer stay and recovery.
In the case of natural childbirth , to manage pain it is possible to resort to breathing techniques or analgesics administered via the venous route, or to require epidural anesthesia. In the case of caesarean section , generally a loco-regional anesthesia is used , of a spinal or epidural type : in emergencies, a general anesthesia can be used.
Complications for mother and child
Even if the birth is completed and the risks of complications are significantly lower than the preterm and post-term ones, complications may occur which must be managed promptly and in an appropriate manner to avoid risks for the mother and child.
Most complications can be predicted before the labor phase begins .Among these, the main ones are:
fetal dystocia (abnormal position or size);
preeclampsia (arterial hypertension associated with protein in the urine);
placenta previa (ie positioned in the lower part of the uterus at the level of the internal uterine orifice);
Then there are unforeseeable complications that can occur before labor . These include preterm rupture of membranes , which can increase the risk of infections for mom and baby. For this reason, we generally proceed with the induction of childbirth. Among other unforeseeable complications, there are detachment or abnormalities of the placenta.
Some complications can also occur suddenly during labor (among these, embolism from amniotic fluid and shoulder dystocia or umbilical cord prolapse), or during childbirth : for example, in the case of prolonged labor and above all failure to undergo (failure to expel the placenta after the birth of the baby) we must think of the placenta accreta, that is firmly attached to the uterus. Some problems can also occur immediately after the birth of the child, at the time of expulsion of the placenta. The most common one is postpartum hemorrhage.
Preterm birth means a birth that takes place before the 37th week of gestation .
More in detail, the preterm birth is distinguished in:
Late (Late Preterm): 32-36 + 6 weeks
Early (Low Preterm): 24-31 + 6 weeks
Extremely early condition: before 23 + 6 weeks
In about 50% of cases , labor occurs spontaneously with contractions and changes in the cervix with intact membranes , in 30% after a premature rupture of the membranes (PROM) . In 20% of the cases, the birth is induced when the continuation of the pregnancy involves a risk for the mother and / or the child, or for a maternal pathology (pre-eclampsia) and / or fetal (defect / growth arrest) or due to an obstetric condition (placental detachment, placenta previa, fetal endouterine death).
The WHO has reported an increase in preterm birth rates over the past two decades.
In Italy, the 2010 CEDAP (Certificate of Assistance to the Childbirth) data shows a percentage of preterm parties equal to 6.6 %: among these, the parties that took place before the 32nd week represent 0.9%. Among the reasons for this increase, there are the greatest number of twin pregnancies associated with infertility therapies and the advancement of maternal age in the search for pregnancy.
Preterm birth: risk factors
Below are the main risk factors reported in the literature for single pregnancies:
maternal age : women under the age of 18 and over 40 have a greater risk of preterm birth;
ethnicity : the black population has a consistently higher risk than the white one;
marital status : pregnancy in unmarried women is associated with an increased risk of preterm birth;
body mass index : a BMI less than 18 is associated with an increased risk of preterm birth, while there is no agreement that obesity is a risk factor;
previous obstetric history : a previous spontaneous preterm birth between the 24th and 36th week is the most important risk factor;
assisted reproduction techniques : medically assisted reproductive pregnancies, especially those with a high level of technology used, have a greater risk of preterm birth, regardless of twinning;
interval between pregnancies : an interval less than 6 months between two pregnancies involves a risk of preterm birth;
urinary tract infections increase the risk of pyelonephritis that increase the risk of preterm birth.
Dangers for the child and the mother
In high-income countries, 6-11% of children born alive before 37 weeks do not survive(source: EURO-PERISTAT 2008). The children born before the 32th week of gestation are at particularly high risk of adverse outcomes, with infant mortality rates of around 10-15% and cerebral palsy at 5-10% . Even newborns born between 32nd and 36th weeks of gestationhave worse outcomes at birth and in infants than full-term infants.
Preterm birth also predisposes infants to a greater risk of premature remote mortality and the development of chronic diseases .
However, the survival of highly premature infants has greatly improved in recent decades due to advances in perinatal medicine, such as the use of corticosteroids and surfactant.
The signals that indicate that the woman is at risk of preterm labor are different. The most characteristic are the uterine contractions (the woman feels her belly harden), which are also evident in the cardiotocographic monitoring, the shortening of the uterine neck , the loss of the amniotic fluid before the end .
A reasonable algorithm (modified SLOG – Società Lombarda Ostetricia e Ginecologia, 2014) for the diagnosis of preterm birth involves:
patient history and accurate identification of possible risk factors
clinical evaluation of the signs and symptoms of preterm labor
evaluation with the speculum, to exclude PROM
if the cervicometria is <30 mm, measurement in the cervico-vaginal secretions of the fFN (fetal fibronectin), of the phIGFBP-1 (insulin-like growth factor) or of the PAMG-1 (alpha microglobulin-1 placenta)
digital evaluation of cervical dilatation and cervical features.
The cervicometria is an ultrasound examination that allows to measure the length of the cervical canal . It allows you to recognize many of the cases that can evolve into a preterm birth. The risk of spontaneous preterm birth increases, in fact, as the length of the uterine cervix decreases .
In general, a length of less than 25 mm leads to a high risk of premature birth before the 34th week and indicates the need to activate an adequate prophylactic and therapeutic treatment, as described in the guideline (NICE – National Institute for Health and Clinical Excellence) . As we shall see later, these guidelines recommend, in the case of cervicometry less than 25 mm and a history of previous pregnancy with rupture of the membranes, or premature birth, the use of progesterone or cerclage .
The ultrasound examination of the cervix can be performed transabdominal (ETA), transvaginal (ETV) or transperineal (ETP). The ETV is the most reliable and most widespread technique for measuring the cervical canal, it does not involve risks for the mother and the fetus and is easy to perform.
The ultrasound measurement of the cervical canal is a good predictor of spontaneous PPT in both asymptomatic pregnant women and in women with the threat of preterm birth , although it should not be taken as an isolated indicator because prematurity has a multifactorial origin.
In the case where the cervicometria has found a length of the cervical canal inferior to 30 mm, it is opportune to proceed with the measurement in the cervico-vaginal secretions of the fFN (fibronectin) , a glycoprotein produced by the chorion (the most external membrane of the fertilized egg) which is normally found in cervico-vaginal secretions up to 16 weeks of gestation and reappears at the end of pregnancy when the signs of labor begin . This test is normally used to rule out the risk of preterm labor. Among the other biochemical tests used in the diagnosis are phIGF-BP1 and PAMG-1.
Management of preterm labor
Tocolysis (from the Greek tokos act of giving birth and lysis dissolution, splitting) consists in the preventive administration of drugs to stop or decrease uterine contractions .
This procedure may allow delayed preterm labor of a few hours / days to allow the administration of corticosteroids and / or transfer to the uterus in a more appropriate center for newborn care . The use of tocolitico, in fact, is associated with a delay of delivery of 24-48 hours up to a maximum of 7 days , but does not reduce the incidence of preterm birth .
Tocolytics do not reduce morbidity (disease incidence) and perinatal mortality related to prematurity.
The use of tocolysis is recommended in the presence of a consolidated diagnosis of preterm delivery within 34.6 weeks , but it is contraindicated when it is harmful or impossible to prolong the pregnancy , for example in cases of unstoppable labor, severe preeclampsia, placental detachment.
The main tocolytic agents to be used include:
inhibitors of prostaglandin synthesis (indomethacin)
calcium antagonists (nifedipine)
beta-sympathomimetics (ritodrine, terbutaline)
oxytocin antagonists (atosiban)
magnesium sulfate: prophylactic administration to the mother near the birth before 30-32 weeks reduces the risk of infantile cerebral palsy.
The choice of agents to use must be based on the gestational age, but also on the possible side effects for mother and child, which can also be very severe.
Progesterone also plays an essential role in maintaining pregnancy , so its use is recommended in the prophylaxis and treatment of premature birth in women at risk . It is in fact responsible for the inhibition of cervical maturation which plays a fundamental role “closing” the uterus. It also acts on the muscle fibers by inhibiting the fundamental changes for labor, so a decrease in progesterone could lead to premature labor
This surgical treatment can be used to correct or prevent “cervical insufficiency” which can lead to late abortion or preterm labor in women considered at risk. In practice, this practice is adopted when the cervix is unable to adequately contain the fetus and shortens and expands many weeks before the expected date of birth. The operation, of a few minutes under general anesthesia, consists in placing a small tape on the cervix that will keep it closed and that it will be removed without anesthesia near the end of the pregnancy or as soon as labor contractions appear. Usually it proceeds vaginally, except in cases of cervical hypoplasia, previous surgical therapies or obstetric traumas, when it is preferable to carry out the cerclage through the transabdominal route or in laparoscopy.
This gynecological practice is contraindicated in the presence of preterm contractile activity, continuous vaginal bleeding, PROM (premature rupture of the membranes), fetal impairment.
The pessary is a non-invasive intravaginal device that can be used in women with a shortened cervix (18-22 weeks). Its use in prophylaxis of preterm birth seems to be promising, but further evidence is needed to prove its effectiveness.
Preterm birth and PPROM (premature rupture of membranes)
Premature rupture of membranes (PPROM) is associated with 30% of preterm parts .
The term PPROM ( pre-term premature rupture of membrane s) refers to the spontaneous rupture of the membranes before the 37th week of gestation , with consequent leakage of amniotic fluid surrounding the fetus (while the PROM, or premature rupture of membranes , is the rupture of amniocional membranes before the onset of labor).
PPROM may depend on several factors, but it is mainly due to the presence of infections or inflammations .
In 50% of the cases, the birth takes place within a week of the break, in the other half of the cases the timing of the birth is linked to the gestational age in which the break occurred.
Among the main risks for the newborn associated with pPROM are prematurity, sepsis and pulmonary hypoplasia.
There are a series of tests that allow you to assess that you are actually in the presence of a PPROM :
nitrazine test , for the evaluation of vaginal pH (in general the vaginal pH is between 4.5 and 6. in the presence of amniotic fluid it becomes higher than 7).
Ferning test , which evaluates the ability of crystallization of amniotic fluid for high salt content (sodium chloride) and proteins.
Biochemical tests such as alpha-microglobulin-1 , a placental glycoprotein abundantly present in amniotic fluid and found, in much lower concentrations, in maternal blood and cervico-vaginal secretions in the absence of ruptured membranes.
In all patients with PPROM, it is advisable to evaluate the probability of delivery, fetal well-being and the presence of a maternal / fetal infection.
In the absence of complications requiring childbirth to proceed immediately (for example a placenta detachment), the choice to have a woman give birth or to wait depends on the gestational age in which the rupture occurred.
Transport in utero (STAM) in case of severe prematurity
The Maternal Assisted Transportation Service (STAM) provides for the transfer of the pregnant patient to an appropriate level hospital . This procedure is used in case of severe prematurity, to ensure adequate assistance to the woman and / or the newborn . In fact, STAM has proven efficacy in reducing perinatal mortality in highly preterm newborns. In contrast, those born outside of facilities with dedicated neonatal intensive care facilities are at increased risk of developing major neonatal complications, including neurodevelopmental defects. Furthermore, intensive care is more effective if performed in utero rather than in the neonatal period, especially for those born before the 30th week.
However, STAM is contraindicated in case of instability of maternal conditions, instability or possibility of rapid deterioration of fetal conditions , imminent birth.
Guaranteed assistance in this type of service allows you to have highly specialized personnel in the management of premature and risky pregnancies for your mother and newborn. In particular, neonatal and personal intensive care is guaranteed to the newborn, able to manage the complicated respiratory and systemic problems associated with premature birth.
Antenatal corticosteroid prophylaxis
The antenatal administration of steroids is, together with STAM, one of the only two interventions able to reduce mortality and perinatal morbidity in women at risk of preterm delivery between 24 and 34 gestational weeks . Corticosteroid prophylaxis promotes the maturation of organs and other tissues. Their use does not increase severe, infectious or hypertensive maternal complications.
Inflammation and infection of amniotic fluid are risk factors for preterm labor. The use of broad-spectrum antibiotics is recommended when premature rupture of the membranes occurs before the onset of labor (PPROM) , but it is not indicated in a threat of preterm labor without rupture of the membranes (intact membranes).
Prevention of preterm birth
It is possible to implement primary and secondary prevention interventions.
Primary prevention consists in the implementation of strategies that aim to reduce, before pregnancy, the known risk factors of premature birth . Between these:
promotion / facilitation of access to prenatal public care for adolescents, poor women, immigrants, socially disadvantaged;
counseling to women with previous preterm birth to try to identify the causes, quantify the risk, suggest possible changes in habits;
promotion of healthy lifestyles (healthy eating, smoking reduction).
However, there are no international epidemiological studies or studies in the Italian population that have evaluated the preventive impact of these measures.
Among the interventions aimed at eliminating or reducing existing risk factors, which have proven to be effective, there are:
adequate therapeutic control of pregnant women with chronic diseases that put them at risk of preterm birth (pre-gestational diabetes, chronic hypertension complicated with preeclampsia, ulcerative colitis);
early screening in the 2nd trimester and timely treatment of bacterial vaginosis;
cervicometria in women with previous preterm birth and appropriate treatment (progesterone, cerclage).
Post-term pregnancy is a gestation that has a duration greater than or equal to 42 weeks .
The incidence of post-term pregnancy is generally between 4 and 10% of cases .
Causes and risk factors
The causes of prolonged pregnancy are poorly understood. Fetal conditions (such as anencephaly) or placenta may be associated with this event. Male fetal sex and genetic factors seem to be related to maternal conditions such as obesity, having no previous parts and advanced age .
The symptom is the failure to start labor after 42 weeks.
The best diagnosis is based not on the amenorrhea (date of the last menstruation) but on the ultrasound evaluation (fetal biometry) performed early in pregnancy in order to allow a more correct dating of the pregnancy .
Post-term delivery management
There are basically two recommended treatments . The first consists in avoiding the continuation of the pregnancy inducing the birth before the 42nd week . The second is represented by the expectation, under close supervision , by applying an active treatment (induction or cesarean) on specific indication.
Surveillance is characterized by cardiotocography or CTG or fetal monitoring, useful for assessing the contractile activity of the uterus and the cardiac activity of the fetus, and an ultrasound check in which it is essential to evaluate the amniotic fluid, fetal biometry, excluding the risk of fetus with reduced growth, and evaluation of flows (ie blood that nourishes the fetus).
In both cases a correct dating of the gestational age is a fundamental prerequisite.
Risks for mother and child and possible complications
Epidemiological studies have shown that the frequency of fetal, maternal and neonatal complications increases after the 41st week of gestation . As a result, post-term delivery monitoring and treatment are very important.
An increased risk of macrosomic fetuses with high birth weight and perinatal death may occur . Post-natal risks are different. Among these, low Apgar Index (evaluation of the efficiency of the most important functions for the organism and therefore of the general state of health of the newborn), acidemia, admission to neonatal intensive care (TIN), meconial fluid, meconium aspiration syndrome , clavicle fractures and brachial paralysis. Maternal complications include dysfunctional labor, shoulder dystocia, obstetric trauma and postpartum hemorrhage.
Prevention of post-term birth
It is not possible to prevent post-term birth except through induction of the part . It is fundamental to carry out a correct monitoring of the pregnancy in order to identify possible changes in growth and flows as soon as possible .
Abortion and intrauterine death
Unfortunately, it may happen that the pregnancy is not completed due to the death of the fetus in utero. This event, which is dramatic for a woman, often occurs in the first few weeks, but sometimes it can happen at a rather advanced pregnancy, beyond the first trimester. Depending on the period in which it occurs, it is called abortion or fetal intrauterine death.
Abortion and fetal intrauterine death are two conditions characterized by the termination of pregnancy. We talk about ” abortion ” if it occurs within the 22nd week of gestation and ” fetal intrauterine death ” (also called “fetal endouterine death” or “MEF”) in or after the 22nd week of gestational age.
About 10-25% of pregnancies end in a miscarriage . Most spontaneous abortions occur during the first weeks of pregnancy. Depending on the studies, the percentage of intrauterine fetal death fluctuates between 4 and 12 per thousand .
Causes and risk factors
The miscarriages are caused by chromosomal abnormalities, viruses, immunological abnormalities, major trauma and uterine anomalies such as the presence of adhesions. Generally, the cause is unknown. The risk factors associated with spontaneous abortion are over 35 years of age, having already had a miscarriage, smoking, the use of some drugs (among the teratogenic drugs there are chemotherapeutic drugs, some anticoagulants, antiepileptics or antidepressants) or a poorly controlled chronic disease such as diabetes or thyroid disorders in the mother .
The causes of intrauterine death are different and are often difficult to interpret. Some of the main risk factors identified are: advanced maternal age, consanguinity, previous preterm birth , isoimmunization, placental detachment, hypertension, preeclampsia, umbilical cord diseases . However, the data shows that over 50% of fetal deaths remain unexplained.
The miscarriage symptoms are pelvic pain of cramp-type, blood loss and finally the expulsion of material. Spontaneous late abortion can begin with an abundant loss of fluid when the membranes break. The spontaneous abortion can be “complete” (total spontaneous expulsion of the embryo or lifeless fetus) or “incomplete” or “retained” : in this case, the only sign will be the absence of an embryo or lack of activity cardiac .
The intrauterine death of the fetus can be suspected when you have the disappearance of the signs and symptoms associated with pregnancy or, more often, we note the ‘ absence of the previously perceived fetal movements .
Ultrasound is the fastest and most effective way to confirm the diagnosis.
If the event has occurred for some time, it is also possible to find lower fetal dimensions than at the time of pregnancy, in addition to other characteristic echographic signs.
How to intervene in case of abortive birth
The treatment of abortions, incomplete or internal, is the surgical procedure called revision of the uterine cavity or the expectation of spontaneous expulsion . The intervention generally involves a curettage with suction.
Once an intrauterine fetal death has occurred, labor of birth arises spontaneously within 2 to 3 weeks. However, the conduct used to date is the pharmacological induction of childbirth so as not to lead the woman to a long wait, which is difficult to sustain emotionally.
Risks for women and possible complications
In spontaneous abortion the risks relate to failure to expel , excessive blood loss and surgery, which lasts about 15 minutes.
Very unlikely condition is the possibility that a disseminated intravascular coagulation can be triggered within 4 weeks of endouterine death. This pathology is a very serious condition in which there is an alteration of the coagulation system , with thrombi and hemorrhages that are difficult to control . The triggering causes can be various, including sepsis, large burns, haematological malignancies or, as already mentioned, obstetric complications.
Prevention of abortion
A close monitoring of pregnancy and an early detection of risk factors are essential for proper prevention.