With the increasing age of childbearing, late pregnancies are more and more frequent and it is not uncommon today to have a child at 40 years old. Thus among the newborns in 2015, 5% had a mother aged 40 or over (1). Being pregnant at 40 is nonetheless a risky situation requiring careful monitoring.

The fertility window, that is to say the period during which a woman can have a baby, corresponds to that of the rules: it begins at puberty and ends at menopause. But during this window, the quality of fertility varies: it is maximum until the age of 35, then it gradually decreases to drop rapidly after your forties. One of the reasons is ovarian aging in quality (poorer quality oocytes) and in quantity (decrease in the number of oocytes).

Getting pregnant at 40 is therefore more difficult than at 20, 30, 35, and it usually takes longer. According to the simulation model developed by French epidemiologist Henri Leridon (2), a woman seeking to have a child has:

• 75% chance of achieving it in 12 months around age 30;
• 66% chance if it starts at 35;
• 44% if it starts at age 40.

The risks of not having a pregnancy also increase with age: they are 8% at 30 years old, 15% at 35 years old, 36% at 40 years old.

AMP (medically assisted procreation) does not always solve this age-related fertility problem, because the success rate of the various techniques also decreases with age. AMP mainly makes it possible to obtain better ovulation and better fertilization, but it cannot compensate for all the physiological factors underlying the decline in fertility with age, and in particular the decrease in the stock of oocytes and their aging.

From 12 to 15% before the age of 30, the risk of miscarriage is around 30% between 40 and 44 years and rises to 40% between 45 and 49 years (3).

This increase in the number of miscarriages with age is partly explained by the aging of the oocytes, the quality of which deteriorates over the years. Studies on the oocytes used in IVF have also shown that the rate of aneuploidy (cell without the normal number of chromosomes) increases with age: from 10% to 35 years, it increases to 30% at 40 years old, 40% at 43 years old and 100% in women over 45 years old (4). However, chromosomal abnormalities on the gametes (oocyte or spermatozoon) lead to a miscarriage.

In addition, with age, certain uterine pathologies are more frequent: fibroma, adenomyosis, vascularization disorders. They can prevent implantation and lead to miscarriage.

A pregnancy after 40 years is indeed considered a risk pregnancy for the baby and for the mother-to-be..

For the mom

In its report on pregnancies after 40 years (5), the French National College of Gynecologists and Obstetricians (CNGOF) recalls that late pregnancies are pregnancies at increased risk of:

• Gestational Diabetes ;
• arterial hypertension and pre-eclampsia;
• Preliminary cake;
• retroplacental hematoma;
• hemorrhage from delivery;
• maternal mortality.

Pre-existing hypertension, smoking, overweight increase these risks.

For the baby

A late pregnancy is also a risky situation for the baby, as the same CNGOF report reminds us. Babies whose mothers are over 40 have an increased risk of:

• chromosomal abnormality, and in particular trisomy 21. The rate of chromosomal abnormality is multiplied by 10 after 39 years (6)
• congenital malformations: from 3,5% at 25 years, the prevalence increases to 5% at 40 years;
• growth retardation in utero (IUGR);
• macrosome (baby over 4 kg);
• prematurity.

To prevent and detect these various complications as early as possible, the expectant mother over 40 years of age benefits from careful monitoring. Pregnancy monitoring can be done by an obstetrician-gynecologist or a midwife, but the advice of an obstetrician-gynecologist is recommended for pregnancies over 35 years (recommendations of the HAS (7)).

The number of prenatal consultations is the same as for all future mothers, with a monthly visit from the 3rd month, but the gynecologist will be particularly attentive to certain points: tension, weight gain, etc.

The future mother will benefit from 3 ultrasounds as in the classic follow-up, but during the first and the second ultrasound, the practitioner will be particularly attentive in order to detect a possible congenital malformation or a karyotype anomaly.

Amniocentesis is not systematic in late pregnancy. As for all pregnancies, screening for trisomy 21 is based on combined screening in the first trimester, systematically offered but not compulsory. Maternal age is taken into account in the calculation of the combined risk, alongside the measurement of nuchal translucency at the first ultrasound and the assay of serum markers. As for all mothers, a karyotype (by amniocentesis or trophoblast biopsy) will be offered in the event of a risk greater than 1/250.

Screening for gestational diabetes is not mandatory either, but is systematically offered in cases of late pregnancy.

With this follow-up, late pregnancies, although considered risky, generally go well.

After 40, childbirth can indeed be more difficult.

Breech presentation is slightly more frequent after 40 years (7% of deliveries after 40 years against 5% between 20 and 34 years (8), as is the risk of long labor and obstructed labor. The risk of hemorrhage during delivery is also a little bit high after 40 years, especially during the first childbirth.

The cesarean rate is doubled in late pregnancy. Specialists put forward several explanations: the quality of the uterus (fibromatous) which makes contractions less effective for labor, breech presentation, macrosomia (large baby, frequent in cases of gestational diabetes), longer working time , the higher frequency of obstructed labor, but also the attitude of the obstetrician who would tend to take more precautions when faced with a future mother over 40 years old.